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GeezerVison is showing github.com — lmdbjava/src/main/java/org/lmdbjava/CursorIterable.java at master · lmdbjava/lmdbjava Expand file tree/ Copy pathCursorIterable.javaMore file actions 361 lines (326 loc) · 10.1 KB / Copy pathCursorIterable.javaFile metadata and controls361 lines (326 loc) · 10.1 KB 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 /* * Copyright © 2016-2025 The LmdbJava Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.lmdbjava; import static org.lmdbjava.CursorIterable.State.RELEASED; import static org.lmdbjava.CursorIterable.State.REQUIRES_INITIAL_OP; import static org.lmdbjava.CursorIterable.State.REQUIRES_ITERATOR_OP; import static org.lmdbjava.CursorIterable.State.REQUIRES_NEXT_OP; import static org.lmdbjava.CursorIterable.State.TERMINATED; import static org.lmdbjava.GetOp.MDB_SET_RANGE; import static org.lmdbjava.Library.LIB; import java.util.Comparator; import java.util.Iterator; import java.util.NoSuchElementException; import java.util.Objects; import java.util.function.Supplier; import jnr.ffi.Pointer; import org.lmdbjava.KeyRangeType.CursorOp; import org.lmdbjava.KeyRangeType.IteratorOp; /** * {@link Iterable} that creates a single {@link Iterator} that will iterate over a {@link Cursor} * as specified by a {@link KeyRange}. * * <p>An instance will create and close its own cursor. * * @param <T> buffer type */ public final class CursorIterable<T> implements Iterable<CursorIterable.KeyVal<T>>, AutoCloseable { private final RangeComparator rangeComparator; private final Cursor<T> cursor; private final KeyVal<T> entry; private boolean iteratorReturned; private final KeyRange<T> range; private State state = REQUIRES_INITIAL_OP; CursorIterable( final Txn<T> txn, final Dbi<T> dbi, final KeyRange<T> range, final Comparator<T> comparator, final BufferProxy<T> proxy) { this.cursor = dbi.openCursor(txn); this.range = range; this.entry = new KeyVal<>(); if (comparator != null) { // User supplied Java-side comparator so use that this.rangeComparator = new JavaRangeComparator<>(range, comparator, cursor::key); } else { // No Java-side comparator, so call down to LMDB to do the comparison this.rangeComparator = new LmdbRangeComparator<>(txn, dbi, cursor, range, proxy); } } @Override public void close() { cursor.close(); try { rangeComparator.close(); } catch (Exception e) { throw new RuntimeException(e); } } /** * Obtain an iterator. * * <p>As iteration of the returned iterator will cause movement of the underlying LMDB cursor, an * {@link IllegalStateException} is thrown if an attempt is made to obtain the iterator more than * once. For advanced cursor control (such as being able to iterate over the same data multiple * times etc) please instead refer to {@link Dbi#openCursor(org.lmdbjava.Txn)}. * * @return an iterator */ @Override public Iterator<KeyVal<T>> iterator() { if (iteratorReturned) { throw new IllegalStateException("Iterator can only be returned once"); } iteratorReturned = true; return new Iterator<KeyVal<T>>() { @Override public boolean hasNext() { while (state != RELEASED && state != TERMINATED) { update(); } return state == RELEASED; } @Override public KeyVal<T> next() { if (!hasNext()) { throw new NoSuchElementException(); } state = REQUIRES_NEXT_OP; return entry; } @Override public void remove() { cursor.delete(PutFlags.EMPTY); } }; } private void executeCursorOp(final CursorOp op) { boolean found; switch (op) { case FIRST: found = cursor.first(); break; case LAST: found = cursor.last(); break; case NEXT: found = cursor.next(); break; case PREV: found = cursor.prev(); break; case GET_START_KEY: found = cursor.get(range.getStart(), MDB_SET_RANGE); break; case GET_START_KEY_BACKWARD: found = cursor.get(range.getStart(), MDB_SET_RANGE); if (found) { if (!range.getType().isDirectionForward() && range.getType().isStartKeyRequired() && range.getType().isStartKeyInclusive()) { // We need to ensure we move to the last matching key if using DUPSORT, see issue 267 boolean loop = true; while (loop) { if (rangeComparator.compareToStartKey() <= 0) { found = cursor.next(); if (!found) { // We got to the end so move last. found = cursor.last(); loop = false; } } else { // We have moved past so go back one. found = cursor.prev(); loop = false; } } } } else { found = cursor.last(); } break; default: throw new IllegalStateException("Unknown cursor operation"); } entry.setK(found ? cursor.key() : null); entry.setV(found ? cursor.val() : null); } private void executeIteratorOp() { final IteratorOp op = range.getType().iteratorOp(entry.key(), rangeComparator); switch (op) { case CALL_NEXT_OP: executeCursorOp(range.getType().nextOp()); state = REQUIRES_ITERATOR_OP; break; case TERMINATE: state = TERMINATED; break; case RELEASE: state = RELEASED; break; default: throw new IllegalStateException("Unknown operation"); } } private void update() { switch (state) { case REQUIRES_INITIAL_OP: executeCursorOp(range.getType().initialOp()); state = REQUIRES_ITERATOR_OP; break; case REQUIRES_NEXT_OP: executeCursorOp(range.getType().nextOp()); state = REQUIRES_ITERATOR_OP; break; case REQUIRES_ITERATOR_OP: executeIteratorOp(); break; case TERMINATED: break; default: throw new IllegalStateException("Unknown state"); } } /** * Holder for a key and value pair. * * <p>The same holder instance will always be returned for a given iterator. The returned keys and * values may change or point to different memory locations following changes in the iterator, * cursor or transaction. * * @param <T> buffer type */ public static final class KeyVal<T> { private T k; private T v; /** Explicitly-defined default constructor to avoid warnings. */ public KeyVal() {} /** * The key. * * @return key */ public T key() { return k; } /** * The value. * * @return value */ public T val() { return v; } void setK(final T key) { this.k = key; } void setV(final T val) { this.v = val; } } /** Represents the internal {@link CursorIterable} state. */ enum State { REQUIRES_INITIAL_OP, REQUIRES_NEXT_OP, REQUIRES_ITERATOR_OP, RELEASED, TERMINATED } static class JavaRangeComparator<T> implements RangeComparator { private final Comparator<T> comparator; private final Supplier<T> currentKeySupplier; private final T start; private final T stop; JavaRangeComparator( final KeyRange<T> range, final Comparator<T> comparator, final Supplier<T> currentKeySupplier) { this.comparator = comparator; this.currentKeySupplier = currentKeySupplier; this.start = range.getStart(); this.stop = range.getStop(); } @Override public int compareToStartKey() { return comparator.compare(currentKeySupplier.get(), start); } @Override public int compareToStopKey() { return comparator.compare(currentKeySupplier.get(), stop); } @Override public void close() throws Exception { // Nothing to close } } /** * Calls down to mdb_cmp to make use of the comparator that LMDB uses for insertion order. Has a * very slight overhead as compared to {@link JavaRangeComparator}. */ private static class LmdbRangeComparator<T> implements RangeComparator { private final Pointer txnPointer; private final Pointer dbiPointer; private final Pointer cursorKeyPointer; private final Key<T> startKey; private final Key<T> stopKey; private final Pointer startKeyPointer; private final Pointer stopKeyPointer; public LmdbRangeComparator( final Txn<T> txn, final Dbi<T> dbi, final Cursor<T> cursor, final KeyRange<T> range, final BufferProxy<T> proxy) { txnPointer = Objects.requireNonNull(txn).pointer(); dbiPointer = Objects.requireNonNull(dbi).pointer(); cursorKeyPointer = Objects.requireNonNull(cursor).keyVal().pointerKey(); // Allocate buffers for use with the start/stop keys if required. // Saves us copying bytes on each comparison Objects.requireNonNull(range); startKey = createKey(range.getStart(), proxy); stopKey = createKey(range.getStop(), proxy); startKeyPointer = startKey != null ? startKey.pointer() : null; stopKeyPointer = stopKey != null ? stopKey.pointer() : null; } @Override public int compareToStartKey() { return LIB.mdb_cmp(txnPointer, dbiPointer, cursorKeyPointer, startKeyPointer); } @Override public int compareToStopKey() { return LIB.mdb_cmp(txnPointer, dbiPointer, cursorKeyPointer, stopKeyPointer); } @Override public void close() { if (startKey != null) { startKey.close(); } if (stopKey != null) { stopKey.close(); } } private Key<T> createKey(final T keyBuffer, final BufferProxy<T> proxy) { if (keyBuffer != null) { final Key<T> key = proxy.key(); key.keyIn(keyBuffer); return key; } else { return null; } } } } |
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