[30193] | 1 | /*
|
---|
| 2 | * Copyright (C) 2015 Greenstone Digital Libraries, University of Waikato
|
---|
| 3 | * $Id$
|
---|
| 4 | *
|
---|
| 5 | * This program is free software; you can redistribute it and/or modify
|
---|
| 6 | * it under the terms of the GNU General Public License as published by
|
---|
| 7 | * the Free Software Foundation; either version 2 of the License, or
|
---|
| 8 | * (at your option) any later version.
|
---|
| 9 | *
|
---|
| 10 | * This program is distributed in the hope that it will be useful,
|
---|
| 11 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
|
---|
| 12 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
---|
| 13 | * GNU General Public License for more details.
|
---|
| 14 | *
|
---|
| 15 | * You should have received a copy of the GNU General Public License
|
---|
| 16 | * along with this program; if not, write to the Free Software
|
---|
| 17 | * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
|
---|
| 18 | */
|
---|
| 19 |
|
---|
| 20 | package org.greenstone.tdbjava;
|
---|
| 21 |
|
---|
| 22 | import java.io.Closeable;
|
---|
| 23 | import java.lang.System;
|
---|
| 24 | import java.util.Enumeration;
|
---|
[30270] | 25 | import java.util.HashMap;
|
---|
[30193] | 26 |
|
---|
| 27 | import org.greenstone.tdbjava.TDBJavaException;
|
---|
| 28 | import org.greenstone.tdbjava.TDBJavaKeyEnumeration;
|
---|
| 29 |
|
---|
| 30 | /** Java interface to a TDB database table.
|
---|
| 31 | *
|
---|
| 32 | * <P>This database is a simple on-disk hash table.
|
---|
| 33 | *
|
---|
| 34 | * <P>Both the hash keys and values are binary strings of any length. They
|
---|
| 35 | * are converted to and from Java objects using customizable packing
|
---|
| 36 | * strategies.
|
---|
| 37 | *
|
---|
| 38 | * <P>The implementation of this class consists of two levels: a Java-level
|
---|
| 39 | * interface, and a set of private native functions implemented in C. As much
|
---|
| 40 | * functionality as possible is implemented in Java: the C functions generally
|
---|
| 41 | * just marshal the information for presentation to the native GDBM library.
|
---|
| 42 | *
|
---|
| 43 | * <P>The native library <CODE>tdbjava</CODE> must be available for dynamic
|
---|
| 44 | * loading in a system-dependant manner.
|
---|
| 45 | *
|
---|
| 46 | * <p>See the <A HREF="https://tdb.samba.org">TDB home page</A> for more
|
---|
| 47 | * information.
|
---|
| 48 | *
|
---|
| 49 | * @author John Thompson ([email protected])
|
---|
| 50 | * @author Martin Pool (original author - GdbmJava)
|
---|
| 51 | */
|
---|
| 52 | public class TDBJava
|
---|
| 53 | implements Closeable
|
---|
| 54 | {
|
---|
[30270] | 55 |
|
---|
| 56 | /** A cache of TDBJava objects that have been created keyed by filepath */
|
---|
| 57 | private static HashMap<String, TDBJava> connection_cache;
|
---|
| 58 |
|
---|
[30193] | 59 | static
|
---|
| 60 | {
|
---|
| 61 | // Load native library mapping at runtime (libTDBJava.so)
|
---|
| 62 | System.loadLibrary("TDBJava");
|
---|
[30270] | 63 | connection_cache = new HashMap<String, TDBJava>();
|
---|
[30193] | 64 | }
|
---|
| 65 |
|
---|
[30270] | 66 | /** @function getConnection(String)
|
---|
| 67 | * Factory method - uses an existing cached TDBJava otherwise creates
|
---|
| 68 | * a new one. This should get around the issue with a single process of
|
---|
| 69 | * the libTDBJava.so above throwing EBUSY errors when trying to open
|
---|
| 70 | * multiple copies of the same database.
|
---|
| 71 | */
|
---|
| 72 | public static TDBJava getConnection(String filename)
|
---|
| 73 | throws TDBJavaException
|
---|
| 74 | {
|
---|
| 75 | TDBJava the_connection = connection_cache.get(filename);
|
---|
| 76 | if (null == the_connection) {
|
---|
| 77 | the_connection = new TDBJava(filename);
|
---|
| 78 | connection_cache.put(filename, the_connection);
|
---|
| 79 | }
|
---|
| 80 | // Keep track of the number of times this connection has been
|
---|
| 81 | // handed out
|
---|
| 82 | the_connection.registerCaller();
|
---|
| 83 | return the_connection;
|
---|
| 84 | }
|
---|
| 85 | /** getConnection(String) **/
|
---|
| 86 |
|
---|
| 87 | public static TDBJava newConnection(String filename)
|
---|
| 88 | throws TDBJavaException
|
---|
| 89 | {
|
---|
| 90 | TDBJava the_connection = connection_cache.get(filename);
|
---|
| 91 | if (null == the_connection) {
|
---|
| 92 | the_connection = new TDBJava(filename);
|
---|
| 93 | connection_cache.put(filename, the_connection);
|
---|
| 94 | }
|
---|
| 95 | // delete all the records in an open connection
|
---|
| 96 | Enumeration keys = the_connection.keys();
|
---|
| 97 | while (keys.hasMoreElements()) {
|
---|
| 98 | the_connection.delete((String) keys.nextElement());
|
---|
| 99 | }
|
---|
| 100 | // Keep track of the number of times this connection has been
|
---|
| 101 | // handed out
|
---|
| 102 | the_connection.registerCaller();
|
---|
| 103 | return the_connection;
|
---|
| 104 | }
|
---|
| 105 | /** newConnection(String) **/
|
---|
| 106 |
|
---|
[30193] | 107 | /* ===== Declare mappings to native methods ===== */
|
---|
| 108 |
|
---|
| 109 | /**
|
---|
| 110 | * @brief Determine the version number of the TDB library.
|
---|
| 111 | */
|
---|
| 112 | private static native String tdbGetVersion();
|
---|
| 113 |
|
---|
| 114 | /**
|
---|
| 115 | * @brief Determine the version number of the JNI TDB warapper.
|
---|
| 116 | */
|
---|
| 117 | private static native String tdbWrapperVersion();
|
---|
| 118 |
|
---|
| 119 | /**
|
---|
| 120 | * @brief Open the database and creating it if necessary.
|
---|
| 121 | */
|
---|
| 122 | private native long tdbOpen(String filename,
|
---|
| 123 | int tdb_flags,
|
---|
| 124 | int open_flags)
|
---|
| 125 | throws TDBJavaException;
|
---|
| 126 |
|
---|
| 127 | /**
|
---|
| 128 | * @brief Close a database.
|
---|
| 129 | */
|
---|
| 130 | private native void tdbClose(long dbf);
|
---|
| 131 |
|
---|
| 132 | /**
|
---|
| 133 | * @brief Store an element in the database.
|
---|
| 134 | */
|
---|
| 135 | private native void tdbStore(long dbf,
|
---|
| 136 | byte[] key,
|
---|
| 137 | byte[] content,
|
---|
| 138 | boolean replace);
|
---|
| 139 |
|
---|
| 140 | /**
|
---|
| 141 | * @brief Fetch an entry in the database given a key.
|
---|
| 142 | */
|
---|
| 143 | private native byte[] tdbFetch(long dbf,
|
---|
| 144 | byte[] key);
|
---|
| 145 |
|
---|
| 146 | /**
|
---|
| 147 | * @brief Check if an entry in the database exists.
|
---|
| 148 | */
|
---|
| 149 | private native boolean tdbExists(long dbf,
|
---|
| 150 | byte[] key);
|
---|
| 151 |
|
---|
| 152 | /**
|
---|
| 153 | * @brief Delete an entry in the database given a key.
|
---|
| 154 | */
|
---|
| 155 | private native void tdbDelete(long dbf,
|
---|
| 156 | byte[] key);
|
---|
| 157 |
|
---|
| 158 | /**
|
---|
| 159 | * @brief Find the first entry in the database and return its key.
|
---|
| 160 | */
|
---|
| 161 | private native byte[] tdbFirstKey(long dbf)
|
---|
| 162 | throws TDBJavaException;
|
---|
| 163 |
|
---|
| 164 | /**
|
---|
| 165 | * @brief Find the next entry in the database, returning its key.
|
---|
| 166 | */
|
---|
| 167 | private native byte[] tdbNextKey(long dbf,
|
---|
| 168 | byte[] key)
|
---|
| 169 | throws TDBJavaException;
|
---|
| 170 |
|
---|
| 171 | /* ===== Normal variable and function declarations ===== */
|
---|
| 172 | /* (should match GdbmFile) */
|
---|
| 173 |
|
---|
| 174 | /* TDB flags */
|
---|
| 175 | /** When set, default behaviour (included for readability) */
|
---|
| 176 | public final static int TDB_DEFAULT = 0;
|
---|
| 177 | /** When set, causes any existing TDB table to be cleared on first open */
|
---|
| 178 | public final static int TDB_CLEAR_IF_FIRST = 1;
|
---|
| 179 | /** When set, causes TDB table to be in-memory (no file access) */
|
---|
| 180 | public final static int TDB_INTERNAL = 2;
|
---|
| 181 | /** When set, suppresses file locking (flock) */
|
---|
| 182 | public final static int TDB_NOLOCK = 4;
|
---|
| 183 |
|
---|
| 184 | /** Open database possibilities **/
|
---|
| 185 | public final static int O_DEFAULT = 0;
|
---|
| 186 | public final static int O_READONLY = 1;
|
---|
| 187 |
|
---|
| 188 | /** The parameters used to open the database. */
|
---|
| 189 | private String filename;
|
---|
| 190 | private int tdb_flags;
|
---|
| 191 | private int open_flags;
|
---|
| 192 |
|
---|
[30270] | 193 | /** We need to keep a reference of the number of times this connection
|
---|
| 194 | * has been opened, and not process a close until they have *all* asked
|
---|
| 195 | * to close. */
|
---|
| 196 | private int caller_count;
|
---|
| 197 |
|
---|
[30193] | 198 | /** The TDB handle for the database file, or 0 if the database has
|
---|
| 199 | * been closed. Java doesn't understand it, but it stores it and
|
---|
| 200 | * passes it to the C routines. */
|
---|
| 201 | private transient volatile long dbf;
|
---|
| 202 |
|
---|
| 203 | /** Create a new TDBJava object which automatically wraps a connection to
|
---|
| 204 | * an underlying TDB database (using the TDB library via the JNI wrapper).
|
---|
| 205 | *
|
---|
| 206 | * @param filename the disk filename in which the data will be stored
|
---|
| 207 | */
|
---|
| 208 | public TDBJava(String filename)
|
---|
| 209 | throws TDBJavaException
|
---|
| 210 | {
|
---|
[30270] | 211 | this.filename = filename;
|
---|
| 212 | this.tdb_flags = TDBJava.TDB_DEFAULT;
|
---|
| 213 | this.open_flags = TDBJava.O_DEFAULT;
|
---|
| 214 | this.dbf = this.tdbOpen(this.filename, this.tdb_flags, this.open_flags);
|
---|
| 215 | this.caller_count = 0;
|
---|
| 216 | // Replacement for System.runFinalizersOnExit(true);
|
---|
| 217 | Thread shutdown_thread = new TDBJavaShutdownThread(this);
|
---|
| 218 | Runtime.getRuntime().addShutdownHook(shutdown_thread);
|
---|
[30193] | 219 | }
|
---|
[30270] | 220 | /** TDBJava(String) **/
|
---|
[30193] | 221 |
|
---|
[30270] | 222 | /** @function TDBJava(String, int)
|
---|
| 223 | * @param filename the disk filename in which the data will be stored
|
---|
| 224 | * @param tdb_flags any of TDB_DEFAULT, TDB_CLEAR_IF_FIRST, TDB_INTERNAL,
|
---|
| 225 | * and TDB_NOLOCK
|
---|
| 226 | */
|
---|
| 227 | /*
|
---|
[30193] | 228 | public TDBJava(String filename, int tdb_flags)
|
---|
| 229 | throws TDBJavaException
|
---|
| 230 | {
|
---|
| 231 | }
|
---|
[30270] | 232 | */
|
---|
| 233 | /** **/
|
---|
[30193] | 234 |
|
---|
[30270] | 235 | /* disabled for now to simplify caching
|
---|
| 236 | *
|
---|
[30193] | 237 | public TDBJava(String filename, int tdb_flags, int open_flags)
|
---|
| 238 | throws TDBJavaException
|
---|
| 239 | {
|
---|
| 240 | this.filename = filename;
|
---|
| 241 | this.tdb_flags = tdb_flags;
|
---|
| 242 | this.open_flags = open_flags;
|
---|
| 243 | this.dbf = this.tdbOpen(this.filename, this.tdb_flags, this.open_flags);
|
---|
| 244 | // Replacement for System.runFinalizersOnExit(true);
|
---|
| 245 | Thread shutdown_thread = new TDBJavaShutdownThread(this);
|
---|
| 246 | Runtime.getRuntime().addShutdownHook(shutdown_thread);
|
---|
| 247 | }
|
---|
[30270] | 248 | */
|
---|
[30193] | 249 |
|
---|
[30270] | 250 | /** @function registerCaller()
|
---|
| 251 | */
|
---|
| 252 | public synchronized void registerCaller()
|
---|
| 253 | {
|
---|
| 254 | this.caller_count++;
|
---|
| 255 | }
|
---|
| 256 | /** registerCaller() **/
|
---|
| 257 |
|
---|
[30193] | 258 | /** Close the database file if it is still open.
|
---|
| 259 | */
|
---|
| 260 | public synchronized void close()
|
---|
| 261 | throws TDBJavaException
|
---|
| 262 | {
|
---|
| 263 | if (this.dbf != 0) {
|
---|
[30270] | 264 | if (this.caller_count == 1) {
|
---|
| 265 | this.tdbClose(this.dbf);
|
---|
| 266 | this.dbf = 0;
|
---|
| 267 | // And remove from the cache
|
---|
| 268 | connection_cache.remove(this.filename);
|
---|
| 269 | }
|
---|
| 270 | else {
|
---|
| 271 | this.caller_count--;
|
---|
| 272 | }
|
---|
[30193] | 273 | }
|
---|
| 274 | }
|
---|
[30270] | 275 | /** close() **/
|
---|
[30193] | 276 |
|
---|
| 277 | /** Close the database when the TDBJava is garbage-collected.
|
---|
| 278 | */
|
---|
| 279 | public void finalize()
|
---|
| 280 | throws TDBJavaException
|
---|
| 281 | {
|
---|
[30270] | 282 | // If we've got here, then we can't have any callers left
|
---|
| 283 | this.caller_count = 0;
|
---|
[30193] | 284 | this.close();
|
---|
| 285 | }
|
---|
| 286 |
|
---|
| 287 | /** Returns a string indicating the version of the underlying TDB
|
---|
| 288 | * library.
|
---|
| 289 | *
|
---|
| 290 | * @return the version of the native TDB library.
|
---|
| 291 | *
|
---|
| 292 | **/
|
---|
| 293 | public static String getLibraryVersion()
|
---|
| 294 | {
|
---|
| 295 | return TDBJava.tdbGetVersion();
|
---|
| 296 | }
|
---|
| 297 |
|
---|
| 298 | /** Return a string indicating the version of the JNI TDB library
|
---|
| 299 | * wrapper.
|
---|
| 300 | *
|
---|
| 301 | * @return the release number of the wrapper
|
---|
| 302 | *
|
---|
| 303 | **/
|
---|
| 304 | public static String getWrapperVersion()
|
---|
| 305 | {
|
---|
| 306 | return TDBJava.tdbWrapperVersion();
|
---|
| 307 | }
|
---|
| 308 |
|
---|
| 309 | /** Indicate whether the database is writable.
|
---|
| 310 | *
|
---|
| 311 | * @return true if the database may be written; otherwise false.
|
---|
| 312 | *
|
---|
| 313 | */
|
---|
| 314 | public boolean isWritable()
|
---|
| 315 | {
|
---|
| 316 | return (TDBJava.O_READONLY != this.open_flags);
|
---|
| 317 | }
|
---|
| 318 |
|
---|
| 319 | /** Indicate whether the database is open or not.
|
---|
| 320 | *
|
---|
| 321 | * @return false if the database has been closed; otherwise true.
|
---|
| 322 | *
|
---|
| 323 | */
|
---|
| 324 | public boolean isOpen()
|
---|
| 325 | {
|
---|
| 326 | return (this.dbf != 0);
|
---|
| 327 | }
|
---|
| 328 |
|
---|
| 329 | /** Compact the database file - not necessary for TDB.
|
---|
| 330 | */
|
---|
| 331 | public void reorganize()
|
---|
| 332 | throws TDBJavaException
|
---|
| 333 | {
|
---|
| 334 | // Not applicable
|
---|
| 335 | }
|
---|
| 336 |
|
---|
| 337 | /** Was used to define key Packing mechanism - no longer used as TDB always
|
---|
| 338 | * uses String to byte array.
|
---|
| 339 | */
|
---|
| 340 | public void setKeyPacking(Object packing)
|
---|
| 341 | {
|
---|
| 342 | // Not applicable
|
---|
| 343 | }
|
---|
| 344 |
|
---|
| 345 | /** Was used to define value Packing mechanism - no longer used as TDB
|
---|
| 346 | * always uses byte array to String
|
---|
| 347 | */
|
---|
| 348 | public void setValuePacking(Object packing)
|
---|
| 349 | {
|
---|
| 350 | // Not applicable
|
---|
| 351 | }
|
---|
| 352 |
|
---|
| 353 | /** Flush changes to disk - not necessary for TDB.
|
---|
| 354 | */
|
---|
| 355 | public void sync()
|
---|
| 356 | throws TDBJavaException
|
---|
| 357 | {
|
---|
| 358 | // Not applicable
|
---|
| 359 | }
|
---|
| 360 |
|
---|
| 361 | /** Retrieve the value corresponding to a particular key.
|
---|
| 362 | *
|
---|
| 363 | * @param key the string identifying the record to be retrieved
|
---|
| 364 | *
|
---|
| 365 | * @return the value of the record with the specified key; or
|
---|
| 366 | * null if the key is not present in the database.
|
---|
| 367 | */
|
---|
| 368 | public String fetch(String key)
|
---|
| 369 | throws TDBJavaException
|
---|
| 370 | {
|
---|
| 371 | if (!this.isOpen()) {
|
---|
| 372 | throw new TDBJavaException("Database is not open: " + this.filename);
|
---|
| 373 | }
|
---|
| 374 | byte[] key_bytes = this.toBytes(key);
|
---|
| 375 | byte[] value_bytes = this.tdbFetch(this.dbf, key_bytes);
|
---|
| 376 | if (null == value_bytes) {
|
---|
| 377 | throw new TDBJavaException("Key not found: \"" + key + "\"");
|
---|
| 378 | }
|
---|
| 379 | String value = this.fromBytes(value_bytes);
|
---|
| 380 | return value;
|
---|
| 381 | }
|
---|
| 382 |
|
---|
| 383 | /** Indicate whether the specified key is in the database,
|
---|
| 384 | * without returning the value.
|
---|
| 385 | *
|
---|
| 386 | * @param key the key of the record to be retrieved
|
---|
| 387 | *
|
---|
| 388 | * @return true if a record with the specified key is present;
|
---|
| 389 | * otherwise false.
|
---|
| 390 | */
|
---|
| 391 | public boolean exists(String key)
|
---|
| 392 | throws TDBJavaException
|
---|
| 393 | {
|
---|
| 394 | if (!this.isOpen()) {
|
---|
| 395 | throw new TDBJavaException("Database is not open: " + this.filename);
|
---|
| 396 | }
|
---|
| 397 | byte[] key_bytes = this.toBytes(key);
|
---|
| 398 | return this.tdbExists(this.dbf, key_bytes);
|
---|
| 399 | }
|
---|
| 400 |
|
---|
| 401 | /** Store a value in the database, replacing any existing value with the
|
---|
| 402 | * same key.
|
---|
| 403 | *
|
---|
| 404 | * @param key key under which to store the value
|
---|
| 405 | *
|
---|
| 406 | * @param value value to be stored
|
---|
| 407 | *
|
---|
| 408 | * @exception TDBJavaException if an IO error occurs
|
---|
| 409 | */
|
---|
| 410 | public void store(String key, String value)
|
---|
| 411 | throws TDBJavaException
|
---|
| 412 | {
|
---|
| 413 | if (!this.isOpen()) {
|
---|
| 414 | throw new TDBJavaException("Database is not open: " + this.filename);
|
---|
| 415 | }
|
---|
| 416 | if (!this.isWritable()) {
|
---|
| 417 | throw new TDBJavaException("Database is read only: " + this.filename);
|
---|
| 418 | }
|
---|
| 419 | byte[] key_bytes = this.toBytes(key);
|
---|
| 420 | byte[] value_bytes = this.toBytes(value);
|
---|
| 421 | this.tdbStore(this.dbf, key_bytes, value_bytes, true);
|
---|
| 422 | }
|
---|
| 423 |
|
---|
| 424 | /** Remove a record from the database.
|
---|
| 425 | *
|
---|
| 426 | * @param key key of the record to be removed
|
---|
| 427 | *
|
---|
| 428 | * @exception TDBJavaException if there is no record with the specified key; or
|
---|
| 429 | * if an IO error occurs.
|
---|
| 430 | */
|
---|
| 431 | public void delete(String key)
|
---|
| 432 | throws TDBJavaException
|
---|
| 433 | {
|
---|
| 434 | if (!this.isOpen()) {
|
---|
| 435 | throw new TDBJavaException("Database is not open: " + this.filename);
|
---|
| 436 | }
|
---|
| 437 | if (!this.isWritable()) {
|
---|
| 438 | throw new TDBJavaException("Database is read only: " + this.filename);
|
---|
| 439 | }
|
---|
| 440 | byte[] key_bytes = this.toBytes(key);
|
---|
| 441 | this.tdbDelete(this.dbf, key_bytes);
|
---|
| 442 | }
|
---|
| 443 |
|
---|
| 444 | /** Return an enumeration which will return all of the keys for the
|
---|
| 445 | * database of the file in (apparently) random order.
|
---|
| 446 | *
|
---|
| 447 | * <P><B>Caution:</B> If the database is modified while
|
---|
| 448 | * an enumeration is in progress,
|
---|
| 449 | * then changes in the hash table may cause the enumeration to
|
---|
| 450 | * miss some records.
|
---|
| 451 | */
|
---|
| 452 | public Enumeration keys()
|
---|
| 453 | throws TDBJavaException
|
---|
| 454 | {
|
---|
| 455 | if (!this.isOpen()) {
|
---|
| 456 | throw new TDBJavaException("Database is not open: " + this.filename);
|
---|
| 457 | }
|
---|
| 458 | // Return an inner class which will do the iteration in the
|
---|
| 459 | // context of this GdbmFile object.
|
---|
| 460 | Enumeration keys = new TDBJavaKeyEnumeration(this);
|
---|
| 461 | return keys;
|
---|
| 462 | }
|
---|
| 463 |
|
---|
| 464 | /** Start a visit to all keys in the hashtable.
|
---|
| 465 | *
|
---|
| 466 | * @return the first key in the hash table as a String; or null if
|
---|
| 467 | * the database is empty. */
|
---|
| 468 | String getFirstKey()
|
---|
| 469 | throws TDBJavaException
|
---|
| 470 | {
|
---|
| 471 | if (!this.isOpen()) {
|
---|
| 472 | throw new TDBJavaException("Database is not open: " + this.filename);
|
---|
| 473 | }
|
---|
| 474 | byte[] first_key_bytes = this.tdbFirstKey(this.dbf);
|
---|
| 475 | String first_key = null;
|
---|
| 476 | if (null != first_key_bytes) {
|
---|
| 477 | first_key = this.fromBytes(first_key_bytes);
|
---|
| 478 | }
|
---|
| 479 | return first_key;
|
---|
| 480 | }
|
---|
| 481 | /** getFirstKey() **/
|
---|
| 482 |
|
---|
| 483 |
|
---|
| 484 | /** Find and read the next key in the hashtable.
|
---|
| 485 | *
|
---|
| 486 | * @return the next key; or null if given the last key in the hashtable.
|
---|
| 487 | */
|
---|
| 488 | String getNextKey(String current_key)
|
---|
| 489 | throws TDBJavaException
|
---|
| 490 | {
|
---|
| 491 | if (!this.isOpen()) {
|
---|
| 492 | throw new TDBJavaException("Database is not open: " + this.filename);
|
---|
| 493 | }
|
---|
| 494 | byte[] current_key_bytes = this.toBytes(current_key);
|
---|
| 495 | byte[] next_key_bytes = this.tdbNextKey(this.dbf, current_key_bytes);
|
---|
| 496 | String next_key = null;
|
---|
| 497 | if (null != next_key_bytes) {
|
---|
| 498 | next_key = this.fromBytes(next_key_bytes);
|
---|
| 499 | }
|
---|
| 500 | return next_key;
|
---|
| 501 | }
|
---|
| 502 | /** getNextKey(String) **/
|
---|
| 503 |
|
---|
| 504 |
|
---|
| 505 | /* ===== Private and Protected Functions ===== */
|
---|
| 506 |
|
---|
| 507 | /** Convert String to byte array - simplified replacement for Packing
|
---|
| 508 | * mechanism in GDBMJava.
|
---|
| 509 | */
|
---|
| 510 | protected byte[] toBytes(String input_string)
|
---|
| 511 | {
|
---|
| 512 | byte[] output_bytes;
|
---|
| 513 | try {
|
---|
| 514 | output_bytes = input_string.getBytes("UTF-8");
|
---|
| 515 | }
|
---|
| 516 | catch (Exception e) {
|
---|
| 517 | System.err.println("TDBJava::toBytes() - UTF-8 encoding not supported");
|
---|
| 518 | output_bytes = input_string.getBytes();
|
---|
| 519 | }
|
---|
| 520 | return output_bytes;
|
---|
| 521 | }
|
---|
| 522 |
|
---|
| 523 | /** Convert bytes array to String - simplified replacement for Packing
|
---|
| 524 | * mechanism in GDBMJava.
|
---|
| 525 | */
|
---|
| 526 | protected String fromBytes(byte[] input_bytes)
|
---|
| 527 | {
|
---|
| 528 | String output_string;
|
---|
| 529 | try {
|
---|
| 530 | output_string = new String(input_bytes, "UTF-8");
|
---|
| 531 | }
|
---|
| 532 | catch (Exception e) {
|
---|
| 533 | System.err.println("TDBJava::fromBytes() - UTF-8 encoding not supported");
|
---|
| 534 | output_string = new String(input_bytes);
|
---|
| 535 | }
|
---|
| 536 | return output_string;
|
---|
| 537 | }
|
---|
| 538 | }
|
---|