source: main/trunk/greenstone2/perllib/multiread.pm@ 21207

###########################################################################
#
# multiread.pm --
#
# Copyright (C) 1999 DigiLib Systems Limited, NZ
# Copyright (C) 2005 New Zealand Digital Library project
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
#
###########################################################################

# the multiread object will read in a number of encodings,
# the results are always returned in the utf-8 format

# encodings currently supported are
#
# utf8             - either utf8 or unicode (automatically detected)
# unicode          - 2-byte UCS (does endian detection)
#
# plus all encodings in the "encodings" package

package multiread;

eval {require bytes};

use strict;
no strict 'refs'; # allow filehandles to be variables and viceversa

use unicode;

sub new {
    my ($class) = @_;

    my $self = {'handle'    => "",
        'first'     => 1,
        'encoding'  => "utf8",
        'bigendian' => 1};

    return bless $self, $class;
}

# set_handle expects the file to be already open but
# not read yet
sub set_handle {
    my $self = shift;
    $self->{'handle'} = shift;
    binmode( $self->{'handle'} );
    $self->{'first'} = 1;
    $self->{'encoding'} = "utf8";
    $self->{'bigendian'} = 1;
}

# set_encoding should be called after set_handle
sub set_encoding {
    my $self = shift;
    $self->{'encoding'} = shift;
}

sub get_encoding {
    my $self = shift (@_);
    return $self->{'encoding'};
}

# undef will be returned if the eof has been reached
# the result will always be returned in utf-8

sub read_unicode_char {
    my $self = shift (@_);

    # make sure we have a file handle
    return undef if ($self->{'handle'} eq "");
    my $handle = $self->{'handle'};

    if ($self->{'encoding'} eq "utf8") {
    # utf-8 text, how many characters we get depends 
    # on what we find
    my $c1 = "";
    my $c2 = "";
    my $c3 = "";

    while (!eof ($handle)) {
        $c1 = ord (getc ($handle));

        if ($c1 <= 0x7f) {
        # one byte character
        return chr ($c1);

        } elsif ($c1 >= 0xc0 && $c1 <= 0xdf) {
        # two byte character
        $c2 = getc ($handle) if (!eof ($handle));
        return chr ($c1) . $c2;

        } elsif ($c1 >= 0xe0 && $c1 <= 0xef) {
        # three byte character
        $c2 = getc ($handle) if (!eof ($handle));
        $c3 = getc ($handle) if (!eof ($handle));
        return chr ($c1) . $c2 . $c3;
        }

        # if we get here there was an error in the file, we should
        # be able to recover from it however, maybe the file is in
        # another encoding
    }

    return undef if (eof ($handle));
    }

    if ($self->{'encoding'} eq "unicode") {
    # unicode text, get the next two characters
    return undef if (eof ($handle));
    my $c1 = ord (getc ($handle));
    return undef if (eof ($handle));
    my $c2 = ord (getc ($handle));

    return &unicode::unicode2utf8 ([(($self->{'bigendian'}) ? ($c1*256+$c2) : ($c2*256+$c1))]);
    }

    return undef;
}


sub unicodechar_to_ord
{
    my $self = shift (@_);
    my ($unicode_text) = @_;

    my $bigendian_ord_array = [];

    my @unicodechar_array = ($unicode_text =~ m/(..)/g);

    foreach my $pair (@unicodechar_array) {
    # for each 2 byte pair       
    my $c1=ord(substr($pair,0,1));
    my $c2=ord(substr($pair,1,1));

    my $be_ord = ($self->{'bigendian'}) ? $c1*256+$c2 : $c2*256+$c1;
    push(@$bigendian_ord_array,$be_ord);
    }

    return $bigendian_ord_array;
}


# undef will be returned if the eof has been reached
# the result will always be returned in utf-8
sub read_line {
    my $self = shift (@_);

    # make sure we have a file handle
    return undef if ($self->{'handle'} eq "");

    my $handle = $self->{'handle'};

    if ($self->{'encoding'} eq "utf8") {
    # utf-8 line
    return <$handle>;
    }

    if ($self->{'encoding'} eq "unicode") {
    # unicode line
    my $c = "";
    my ($c1, $c2) = ("", "");
    my $out = "";
    while (read ($handle, $c, 2) == 2) {
        $c1 = ord (substr ($c, 0, 1));
        $c2 = ord (substr ($c, 1, 1));
        $c = &unicode::unicode2utf8([(($self->{'bigendian'}) ? ($c1*256+$c2) : ($c2*256+$c1))]);
        $out .= $c;
        last if ($c eq "\n");
    }

    return $out if (length ($out) > 0);
    return undef;
    }

    if ($self->{'encoding'} eq "iso_8859_1") {
    # we'll use ascii2utf8() for this as it's faster than going
    # through convert2unicode()
    my $line = "";
    if (defined ($line = <$handle>)) {
        return &unicode::ascii2utf8 (\$line);
    }
    }

    # everything else uses unicode::convert2unicode
    my $line = "";
    if (defined ($line = <$handle>)) {
    return &unicode::unicode2utf8 (&unicode::convert2unicode ($self->{'encoding'}, \$line));
    }

    return undef;
}



# this will look for a Byte Order Marker at the start of the file, and
# set the encoding appropriately if there is one, returning any
# non-marker text on the first line (or returns undef).
sub find_unicode_bom {
    my $self=shift;

    my $non_bom_text=""; # to return if we read in 'real' text

    if ($self->{'first'} == 0) { return }

    # make sure we have a file handle
    return if ($self->{'handle'} eq "");
    my $handle = $self->{'handle'};

    $self->{'first'} = 0;

    my $gc = getc ($handle);
    my $b1 = ord($gc);
    my $b2;
    my $b3;

    if ($b1 == 0xfe || $b1 == 0xff) {
    $b2 = ord (getc ($handle)) if (!eof ($handle));
    if ($b1 == 0xff && $b2 == 0xfe) {
        $self->{'encoding'} = "unicode";
        $self->{'bigendian'} = 0;
        return;
    } elsif ($b1 == 0xfe && $b2 == 0xff) {
        $self->{'encoding'} = "unicode";
        $self->{'bigendian'} = 1;
        return;
    } elsif ($b1 == 0xef && $b2 == 0xbb) {
        $b3 = ord(getc($handle));
        if ($b3 == 0xbf) {
        $self->{'encoding'} = "utf8";
        $self->{'bigendian'} = 1;
        return;
        }
        else {
        # put back all three bytes
        $handle->ungetc($b3);
        $handle->ungetc($b2);
        $handle->ungetc($b1); return;

        }
    }
    else {
        # put back two bytes read
        $handle->ungetc($b2);
        $handle->ungetc($b1); return;
    }
    } else { # $b1 != fe or ff
    # put back the one byte read
    $handle->ungetc($b1); return;
    }
}


sub read_file_no_decoding
{
    my $self = shift (@_);
    my ($outputref) = @_;

    # make sure we have a file handle
    return if ($self->{'handle'} eq "");

    my $handle = $self->{'handle'};

    # if encoding is set to utf8 or unicode, sniff to see if there is a 
    # byte order marker
    if ($self->{'first'} &&
    ($self->{'encoding'} eq "utf8" || $self->{'encoding'} eq 'unicode')) {

    # this will change $self's encoding if there is a BOM (but won't consume any characters)
    $self->find_unicode_bom(); 
    }

    undef $/;
    $$outputref .=  <$handle>;
    $/ = "\n";

}


# will convert entire contents of file to utf8 and append result to $outputref
# this may be a slightly faster way to get the contents of a file than by 
# recursively calling read_line()
sub decode_text {
    my $self = shift (@_);

    my ($raw_text,$decoded_text_ref) = @_;

    if ($self->{'encoding'} eq "utf8") {
    # Nothing to do, raw text is in utf 8
    $$decoded_text_ref .= $raw_text;
    return;
    }

    if ($self->{'encoding'} eq "unicode") {
    my $unicode_array = $self->unicodechar_to_ord($raw_text);
    $$decoded_text_ref .= &unicode::unicode2utf8($unicode_array);
    return;
    }

    if ($self->{'encoding'} eq "iso_8859_1" || $self->{'encoding'} eq "ascii") {
    # we'll use ascii2utf8() for this as it's faster than going
    # through convert2unicode()
    $$decoded_text_ref .= &unicode::ascii2utf8 (\$raw_text);
    return;
    }

    # everything else uses unicode::convert2unicode
    my $unicode_text = &unicode::convert2unicode ($self->{'encoding'}, \$raw_text);

    $$decoded_text_ref .= &unicode::unicode2utf8 ($unicode_text);

###    print STDERR "!!! decoded ", join(":",map { ord($_) } split(//,$$decoded_text_ref)), "\n";
}



# will convert entire contents of file to utf8 and append result to $outputref
# this may be a slightly faster way to get the contents of a file than by 
# recursively calling read_line()
sub read_file {
    my $self = shift (@_);
    my ($outputref) = @_;

    # While unusual, $raw_text is initialized to $$outputref
    # to be consistent with code before refactoring
    my $raw_text = $$outputref; 

    $self->read_file_no_decoding(\$raw_text);
    $self->decode_text($raw_text,$outputref);
}

1;