1 | /*
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2 | * Copyright (C) 2015 Greenstone Digital Libraries, University of Waikato
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3 | * $Id$
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4 | *
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5 | * This program is free software; you can redistribute it and/or modify
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6 | * it under the terms of the GNU General Public License as published by
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7 | * the Free Software Foundation; either version 2 of the License, or
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8 | * (at your option) any later version.
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9 | *
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10 | * This program is distributed in the hope that it will be useful,
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11 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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12 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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13 | * GNU General Public License for more details.
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14 | *
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15 | * You should have received a copy of the GNU General Public License
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16 | * along with this program; if not, write to the Free Software
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17 | * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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18 | */
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19 |
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20 | package org.greenstone.tdbjava;
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21 |
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22 | import java.io.Closeable;
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23 | import java.lang.System;
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24 | import java.util.Enumeration;
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25 |
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26 | import org.greenstone.tdbjava.TDBJavaException;
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27 | import org.greenstone.tdbjava.TDBJavaKeyEnumeration;
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28 |
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29 | /** Java interface to a TDB database table.
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30 | *
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31 | * <P>This database is a simple on-disk hash table.
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32 | *
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33 | * <P>Both the hash keys and values are binary strings of any length. They
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34 | * are converted to and from Java objects using customizable packing
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35 | * strategies.
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36 | *
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37 | * <P>The implementation of this class consists of two levels: a Java-level
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38 | * interface, and a set of private native functions implemented in C. As much
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39 | * functionality as possible is implemented in Java: the C functions generally
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40 | * just marshal the information for presentation to the native GDBM library.
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41 | *
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42 | * <P>The native library <CODE>tdbjava</CODE> must be available for dynamic
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43 | * loading in a system-dependant manner.
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44 | *
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45 | * <p>See the <A HREF="https://tdb.samba.org">TDB home page</A> for more
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46 | * information.
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47 | *
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48 | * @author John Thompson ([email protected])
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49 | * @author Martin Pool (original author - GdbmJava)
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50 | */
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51 | public class TDBJava
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52 | implements Closeable
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53 | {
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54 | static
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55 | {
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56 | // Load native library mapping at runtime (libTDBJava.so)
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57 | System.loadLibrary("TDBJava");
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58 | }
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59 |
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60 | /* ===== Declare mappings to native methods ===== */
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61 |
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62 | /**
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63 | * @brief Determine the version number of the TDB library.
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64 | */
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65 | private static native String tdbGetVersion();
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66 |
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67 | /**
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68 | * @brief Determine the version number of the JNI TDB warapper.
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69 | */
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70 | private static native String tdbWrapperVersion();
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71 |
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72 | /**
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73 | * @brief Open the database and creating it if necessary.
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74 | */
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75 | private native long tdbOpen(String filename,
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76 | int tdb_flags,
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77 | int open_flags)
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78 | throws TDBJavaException;
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79 |
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80 | /**
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81 | * @brief Close a database.
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82 | */
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83 | private native void tdbClose(long dbf);
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84 |
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85 | /**
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86 | * @brief Store an element in the database.
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87 | */
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88 | private native void tdbStore(long dbf,
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89 | byte[] key,
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90 | byte[] content,
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91 | boolean replace);
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92 |
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93 | /**
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94 | * @brief Fetch an entry in the database given a key.
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95 | */
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96 | private native byte[] tdbFetch(long dbf,
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97 | byte[] key);
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98 |
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99 | /**
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100 | * @brief Check if an entry in the database exists.
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101 | */
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102 | private native boolean tdbExists(long dbf,
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103 | byte[] key);
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104 |
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105 | /**
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106 | * @brief Delete an entry in the database given a key.
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107 | */
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108 | private native void tdbDelete(long dbf,
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109 | byte[] key);
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110 |
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111 | /**
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112 | * @brief Find the first entry in the database and return its key.
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113 | */
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114 | private native byte[] tdbFirstKey(long dbf)
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115 | throws TDBJavaException;
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116 |
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117 | /**
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118 | * @brief Find the next entry in the database, returning its key.
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119 | */
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120 | private native byte[] tdbNextKey(long dbf,
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121 | byte[] key)
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122 | throws TDBJavaException;
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123 |
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124 | /* ===== Normal variable and function declarations ===== */
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125 | /* (should match GdbmFile) */
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126 |
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127 | /* TDB flags */
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128 | /** When set, default behaviour (included for readability) */
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129 | public final static int TDB_DEFAULT = 0;
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130 | /** When set, causes any existing TDB table to be cleared on first open */
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131 | public final static int TDB_CLEAR_IF_FIRST = 1;
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132 | /** When set, causes TDB table to be in-memory (no file access) */
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133 | public final static int TDB_INTERNAL = 2;
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134 | /** When set, suppresses file locking (flock) */
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135 | public final static int TDB_NOLOCK = 4;
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136 |
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137 | /** Open database possibilities **/
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138 | public final static int O_DEFAULT = 0;
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139 | public final static int O_READONLY = 1;
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140 |
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141 | /** The parameters used to open the database. */
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142 | private String filename;
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143 | private int tdb_flags;
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144 | private int open_flags;
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145 |
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146 | /** The TDB handle for the database file, or 0 if the database has
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147 | * been closed. Java doesn't understand it, but it stores it and
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148 | * passes it to the C routines. */
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149 | private transient volatile long dbf;
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150 |
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151 | /** Create a new TDBJava object which automatically wraps a connection to
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152 | * an underlying TDB database (using the TDB library via the JNI wrapper).
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153 | *
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154 | * @param filename the disk filename in which the data will be stored
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155 | * @param flags any of TDB_DEFAULT, TDB_CLEAR_IF_FIRST, TDB_INTERNAL, and
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156 | * TDB_NOLOCK
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157 | *
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158 | */
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159 | public TDBJava(String filename)
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160 | throws TDBJavaException
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161 | {
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162 | this(filename, TDBJava.TDB_DEFAULT, TDBJava.O_DEFAULT);
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163 | }
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164 |
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165 | public TDBJava(String filename, int tdb_flags)
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166 | throws TDBJavaException
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167 | {
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168 | this(filename, tdb_flags, TDBJava.O_DEFAULT);
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169 | }
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170 |
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171 | public TDBJava(String filename, int tdb_flags, int open_flags)
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172 | throws TDBJavaException
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173 | {
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174 | this.filename = filename;
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175 | this.tdb_flags = tdb_flags;
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176 | this.open_flags = open_flags;
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177 | this.dbf = this.tdbOpen(this.filename, this.tdb_flags, this.open_flags);
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178 | // Replacement for System.runFinalizersOnExit(true);
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179 | Thread shutdown_thread = new TDBJavaShutdownThread(this);
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180 | Runtime.getRuntime().addShutdownHook(shutdown_thread);
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181 | }
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182 |
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183 | /** Close the database file if it is still open.
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184 | */
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185 | public synchronized void close()
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186 | throws TDBJavaException
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187 | {
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188 | if (this.dbf != 0) {
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189 | this.tdbClose(this.dbf);
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190 | }
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191 | // opened or created
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192 | this.dbf = 0;
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193 | }
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194 |
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195 | /** Close the database when the TDBJava is garbage-collected.
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196 | */
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197 | public void finalize()
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198 | throws TDBJavaException
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199 | {
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200 | this.close();
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201 | }
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202 |
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203 | /** Returns a string indicating the version of the underlying TDB
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204 | * library.
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205 | *
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206 | * @return the version of the native TDB library.
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207 | *
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208 | **/
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209 | public static String getLibraryVersion()
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210 | {
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211 | return TDBJava.tdbGetVersion();
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212 | }
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213 |
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214 | /** Return a string indicating the version of the JNI TDB library
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215 | * wrapper.
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216 | *
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217 | * @return the release number of the wrapper
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218 | *
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219 | **/
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220 | public static String getWrapperVersion()
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221 | {
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222 | return TDBJava.tdbWrapperVersion();
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223 | }
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224 |
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225 | /** Indicate whether the database is writable.
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226 | *
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227 | * @return true if the database may be written; otherwise false.
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228 | *
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229 | */
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230 | public boolean isWritable()
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231 | {
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232 | return (TDBJava.O_READONLY != this.open_flags);
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233 | }
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234 |
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235 | /** Indicate whether the database is open or not.
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236 | *
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237 | * @return false if the database has been closed; otherwise true.
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238 | *
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239 | */
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240 | public boolean isOpen()
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241 | {
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242 | return (this.dbf != 0);
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243 | }
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244 |
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245 | /** Compact the database file - not necessary for TDB.
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246 | */
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247 | public void reorganize()
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248 | throws TDBJavaException
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249 | {
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250 | // Not applicable
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251 | }
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252 |
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253 | /** Was used to define key Packing mechanism - no longer used as TDB always
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254 | * uses String to byte array.
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255 | */
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256 | public void setKeyPacking(Object packing)
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257 | {
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258 | // Not applicable
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259 | }
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260 |
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261 | /** Was used to define value Packing mechanism - no longer used as TDB
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262 | * always uses byte array to String
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263 | */
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264 | public void setValuePacking(Object packing)
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265 | {
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266 | // Not applicable
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267 | }
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268 |
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269 | /** Flush changes to disk - not necessary for TDB.
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270 | */
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271 | public void sync()
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272 | throws TDBJavaException
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273 | {
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274 | // Not applicable
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275 | }
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276 |
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277 | /** Retrieve the value corresponding to a particular key.
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278 | *
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279 | * @param key the string identifying the record to be retrieved
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280 | *
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281 | * @return the value of the record with the specified key; or
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282 | * null if the key is not present in the database.
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283 | */
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284 | public String fetch(String key)
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285 | throws TDBJavaException
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286 | {
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287 | if (!this.isOpen()) {
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288 | throw new TDBJavaException("Database is not open: " + this.filename);
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289 | }
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290 | byte[] key_bytes = this.toBytes(key);
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291 | byte[] value_bytes = this.tdbFetch(this.dbf, key_bytes);
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292 | if (null == value_bytes) {
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293 | throw new TDBJavaException("Key not found: \"" + key + "\"");
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294 | }
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295 | String value = this.fromBytes(value_bytes);
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296 | return value;
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297 | }
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298 |
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299 | /** Indicate whether the specified key is in the database,
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300 | * without returning the value.
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301 | *
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302 | * @param key the key of the record to be retrieved
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303 | *
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304 | * @return true if a record with the specified key is present;
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305 | * otherwise false.
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306 | */
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307 | public boolean exists(String key)
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308 | throws TDBJavaException
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309 | {
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310 | if (!this.isOpen()) {
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311 | throw new TDBJavaException("Database is not open: " + this.filename);
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312 | }
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313 | byte[] key_bytes = this.toBytes(key);
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314 | return this.tdbExists(this.dbf, key_bytes);
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315 | }
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316 |
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317 | /** Store a value in the database, replacing any existing value with the
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318 | * same key.
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319 | *
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320 | * @param key key under which to store the value
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321 | *
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322 | * @param value value to be stored
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323 | *
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324 | * @exception TDBJavaException if an IO error occurs
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325 | */
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326 | public void store(String key, String value)
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327 | throws TDBJavaException
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328 | {
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329 | if (!this.isOpen()) {
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330 | throw new TDBJavaException("Database is not open: " + this.filename);
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331 | }
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332 | if (!this.isWritable()) {
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333 | throw new TDBJavaException("Database is read only: " + this.filename);
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334 | }
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335 | byte[] key_bytes = this.toBytes(key);
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336 | byte[] value_bytes = this.toBytes(value);
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337 | this.tdbStore(this.dbf, key_bytes, value_bytes, true);
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338 | }
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339 |
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340 | /** Remove a record from the database.
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341 | *
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342 | * @param key key of the record to be removed
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343 | *
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344 | * @exception TDBJavaException if there is no record with the specified key; or
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345 | * if an IO error occurs.
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346 | */
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347 | public void delete(String key)
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348 | throws TDBJavaException
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349 | {
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350 | if (!this.isOpen()) {
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351 | throw new TDBJavaException("Database is not open: " + this.filename);
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352 | }
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353 | if (!this.isWritable()) {
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354 | throw new TDBJavaException("Database is read only: " + this.filename);
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355 | }
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356 | byte[] key_bytes = this.toBytes(key);
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357 | this.tdbDelete(this.dbf, key_bytes);
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358 | }
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359 |
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360 | /** Return an enumeration which will return all of the keys for the
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361 | * database of the file in (apparently) random order.
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362 | *
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363 | * <P><B>Caution:</B> If the database is modified while
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364 | * an enumeration is in progress,
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365 | * then changes in the hash table may cause the enumeration to
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366 | * miss some records.
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367 | */
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368 | public Enumeration keys()
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369 | throws TDBJavaException
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370 | {
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371 | if (!this.isOpen()) {
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372 | throw new TDBJavaException("Database is not open: " + this.filename);
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373 | }
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374 | // Return an inner class which will do the iteration in the
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375 | // context of this GdbmFile object.
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376 | Enumeration keys = new TDBJavaKeyEnumeration(this);
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377 | return keys;
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378 | }
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379 |
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380 | /** Start a visit to all keys in the hashtable.
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381 | *
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382 | * @return the first key in the hash table as a String; or null if
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383 | * the database is empty. */
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384 | String getFirstKey()
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385 | throws TDBJavaException
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386 | {
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387 | if (!this.isOpen()) {
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388 | throw new TDBJavaException("Database is not open: " + this.filename);
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389 | }
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390 | byte[] first_key_bytes = this.tdbFirstKey(this.dbf);
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391 | String first_key = null;
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392 | if (null != first_key_bytes) {
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393 | first_key = this.fromBytes(first_key_bytes);
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394 | }
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395 | return first_key;
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396 | }
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397 | /** getFirstKey() **/
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398 |
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399 |
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400 | /** Find and read the next key in the hashtable.
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401 | *
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402 | * @return the next key; or null if given the last key in the hashtable.
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403 | */
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404 | String getNextKey(String current_key)
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405 | throws TDBJavaException
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406 | {
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407 | if (!this.isOpen()) {
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408 | throw new TDBJavaException("Database is not open: " + this.filename);
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409 | }
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410 | byte[] current_key_bytes = this.toBytes(current_key);
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411 | byte[] next_key_bytes = this.tdbNextKey(this.dbf, current_key_bytes);
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412 | String next_key = null;
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413 | if (null != next_key_bytes) {
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414 | next_key = this.fromBytes(next_key_bytes);
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415 | }
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416 | return next_key;
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417 | }
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418 | /** getNextKey(String) **/
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419 |
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420 |
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421 | /* ===== Private and Protected Functions ===== */
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422 |
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423 | /** Convert String to byte array - simplified replacement for Packing
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424 | * mechanism in GDBMJava.
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425 | */
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426 | protected byte[] toBytes(String input_string)
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427 | {
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428 | byte[] output_bytes;
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429 | try {
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430 | output_bytes = input_string.getBytes("UTF-8");
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431 | }
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432 | catch (Exception e) {
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433 | System.err.println("TDBJava::toBytes() - UTF-8 encoding not supported");
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434 | output_bytes = input_string.getBytes();
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435 | }
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436 | return output_bytes;
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437 | }
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438 |
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439 | /** Convert bytes array to String - simplified replacement for Packing
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440 | * mechanism in GDBMJava.
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441 | */
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442 | protected String fromBytes(byte[] input_bytes)
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443 | {
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444 | String output_string;
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445 | try {
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446 | output_string = new String(input_bytes, "UTF-8");
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447 | }
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448 | catch (Exception e) {
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449 | System.err.println("TDBJava::fromBytes() - UTF-8 encoding not supported");
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450 | output_string = new String(input_bytes);
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451 | }
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452 | return output_string;
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453 | }
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454 | }
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