1 |
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2 | package Tie::File;
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3 | require 5.005;
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4 | use Carp ':DEFAULT', 'confess';
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5 | use POSIX 'SEEK_SET';
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6 | use Fcntl 'O_CREAT', 'O_RDWR', 'LOCK_EX', 'LOCK_SH', 'O_WRONLY', 'O_RDONLY';
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7 | sub O_ACCMODE () { O_RDONLY | O_RDWR | O_WRONLY }
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8 |
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9 |
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10 | $VERSION = "0.97";
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11 | my $DEFAULT_MEMORY_SIZE = 1<<21; # 2 megabytes
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12 | my $DEFAULT_AUTODEFER_THRESHHOLD = 3; # 3 records
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13 | my $DEFAULT_AUTODEFER_FILELEN_THRESHHOLD = 65536; # 16 disk blocksful
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14 |
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15 | my %good_opt = map {$_ => 1, "-$_" => 1}
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16 | qw(memory dw_size mode recsep discipline
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17 | autodefer autochomp autodefer_threshhold concurrent);
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18 |
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19 | sub TIEARRAY {
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20 | if (@_ % 2 != 0) {
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21 | croak "usage: tie \@array, $_[0], filename, [option => value]...";
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22 | }
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23 | my ($pack, $file, %opts) = @_;
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24 |
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25 | # transform '-foo' keys into 'foo' keys
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26 | for my $key (keys %opts) {
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27 | unless ($good_opt{$key}) {
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28 | croak("$pack: Unrecognized option '$key'\n");
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29 | }
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30 | my $okey = $key;
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31 | if ($key =~ s/^-+//) {
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32 | $opts{$key} = delete $opts{$okey};
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33 | }
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34 | }
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35 |
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36 | if ($opts{concurrent}) {
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37 | croak("$pack: concurrent access not supported yet\n");
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38 | }
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39 |
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40 | unless (defined $opts{memory}) {
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41 | # default is the larger of the default cache size and the
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42 | # deferred-write buffer size (if specified)
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43 | $opts{memory} = $DEFAULT_MEMORY_SIZE;
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44 | $opts{memory} = $opts{dw_size}
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45 | if defined $opts{dw_size} && $opts{dw_size} > $DEFAULT_MEMORY_SIZE;
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46 | # Dora Winifred Read
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47 | }
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48 | $opts{dw_size} = $opts{memory} unless defined $opts{dw_size};
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49 | if ($opts{dw_size} > $opts{memory}) {
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50 | croak("$pack: dw_size may not be larger than total memory allocation\n");
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51 | }
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52 | # are we in deferred-write mode?
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53 | $opts{defer} = 0 unless defined $opts{defer};
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54 | $opts{deferred} = {}; # no records are presently deferred
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55 | $opts{deferred_s} = 0; # count of total bytes in ->{deferred}
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56 | $opts{deferred_max} = -1; # empty
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57 |
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58 | # What's a good way to arrange that this class can be overridden?
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59 | $opts{cache} = Tie::File::Cache->new($opts{memory});
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60 |
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61 | # autodeferment is enabled by default
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62 | $opts{autodefer} = 1 unless defined $opts{autodefer};
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63 | $opts{autodeferring} = 0; # but is not initially active
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64 | $opts{ad_history} = [];
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65 | $opts{autodefer_threshhold} = $DEFAULT_AUTODEFER_THRESHHOLD
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66 | unless defined $opts{autodefer_threshhold};
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67 | $opts{autodefer_filelen_threshhold} = $DEFAULT_AUTODEFER_FILELEN_THRESHHOLD
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68 | unless defined $opts{autodefer_filelen_threshhold};
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69 |
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70 | $opts{offsets} = [0];
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71 | $opts{filename} = $file;
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72 | unless (defined $opts{recsep}) {
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73 | $opts{recsep} = _default_recsep();
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74 | }
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75 | $opts{recseplen} = length($opts{recsep});
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76 | if ($opts{recseplen} == 0) {
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77 | croak "Empty record separator not supported by $pack";
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78 | }
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79 |
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80 | $opts{autochomp} = 1 unless defined $opts{autochomp};
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81 |
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82 | $opts{mode} = O_CREAT|O_RDWR unless defined $opts{mode};
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83 | $opts{rdonly} = (($opts{mode} & O_ACCMODE) == O_RDONLY);
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84 | $opts{sawlastrec} = undef;
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85 |
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86 | my $fh;
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87 |
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88 | if (UNIVERSAL::isa($file, 'GLOB')) {
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89 | # We use 1 here on the theory that some systems
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90 | # may not indicate failure if we use 0.
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91 | # MSWin32 does not indicate failure with 0, but I don't know if
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92 | # it will indicate failure with 1 or not.
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93 | unless (seek $file, 1, SEEK_SET) {
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94 | croak "$pack: your filehandle does not appear to be seekable";
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95 | }
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96 | seek $file, 0, SEEK_SET # put it back
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97 | $fh = $file; # setting binmode is the user's problem
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98 | } elsif (ref $file) {
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99 | croak "usage: tie \@array, $pack, filename, [option => value]...";
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100 | } else {
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101 | # $fh = \do { local *FH }; # XXX this is buggy
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102 | if ($] < 5.006) {
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103 | # perl 5.005 and earlier don't autovivify filehandles
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104 | require Symbol;
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105 | $fh = Symbol::gensym();
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106 | }
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107 | sysopen $fh, $file, $opts{mode}, 0666 or return;
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108 | binmode $fh;
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109 | ++$opts{ourfh};
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110 | }
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111 | { my $ofh = select $fh; $| = 1; select $ofh } # autoflush on write
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112 | if (defined $opts{discipline} && $] >= 5.006) {
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113 | # This avoids a compile-time warning under 5.005
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114 | eval 'binmode($fh, $opts{discipline})';
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115 | croak $@ if $@ =~ /unknown discipline/i;
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116 | die if $@;
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117 | }
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118 | $opts{fh} = $fh;
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119 |
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120 | bless \%opts => $pack;
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121 | }
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122 |
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123 | sub FETCH {
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124 | my ($self, $n) = @_;
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125 | my $rec;
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126 |
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127 | # check the defer buffer
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128 | $rec = $self->{deferred}{$n} if exists $self->{deferred}{$n};
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129 | $rec = $self->_fetch($n) unless defined $rec;
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130 |
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131 | # inlined _chomp1
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132 | substr($rec, - $self->{recseplen}) = ""
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133 | if defined $rec && $self->{autochomp};
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134 | $rec;
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135 | }
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136 |
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137 | # Chomp many records in-place; return nothing useful
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138 | sub _chomp {
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139 | my $self = shift;
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140 | return unless $self->{autochomp};
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141 | if ($self->{autochomp}) {
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142 | for (@_) {
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143 | next unless defined;
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144 | substr($_, - $self->{recseplen}) = "";
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145 | }
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146 | }
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147 | }
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148 |
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149 | # Chomp one record in-place; return modified record
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150 | sub _chomp1 {
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151 | my ($self, $rec) = @_;
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152 | return $rec unless $self->{autochomp};
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153 | return unless defined $rec;
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154 | substr($rec, - $self->{recseplen}) = "";
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155 | $rec;
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156 | }
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157 |
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158 | sub _fetch {
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159 | my ($self, $n) = @_;
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160 |
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161 | # check the record cache
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162 | { my $cached = $self->{cache}->lookup($n);
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163 | return $cached if defined $cached;
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164 | }
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165 |
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166 | if ($#{$self->{offsets}} < $n) {
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167 | return if $self->{eof}; # request for record beyond end of file
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168 | my $o = $self->_fill_offsets_to($n);
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169 | # If it's still undefined, there is no such record, so return 'undef'
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170 | return unless defined $o;
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171 | }
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172 |
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173 | my $fh = $self->{FH};
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174 | $self->_seek($n); # we can do this now that offsets is populated
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175 | my $rec = $self->_read_record;
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176 |
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177 | # If we happen to have just read the first record, check to see if
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178 | # the length of the record matches what 'tell' says. If not, Tie::File
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179 | # won't work, and should drop dead.
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180 | #
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181 | # if ($n == 0 && defined($rec) && tell($self->{fh}) != length($rec)) {
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182 | # if (defined $self->{discipline}) {
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183 | # croak "I/O discipline $self->{discipline} not supported";
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184 | # } else {
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185 | # croak "File encoding not supported";
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186 | # }
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187 | # }
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188 |
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189 | $self->{cache}->insert($n, $rec) if defined $rec && not $self->{flushing};
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190 | $rec;
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191 | }
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192 |
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193 | sub STORE {
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194 | my ($self, $n, $rec) = @_;
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195 | die "STORE called from _check_integrity!" if $DIAGNOSTIC;
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196 |
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197 | $self->_fixrecs($rec);
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198 |
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199 | if ($self->{autodefer}) {
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200 | $self->_annotate_ad_history($n);
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201 | }
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202 |
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203 | return $self->_store_deferred($n, $rec) if $self->_is_deferring;
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204 |
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205 |
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206 | # We need this to decide whether the new record will fit
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207 | # It incidentally populates the offsets table
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208 | # Note we have to do this before we alter the cache
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209 | # 20020324 Wait, but this DOES alter the cache. TODO BUG?
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210 | my $oldrec = $self->_fetch($n);
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211 |
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212 | if (not defined $oldrec) {
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213 | # We're storing a record beyond the end of the file
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214 | $self->_extend_file_to($n+1);
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215 | $oldrec = $self->{recsep};
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216 | }
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217 | # return if $oldrec eq $rec; # don't bother
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218 | my $len_diff = length($rec) - length($oldrec);
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219 |
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220 | # length($oldrec) here is not consistent with text mode TODO XXX BUG
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221 | $self->_mtwrite($rec, $self->{offsets}[$n], length($oldrec));
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222 | $self->_oadjust([$n, 1, $rec]);
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223 | $self->{cache}->update($n, $rec);
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224 | }
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225 |
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226 | sub _store_deferred {
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227 | my ($self, $n, $rec) = @_;
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228 | $self->{cache}->remove($n);
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229 | my $old_deferred = $self->{deferred}{$n};
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230 |
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231 | if (defined $self->{deferred_max} && $n > $self->{deferred_max}) {
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232 | $self->{deferred_max} = $n;
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233 | }
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234 | $self->{deferred}{$n} = $rec;
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235 |
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236 | my $len_diff = length($rec);
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237 | $len_diff -= length($old_deferred) if defined $old_deferred;
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238 | $self->{deferred_s} += $len_diff;
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239 | $self->{cache}->adj_limit(-$len_diff);
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240 | if ($self->{deferred_s} > $self->{dw_size}) {
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241 | $self->_flush;
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242 | } elsif ($self->_cache_too_full) {
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243 | $self->_cache_flush;
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244 | }
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245 | }
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246 |
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247 | # Remove a single record from the deferred-write buffer without writing it
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248 | # The record need not be present
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249 | sub _delete_deferred {
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250 | my ($self, $n) = @_;
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251 | my $rec = delete $self->{deferred}{$n};
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252 | return unless defined $rec;
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253 |
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254 | if (defined $self->{deferred_max}
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255 | && $n == $self->{deferred_max}) {
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256 | undef $self->{deferred_max};
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257 | }
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258 |
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259 | $self->{deferred_s} -= length $rec;
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260 | $self->{cache}->adj_limit(length $rec);
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261 | }
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262 |
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263 | sub FETCHSIZE {
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264 | my $self = shift;
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265 | my $n = $self->{eof} ? $#{$self->{offsets}} : $self->_fill_offsets;
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266 |
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267 | my $top_deferred = $self->_defer_max;
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268 | $n = $top_deferred+1 if defined $top_deferred && $n < $top_deferred+1;
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269 | $n;
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270 | }
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271 |
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272 | sub STORESIZE {
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273 | my ($self, $len) = @_;
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274 |
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275 | if ($self->{autodefer}) {
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276 | $self->_annotate_ad_history('STORESIZE');
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277 | }
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278 |
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279 | my $olen = $self->FETCHSIZE;
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280 | return if $len == $olen; # Woo-hoo!
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281 |
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282 | # file gets longer
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283 | if ($len > $olen) {
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284 | if ($self->_is_deferring) {
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285 | for ($olen .. $len-1) {
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286 | $self->_store_deferred($_, $self->{recsep});
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287 | }
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288 | } else {
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289 | $self->_extend_file_to($len);
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290 | }
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291 | return;
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292 | }
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293 |
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294 | # file gets shorter
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295 | if ($self->_is_deferring) {
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296 | # TODO maybe replace this with map-plus-assignment?
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297 | for (grep $_ >= $len, keys %{$self->{deferred}}) {
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298 | $self->_delete_deferred($_);
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299 | }
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300 | $self->{deferred_max} = $len-1;
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301 | }
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302 |
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303 | $self->_seek($len);
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304 | $self->_chop_file;
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305 | $#{$self->{offsets}} = $len;
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306 | # $self->{offsets}[0] = 0; # in case we just chopped this
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307 |
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308 | $self->{cache}->remove(grep $_ >= $len, $self->{cache}->ckeys);
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309 | }
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310 |
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311 | ### OPTIMIZE ME
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312 | ### It should not be necessary to do FETCHSIZE
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313 | ### Just seek to the end of the file.
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314 | sub PUSH {
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315 | my $self = shift;
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316 | $self->SPLICE($self->FETCHSIZE, scalar(@_), @_);
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317 |
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318 | # No need to return:
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319 | # $self->FETCHSIZE; # because av.c takes care of this for me
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320 | }
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321 |
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322 | sub POP {
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323 | my $self = shift;
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324 | my $size = $self->FETCHSIZE;
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325 | return if $size == 0;
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326 | # print STDERR "# POPPITY POP POP POP\n";
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327 | scalar $self->SPLICE($size-1, 1);
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328 | }
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329 |
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330 | sub SHIFT {
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331 | my $self = shift;
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332 | scalar $self->SPLICE(0, 1);
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333 | }
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334 |
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335 | sub UNSHIFT {
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336 | my $self = shift;
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337 | $self->SPLICE(0, 0, @_);
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338 | # $self->FETCHSIZE; # av.c takes care of this for me
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339 | }
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340 |
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341 | sub CLEAR {
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342 | my $self = shift;
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343 |
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344 | if ($self->{autodefer}) {
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345 | $self->_annotate_ad_history('CLEAR');
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346 | }
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347 |
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348 | $self->_seekb(0);
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349 | $self->_chop_file;
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350 | $self->{cache}->set_limit($self->{memory});
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351 | $self->{cache}->empty;
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352 | @{$self->{offsets}} = (0);
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353 | %{$self->{deferred}}= ();
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354 | $self->{deferred_s} = 0;
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355 | $self->{deferred_max} = -1;
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356 | }
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357 |
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358 | sub EXTEND {
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359 | my ($self, $n) = @_;
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360 |
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361 | # No need to pre-extend anything in this case
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362 | return if $self->_is_deferring;
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363 |
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364 | $self->_fill_offsets_to($n);
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365 | $self->_extend_file_to($n);
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366 | }
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367 |
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368 | sub DELETE {
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369 | my ($self, $n) = @_;
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370 |
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371 | if ($self->{autodefer}) {
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372 | $self->_annotate_ad_history('DELETE');
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373 | }
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374 |
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375 | my $lastrec = $self->FETCHSIZE-1;
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376 | my $rec = $self->FETCH($n);
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377 | $self->_delete_deferred($n) if $self->_is_deferring;
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378 | if ($n == $lastrec) {
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379 | $self->_seek($n);
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380 | $self->_chop_file;
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381 | $#{$self->{offsets}}--;
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382 | $self->{cache}->remove($n);
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383 | # perhaps in this case I should also remove trailing null records?
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384 | # 20020316
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385 | # Note that delete @a[-3..-1] deletes the records in the wrong order,
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386 | # so we only chop the very last one out of the file. We could repair this
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387 | # by tracking deleted records inside the object.
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388 | } elsif ($n < $lastrec) {
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389 | $self->STORE($n, "");
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390 | }
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391 | $rec;
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392 | }
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393 |
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394 | sub EXISTS {
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395 | my ($self, $n) = @_;
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396 | return 1 if exists $self->{deferred}{$n};
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397 | $n < $self->FETCHSIZE;
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398 | }
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399 |
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400 | sub SPLICE {
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401 | my $self = shift;
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402 |
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403 | if ($self->{autodefer}) {
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404 | $self->_annotate_ad_history('SPLICE');
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405 | }
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406 |
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407 | $self->_flush if $self->_is_deferring; # move this up?
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408 | if (wantarray) {
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409 | $self->_chomp(my @a = $self->_splice(@_));
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410 | @a;
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411 | } else {
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412 | $self->_chomp1(scalar $self->_splice(@_));
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413 | }
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414 | }
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415 |
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416 | sub DESTROY {
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417 | my $self = shift;
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418 | $self->flush if $self->_is_deferring;
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419 | $self->{cache}->delink if defined $self->{cache}; # break circular link
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420 | if ($self->{fh} and $self->{ourfh}) {
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421 | delete $self->{ourfh};
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422 | close delete $self->{fh};
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423 | }
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424 | }
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425 |
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426 | sub _splice {
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427 | my ($self, $pos, $nrecs, @data) = @_;
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428 | my @result;
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429 |
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430 | $pos = 0 unless defined $pos;
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431 |
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432 | # Deal with negative and other out-of-range positions
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433 | # Also set default for $nrecs
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434 | {
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435 | my $oldsize = $self->FETCHSIZE;
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436 | $nrecs = $oldsize unless defined $nrecs;
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437 | my $oldpos = $pos;
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438 |
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439 | if ($pos < 0) {
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440 | $pos += $oldsize;
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441 | if ($pos < 0) {
|
---|
442 | croak "Modification of non-creatable array value attempted, subscript $oldpos";
|
---|
443 | }
|
---|
444 | }
|
---|
445 |
|
---|
446 | if ($pos > $oldsize) {
|
---|
447 | return unless @data;
|
---|
448 | $pos = $oldsize; # This is what perl does for normal arrays
|
---|
449 | }
|
---|
450 |
|
---|
451 | # The manual is very unclear here
|
---|
452 | if ($nrecs < 0) {
|
---|
453 | $nrecs = $oldsize - $pos + $nrecs;
|
---|
454 | $nrecs = 0 if $nrecs < 0;
|
---|
455 | }
|
---|
456 |
|
---|
457 | # nrecs is too big---it really means "until the end"
|
---|
458 | # 20030507
|
---|
459 | if ($nrecs + $pos > $oldsize) {
|
---|
460 | $nrecs = $oldsize - $pos;
|
---|
461 | }
|
---|
462 | }
|
---|
463 |
|
---|
464 | $self->_fixrecs(@data);
|
---|
465 | my $data = join '', @data;
|
---|
466 | my $datalen = length $data;
|
---|
467 | my $oldlen = 0;
|
---|
468 |
|
---|
469 | # compute length of data being removed
|
---|
470 | for ($pos .. $pos+$nrecs-1) {
|
---|
471 | last unless defined $self->_fill_offsets_to($_);
|
---|
472 | my $rec = $self->_fetch($_);
|
---|
473 | last unless defined $rec;
|
---|
474 | push @result, $rec;
|
---|
475 |
|
---|
476 | # Why don't we just use length($rec) here?
|
---|
477 | # Because that record might have come from the cache. _splice
|
---|
478 | # might have been called to flush out the deferred-write records,
|
---|
479 | # and in this case length($rec) is the length of the record to be
|
---|
480 | # *written*, not the length of the actual record in the file. But
|
---|
481 | # the offsets are still true. 20020322
|
---|
482 | $oldlen += $self->{offsets}[$_+1] - $self->{offsets}[$_]
|
---|
483 | if defined $self->{offsets}[$_+1];
|
---|
484 | }
|
---|
485 | $self->_fill_offsets_to($pos+$nrecs);
|
---|
486 |
|
---|
487 | # Modify the file
|
---|
488 | $self->_mtwrite($data, $self->{offsets}[$pos], $oldlen);
|
---|
489 | # Adjust the offsets table
|
---|
490 | $self->_oadjust([$pos, $nrecs, @data]);
|
---|
491 |
|
---|
492 | { # Take this read cache stuff out into a separate function
|
---|
493 | # You made a half-attempt to put it into _oadjust.
|
---|
494 | # Finish something like that up eventually.
|
---|
495 | # STORE also needs to do something similarish
|
---|
496 |
|
---|
497 | # update the read cache, part 1
|
---|
498 | # modified records
|
---|
499 | for ($pos .. $pos+$nrecs-1) {
|
---|
500 | my $new = $data[$_-$pos];
|
---|
501 | if (defined $new) {
|
---|
502 | $self->{cache}->update($_, $new);
|
---|
503 | } else {
|
---|
504 | $self->{cache}->remove($_);
|
---|
505 | }
|
---|
506 | }
|
---|
507 |
|
---|
508 | # update the read cache, part 2
|
---|
509 | # moved records - records past the site of the change
|
---|
510 | # need to be renumbered
|
---|
511 | # Maybe merge this with the previous block?
|
---|
512 | {
|
---|
513 | my @oldkeys = grep $_ >= $pos + $nrecs, $self->{cache}->ckeys;
|
---|
514 | my @newkeys = map $_-$nrecs+@data, @oldkeys;
|
---|
515 | $self->{cache}->rekey(\@oldkeys, \@newkeys);
|
---|
516 | }
|
---|
517 |
|
---|
518 | # Now there might be too much data in the cache, if we spliced out
|
---|
519 | # some short records and spliced in some long ones. If so, flush
|
---|
520 | # the cache.
|
---|
521 | $self->_cache_flush;
|
---|
522 | }
|
---|
523 |
|
---|
524 | # Yes, the return value of 'splice' *is* actually this complicated
|
---|
525 | wantarray ? @result : @result ? $result[-1] : undef;
|
---|
526 | }
|
---|
527 |
|
---|
528 |
|
---|
529 | # write data into the file
|
---|
530 | # $data is the data to be written.
|
---|
531 | # it should be written at position $pos, and should overwrite
|
---|
532 | # exactly $len of the following bytes.
|
---|
533 | # Note that if length($data) > $len, the subsequent bytes will have to
|
---|
534 | # be moved up, and if length($data) < $len, they will have to
|
---|
535 | # be moved down
|
---|
536 | sub _twrite {
|
---|
537 | my ($self, $data, $pos, $len) = @_;
|
---|
538 |
|
---|
539 | unless (defined $pos) {
|
---|
540 | die "\$pos was undefined in _twrite";
|
---|
541 | }
|
---|
542 |
|
---|
543 | my $len_diff = length($data) - $len;
|
---|
544 |
|
---|
545 | if ($len_diff == 0) { # Woo-hoo!
|
---|
546 | my $fh = $self->{fh};
|
---|
547 | $self->_seekb($pos);
|
---|
548 | $self->_write_record($data);
|
---|
549 | return; # well, that was easy.
|
---|
550 | }
|
---|
551 |
|
---|
552 | # the two records are of different lengths
|
---|
553 | # our strategy here: rewrite the tail of the file,
|
---|
554 | # reading ahead one buffer at a time
|
---|
555 | # $bufsize is required to be at least as large as the data we're overwriting
|
---|
556 | my $bufsize = _bufsize($len_diff);
|
---|
557 | my ($writepos, $readpos) = ($pos, $pos+$len);
|
---|
558 | my $next_block;
|
---|
559 | my $more_data;
|
---|
560 |
|
---|
561 | # Seems like there ought to be a way to avoid the repeated code
|
---|
562 | # and the special case here. The read(1) is also a little weird.
|
---|
563 | # Think about this.
|
---|
564 | do {
|
---|
565 | $self->_seekb($readpos);
|
---|
566 | my $br = read $self->{fh}, $next_block, $bufsize;
|
---|
567 | $more_data = read $self->{fh}, my($dummy), 1;
|
---|
568 | $self->_seekb($writepos);
|
---|
569 | $self->_write_record($data);
|
---|
570 | $readpos += $br;
|
---|
571 | $writepos += length $data;
|
---|
572 | $data = $next_block;
|
---|
573 | } while $more_data;
|
---|
574 | $self->_seekb($writepos);
|
---|
575 | $self->_write_record($next_block);
|
---|
576 |
|
---|
577 | # There might be leftover data at the end of the file
|
---|
578 | $self->_chop_file if $len_diff < 0;
|
---|
579 | }
|
---|
580 |
|
---|
581 | # _iwrite(D, S, E)
|
---|
582 | # Insert text D at position S.
|
---|
583 | # Let C = E-S-|D|. If C < 0; die.
|
---|
584 | # Data in [S,S+C) is copied to [S+D,S+D+C) = [S+D,E).
|
---|
585 | # Data in [S+C = E-D, E) is returned. Data in [E, oo) is untouched.
|
---|
586 | #
|
---|
587 | # In a later version, don't read the entire intervening area into
|
---|
588 | # memory at once; do the copying block by block.
|
---|
589 | sub _iwrite {
|
---|
590 | my $self = shift;
|
---|
591 | my ($D, $s, $e) = @_;
|
---|
592 | my $d = length $D;
|
---|
593 | my $c = $e-$s-$d;
|
---|
594 | local *FH = $self->{fh};
|
---|
595 | confess "Not enough space to insert $d bytes between $s and $e"
|
---|
596 | if $c < 0;
|
---|
597 | confess "[$s,$e) is an invalid insertion range" if $e < $s;
|
---|
598 |
|
---|
599 | $self->_seekb($s);
|
---|
600 | read FH, my $buf, $e-$s;
|
---|
601 |
|
---|
602 | $D .= substr($buf, 0, $c, "");
|
---|
603 |
|
---|
604 | $self->_seekb($s);
|
---|
605 | $self->_write_record($D);
|
---|
606 |
|
---|
607 | return $buf;
|
---|
608 | }
|
---|
609 |
|
---|
610 | # Like _twrite, but the data-pos-len triple may be repeated; you may
|
---|
611 | # write several chunks. All the writing will be done in
|
---|
612 | # one pass. Chunks SHALL be in ascending order and SHALL NOT overlap.
|
---|
613 | sub _mtwrite {
|
---|
614 | my $self = shift;
|
---|
615 | my $unwritten = "";
|
---|
616 | my $delta = 0;
|
---|
617 |
|
---|
618 | @_ % 3 == 0
|
---|
619 | or die "Arguments to _mtwrite did not come in groups of three";
|
---|
620 |
|
---|
621 | while (@_) {
|
---|
622 | my ($data, $pos, $len) = splice @_, 0, 3;
|
---|
623 | my $end = $pos + $len; # The OLD end of the segment to be replaced
|
---|
624 | $data = $unwritten . $data;
|
---|
625 | $delta -= length($unwritten);
|
---|
626 | $unwritten = "";
|
---|
627 | $pos += $delta; # This is where the data goes now
|
---|
628 | my $dlen = length $data;
|
---|
629 | $self->_seekb($pos);
|
---|
630 | if ($len >= $dlen) { # the data will fit
|
---|
631 | $self->_write_record($data);
|
---|
632 | $delta += ($dlen - $len); # everything following moves down by this much
|
---|
633 | $data = ""; # All the data in the buffer has been written
|
---|
634 | } else { # won't fit
|
---|
635 | my $writable = substr($data, 0, $len - $delta, "");
|
---|
636 | $self->_write_record($writable);
|
---|
637 | $delta += ($dlen - $len); # everything following moves down by this much
|
---|
638 | }
|
---|
639 |
|
---|
640 | # At this point we've written some but maybe not all of the data.
|
---|
641 | # There might be a gap to close up, or $data might still contain a
|
---|
642 | # bunch of unwritten data that didn't fit.
|
---|
643 | my $ndlen = length $data;
|
---|
644 | if ($delta == 0) {
|
---|
645 | $self->_write_record($data);
|
---|
646 | } elsif ($delta < 0) {
|
---|
647 | # upcopy (close up gap)
|
---|
648 | if (@_) {
|
---|
649 | $self->_upcopy($end, $end + $delta, $_[1] - $end);
|
---|
650 | } else {
|
---|
651 | $self->_upcopy($end, $end + $delta);
|
---|
652 | }
|
---|
653 | } else {
|
---|
654 | # downcopy (insert data that didn't fit; replace this data in memory
|
---|
655 | # with _later_ data that doesn't fit)
|
---|
656 | if (@_) {
|
---|
657 | $unwritten = $self->_downcopy($data, $end, $_[1] - $end);
|
---|
658 | } else {
|
---|
659 | # Make the file longer to accomodate the last segment that doesn'
|
---|
660 | $unwritten = $self->_downcopy($data, $end);
|
---|
661 | }
|
---|
662 | }
|
---|
663 | }
|
---|
664 | }
|
---|
665 |
|
---|
666 | # Copy block of data of length $len from position $spos to position $dpos
|
---|
667 | # $dpos must be <= $spos
|
---|
668 | #
|
---|
669 | # If $len is undefined, go all the way to the end of the file
|
---|
670 | # and then truncate it ($spos - $dpos bytes will be removed)
|
---|
671 | sub _upcopy {
|
---|
672 | my $blocksize = 8192;
|
---|
673 | my ($self, $spos, $dpos, $len) = @_;
|
---|
674 | if ($dpos > $spos) {
|
---|
675 | die "source ($spos) was upstream of destination ($dpos) in _upcopy";
|
---|
676 | } elsif ($dpos == $spos) {
|
---|
677 | return;
|
---|
678 | }
|
---|
679 |
|
---|
680 | while (! defined ($len) || $len > 0) {
|
---|
681 | my $readsize = ! defined($len) ? $blocksize
|
---|
682 | : $len > $blocksize ? $blocksize
|
---|
683 | : $len;
|
---|
684 |
|
---|
685 | my $fh = $self->{fh};
|
---|
686 | $self->_seekb($spos);
|
---|
687 | my $bytes_read = read $fh, my($data), $readsize;
|
---|
688 | $self->_seekb($dpos);
|
---|
689 | if ($data eq "") {
|
---|
690 | $self->_chop_file;
|
---|
691 | last;
|
---|
692 | }
|
---|
693 | $self->_write_record($data);
|
---|
694 | $spos += $bytes_read;
|
---|
695 | $dpos += $bytes_read;
|
---|
696 | $len -= $bytes_read if defined $len;
|
---|
697 | }
|
---|
698 | }
|
---|
699 |
|
---|
700 | # Write $data into a block of length $len at position $pos,
|
---|
701 | # moving everything in the block forwards to make room.
|
---|
702 | # Instead of writing the last length($data) bytes from the block
|
---|
703 | # (because there isn't room for them any longer) return them.
|
---|
704 | #
|
---|
705 | # Undefined $len means 'until the end of the file'
|
---|
706 | sub _downcopy {
|
---|
707 | my $blocksize = 8192;
|
---|
708 | my ($self, $data, $pos, $len) = @_;
|
---|
709 | my $fh = $self->{fh};
|
---|
710 |
|
---|
711 | while (! defined $len || $len > 0) {
|
---|
712 | my $readsize = ! defined($len) ? $blocksize
|
---|
713 | : $len > $blocksize? $blocksize : $len;
|
---|
714 | $self->_seekb($pos);
|
---|
715 | read $fh, my($old), $readsize;
|
---|
716 | my $last_read_was_short = length($old) < $readsize;
|
---|
717 | $data .= $old;
|
---|
718 | my $writable;
|
---|
719 | if ($last_read_was_short) {
|
---|
720 | # If last read was short, then $data now contains the entire rest
|
---|
721 | # of the file, so there's no need to write only one block of it
|
---|
722 | $writable = $data;
|
---|
723 | $data = "";
|
---|
724 | } else {
|
---|
725 | $writable = substr($data, 0, $readsize, "");
|
---|
726 | }
|
---|
727 | last if $writable eq "";
|
---|
728 | $self->_seekb($pos);
|
---|
729 | $self->_write_record($writable);
|
---|
730 | last if $last_read_was_short && $data eq "";
|
---|
731 | $len -= $readsize if defined $len;
|
---|
732 | $pos += $readsize;
|
---|
733 | }
|
---|
734 | return $data;
|
---|
735 | }
|
---|
736 |
|
---|
737 | # Adjust the object data structures following an '_mtwrite'
|
---|
738 | # Arguments are
|
---|
739 | # [$pos, $nrecs, @length] items
|
---|
740 | # indicating that $nrecs records were removed at $recpos (a record offset)
|
---|
741 | # and replaced with records of length @length...
|
---|
742 | # Arguments guarantee that $recpos is strictly increasing.
|
---|
743 | # No return value
|
---|
744 | sub _oadjust {
|
---|
745 | my $self = shift;
|
---|
746 | my $delta = 0;
|
---|
747 | my $delta_recs = 0;
|
---|
748 | my $prev_end = -1;
|
---|
749 | my %newkeys;
|
---|
750 |
|
---|
751 | for (@_) {
|
---|
752 | my ($pos, $nrecs, @data) = @$_;
|
---|
753 | $pos += $delta_recs;
|
---|
754 |
|
---|
755 | # Adjust the offsets of the records after the previous batch up
|
---|
756 | # to the first new one of this batch
|
---|
757 | for my $i ($prev_end+2 .. $pos - 1) {
|
---|
758 | $self->{offsets}[$i] += $delta;
|
---|
759 | $newkey{$i} = $i + $delta_recs;
|
---|
760 | }
|
---|
761 |
|
---|
762 | $prev_end = $pos + @data - 1; # last record moved on this pass
|
---|
763 |
|
---|
764 | # Remove the offsets for the removed records;
|
---|
765 | # replace with the offsets for the inserted records
|
---|
766 | my @newoff = ($self->{offsets}[$pos] + $delta);
|
---|
767 | for my $i (0 .. $#data) {
|
---|
768 | my $newlen = length $data[$i];
|
---|
769 | push @newoff, $newoff[$i] + $newlen;
|
---|
770 | $delta += $newlen;
|
---|
771 | }
|
---|
772 |
|
---|
773 | for my $i ($pos .. $pos+$nrecs-1) {
|
---|
774 | last if $i+1 > $#{$self->{offsets}};
|
---|
775 | my $oldlen = $self->{offsets}[$i+1] - $self->{offsets}[$i];
|
---|
776 | $delta -= $oldlen;
|
---|
777 | }
|
---|
778 |
|
---|
779 | # # also this data has changed, so update it in the cache
|
---|
780 | # for (0 .. $#data) {
|
---|
781 | # $self->{cache}->update($pos + $_, $data[$_]);
|
---|
782 | # }
|
---|
783 | # if ($delta_recs) {
|
---|
784 | # my @oldkeys = grep $_ >= $pos + @data, $self->{cache}->ckeys;
|
---|
785 | # my @newkeys = map $_ + $delta_recs, @oldkeys;
|
---|
786 | # $self->{cache}->rekey(\@oldkeys, \@newkeys);
|
---|
787 | # }
|
---|
788 |
|
---|
789 | # replace old offsets with new
|
---|
790 | splice @{$self->{offsets}}, $pos, $nrecs+1, @newoff;
|
---|
791 | # What if we just spliced out the end of the offsets table?
|
---|
792 | # shouldn't we clear $self->{eof}? Test for this XXX BUG TODO
|
---|
793 |
|
---|
794 | $delta_recs += @data - $nrecs; # net change in total number of records
|
---|
795 | }
|
---|
796 |
|
---|
797 | # The trailing records at the very end of the file
|
---|
798 | if ($delta) {
|
---|
799 | for my $i ($prev_end+2 .. $#{$self->{offsets}}) {
|
---|
800 | $self->{offsets}[$i] += $delta;
|
---|
801 | }
|
---|
802 | }
|
---|
803 |
|
---|
804 | # If we scrubbed out all known offsets, regenerate the trivial table
|
---|
805 | # that knows that the file does indeed start at 0.
|
---|
806 | $self->{offsets}[0] = 0 unless @{$self->{offsets}};
|
---|
807 | # If the file got longer, the offsets table is no longer complete
|
---|
808 | # $self->{eof} = 0 if $delta_recs > 0;
|
---|
809 |
|
---|
810 | # Now there might be too much data in the cache, if we spliced out
|
---|
811 | # some short records and spliced in some long ones. If so, flush
|
---|
812 | # the cache.
|
---|
813 | $self->_cache_flush;
|
---|
814 | }
|
---|
815 |
|
---|
816 | # If a record does not already end with the appropriate terminator
|
---|
817 | # string, append one.
|
---|
818 | sub _fixrecs {
|
---|
819 | my $self = shift;
|
---|
820 | for (@_) {
|
---|
821 | $_ = "" unless defined $_;
|
---|
822 | $_ .= $self->{recsep}
|
---|
823 | unless substr($_, - $self->{recseplen}) eq $self->{recsep};
|
---|
824 | }
|
---|
825 | }
|
---|
826 |
|
---|
827 |
|
---|
828 | ################################################################
|
---|
829 | #
|
---|
830 | # Basic read, write, and seek
|
---|
831 | #
|
---|
832 |
|
---|
833 | # seek to the beginning of record #$n
|
---|
834 | # Assumes that the offsets table is already correctly populated
|
---|
835 | #
|
---|
836 | # Note that $n=-1 has a special meaning here: It means the start of
|
---|
837 | # the last known record; this may or may not be the very last record
|
---|
838 | # in the file, depending on whether the offsets table is fully populated.
|
---|
839 | #
|
---|
840 | sub _seek {
|
---|
841 | my ($self, $n) = @_;
|
---|
842 | my $o = $self->{offsets}[$n];
|
---|
843 | defined($o)
|
---|
844 | or confess("logic error: undefined offset for record $n");
|
---|
845 | seek $self->{fh}, $o, SEEK_SET
|
---|
846 | or confess "Couldn't seek filehandle: $!"; # "Should never happen."
|
---|
847 | }
|
---|
848 |
|
---|
849 | # seek to byte $b in the file
|
---|
850 | sub _seekb {
|
---|
851 | my ($self, $b) = @_;
|
---|
852 | seek $self->{fh}, $b, SEEK_SET
|
---|
853 | or die "Couldn't seek filehandle: $!"; # "Should never happen."
|
---|
854 | }
|
---|
855 |
|
---|
856 | # populate the offsets table up to the beginning of record $n
|
---|
857 | # return the offset of record $n
|
---|
858 | sub _fill_offsets_to {
|
---|
859 | my ($self, $n) = @_;
|
---|
860 |
|
---|
861 | return $self->{offsets}[$n] if $self->{eof};
|
---|
862 |
|
---|
863 | my $fh = $self->{fh};
|
---|
864 | local *OFF = $self->{offsets};
|
---|
865 | my $rec;
|
---|
866 |
|
---|
867 | until ($#OFF >= $n) {
|
---|
868 | $self->_seek(-1); # tricky -- see comment at _seek
|
---|
869 | $rec = $self->_read_record;
|
---|
870 | if (defined $rec) {
|
---|
871 | push @OFF, int(tell $fh); # Tels says that int() saves memory here
|
---|
872 | } else {
|
---|
873 | $self->{eof} = 1;
|
---|
874 | return; # It turns out there is no such record
|
---|
875 | }
|
---|
876 | }
|
---|
877 |
|
---|
878 | # we have now read all the records up to record n-1,
|
---|
879 | # so we can return the offset of record n
|
---|
880 | $OFF[$n];
|
---|
881 | }
|
---|
882 |
|
---|
883 | sub _fill_offsets {
|
---|
884 | my ($self) = @_;
|
---|
885 |
|
---|
886 | my $fh = $self->{fh};
|
---|
887 | local *OFF = $self->{offsets};
|
---|
888 |
|
---|
889 | $self->_seek(-1); # tricky -- see comment at _seek
|
---|
890 |
|
---|
891 | # Tels says that inlining read_record() would make this loop
|
---|
892 | # five times faster. 20030508
|
---|
893 | while ( defined $self->_read_record()) {
|
---|
894 | # int() saves us memory here
|
---|
895 | push @OFF, int(tell $fh);
|
---|
896 | }
|
---|
897 |
|
---|
898 | $self->{eof} = 1;
|
---|
899 | $#OFF;
|
---|
900 | }
|
---|
901 |
|
---|
902 | # assumes that $rec is already suitably terminated
|
---|
903 | sub _write_record {
|
---|
904 | my ($self, $rec) = @_;
|
---|
905 | my $fh = $self->{fh};
|
---|
906 | local $\ = "";
|
---|
907 | print $fh $rec
|
---|
908 | or die "Couldn't write record: $!"; # "Should never happen."
|
---|
909 | # $self->{_written} += length($rec);
|
---|
910 | }
|
---|
911 |
|
---|
912 | sub _read_record {
|
---|
913 | my $self = shift;
|
---|
914 | my $rec;
|
---|
915 | { local $/ = $self->{recsep};
|
---|
916 | my $fh = $self->{fh};
|
---|
917 | $rec = <$fh>;
|
---|
918 | }
|
---|
919 | return unless defined $rec;
|
---|
920 | if (substr($rec, -$self->{recseplen}) ne $self->{recsep}) {
|
---|
921 | # improperly terminated final record --- quietly fix it.
|
---|
922 | # my $ac = substr($rec, -$self->{recseplen});
|
---|
923 | # $ac =~ s/\n/\\n/g;
|
---|
924 | $self->{sawlastrec} = 1;
|
---|
925 | unless ($self->{rdonly}) {
|
---|
926 | local $\ = "";
|
---|
927 | my $fh = $self->{fh};
|
---|
928 | print $fh $self->{recsep};
|
---|
929 | }
|
---|
930 | $rec .= $self->{recsep};
|
---|
931 | }
|
---|
932 | # $self->{_read} += length($rec) if defined $rec;
|
---|
933 | $rec;
|
---|
934 | }
|
---|
935 |
|
---|
936 | sub _rw_stats {
|
---|
937 | my $self = shift;
|
---|
938 | @{$self}{'_read', '_written'};
|
---|
939 | }
|
---|
940 |
|
---|
941 | ################################################################
|
---|
942 | #
|
---|
943 | # Read cache management
|
---|
944 |
|
---|
945 | sub _cache_flush {
|
---|
946 | my ($self) = @_;
|
---|
947 | $self->{cache}->reduce_size_to($self->{memory} - $self->{deferred_s});
|
---|
948 | }
|
---|
949 |
|
---|
950 | sub _cache_too_full {
|
---|
951 | my $self = shift;
|
---|
952 | $self->{cache}->bytes + $self->{deferred_s} >= $self->{memory};
|
---|
953 | }
|
---|
954 |
|
---|
955 | ################################################################
|
---|
956 | #
|
---|
957 | # File custodial services
|
---|
958 | #
|
---|
959 |
|
---|
960 |
|
---|
961 | # We have read to the end of the file and have the offsets table
|
---|
962 | # entirely populated. Now we need to write a new record beyond
|
---|
963 | # the end of the file. We prepare for this by writing
|
---|
964 | # empty records into the file up to the position we want
|
---|
965 | #
|
---|
966 | # assumes that the offsets table already contains the offset of record $n,
|
---|
967 | # if it exists, and extends to the end of the file if not.
|
---|
968 | sub _extend_file_to {
|
---|
969 | my ($self, $n) = @_;
|
---|
970 | $self->_seek(-1); # position after the end of the last record
|
---|
971 | my $pos = $self->{offsets}[-1];
|
---|
972 |
|
---|
973 | # the offsets table has one entry more than the total number of records
|
---|
974 | my $extras = $n - $#{$self->{offsets}};
|
---|
975 |
|
---|
976 | # Todo : just use $self->{recsep} x $extras here?
|
---|
977 | while ($extras-- > 0) {
|
---|
978 | $self->_write_record($self->{recsep});
|
---|
979 | push @{$self->{offsets}}, int(tell $self->{fh});
|
---|
980 | }
|
---|
981 | }
|
---|
982 |
|
---|
983 | # Truncate the file at the current position
|
---|
984 | sub _chop_file {
|
---|
985 | my $self = shift;
|
---|
986 | truncate $self->{fh}, tell($self->{fh});
|
---|
987 | }
|
---|
988 |
|
---|
989 |
|
---|
990 | # compute the size of a buffer suitable for moving
|
---|
991 | # all the data in a file forward $n bytes
|
---|
992 | # ($n may be negative)
|
---|
993 | # The result should be at least $n.
|
---|
994 | sub _bufsize {
|
---|
995 | my $n = shift;
|
---|
996 | return 8192 if $n <= 0;
|
---|
997 | my $b = $n & ~8191;
|
---|
998 | $b += 8192 if $n & 8191;
|
---|
999 | $b;
|
---|
1000 | }
|
---|
1001 |
|
---|
1002 | ################################################################
|
---|
1003 | #
|
---|
1004 | # Miscellaneous public methods
|
---|
1005 | #
|
---|
1006 |
|
---|
1007 | # Lock the file
|
---|
1008 | sub flock {
|
---|
1009 | my ($self, $op) = @_;
|
---|
1010 | unless (@_ <= 3) {
|
---|
1011 | my $pack = ref $self;
|
---|
1012 | croak "Usage: $pack\->flock([OPERATION])";
|
---|
1013 | }
|
---|
1014 | my $fh = $self->{fh};
|
---|
1015 | $op = LOCK_EX unless defined $op;
|
---|
1016 | my $locked = flock $fh, $op;
|
---|
1017 |
|
---|
1018 | if ($locked && ($op & (LOCK_EX | LOCK_SH))) {
|
---|
1019 | # If you're locking the file, then presumably it's because
|
---|
1020 | # there might have been a write access by another process.
|
---|
1021 | # In that case, the read cache contents and the offsets table
|
---|
1022 | # might be invalid, so discard them. 20030508
|
---|
1023 | $self->{offsets} = [0];
|
---|
1024 | $self->{cache}->empty;
|
---|
1025 | }
|
---|
1026 |
|
---|
1027 | $locked;
|
---|
1028 | }
|
---|
1029 |
|
---|
1030 | # Get/set autochomp option
|
---|
1031 | sub autochomp {
|
---|
1032 | my $self = shift;
|
---|
1033 | if (@_) {
|
---|
1034 | my $old = $self->{autochomp};
|
---|
1035 | $self->{autochomp} = shift;
|
---|
1036 | $old;
|
---|
1037 | } else {
|
---|
1038 | $self->{autochomp};
|
---|
1039 | }
|
---|
1040 | }
|
---|
1041 |
|
---|
1042 | # Get offset table entries; returns offset of nth record
|
---|
1043 | sub offset {
|
---|
1044 | my ($self, $n) = @_;
|
---|
1045 |
|
---|
1046 | if ($#{$self->{offsets}} < $n) {
|
---|
1047 | return if $self->{eof}; # request for record beyond the end of file
|
---|
1048 | my $o = $self->_fill_offsets_to($n);
|
---|
1049 | # If it's still undefined, there is no such record, so return 'undef'
|
---|
1050 | return unless defined $o;
|
---|
1051 | }
|
---|
1052 |
|
---|
1053 | $self->{offsets}[$n];
|
---|
1054 | }
|
---|
1055 |
|
---|
1056 | sub discard_offsets {
|
---|
1057 | my $self = shift;
|
---|
1058 | $self->{offsets} = [0];
|
---|
1059 | }
|
---|
1060 |
|
---|
1061 | ################################################################
|
---|
1062 | #
|
---|
1063 | # Matters related to deferred writing
|
---|
1064 | #
|
---|
1065 |
|
---|
1066 | # Defer writes
|
---|
1067 | sub defer {
|
---|
1068 | my $self = shift;
|
---|
1069 | $self->_stop_autodeferring;
|
---|
1070 | @{$self->{ad_history}} = ();
|
---|
1071 | $self->{defer} = 1;
|
---|
1072 | }
|
---|
1073 |
|
---|
1074 | # Flush deferred writes
|
---|
1075 | #
|
---|
1076 | # This could be better optimized to write the file in one pass, instead
|
---|
1077 | # of one pass per block of records. But that will require modifications
|
---|
1078 | # to _twrite, so I should have a good _twrite test suite first.
|
---|
1079 | sub flush {
|
---|
1080 | my $self = shift;
|
---|
1081 |
|
---|
1082 | $self->_flush;
|
---|
1083 | $self->{defer} = 0;
|
---|
1084 | }
|
---|
1085 |
|
---|
1086 | sub _old_flush {
|
---|
1087 | my $self = shift;
|
---|
1088 | my @writable = sort {$a<=>$b} (keys %{$self->{deferred}});
|
---|
1089 |
|
---|
1090 | while (@writable) {
|
---|
1091 | # gather all consecutive records from the front of @writable
|
---|
1092 | my $first_rec = shift @writable;
|
---|
1093 | my $last_rec = $first_rec+1;
|
---|
1094 | ++$last_rec, shift @writable while @writable && $last_rec == $writable[0];
|
---|
1095 | --$last_rec;
|
---|
1096 | $self->_fill_offsets_to($last_rec);
|
---|
1097 | $self->_extend_file_to($last_rec);
|
---|
1098 | $self->_splice($first_rec, $last_rec-$first_rec+1,
|
---|
1099 | @{$self->{deferred}}{$first_rec .. $last_rec});
|
---|
1100 | }
|
---|
1101 |
|
---|
1102 | $self->_discard; # clear out defered-write-cache
|
---|
1103 | }
|
---|
1104 |
|
---|
1105 | sub _flush {
|
---|
1106 | my $self = shift;
|
---|
1107 | my @writable = sort {$a<=>$b} (keys %{$self->{deferred}});
|
---|
1108 | my @args;
|
---|
1109 | my @adjust;
|
---|
1110 |
|
---|
1111 | while (@writable) {
|
---|
1112 | # gather all consecutive records from the front of @writable
|
---|
1113 | my $first_rec = shift @writable;
|
---|
1114 | my $last_rec = $first_rec+1;
|
---|
1115 | ++$last_rec, shift @writable while @writable && $last_rec == $writable[0];
|
---|
1116 | --$last_rec;
|
---|
1117 | my $end = $self->_fill_offsets_to($last_rec+1);
|
---|
1118 | if (not defined $end) {
|
---|
1119 | $self->_extend_file_to($last_rec);
|
---|
1120 | $end = $self->{offsets}[$last_rec];
|
---|
1121 | }
|
---|
1122 | my ($start) = $self->{offsets}[$first_rec];
|
---|
1123 | push @args,
|
---|
1124 | join("", @{$self->{deferred}}{$first_rec .. $last_rec}), # data
|
---|
1125 | $start, # position
|
---|
1126 | $end-$start; # length
|
---|
1127 | push @adjust, [$first_rec, # starting at this position...
|
---|
1128 | $last_rec-$first_rec+1, # this many records...
|
---|
1129 | # are replaced with these...
|
---|
1130 | @{$self->{deferred}}{$first_rec .. $last_rec},
|
---|
1131 | ];
|
---|
1132 | }
|
---|
1133 |
|
---|
1134 | $self->_mtwrite(@args); # write multiple record groups
|
---|
1135 | $self->_discard; # clear out defered-write-cache
|
---|
1136 | $self->_oadjust(@adjust);
|
---|
1137 | }
|
---|
1138 |
|
---|
1139 | # Discard deferred writes and disable future deferred writes
|
---|
1140 | sub discard {
|
---|
1141 | my $self = shift;
|
---|
1142 | $self->_discard;
|
---|
1143 | $self->{defer} = 0;
|
---|
1144 | }
|
---|
1145 |
|
---|
1146 | # Discard deferred writes, but retain old deferred writing mode
|
---|
1147 | sub _discard {
|
---|
1148 | my $self = shift;
|
---|
1149 | %{$self->{deferred}} = ();
|
---|
1150 | $self->{deferred_s} = 0;
|
---|
1151 | $self->{deferred_max} = -1;
|
---|
1152 | $self->{cache}->set_limit($self->{memory});
|
---|
1153 | }
|
---|
1154 |
|
---|
1155 | # Deferred writing is enabled, either explicitly ($self->{defer})
|
---|
1156 | # or automatically ($self->{autodeferring})
|
---|
1157 | sub _is_deferring {
|
---|
1158 | my $self = shift;
|
---|
1159 | $self->{defer} || $self->{autodeferring};
|
---|
1160 | }
|
---|
1161 |
|
---|
1162 | # The largest record number of any deferred record
|
---|
1163 | sub _defer_max {
|
---|
1164 | my $self = shift;
|
---|
1165 | return $self->{deferred_max} if defined $self->{deferred_max};
|
---|
1166 | my $max = -1;
|
---|
1167 | for my $key (keys %{$self->{deferred}}) {
|
---|
1168 | $max = $key if $key > $max;
|
---|
1169 | }
|
---|
1170 | $self->{deferred_max} = $max;
|
---|
1171 | $max;
|
---|
1172 | }
|
---|
1173 |
|
---|
1174 | ################################################################
|
---|
1175 | #
|
---|
1176 | # Matters related to autodeferment
|
---|
1177 | #
|
---|
1178 |
|
---|
1179 | # Get/set autodefer option
|
---|
1180 | sub autodefer {
|
---|
1181 | my $self = shift;
|
---|
1182 | if (@_) {
|
---|
1183 | my $old = $self->{autodefer};
|
---|
1184 | $self->{autodefer} = shift;
|
---|
1185 | if ($old) {
|
---|
1186 | $self->_stop_autodeferring;
|
---|
1187 | @{$self->{ad_history}} = ();
|
---|
1188 | }
|
---|
1189 | $old;
|
---|
1190 | } else {
|
---|
1191 | $self->{autodefer};
|
---|
1192 | }
|
---|
1193 | }
|
---|
1194 |
|
---|
1195 | # The user is trying to store record #$n Record that in the history,
|
---|
1196 | # and then enable (or disable) autodeferment if that seems useful.
|
---|
1197 | # Note that it's OK for $n to be a non-number, as long as the function
|
---|
1198 | # is prepared to deal with that. Nobody else looks at the ad_history.
|
---|
1199 | #
|
---|
1200 | # Now, what does the ad_history mean, and what is this function doing?
|
---|
1201 | # Essentially, the idea is to enable autodeferring when we see that the
|
---|
1202 | # user has made three consecutive STORE calls to three consecutive records.
|
---|
1203 | # ("Three" is actually ->{autodefer_threshhold}.)
|
---|
1204 | # A STORE call for record #$n inserts $n into the autodefer history,
|
---|
1205 | # and if the history contains three consecutive records, we enable
|
---|
1206 | # autodeferment. An ad_history of [X, Y] means that the most recent
|
---|
1207 | # STOREs were for records X, X+1, ..., Y, in that order.
|
---|
1208 | #
|
---|
1209 | # Inserting a nonconsecutive number erases the history and starts over.
|
---|
1210 | #
|
---|
1211 | # Performing a special operation like SPLICE erases the history.
|
---|
1212 | #
|
---|
1213 | # There's one special case: CLEAR means that CLEAR was just called.
|
---|
1214 | # In this case, we prime the history with [-2, -1] so that if the next
|
---|
1215 | # write is for record 0, autodeferring goes on immediately. This is for
|
---|
1216 | # the common special case of "@a = (...)".
|
---|
1217 | #
|
---|
1218 | sub _annotate_ad_history {
|
---|
1219 | my ($self, $n) = @_;
|
---|
1220 | return unless $self->{autodefer}; # feature is disabled
|
---|
1221 | return if $self->{defer}; # already in explicit defer mode
|
---|
1222 | return unless $self->{offsets}[-1] >= $self->{autodefer_filelen_threshhold};
|
---|
1223 |
|
---|
1224 | local *H = $self->{ad_history};
|
---|
1225 | if ($n eq 'CLEAR') {
|
---|
1226 | @H = (-2, -1); # prime the history with fake records
|
---|
1227 | $self->_stop_autodeferring;
|
---|
1228 | } elsif ($n =~ /^\d+$/) {
|
---|
1229 | if (@H == 0) {
|
---|
1230 | @H = ($n, $n);
|
---|
1231 | } else { # @H == 2
|
---|
1232 | if ($H[1] == $n-1) { # another consecutive record
|
---|
1233 | $H[1]++;
|
---|
1234 | if ($H[1] - $H[0] + 1 >= $self->{autodefer_threshhold}) {
|
---|
1235 | $self->{autodeferring} = 1;
|
---|
1236 | }
|
---|
1237 | } else { # nonconsecutive- erase and start over
|
---|
1238 | @H = ($n, $n);
|
---|
1239 | $self->_stop_autodeferring;
|
---|
1240 | }
|
---|
1241 | }
|
---|
1242 | } else { # SPLICE or STORESIZE or some such
|
---|
1243 | @H = ();
|
---|
1244 | $self->_stop_autodeferring;
|
---|
1245 | }
|
---|
1246 | }
|
---|
1247 |
|
---|
1248 | # If autodeferring was enabled, cut it out and discard the history
|
---|
1249 | sub _stop_autodeferring {
|
---|
1250 | my $self = shift;
|
---|
1251 | if ($self->{autodeferring}) {
|
---|
1252 | $self->_flush;
|
---|
1253 | }
|
---|
1254 | $self->{autodeferring} = 0;
|
---|
1255 | }
|
---|
1256 |
|
---|
1257 | ################################################################
|
---|
1258 |
|
---|
1259 |
|
---|
1260 | # This is NOT a method. It is here for two reasons:
|
---|
1261 | # 1. To factor a fairly complicated block out of the constructor
|
---|
1262 | # 2. To provide access for the test suite, which need to be sure
|
---|
1263 | # files are being written properly.
|
---|
1264 | sub _default_recsep {
|
---|
1265 | my $recsep = $/;
|
---|
1266 | if ($^O eq 'MSWin32') { # Dos too?
|
---|
1267 | # Windows users expect files to be terminated with \r\n
|
---|
1268 | # But $/ is set to \n instead
|
---|
1269 | # Note that this also transforms \n\n into \r\n\r\n.
|
---|
1270 | # That is a feature.
|
---|
1271 | $recsep =~ s/\n/\r\n/g;
|
---|
1272 | }
|
---|
1273 | $recsep;
|
---|
1274 | }
|
---|
1275 |
|
---|
1276 | # Utility function for _check_integrity
|
---|
1277 | sub _ci_warn {
|
---|
1278 | my $msg = shift;
|
---|
1279 | $msg =~ s/\n/\\n/g;
|
---|
1280 | $msg =~ s/\r/\\r/g;
|
---|
1281 | print "# $msg\n";
|
---|
1282 | }
|
---|
1283 |
|
---|
1284 | # Given a file, make sure the cache is consistent with the
|
---|
1285 | # file contents and the internal data structures are consistent with
|
---|
1286 | # each other. Returns true if everything checks out, false if not
|
---|
1287 | #
|
---|
1288 | # The $file argument is no longer used. It is retained for compatibility
|
---|
1289 | # with the existing test suite.
|
---|
1290 | sub _check_integrity {
|
---|
1291 | my ($self, $file, $warn) = @_;
|
---|
1292 | my $rsl = $self->{recseplen};
|
---|
1293 | my $rs = $self->{recsep};
|
---|
1294 | my $good = 1;
|
---|
1295 | local *_; # local $_ does not work here
|
---|
1296 | local $DIAGNOSTIC = 1;
|
---|
1297 |
|
---|
1298 | if (not defined $rs) {
|
---|
1299 | _ci_warn("recsep is undef!");
|
---|
1300 | $good = 0;
|
---|
1301 | } elsif ($rs eq "") {
|
---|
1302 | _ci_warn("recsep is empty!");
|
---|
1303 | $good = 0;
|
---|
1304 | } elsif ($rsl != length $rs) {
|
---|
1305 | my $ln = length $rs;
|
---|
1306 | _ci_warn("recsep <$rs> has length $ln, should be $rsl");
|
---|
1307 | $good = 0;
|
---|
1308 | }
|
---|
1309 |
|
---|
1310 | if (not defined $self->{offsets}[0]) {
|
---|
1311 | _ci_warn("offset 0 is missing!");
|
---|
1312 | $good = 0;
|
---|
1313 |
|
---|
1314 | } elsif ($self->{offsets}[0] != 0) {
|
---|
1315 | _ci_warn("rec 0: offset <$self->{offsets}[0]> s/b 0!");
|
---|
1316 | $good = 0;
|
---|
1317 | }
|
---|
1318 |
|
---|
1319 | my $cached = 0;
|
---|
1320 | {
|
---|
1321 | local *F = $self->{fh};
|
---|
1322 | seek F, 0, SEEK_SET;
|
---|
1323 | local $. = 0;
|
---|
1324 | local $/ = $rs;
|
---|
1325 |
|
---|
1326 | while (<F>) {
|
---|
1327 | my $n = $. - 1;
|
---|
1328 | my $cached = $self->{cache}->_produce($n);
|
---|
1329 | my $offset = $self->{offsets}[$.];
|
---|
1330 | my $ao = tell F;
|
---|
1331 | if (defined $offset && $offset != $ao) {
|
---|
1332 | _ci_warn("rec $n: offset <$offset> actual <$ao>");
|
---|
1333 | $good = 0;
|
---|
1334 | }
|
---|
1335 | if (defined $cached && $_ ne $cached && ! $self->{deferred}{$n}) {
|
---|
1336 | $good = 0;
|
---|
1337 | _ci_warn("rec $n: cached <$cached> actual <$_>");
|
---|
1338 | }
|
---|
1339 | if (defined $cached && substr($cached, -$rsl) ne $rs) {
|
---|
1340 | $good = 0;
|
---|
1341 | _ci_warn("rec $n in the cache is missing the record separator");
|
---|
1342 | }
|
---|
1343 | if (! defined $offset && $self->{eof}) {
|
---|
1344 | $good = 0;
|
---|
1345 | _ci_warn("The offset table was marked complete, but it is missing element $.");
|
---|
1346 | }
|
---|
1347 | }
|
---|
1348 | if (@{$self->{offsets}} > $.+1) {
|
---|
1349 | $good = 0;
|
---|
1350 | my $n = @{$self->{offsets}};
|
---|
1351 | _ci_warn("The offset table has $n items, but the file has only $.");
|
---|
1352 | }
|
---|
1353 |
|
---|
1354 | my $deferring = $self->_is_deferring;
|
---|
1355 | for my $n ($self->{cache}->ckeys) {
|
---|
1356 | my $r = $self->{cache}->_produce($n);
|
---|
1357 | $cached += length($r);
|
---|
1358 | next if $n+1 <= $.; # checked this already
|
---|
1359 | _ci_warn("spurious caching of record $n");
|
---|
1360 | $good = 0;
|
---|
1361 | }
|
---|
1362 | my $b = $self->{cache}->bytes;
|
---|
1363 | if ($cached != $b) {
|
---|
1364 | _ci_warn("cache size is $b, should be $cached");
|
---|
1365 | $good = 0;
|
---|
1366 | }
|
---|
1367 | }
|
---|
1368 |
|
---|
1369 | # That cache has its own set of tests
|
---|
1370 | $good = 0 unless $self->{cache}->_check_integrity;
|
---|
1371 |
|
---|
1372 | # Now let's check the deferbuffer
|
---|
1373 | # Unless deferred writing is enabled, it should be empty
|
---|
1374 | if (! $self->_is_deferring && %{$self->{deferred}}) {
|
---|
1375 | _ci_warn("deferred writing disabled, but deferbuffer nonempty");
|
---|
1376 | $good = 0;
|
---|
1377 | }
|
---|
1378 |
|
---|
1379 | # Any record in the deferbuffer should *not* be present in the readcache
|
---|
1380 | my $deferred_s = 0;
|
---|
1381 | while (my ($n, $r) = each %{$self->{deferred}}) {
|
---|
1382 | $deferred_s += length($r);
|
---|
1383 | if (defined $self->{cache}->_produce($n)) {
|
---|
1384 | _ci_warn("record $n is in the deferbuffer *and* the readcache");
|
---|
1385 | $good = 0;
|
---|
1386 | }
|
---|
1387 | if (substr($r, -$rsl) ne $rs) {
|
---|
1388 | _ci_warn("rec $n in the deferbuffer is missing the record separator");
|
---|
1389 | $good = 0;
|
---|
1390 | }
|
---|
1391 | }
|
---|
1392 |
|
---|
1393 | # Total size of deferbuffer should match internal total
|
---|
1394 | if ($deferred_s != $self->{deferred_s}) {
|
---|
1395 | _ci_warn("buffer size is $self->{deferred_s}, should be $deferred_s");
|
---|
1396 | $good = 0;
|
---|
1397 | }
|
---|
1398 |
|
---|
1399 | # Total size of deferbuffer should not exceed the specified limit
|
---|
1400 | if ($deferred_s > $self->{dw_size}) {
|
---|
1401 | _ci_warn("buffer size is $self->{deferred_s} which exceeds the limit of $self->{dw_size}");
|
---|
1402 | $good = 0;
|
---|
1403 | }
|
---|
1404 |
|
---|
1405 | # Total size of cached data should not exceed the specified limit
|
---|
1406 | if ($deferred_s + $cached > $self->{memory}) {
|
---|
1407 | my $total = $deferred_s + $cached;
|
---|
1408 | _ci_warn("total stored data size is $total which exceeds the limit of $self->{memory}");
|
---|
1409 | $good = 0;
|
---|
1410 | }
|
---|
1411 |
|
---|
1412 | # Stuff related to autodeferment
|
---|
1413 | if (!$self->{autodefer} && @{$self->{ad_history}}) {
|
---|
1414 | _ci_warn("autodefer is disabled, but ad_history is nonempty");
|
---|
1415 | $good = 0;
|
---|
1416 | }
|
---|
1417 | if ($self->{autodeferring} && $self->{defer}) {
|
---|
1418 | _ci_warn("both autodeferring and explicit deferring are active");
|
---|
1419 | $good = 0;
|
---|
1420 | }
|
---|
1421 | if (@{$self->{ad_history}} == 0) {
|
---|
1422 | # That's OK, no additional tests required
|
---|
1423 | } elsif (@{$self->{ad_history}} == 2) {
|
---|
1424 | my @non_number = grep !/^-?\d+$/, @{$self->{ad_history}};
|
---|
1425 | if (@non_number) {
|
---|
1426 | my $msg;
|
---|
1427 | { local $" = ')(';
|
---|
1428 | $msg = "ad_history contains non-numbers (@{$self->{ad_history}})";
|
---|
1429 | }
|
---|
1430 | _ci_warn($msg);
|
---|
1431 | $good = 0;
|
---|
1432 | } elsif ($self->{ad_history}[1] < $self->{ad_history}[0]) {
|
---|
1433 | _ci_warn("ad_history has nonsensical values @{$self->{ad_history}}");
|
---|
1434 | $good = 0;
|
---|
1435 | }
|
---|
1436 | } else {
|
---|
1437 | _ci_warn("ad_history has bad length <@{$self->{ad_history}}>");
|
---|
1438 | $good = 0;
|
---|
1439 | }
|
---|
1440 |
|
---|
1441 | $good;
|
---|
1442 | }
|
---|
1443 |
|
---|
1444 | ################################################################
|
---|
1445 | #
|
---|
1446 | # Tie::File::Cache
|
---|
1447 | #
|
---|
1448 | # Read cache
|
---|
1449 |
|
---|
1450 | package Tie::File::Cache;
|
---|
1451 | $Tie::File::Cache::VERSION = $Tie::File::VERSION;
|
---|
1452 | use Carp ':DEFAULT', 'confess';
|
---|
1453 |
|
---|
1454 | sub HEAP () { 0 }
|
---|
1455 | sub HASH () { 1 }
|
---|
1456 | sub MAX () { 2 }
|
---|
1457 | sub BYTES() { 3 }
|
---|
1458 | #sub STAT () { 4 } # Array with request statistics for each record
|
---|
1459 | #sub MISS () { 5 } # Total number of cache misses
|
---|
1460 | #sub REQ () { 6 } # Total number of cache requests
|
---|
1461 | use strict 'vars';
|
---|
1462 |
|
---|
1463 | sub new {
|
---|
1464 | my ($pack, $max) = @_;
|
---|
1465 | local *_;
|
---|
1466 | croak "missing argument to ->new" unless defined $max;
|
---|
1467 | my $self = [];
|
---|
1468 | bless $self => $pack;
|
---|
1469 | @$self = (Tie::File::Heap->new($self), {}, $max, 0);
|
---|
1470 | $self;
|
---|
1471 | }
|
---|
1472 |
|
---|
1473 | sub adj_limit {
|
---|
1474 | my ($self, $n) = @_;
|
---|
1475 | $self->[MAX] += $n;
|
---|
1476 | }
|
---|
1477 |
|
---|
1478 | sub set_limit {
|
---|
1479 | my ($self, $n) = @_;
|
---|
1480 | $self->[MAX] = $n;
|
---|
1481 | }
|
---|
1482 |
|
---|
1483 | # For internal use only
|
---|
1484 | # Will be called by the heap structure to notify us that a certain
|
---|
1485 | # piece of data has moved from one heap element to another.
|
---|
1486 | # $k is the hash key of the item
|
---|
1487 | # $n is the new index into the heap at which it is stored
|
---|
1488 | # If $n is undefined, the item has been removed from the heap.
|
---|
1489 | sub _heap_move {
|
---|
1490 | my ($self, $k, $n) = @_;
|
---|
1491 | if (defined $n) {
|
---|
1492 | $self->[HASH]{$k} = $n;
|
---|
1493 | } else {
|
---|
1494 | delete $self->[HASH]{$k};
|
---|
1495 | }
|
---|
1496 | }
|
---|
1497 |
|
---|
1498 | sub insert {
|
---|
1499 | my ($self, $key, $val) = @_;
|
---|
1500 | local *_;
|
---|
1501 | croak "missing argument to ->insert" unless defined $key;
|
---|
1502 | unless (defined $self->[MAX]) {
|
---|
1503 | confess "undefined max" ;
|
---|
1504 | }
|
---|
1505 | confess "undefined val" unless defined $val;
|
---|
1506 | return if length($val) > $self->[MAX];
|
---|
1507 |
|
---|
1508 | # if ($self->[STAT]) {
|
---|
1509 | # $self->[STAT][$key] = 1;
|
---|
1510 | # return;
|
---|
1511 | # }
|
---|
1512 |
|
---|
1513 | my $oldnode = $self->[HASH]{$key};
|
---|
1514 | if (defined $oldnode) {
|
---|
1515 | my $oldval = $self->[HEAP]->set_val($oldnode, $val);
|
---|
1516 | $self->[BYTES] -= length($oldval);
|
---|
1517 | } else {
|
---|
1518 | $self->[HEAP]->insert($key, $val);
|
---|
1519 | }
|
---|
1520 | $self->[BYTES] += length($val);
|
---|
1521 | $self->flush if $self->[BYTES] > $self->[MAX];
|
---|
1522 | }
|
---|
1523 |
|
---|
1524 | sub expire {
|
---|
1525 | my $self = shift;
|
---|
1526 | my $old_data = $self->[HEAP]->popheap;
|
---|
1527 | return unless defined $old_data;
|
---|
1528 | $self->[BYTES] -= length $old_data;
|
---|
1529 | $old_data;
|
---|
1530 | }
|
---|
1531 |
|
---|
1532 | sub remove {
|
---|
1533 | my ($self, @keys) = @_;
|
---|
1534 | my @result;
|
---|
1535 |
|
---|
1536 | # if ($self->[STAT]) {
|
---|
1537 | # for my $key (@keys) {
|
---|
1538 | # $self->[STAT][$key] = 0;
|
---|
1539 | # }
|
---|
1540 | # return;
|
---|
1541 | # }
|
---|
1542 |
|
---|
1543 | for my $key (@keys) {
|
---|
1544 | next unless exists $self->[HASH]{$key};
|
---|
1545 | my $old_data = $self->[HEAP]->remove($self->[HASH]{$key});
|
---|
1546 | $self->[BYTES] -= length $old_data;
|
---|
1547 | push @result, $old_data;
|
---|
1548 | }
|
---|
1549 | @result;
|
---|
1550 | }
|
---|
1551 |
|
---|
1552 | sub lookup {
|
---|
1553 | my ($self, $key) = @_;
|
---|
1554 | local *_;
|
---|
1555 | croak "missing argument to ->lookup" unless defined $key;
|
---|
1556 |
|
---|
1557 | # if ($self->[STAT]) {
|
---|
1558 | # $self->[MISS]++ if $self->[STAT][$key]++ == 0;
|
---|
1559 | # $self->[REQ]++;
|
---|
1560 | # my $hit_rate = 1 - $self->[MISS] / $self->[REQ];
|
---|
1561 | # # Do some testing to determine this threshhold
|
---|
1562 | # $#$self = STAT - 1 if $hit_rate > 0.20;
|
---|
1563 | # }
|
---|
1564 |
|
---|
1565 | if (exists $self->[HASH]{$key}) {
|
---|
1566 | $self->[HEAP]->lookup($self->[HASH]{$key});
|
---|
1567 | } else {
|
---|
1568 | return;
|
---|
1569 | }
|
---|
1570 | }
|
---|
1571 |
|
---|
1572 | # For internal use only
|
---|
1573 | sub _produce {
|
---|
1574 | my ($self, $key) = @_;
|
---|
1575 | my $loc = $self->[HASH]{$key};
|
---|
1576 | return unless defined $loc;
|
---|
1577 | $self->[HEAP][$loc][2];
|
---|
1578 | }
|
---|
1579 |
|
---|
1580 | # For internal use only
|
---|
1581 | sub _promote {
|
---|
1582 | my ($self, $key) = @_;
|
---|
1583 | $self->[HEAP]->promote($self->[HASH]{$key});
|
---|
1584 | }
|
---|
1585 |
|
---|
1586 | sub empty {
|
---|
1587 | my ($self) = @_;
|
---|
1588 | %{$self->[HASH]} = ();
|
---|
1589 | $self->[BYTES] = 0;
|
---|
1590 | $self->[HEAP]->empty;
|
---|
1591 | # @{$self->[STAT]} = ();
|
---|
1592 | # $self->[MISS] = 0;
|
---|
1593 | # $self->[REQ] = 0;
|
---|
1594 | }
|
---|
1595 |
|
---|
1596 | sub is_empty {
|
---|
1597 | my ($self) = @_;
|
---|
1598 | keys %{$self->[HASH]} == 0;
|
---|
1599 | }
|
---|
1600 |
|
---|
1601 | sub update {
|
---|
1602 | my ($self, $key, $val) = @_;
|
---|
1603 | local *_;
|
---|
1604 | croak "missing argument to ->update" unless defined $key;
|
---|
1605 | if (length($val) > $self->[MAX]) {
|
---|
1606 | my ($oldval) = $self->remove($key);
|
---|
1607 | $self->[BYTES] -= length($oldval) if defined $oldval;
|
---|
1608 | } elsif (exists $self->[HASH]{$key}) {
|
---|
1609 | my $oldval = $self->[HEAP]->set_val($self->[HASH]{$key}, $val);
|
---|
1610 | $self->[BYTES] += length($val);
|
---|
1611 | $self->[BYTES] -= length($oldval) if defined $oldval;
|
---|
1612 | } else {
|
---|
1613 | $self->[HEAP]->insert($key, $val);
|
---|
1614 | $self->[BYTES] += length($val);
|
---|
1615 | }
|
---|
1616 | $self->flush;
|
---|
1617 | }
|
---|
1618 |
|
---|
1619 | sub rekey {
|
---|
1620 | my ($self, $okeys, $nkeys) = @_;
|
---|
1621 | local *_;
|
---|
1622 | my %map;
|
---|
1623 | @map{@$okeys} = @$nkeys;
|
---|
1624 | croak "missing argument to ->rekey" unless defined $nkeys;
|
---|
1625 | croak "length mismatch in ->rekey arguments" unless @$nkeys == @$okeys;
|
---|
1626 | my %adjusted; # map new keys to heap indices
|
---|
1627 | # You should be able to cut this to one loop TODO XXX
|
---|
1628 | for (0 .. $#$okeys) {
|
---|
1629 | $adjusted{$nkeys->[$_]} = delete $self->[HASH]{$okeys->[$_]};
|
---|
1630 | }
|
---|
1631 | while (my ($nk, $ix) = each %adjusted) {
|
---|
1632 | # @{$self->[HASH]}{keys %adjusted} = values %adjusted;
|
---|
1633 | $self->[HEAP]->rekey($ix, $nk);
|
---|
1634 | $self->[HASH]{$nk} = $ix;
|
---|
1635 | }
|
---|
1636 | }
|
---|
1637 |
|
---|
1638 | sub ckeys {
|
---|
1639 | my $self = shift;
|
---|
1640 | my @a = keys %{$self->[HASH]};
|
---|
1641 | @a;
|
---|
1642 | }
|
---|
1643 |
|
---|
1644 | # Return total amount of cached data
|
---|
1645 | sub bytes {
|
---|
1646 | my $self = shift;
|
---|
1647 | $self->[BYTES];
|
---|
1648 | }
|
---|
1649 |
|
---|
1650 | # Expire oldest item from cache until cache size is smaller than $max
|
---|
1651 | sub reduce_size_to {
|
---|
1652 | my ($self, $max) = @_;
|
---|
1653 | until ($self->[BYTES] <= $max) {
|
---|
1654 | # Note that Tie::File::Cache::expire has been inlined here
|
---|
1655 | my $old_data = $self->[HEAP]->popheap;
|
---|
1656 | return unless defined $old_data;
|
---|
1657 | $self->[BYTES] -= length $old_data;
|
---|
1658 | }
|
---|
1659 | }
|
---|
1660 |
|
---|
1661 | # Why not just $self->reduce_size_to($self->[MAX])?
|
---|
1662 | # Try this when things stabilize TODO XXX
|
---|
1663 | # If the cache is too full, expire the oldest records
|
---|
1664 | sub flush {
|
---|
1665 | my $self = shift;
|
---|
1666 | $self->reduce_size_to($self->[MAX]) if $self->[BYTES] > $self->[MAX];
|
---|
1667 | }
|
---|
1668 |
|
---|
1669 | # For internal use only
|
---|
1670 | sub _produce_lru {
|
---|
1671 | my $self = shift;
|
---|
1672 | $self->[HEAP]->expire_order;
|
---|
1673 | }
|
---|
1674 |
|
---|
1675 | BEGIN { *_ci_warn = \&Tie::File::_ci_warn }
|
---|
1676 |
|
---|
1677 | sub _check_integrity { # For CACHE
|
---|
1678 | my $self = shift;
|
---|
1679 | my $good = 1;
|
---|
1680 |
|
---|
1681 | # Test HEAP
|
---|
1682 | $self->[HEAP]->_check_integrity or $good = 0;
|
---|
1683 |
|
---|
1684 | # Test HASH
|
---|
1685 | my $bytes = 0;
|
---|
1686 | for my $k (keys %{$self->[HASH]}) {
|
---|
1687 | if ($k ne '0' && $k !~ /^[1-9][0-9]*$/) {
|
---|
1688 | $good = 0;
|
---|
1689 | _ci_warn "Cache hash key <$k> is non-numeric";
|
---|
1690 | }
|
---|
1691 |
|
---|
1692 | my $h = $self->[HASH]{$k};
|
---|
1693 | if (! defined $h) {
|
---|
1694 | $good = 0;
|
---|
1695 | _ci_warn "Heap index number for key $k is undefined";
|
---|
1696 | } elsif ($h == 0) {
|
---|
1697 | $good = 0;
|
---|
1698 | _ci_warn "Heap index number for key $k is zero";
|
---|
1699 | } else {
|
---|
1700 | my $j = $self->[HEAP][$h];
|
---|
1701 | if (! defined $j) {
|
---|
1702 | $good = 0;
|
---|
1703 | _ci_warn "Heap contents key $k (=> $h) are undefined";
|
---|
1704 | } else {
|
---|
1705 | $bytes += length($j->[2]);
|
---|
1706 | if ($k ne $j->[1]) {
|
---|
1707 | $good = 0;
|
---|
1708 | _ci_warn "Heap contents key $k (=> $h) is $j->[1], should be $k";
|
---|
1709 | }
|
---|
1710 | }
|
---|
1711 | }
|
---|
1712 | }
|
---|
1713 |
|
---|
1714 | # Test BYTES
|
---|
1715 | if ($bytes != $self->[BYTES]) {
|
---|
1716 | $good = 0;
|
---|
1717 | _ci_warn "Total data in cache is $bytes, expected $self->[BYTES]";
|
---|
1718 | }
|
---|
1719 |
|
---|
1720 | # Test MAX
|
---|
1721 | if ($bytes > $self->[MAX]) {
|
---|
1722 | $good = 0;
|
---|
1723 | _ci_warn "Total data in cache is $bytes, exceeds maximum $self->[MAX]";
|
---|
1724 | }
|
---|
1725 |
|
---|
1726 | return $good;
|
---|
1727 | }
|
---|
1728 |
|
---|
1729 | sub delink {
|
---|
1730 | my $self = shift;
|
---|
1731 | $self->[HEAP] = undef; # Bye bye heap
|
---|
1732 | }
|
---|
1733 |
|
---|
1734 | ################################################################
|
---|
1735 | #
|
---|
1736 | # Tie::File::Heap
|
---|
1737 | #
|
---|
1738 | # Heap data structure for use by cache LRU routines
|
---|
1739 |
|
---|
1740 | package Tie::File::Heap;
|
---|
1741 | use Carp ':DEFAULT', 'confess';
|
---|
1742 | $Tie::File::Heap::VERSION = $Tie::File::Cache::VERSION;
|
---|
1743 | sub SEQ () { 0 };
|
---|
1744 | sub KEY () { 1 };
|
---|
1745 | sub DAT () { 2 };
|
---|
1746 |
|
---|
1747 | sub new {
|
---|
1748 | my ($pack, $cache) = @_;
|
---|
1749 | die "$pack: Parent cache object $cache does not support _heap_move method"
|
---|
1750 | unless eval { $cache->can('_heap_move') };
|
---|
1751 | my $self = [[0,$cache,0]];
|
---|
1752 | bless $self => $pack;
|
---|
1753 | }
|
---|
1754 |
|
---|
1755 | # Allocate a new sequence number, larger than all previously allocated numbers
|
---|
1756 | sub _nseq {
|
---|
1757 | my $self = shift;
|
---|
1758 | $self->[0][0]++;
|
---|
1759 | }
|
---|
1760 |
|
---|
1761 | sub _cache {
|
---|
1762 | my $self = shift;
|
---|
1763 | $self->[0][1];
|
---|
1764 | }
|
---|
1765 |
|
---|
1766 | sub _nelts {
|
---|
1767 | my $self = shift;
|
---|
1768 | $self->[0][2];
|
---|
1769 | }
|
---|
1770 |
|
---|
1771 | sub _nelts_inc {
|
---|
1772 | my $self = shift;
|
---|
1773 | ++$self->[0][2];
|
---|
1774 | }
|
---|
1775 |
|
---|
1776 | sub _nelts_dec {
|
---|
1777 | my $self = shift;
|
---|
1778 | --$self->[0][2];
|
---|
1779 | }
|
---|
1780 |
|
---|
1781 | sub is_empty {
|
---|
1782 | my $self = shift;
|
---|
1783 | $self->_nelts == 0;
|
---|
1784 | }
|
---|
1785 |
|
---|
1786 | sub empty {
|
---|
1787 | my $self = shift;
|
---|
1788 | $#$self = 0;
|
---|
1789 | $self->[0][2] = 0;
|
---|
1790 | $self->[0][0] = 0; # might as well reset the sequence numbers
|
---|
1791 | }
|
---|
1792 |
|
---|
1793 | # notify the parent cache object that we moved something
|
---|
1794 | sub _heap_move {
|
---|
1795 | my $self = shift;
|
---|
1796 | $self->_cache->_heap_move(@_);
|
---|
1797 | }
|
---|
1798 |
|
---|
1799 | # Insert a piece of data into the heap with the indicated sequence number.
|
---|
1800 | # The item with the smallest sequence number is always at the top.
|
---|
1801 | # If no sequence number is specified, allocate a new one and insert the
|
---|
1802 | # item at the bottom.
|
---|
1803 | sub insert {
|
---|
1804 | my ($self, $key, $data, $seq) = @_;
|
---|
1805 | $seq = $self->_nseq unless defined $seq;
|
---|
1806 | $self->_insert_new([$seq, $key, $data]);
|
---|
1807 | }
|
---|
1808 |
|
---|
1809 | # Insert a new, fresh item at the bottom of the heap
|
---|
1810 | sub _insert_new {
|
---|
1811 | my ($self, $item) = @_;
|
---|
1812 | my $i = @$self;
|
---|
1813 | $i = int($i/2) until defined $self->[$i/2];
|
---|
1814 | $self->[$i] = $item;
|
---|
1815 | $self->[0][1]->_heap_move($self->[$i][KEY], $i);
|
---|
1816 | $self->_nelts_inc;
|
---|
1817 | }
|
---|
1818 |
|
---|
1819 | # Insert [$data, $seq] pair at or below item $i in the heap.
|
---|
1820 | # If $i is omitted, default to 1 (the top element.)
|
---|
1821 | sub _insert {
|
---|
1822 | my ($self, $item, $i) = @_;
|
---|
1823 | # $self->_check_loc($i) if defined $i;
|
---|
1824 | $i = 1 unless defined $i;
|
---|
1825 | until (! defined $self->[$i]) {
|
---|
1826 | if ($self->[$i][SEQ] > $item->[SEQ]) { # inserted item is older
|
---|
1827 | ($self->[$i], $item) = ($item, $self->[$i]);
|
---|
1828 | $self->[0][1]->_heap_move($self->[$i][KEY], $i);
|
---|
1829 | }
|
---|
1830 | # If either is undefined, go that way. Otherwise, choose at random
|
---|
1831 | my $dir;
|
---|
1832 | $dir = 0 if !defined $self->[2*$i];
|
---|
1833 | $dir = 1 if !defined $self->[2*$i+1];
|
---|
1834 | $dir = int(rand(2)) unless defined $dir;
|
---|
1835 | $i = 2*$i + $dir;
|
---|
1836 | }
|
---|
1837 | $self->[$i] = $item;
|
---|
1838 | $self->[0][1]->_heap_move($self->[$i][KEY], $i);
|
---|
1839 | $self->_nelts_inc;
|
---|
1840 | }
|
---|
1841 |
|
---|
1842 | # Remove the item at node $i from the heap, moving child items upwards.
|
---|
1843 | # The item with the smallest sequence number is always at the top.
|
---|
1844 | # Moving items upwards maintains this condition.
|
---|
1845 | # Return the removed item. Return undef if there was no item at node $i.
|
---|
1846 | sub remove {
|
---|
1847 | my ($self, $i) = @_;
|
---|
1848 | $i = 1 unless defined $i;
|
---|
1849 | my $top = $self->[$i];
|
---|
1850 | return unless defined $top;
|
---|
1851 | while (1) {
|
---|
1852 | my $ii;
|
---|
1853 | my ($L, $R) = (2*$i, 2*$i+1);
|
---|
1854 |
|
---|
1855 | # If either is undefined, go the other way.
|
---|
1856 | # Otherwise, go towards the smallest.
|
---|
1857 | last unless defined $self->[$L] || defined $self->[$R];
|
---|
1858 | $ii = $R if not defined $self->[$L];
|
---|
1859 | $ii = $L if not defined $self->[$R];
|
---|
1860 | unless (defined $ii) {
|
---|
1861 | $ii = $self->[$L][SEQ] < $self->[$R][SEQ] ? $L : $R;
|
---|
1862 | }
|
---|
1863 |
|
---|
1864 | $self->[$i] = $self->[$ii]; # Promote child to fill vacated spot
|
---|
1865 | $self->[0][1]->_heap_move($self->[$i][KEY], $i);
|
---|
1866 | $i = $ii; # Fill new vacated spot
|
---|
1867 | }
|
---|
1868 | $self->[0][1]->_heap_move($top->[KEY], undef);
|
---|
1869 | undef $self->[$i];
|
---|
1870 | $self->_nelts_dec;
|
---|
1871 | return $top->[DAT];
|
---|
1872 | }
|
---|
1873 |
|
---|
1874 | sub popheap {
|
---|
1875 | my $self = shift;
|
---|
1876 | $self->remove(1);
|
---|
1877 | }
|
---|
1878 |
|
---|
1879 | # set the sequence number of the indicated item to a higher number
|
---|
1880 | # than any other item in the heap, and bubble the item down to the
|
---|
1881 | # bottom.
|
---|
1882 | sub promote {
|
---|
1883 | my ($self, $n) = @_;
|
---|
1884 | # $self->_check_loc($n);
|
---|
1885 | $self->[$n][SEQ] = $self->_nseq;
|
---|
1886 | my $i = $n;
|
---|
1887 | while (1) {
|
---|
1888 | my ($L, $R) = (2*$i, 2*$i+1);
|
---|
1889 | my $dir;
|
---|
1890 | last unless defined $self->[$L] || defined $self->[$R];
|
---|
1891 | $dir = $R unless defined $self->[$L];
|
---|
1892 | $dir = $L unless defined $self->[$R];
|
---|
1893 | unless (defined $dir) {
|
---|
1894 | $dir = $self->[$L][SEQ] < $self->[$R][SEQ] ? $L : $R;
|
---|
1895 | }
|
---|
1896 | @{$self}[$i, $dir] = @{$self}[$dir, $i];
|
---|
1897 | for ($i, $dir) {
|
---|
1898 | $self->[0][1]->_heap_move($self->[$_][KEY], $_) if defined $self->[$_];
|
---|
1899 | }
|
---|
1900 | $i = $dir;
|
---|
1901 | }
|
---|
1902 | }
|
---|
1903 |
|
---|
1904 | # Return item $n from the heap, promoting its LRU status
|
---|
1905 | sub lookup {
|
---|
1906 | my ($self, $n) = @_;
|
---|
1907 | # $self->_check_loc($n);
|
---|
1908 | my $val = $self->[$n];
|
---|
1909 | $self->promote($n);
|
---|
1910 | $val->[DAT];
|
---|
1911 | }
|
---|
1912 |
|
---|
1913 |
|
---|
1914 | # Assign a new value for node $n, promoting it to the bottom of the heap
|
---|
1915 | sub set_val {
|
---|
1916 | my ($self, $n, $val) = @_;
|
---|
1917 | # $self->_check_loc($n);
|
---|
1918 | my $oval = $self->[$n][DAT];
|
---|
1919 | $self->[$n][DAT] = $val;
|
---|
1920 | $self->promote($n);
|
---|
1921 | return $oval;
|
---|
1922 | }
|
---|
1923 |
|
---|
1924 | # The hask key has changed for an item;
|
---|
1925 | # alter the heap's record of the hash key
|
---|
1926 | sub rekey {
|
---|
1927 | my ($self, $n, $new_key) = @_;
|
---|
1928 | # $self->_check_loc($n);
|
---|
1929 | $self->[$n][KEY] = $new_key;
|
---|
1930 | }
|
---|
1931 |
|
---|
1932 | sub _check_loc {
|
---|
1933 | my ($self, $n) = @_;
|
---|
1934 | unless (1 || defined $self->[$n]) {
|
---|
1935 | confess "_check_loc($n) failed";
|
---|
1936 | }
|
---|
1937 | }
|
---|
1938 |
|
---|
1939 | BEGIN { *_ci_warn = \&Tie::File::_ci_warn }
|
---|
1940 |
|
---|
1941 | sub _check_integrity {
|
---|
1942 | my $self = shift;
|
---|
1943 | my $good = 1;
|
---|
1944 | my %seq;
|
---|
1945 |
|
---|
1946 | unless (eval {$self->[0][1]->isa("Tie::File::Cache")}) {
|
---|
1947 | _ci_warn "Element 0 of heap corrupt";
|
---|
1948 | $good = 0;
|
---|
1949 | }
|
---|
1950 | $good = 0 unless $self->_satisfies_heap_condition(1);
|
---|
1951 | for my $i (2 .. $#{$self}) {
|
---|
1952 | my $p = int($i/2); # index of parent node
|
---|
1953 | if (defined $self->[$i] && ! defined $self->[$p]) {
|
---|
1954 | _ci_warn "Element $i of heap defined, but parent $p isn't";
|
---|
1955 | $good = 0;
|
---|
1956 | }
|
---|
1957 |
|
---|
1958 | if (defined $self->[$i]) {
|
---|
1959 | if ($seq{$self->[$i][SEQ]}) {
|
---|
1960 | my $seq = $self->[$i][SEQ];
|
---|
1961 | _ci_warn "Nodes $i and $seq{$seq} both have SEQ=$seq";
|
---|
1962 | $good = 0;
|
---|
1963 | } else {
|
---|
1964 | $seq{$self->[$i][SEQ]} = $i;
|
---|
1965 | }
|
---|
1966 | }
|
---|
1967 | }
|
---|
1968 |
|
---|
1969 | return $good;
|
---|
1970 | }
|
---|
1971 |
|
---|
1972 | sub _satisfies_heap_condition {
|
---|
1973 | my $self = shift;
|
---|
1974 | my $n = shift || 1;
|
---|
1975 | my $good = 1;
|
---|
1976 | for (0, 1) {
|
---|
1977 | my $c = $n*2 + $_;
|
---|
1978 | next unless defined $self->[$c];
|
---|
1979 | if ($self->[$n][SEQ] >= $self->[$c]) {
|
---|
1980 | _ci_warn "Node $n of heap does not predate node $c";
|
---|
1981 | $good = 0 ;
|
---|
1982 | }
|
---|
1983 | $good = 0 unless $self->_satisfies_heap_condition($c);
|
---|
1984 | }
|
---|
1985 | return $good;
|
---|
1986 | }
|
---|
1987 |
|
---|
1988 | # Return a list of all the values, sorted by expiration order
|
---|
1989 | sub expire_order {
|
---|
1990 | my $self = shift;
|
---|
1991 | my @nodes = sort {$a->[SEQ] <=> $b->[SEQ]} $self->_nodes;
|
---|
1992 | map { $_->[KEY] } @nodes;
|
---|
1993 | }
|
---|
1994 |
|
---|
1995 | sub _nodes {
|
---|
1996 | my $self = shift;
|
---|
1997 | my $i = shift || 1;
|
---|
1998 | return unless defined $self->[$i];
|
---|
1999 | ($self->[$i], $self->_nodes($i*2), $self->_nodes($i*2+1));
|
---|
2000 | }
|
---|
2001 |
|
---|
2002 | "Cogito, ergo sum."; # don't forget to return a true value from the file
|
---|
2003 |
|
---|
2004 | __END__
|
---|
2005 |
|
---|
2006 | =head1 NAME
|
---|
2007 |
|
---|
2008 | Tie::File - Access the lines of a disk file via a Perl array
|
---|
2009 |
|
---|
2010 | =head1 SYNOPSIS
|
---|
2011 |
|
---|
2012 | # This file documents Tie::File version 0.97
|
---|
2013 | use Tie::File;
|
---|
2014 |
|
---|
2015 | tie @array, 'Tie::File', filename or die ...;
|
---|
2016 |
|
---|
2017 | $array[13] = 'blah'; # line 13 of the file is now 'blah'
|
---|
2018 | print $array[42]; # display line 42 of the file
|
---|
2019 |
|
---|
2020 | $n_recs = @array; # how many records are in the file?
|
---|
2021 | $#array -= 2; # chop two records off the end
|
---|
2022 |
|
---|
2023 |
|
---|
2024 | for (@array) {
|
---|
2025 | s/PERL/Perl/g; # Replace PERL with Perl everywhere in the file
|
---|
2026 | }
|
---|
2027 |
|
---|
2028 | # These are just like regular push, pop, unshift, shift, and splice
|
---|
2029 | # Except that they modify the file in the way you would expect
|
---|
2030 |
|
---|
2031 | push @array, new recs...;
|
---|
2032 | my $r1 = pop @array;
|
---|
2033 | unshift @array, new recs...;
|
---|
2034 | my $r2 = shift @array;
|
---|
2035 | @old_recs = splice @array, 3, 7, new recs...;
|
---|
2036 |
|
---|
2037 | untie @array; # all finished
|
---|
2038 |
|
---|
2039 |
|
---|
2040 | =head1 DESCRIPTION
|
---|
2041 |
|
---|
2042 | C<Tie::File> represents a regular text file as a Perl array. Each
|
---|
2043 | element in the array corresponds to a record in the file. The first
|
---|
2044 | line of the file is element 0 of the array; the second line is element
|
---|
2045 | 1, and so on.
|
---|
2046 |
|
---|
2047 | The file is I<not> loaded into memory, so this will work even for
|
---|
2048 | gigantic files.
|
---|
2049 |
|
---|
2050 | Changes to the array are reflected in the file immediately.
|
---|
2051 |
|
---|
2052 | Lazy people and beginners may now stop reading the manual.
|
---|
2053 |
|
---|
2054 | =head2 C<recsep>
|
---|
2055 |
|
---|
2056 | What is a 'record'? By default, the meaning is the same as for the
|
---|
2057 | C<E<lt>...E<gt>> operator: It's a string terminated by C<$/>, which is
|
---|
2058 | probably C<"\n">. (Minor exception: on DOS and Win32 systems, a
|
---|
2059 | 'record' is a string terminated by C<"\r\n">.) You may change the
|
---|
2060 | definition of "record" by supplying the C<recsep> option in the C<tie>
|
---|
2061 | call:
|
---|
2062 |
|
---|
2063 | tie @array, 'Tie::File', $file, recsep => 'es';
|
---|
2064 |
|
---|
2065 | This says that records are delimited by the string C<es>. If the file
|
---|
2066 | contained the following data:
|
---|
2067 |
|
---|
2068 | Curse these pesky flies!\n
|
---|
2069 |
|
---|
2070 | then the C<@array> would appear to have four elements:
|
---|
2071 |
|
---|
2072 | "Curse th"
|
---|
2073 | "e p"
|
---|
2074 | "ky fli"
|
---|
2075 | "!\n"
|
---|
2076 |
|
---|
2077 | An undefined value is not permitted as a record separator. Perl's
|
---|
2078 | special "paragraph mode" semantics (E<agrave> la C<$/ = "">) are not
|
---|
2079 | emulated.
|
---|
2080 |
|
---|
2081 | Records read from the tied array do not have the record separator
|
---|
2082 | string on the end; this is to allow
|
---|
2083 |
|
---|
2084 | $array[17] .= "extra";
|
---|
2085 |
|
---|
2086 | to work as expected.
|
---|
2087 |
|
---|
2088 | (See L<"autochomp">, below.) Records stored into the array will have
|
---|
2089 | the record separator string appended before they are written to the
|
---|
2090 | file, if they don't have one already. For example, if the record
|
---|
2091 | separator string is C<"\n">, then the following two lines do exactly
|
---|
2092 | the same thing:
|
---|
2093 |
|
---|
2094 | $array[17] = "Cherry pie";
|
---|
2095 | $array[17] = "Cherry pie\n";
|
---|
2096 |
|
---|
2097 | The result is that the contents of line 17 of the file will be
|
---|
2098 | replaced with "Cherry pie"; a newline character will separate line 17
|
---|
2099 | from line 18. This means that this code will do nothing:
|
---|
2100 |
|
---|
2101 | chomp $array[17];
|
---|
2102 |
|
---|
2103 | Because the C<chomp>ed value will have the separator reattached when
|
---|
2104 | it is written back to the file. There is no way to create a file
|
---|
2105 | whose trailing record separator string is missing.
|
---|
2106 |
|
---|
2107 | Inserting records that I<contain> the record separator string is not
|
---|
2108 | supported by this module. It will probably produce a reasonable
|
---|
2109 | result, but what this result will be may change in a future version.
|
---|
2110 | Use 'splice' to insert records or to replace one record with several.
|
---|
2111 |
|
---|
2112 | =head2 C<autochomp>
|
---|
2113 |
|
---|
2114 | Normally, array elements have the record separator removed, so that if
|
---|
2115 | the file contains the text
|
---|
2116 |
|
---|
2117 | Gold
|
---|
2118 | Frankincense
|
---|
2119 | Myrrh
|
---|
2120 |
|
---|
2121 | the tied array will appear to contain C<("Gold", "Frankincense",
|
---|
2122 | "Myrrh")>. If you set C<autochomp> to a false value, the record
|
---|
2123 | separator will not be removed. If the file above was tied with
|
---|
2124 |
|
---|
2125 | tie @gifts, "Tie::File", $gifts, autochomp => 0;
|
---|
2126 |
|
---|
2127 | then the array C<@gifts> would appear to contain C<("Gold\n",
|
---|
2128 | "Frankincense\n", "Myrrh\n")>, or (on Win32 systems) C<("Gold\r\n",
|
---|
2129 | "Frankincense\r\n", "Myrrh\r\n")>.
|
---|
2130 |
|
---|
2131 | =head2 C<mode>
|
---|
2132 |
|
---|
2133 | Normally, the specified file will be opened for read and write access,
|
---|
2134 | and will be created if it does not exist. (That is, the flags
|
---|
2135 | C<O_RDWR | O_CREAT> are supplied in the C<open> call.) If you want to
|
---|
2136 | change this, you may supply alternative flags in the C<mode> option.
|
---|
2137 | See L<Fcntl> for a listing of available flags.
|
---|
2138 | For example:
|
---|
2139 |
|
---|
2140 | # open the file if it exists, but fail if it does not exist
|
---|
2141 | use Fcntl 'O_RDWR';
|
---|
2142 | tie @array, 'Tie::File', $file, mode => O_RDWR;
|
---|
2143 |
|
---|
2144 | # create the file if it does not exist
|
---|
2145 | use Fcntl 'O_RDWR', 'O_CREAT';
|
---|
2146 | tie @array, 'Tie::File', $file, mode => O_RDWR | O_CREAT;
|
---|
2147 |
|
---|
2148 | # open an existing file in read-only mode
|
---|
2149 | use Fcntl 'O_RDONLY';
|
---|
2150 | tie @array, 'Tie::File', $file, mode => O_RDONLY;
|
---|
2151 |
|
---|
2152 | Opening the data file in write-only or append mode is not supported.
|
---|
2153 |
|
---|
2154 | =head2 C<memory>
|
---|
2155 |
|
---|
2156 | This is an upper limit on the amount of memory that C<Tie::File> will
|
---|
2157 | consume at any time while managing the file. This is used for two
|
---|
2158 | things: managing the I<read cache> and managing the I<deferred write
|
---|
2159 | buffer>.
|
---|
2160 |
|
---|
2161 | Records read in from the file are cached, to avoid having to re-read
|
---|
2162 | them repeatedly. If you read the same record twice, the first time it
|
---|
2163 | will be stored in memory, and the second time it will be fetched from
|
---|
2164 | the I<read cache>. The amount of data in the read cache will not
|
---|
2165 | exceed the value you specified for C<memory>. If C<Tie::File> wants
|
---|
2166 | to cache a new record, but the read cache is full, it will make room
|
---|
2167 | by expiring the least-recently visited records from the read cache.
|
---|
2168 |
|
---|
2169 | The default memory limit is 2Mib. You can adjust the maximum read
|
---|
2170 | cache size by supplying the C<memory> option. The argument is the
|
---|
2171 | desired cache size, in bytes.
|
---|
2172 |
|
---|
2173 | # I have a lot of memory, so use a large cache to speed up access
|
---|
2174 | tie @array, 'Tie::File', $file, memory => 20_000_000;
|
---|
2175 |
|
---|
2176 | Setting the memory limit to 0 will inhibit caching; records will be
|
---|
2177 | fetched from disk every time you examine them.
|
---|
2178 |
|
---|
2179 | The C<memory> value is not an absolute or exact limit on the memory
|
---|
2180 | used. C<Tie::File> objects contains some structures besides the read
|
---|
2181 | cache and the deferred write buffer, whose sizes are not charged
|
---|
2182 | against C<memory>.
|
---|
2183 |
|
---|
2184 | The cache itself consumes about 310 bytes per cached record, so if
|
---|
2185 | your file has many short records, you may want to decrease the cache
|
---|
2186 | memory limit, or else the cache overhead may exceed the size of the
|
---|
2187 | cached data.
|
---|
2188 |
|
---|
2189 |
|
---|
2190 | =head2 C<dw_size>
|
---|
2191 |
|
---|
2192 | (This is an advanced feature. Skip this section on first reading.)
|
---|
2193 |
|
---|
2194 | If you use deferred writing (See L<"Deferred Writing">, below) then
|
---|
2195 | data you write into the array will not be written directly to the
|
---|
2196 | file; instead, it will be saved in the I<deferred write buffer> to be
|
---|
2197 | written out later. Data in the deferred write buffer is also charged
|
---|
2198 | against the memory limit you set with the C<memory> option.
|
---|
2199 |
|
---|
2200 | You may set the C<dw_size> option to limit the amount of data that can
|
---|
2201 | be saved in the deferred write buffer. This limit may not exceed the
|
---|
2202 | total memory limit. For example, if you set C<dw_size> to 1000 and
|
---|
2203 | C<memory> to 2500, that means that no more than 1000 bytes of deferred
|
---|
2204 | writes will be saved up. The space available for the read cache will
|
---|
2205 | vary, but it will always be at least 1500 bytes (if the deferred write
|
---|
2206 | buffer is full) and it could grow as large as 2500 bytes (if the
|
---|
2207 | deferred write buffer is empty.)
|
---|
2208 |
|
---|
2209 | If you don't specify a C<dw_size>, it defaults to the entire memory
|
---|
2210 | limit.
|
---|
2211 |
|
---|
2212 | =head2 Option Format
|
---|
2213 |
|
---|
2214 | C<-mode> is a synonym for C<mode>. C<-recsep> is a synonym for
|
---|
2215 | C<recsep>. C<-memory> is a synonym for C<memory>. You get the
|
---|
2216 | idea.
|
---|
2217 |
|
---|
2218 | =head1 Public Methods
|
---|
2219 |
|
---|
2220 | The C<tie> call returns an object, say C<$o>. You may call
|
---|
2221 |
|
---|
2222 | $rec = $o->FETCH($n);
|
---|
2223 | $o->STORE($n, $rec);
|
---|
2224 |
|
---|
2225 | to fetch or store the record at line C<$n>, respectively; similarly
|
---|
2226 | the other tied array methods. (See L<perltie> for details.) You may
|
---|
2227 | also call the following methods on this object:
|
---|
2228 |
|
---|
2229 | =head2 C<flock>
|
---|
2230 |
|
---|
2231 | $o->flock(MODE)
|
---|
2232 |
|
---|
2233 | will lock the tied file. C<MODE> has the same meaning as the second
|
---|
2234 | argument to the Perl built-in C<flock> function; for example
|
---|
2235 | C<LOCK_SH> or C<LOCK_EX | LOCK_NB>. (These constants are provided by
|
---|
2236 | the C<use Fcntl ':flock'> declaration.)
|
---|
2237 |
|
---|
2238 | C<MODE> is optional; the default is C<LOCK_EX>.
|
---|
2239 |
|
---|
2240 | C<Tie::File> maintains an internal table of the byte offset of each
|
---|
2241 | record it has seen in the file.
|
---|
2242 |
|
---|
2243 | When you use C<flock> to lock the file, C<Tie::File> assumes that the
|
---|
2244 | read cache is no longer trustworthy, because another process might
|
---|
2245 | have modified the file since the last time it was read. Therefore, a
|
---|
2246 | successful call to C<flock> discards the contents of the read cache
|
---|
2247 | and the internal record offset table.
|
---|
2248 |
|
---|
2249 | C<Tie::File> promises that the following sequence of operations will
|
---|
2250 | be safe:
|
---|
2251 |
|
---|
2252 | my $o = tie @array, "Tie::File", $filename;
|
---|
2253 | $o->flock;
|
---|
2254 |
|
---|
2255 | In particular, C<Tie::File> will I<not> read or write the file during
|
---|
2256 | the C<tie> call. (Exception: Using C<mode =E<gt> O_TRUNC> will, of
|
---|
2257 | course, erase the file during the C<tie> call. If you want to do this
|
---|
2258 | safely, then open the file without C<O_TRUNC>, lock the file, and use
|
---|
2259 | C<@array = ()>.)
|
---|
2260 |
|
---|
2261 | The best way to unlock a file is to discard the object and untie the
|
---|
2262 | array. It is probably unsafe to unlock the file without also untying
|
---|
2263 | it, because if you do, changes may remain unwritten inside the object.
|
---|
2264 | That is why there is no shortcut for unlocking. If you really want to
|
---|
2265 | unlock the file prematurely, you know what to do; if you don't know
|
---|
2266 | what to do, then don't do it.
|
---|
2267 |
|
---|
2268 | All the usual warnings about file locking apply here. In particular,
|
---|
2269 | note that file locking in Perl is B<advisory>, which means that
|
---|
2270 | holding a lock will not prevent anyone else from reading, writing, or
|
---|
2271 | erasing the file; it only prevents them from getting another lock at
|
---|
2272 | the same time. Locks are analogous to green traffic lights: If you
|
---|
2273 | have a green light, that does not prevent the idiot coming the other
|
---|
2274 | way from plowing into you sideways; it merely guarantees to you that
|
---|
2275 | the idiot does not also have a green light at the same time.
|
---|
2276 |
|
---|
2277 | =head2 C<autochomp>
|
---|
2278 |
|
---|
2279 | my $old_value = $o->autochomp(0); # disable autochomp option
|
---|
2280 | my $old_value = $o->autochomp(1); # enable autochomp option
|
---|
2281 |
|
---|
2282 | my $ac = $o->autochomp(); # recover current value
|
---|
2283 |
|
---|
2284 | See L<"autochomp">, above.
|
---|
2285 |
|
---|
2286 | =head2 C<defer>, C<flush>, C<discard>, and C<autodefer>
|
---|
2287 |
|
---|
2288 | See L<"Deferred Writing">, below.
|
---|
2289 |
|
---|
2290 | =head2 C<offset>
|
---|
2291 |
|
---|
2292 | $off = $o->offset($n);
|
---|
2293 |
|
---|
2294 | This method returns the byte offset of the start of the C<$n>th record
|
---|
2295 | in the file. If there is no such record, it returns an undefined
|
---|
2296 | value.
|
---|
2297 |
|
---|
2298 | =head1 Tying to an already-opened filehandle
|
---|
2299 |
|
---|
2300 | If C<$fh> is a filehandle, such as is returned by C<IO::File> or one
|
---|
2301 | of the other C<IO> modules, you may use:
|
---|
2302 |
|
---|
2303 | tie @array, 'Tie::File', $fh, ...;
|
---|
2304 |
|
---|
2305 | Similarly if you opened that handle C<FH> with regular C<open> or
|
---|
2306 | C<sysopen>, you may use:
|
---|
2307 |
|
---|
2308 | tie @array, 'Tie::File', \*FH, ...;
|
---|
2309 |
|
---|
2310 | Handles that were opened write-only won't work. Handles that were
|
---|
2311 | opened read-only will work as long as you don't try to modify the
|
---|
2312 | array. Handles must be attached to seekable sources of data---that
|
---|
2313 | means no pipes or sockets. If C<Tie::File> can detect that you
|
---|
2314 | supplied a non-seekable handle, the C<tie> call will throw an
|
---|
2315 | exception. (On Unix systems, it can detect this.)
|
---|
2316 |
|
---|
2317 | Note that Tie::File will only close any filehandles that it opened
|
---|
2318 | internally. If you passed it a filehandle as above, you "own" the
|
---|
2319 | filehandle, and are responsible for closing it after you have untied
|
---|
2320 | the @array.
|
---|
2321 |
|
---|
2322 | =head1 Deferred Writing
|
---|
2323 |
|
---|
2324 | (This is an advanced feature. Skip this section on first reading.)
|
---|
2325 |
|
---|
2326 | Normally, modifying a C<Tie::File> array writes to the underlying file
|
---|
2327 | immediately. Every assignment like C<$a[3] = ...> rewrites as much of
|
---|
2328 | the file as is necessary; typically, everything from line 3 through
|
---|
2329 | the end will need to be rewritten. This is the simplest and most
|
---|
2330 | transparent behavior. Performance even for large files is reasonably
|
---|
2331 | good.
|
---|
2332 |
|
---|
2333 | However, under some circumstances, this behavior may be excessively
|
---|
2334 | slow. For example, suppose you have a million-record file, and you
|
---|
2335 | want to do:
|
---|
2336 |
|
---|
2337 | for (@FILE) {
|
---|
2338 | $_ = "> $_";
|
---|
2339 | }
|
---|
2340 |
|
---|
2341 | The first time through the loop, you will rewrite the entire file,
|
---|
2342 | from line 0 through the end. The second time through the loop, you
|
---|
2343 | will rewrite the entire file from line 1 through the end. The third
|
---|
2344 | time through the loop, you will rewrite the entire file from line 2 to
|
---|
2345 | the end. And so on.
|
---|
2346 |
|
---|
2347 | If the performance in such cases is unacceptable, you may defer the
|
---|
2348 | actual writing, and then have it done all at once. The following loop
|
---|
2349 | will perform much better for large files:
|
---|
2350 |
|
---|
2351 | (tied @a)->defer;
|
---|
2352 | for (@a) {
|
---|
2353 | $_ = "> $_";
|
---|
2354 | }
|
---|
2355 | (tied @a)->flush;
|
---|
2356 |
|
---|
2357 | If C<Tie::File>'s memory limit is large enough, all the writing will
|
---|
2358 | done in memory. Then, when you call C<-E<gt>flush>, the entire file
|
---|
2359 | will be rewritten in a single pass.
|
---|
2360 |
|
---|
2361 | (Actually, the preceding discussion is something of a fib. You don't
|
---|
2362 | need to enable deferred writing to get good performance for this
|
---|
2363 | common case, because C<Tie::File> will do it for you automatically
|
---|
2364 | unless you specifically tell it not to. See L<"autodeferring">,
|
---|
2365 | below.)
|
---|
2366 |
|
---|
2367 | Calling C<-E<gt>flush> returns the array to immediate-write mode. If
|
---|
2368 | you wish to discard the deferred writes, you may call C<-E<gt>discard>
|
---|
2369 | instead of C<-E<gt>flush>. Note that in some cases, some of the data
|
---|
2370 | will have been written already, and it will be too late for
|
---|
2371 | C<-E<gt>discard> to discard all the changes. Support for
|
---|
2372 | C<-E<gt>discard> may be withdrawn in a future version of C<Tie::File>.
|
---|
2373 |
|
---|
2374 | Deferred writes are cached in memory up to the limit specified by the
|
---|
2375 | C<dw_size> option (see above). If the deferred-write buffer is full
|
---|
2376 | and you try to write still more deferred data, the buffer will be
|
---|
2377 | flushed. All buffered data will be written immediately, the buffer
|
---|
2378 | will be emptied, and the now-empty space will be used for future
|
---|
2379 | deferred writes.
|
---|
2380 |
|
---|
2381 | If the deferred-write buffer isn't yet full, but the total size of the
|
---|
2382 | buffer and the read cache would exceed the C<memory> limit, the oldest
|
---|
2383 | records will be expired from the read cache until the total size is
|
---|
2384 | under the limit.
|
---|
2385 |
|
---|
2386 | C<push>, C<pop>, C<shift>, C<unshift>, and C<splice> cannot be
|
---|
2387 | deferred. When you perform one of these operations, any deferred data
|
---|
2388 | is written to the file and the operation is performed immediately.
|
---|
2389 | This may change in a future version.
|
---|
2390 |
|
---|
2391 | If you resize the array with deferred writing enabled, the file will
|
---|
2392 | be resized immediately, but deferred records will not be written.
|
---|
2393 | This has a surprising consequence: C<@a = (...)> erases the file
|
---|
2394 | immediately, but the writing of the actual data is deferred. This
|
---|
2395 | might be a bug. If it is a bug, it will be fixed in a future version.
|
---|
2396 |
|
---|
2397 | =head2 Autodeferring
|
---|
2398 |
|
---|
2399 | C<Tie::File> tries to guess when deferred writing might be helpful,
|
---|
2400 | and to turn it on and off automatically.
|
---|
2401 |
|
---|
2402 | for (@a) {
|
---|
2403 | $_ = "> $_";
|
---|
2404 | }
|
---|
2405 |
|
---|
2406 | In this example, only the first two assignments will be done
|
---|
2407 | immediately; after this, all the changes to the file will be deferred
|
---|
2408 | up to the user-specified memory limit.
|
---|
2409 |
|
---|
2410 | You should usually be able to ignore this and just use the module
|
---|
2411 | without thinking about deferring. However, special applications may
|
---|
2412 | require fine control over which writes are deferred, or may require
|
---|
2413 | that all writes be immediate. To disable the autodeferment feature,
|
---|
2414 | use
|
---|
2415 |
|
---|
2416 | (tied @o)->autodefer(0);
|
---|
2417 |
|
---|
2418 | or
|
---|
2419 |
|
---|
2420 | tie @array, 'Tie::File', $file, autodefer => 0;
|
---|
2421 |
|
---|
2422 |
|
---|
2423 | Similarly, C<-E<gt>autodefer(1)> re-enables autodeferment, and
|
---|
2424 | C<-E<gt>autodefer()> recovers the current value of the autodefer setting.
|
---|
2425 |
|
---|
2426 |
|
---|
2427 | =head1 CONCURRENT ACCESS TO FILES
|
---|
2428 |
|
---|
2429 | Caching and deferred writing are inappropriate if you want the same
|
---|
2430 | file to be accessed simultaneously from more than one process. Other
|
---|
2431 | optimizations performed internally by this module are also
|
---|
2432 | incompatible with concurrent access. A future version of this module will
|
---|
2433 | support a C<concurrent =E<gt> 1> option that enables safe concurrent access.
|
---|
2434 |
|
---|
2435 | Previous versions of this documentation suggested using C<memory
|
---|
2436 | =E<gt> 0> for safe concurrent access. This was mistaken. Tie::File
|
---|
2437 | will not support safe concurrent access before version 0.98.
|
---|
2438 |
|
---|
2439 | =head1 CAVEATS
|
---|
2440 |
|
---|
2441 | (That's Latin for 'warnings'.)
|
---|
2442 |
|
---|
2443 | =over 4
|
---|
2444 |
|
---|
2445 | =item *
|
---|
2446 |
|
---|
2447 | Reasonable effort was made to make this module efficient. Nevertheless,
|
---|
2448 | changing the size of a record in the middle of a large file will
|
---|
2449 | always be fairly slow, because everything after the new record must be
|
---|
2450 | moved.
|
---|
2451 |
|
---|
2452 | =item *
|
---|
2453 |
|
---|
2454 | The behavior of tied arrays is not precisely the same as for regular
|
---|
2455 | arrays. For example:
|
---|
2456 |
|
---|
2457 | # This DOES print "How unusual!"
|
---|
2458 | undef $a[10]; print "How unusual!\n" if defined $a[10];
|
---|
2459 |
|
---|
2460 | C<undef>-ing a C<Tie::File> array element just blanks out the
|
---|
2461 | corresponding record in the file. When you read it back again, you'll
|
---|
2462 | get the empty string, so the supposedly-C<undef>'ed value will be
|
---|
2463 | defined. Similarly, if you have C<autochomp> disabled, then
|
---|
2464 |
|
---|
2465 | # This DOES print "How unusual!" if 'autochomp' is disabled
|
---|
2466 | undef $a[10];
|
---|
2467 | print "How unusual!\n" if $a[10];
|
---|
2468 |
|
---|
2469 | Because when C<autochomp> is disabled, C<$a[10]> will read back as
|
---|
2470 | C<"\n"> (or whatever the record separator string is.)
|
---|
2471 |
|
---|
2472 | There are other minor differences, particularly regarding C<exists>
|
---|
2473 | and C<delete>, but in general, the correspondence is extremely close.
|
---|
2474 |
|
---|
2475 | =item *
|
---|
2476 |
|
---|
2477 | I have supposed that since this module is concerned with file I/O,
|
---|
2478 | almost all normal use of it will be heavily I/O bound. This means
|
---|
2479 | that the time to maintain complicated data structures inside the
|
---|
2480 | module will be dominated by the time to actually perform the I/O.
|
---|
2481 | When there was an opportunity to spend CPU time to avoid doing I/O, I
|
---|
2482 | usually tried to take it.
|
---|
2483 |
|
---|
2484 | =item *
|
---|
2485 |
|
---|
2486 | You might be tempted to think that deferred writing is like
|
---|
2487 | transactions, with C<flush> as C<commit> and C<discard> as
|
---|
2488 | C<rollback>, but it isn't, so don't.
|
---|
2489 |
|
---|
2490 | =item *
|
---|
2491 |
|
---|
2492 | There is a large memory overhead for each record offset and for each
|
---|
2493 | cache entry: about 310 bytes per cached data record, and about 21 bytes per offset table entry.
|
---|
2494 |
|
---|
2495 | The per-record overhead will limit the maximum number of records you
|
---|
2496 | can access per file. Note that I<accessing> the length of the array
|
---|
2497 | via C<$x = scalar @tied_file> accesses B<all> records and stores their
|
---|
2498 | offsets. The same for C<foreach (@tied_file)>, even if you exit the
|
---|
2499 | loop early.
|
---|
2500 |
|
---|
2501 | =back
|
---|
2502 |
|
---|
2503 | =head1 SUBCLASSING
|
---|
2504 |
|
---|
2505 | This version promises absolutely nothing about the internals, which
|
---|
2506 | may change without notice. A future version of the module will have a
|
---|
2507 | well-defined and stable subclassing API.
|
---|
2508 |
|
---|
2509 | =head1 WHAT ABOUT C<DB_File>?
|
---|
2510 |
|
---|
2511 | People sometimes point out that L<DB_File> will do something similar,
|
---|
2512 | and ask why C<Tie::File> module is necessary.
|
---|
2513 |
|
---|
2514 | There are a number of reasons that you might prefer C<Tie::File>.
|
---|
2515 | A list is available at C<http://perl.plover.com/TieFile/why-not-DB_File>.
|
---|
2516 |
|
---|
2517 | =head1 AUTHOR
|
---|
2518 |
|
---|
2519 | Mark Jason Dominus
|
---|
2520 |
|
---|
2521 | To contact the author, send email to: C<[email protected]>
|
---|
2522 |
|
---|
2523 | To receive an announcement whenever a new version of this module is
|
---|
2524 | released, send a blank email message to
|
---|
2525 | C<[email protected]>.
|
---|
2526 |
|
---|
2527 | The most recent version of this module, including documentation and
|
---|
2528 | any news of importance, will be available at
|
---|
2529 |
|
---|
2530 | http://perl.plover.com/TieFile/
|
---|
2531 |
|
---|
2532 |
|
---|
2533 | =head1 LICENSE
|
---|
2534 |
|
---|
2535 | C<Tie::File> version 0.97 is copyright (C) 2003 Mark Jason Dominus.
|
---|
2536 |
|
---|
2537 | This library is free software; you may redistribute it and/or modify
|
---|
2538 | it under the same terms as Perl itself.
|
---|
2539 |
|
---|
2540 | These terms are your choice of any of (1) the Perl Artistic Licence,
|
---|
2541 | or (2) version 2 of the GNU General Public License as published by the
|
---|
2542 | Free Software Foundation, or (3) any later version of the GNU General
|
---|
2543 | Public License.
|
---|
2544 |
|
---|
2545 | This library is distributed in the hope that it will be useful,
|
---|
2546 | but WITHOUT ANY WARRANTY; without even the implied warranty of
|
---|
2547 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
---|
2548 | GNU General Public License for more details.
|
---|
2549 |
|
---|
2550 | You should have received a copy of the GNU General Public License
|
---|
2551 | along with this library program; it should be in the file C<COPYING>.
|
---|
2552 | If not, write to the Free Software Foundation, Inc., 59 Temple Place,
|
---|
2553 | Suite 330, Boston, MA 02111 USA
|
---|
2554 |
|
---|
2555 | For licensing inquiries, contact the author at:
|
---|
2556 |
|
---|
2557 | Mark Jason Dominus
|
---|
2558 | 255 S. Warnock St.
|
---|
2559 | Philadelphia, PA 19107
|
---|
2560 |
|
---|
2561 | =head1 WARRANTY
|
---|
2562 |
|
---|
2563 | C<Tie::File> version 0.97 comes with ABSOLUTELY NO WARRANTY.
|
---|
2564 | For details, see the license.
|
---|
2565 |
|
---|
2566 | =head1 THANKS
|
---|
2567 |
|
---|
2568 | Gigantic thanks to Jarkko Hietaniemi, for agreeing to put this in the
|
---|
2569 | core when I hadn't written it yet, and for generally being helpful,
|
---|
2570 | supportive, and competent. (Usually the rule is "choose any one.")
|
---|
2571 | Also big thanks to Abhijit Menon-Sen for all of the same things.
|
---|
2572 |
|
---|
2573 | Special thanks to Craig Berry and Peter Prymmer (for VMS portability
|
---|
2574 | help), Randy Kobes (for Win32 portability help), Clinton Pierce and
|
---|
2575 | Autrijus Tang (for heroic eleventh-hour Win32 testing above and beyond
|
---|
2576 | the call of duty), Michael G Schwern (for testing advice), and the
|
---|
2577 | rest of the CPAN testers (for testing generally).
|
---|
2578 |
|
---|
2579 | Special thanks to Tels for suggesting several speed and memory
|
---|
2580 | optimizations.
|
---|
2581 |
|
---|
2582 | Additional thanks to:
|
---|
2583 | Edward Avis /
|
---|
2584 | Mattia Barbon /
|
---|
2585 | Tom Christiansen /
|
---|
2586 | Gerrit Haase /
|
---|
2587 | Gurusamy Sarathy /
|
---|
2588 | Jarkko Hietaniemi (again) /
|
---|
2589 | Nikola Knezevic /
|
---|
2590 | John Kominetz /
|
---|
2591 | Nick Ing-Simmons /
|
---|
2592 | Tassilo von Parseval /
|
---|
2593 | H. Dieter Pearcey /
|
---|
2594 | Slaven Rezic /
|
---|
2595 | Eric Roode /
|
---|
2596 | Peter Scott /
|
---|
2597 | Peter Somu /
|
---|
2598 | Autrijus Tang (again) /
|
---|
2599 | Tels (again) /
|
---|
2600 | Juerd Waalboer
|
---|
2601 |
|
---|
2602 | =head1 TODO
|
---|
2603 |
|
---|
2604 | More tests. (Stuff I didn't think of yet.)
|
---|
2605 |
|
---|
2606 | Paragraph mode?
|
---|
2607 |
|
---|
2608 | Fixed-length mode. Leave-blanks mode.
|
---|
2609 |
|
---|
2610 | Maybe an autolocking mode?
|
---|
2611 |
|
---|
2612 | For many common uses of the module, the read cache is a liability.
|
---|
2613 | For example, a program that inserts a single record, or that scans the
|
---|
2614 | file once, will have a cache hit rate of zero. This suggests a major
|
---|
2615 | optimization: The cache should be initially disabled. Here's a hybrid
|
---|
2616 | approach: Initially, the cache is disabled, but the cache code
|
---|
2617 | maintains statistics about how high the hit rate would be *if* it were
|
---|
2618 | enabled. When it sees the hit rate get high enough, it enables
|
---|
2619 | itself. The STAT comments in this code are the beginning of an
|
---|
2620 | implementation of this.
|
---|
2621 |
|
---|
2622 | Record locking with fcntl()? Then the module might support an undo
|
---|
2623 | log and get real transactions. What a tour de force that would be.
|
---|
2624 |
|
---|
2625 | Keeping track of the highest cached record. This would allow reads-in-a-row
|
---|
2626 | to skip the cache lookup faster (if reading from 1..N with empty cache at
|
---|
2627 | start, the last cached value will be always N-1).
|
---|
2628 |
|
---|
2629 | More tests.
|
---|
2630 |
|
---|
2631 | =cut
|
---|
2632 |
|
---|