001/* 002 * Copyright (C) 2017 The Guava Authors 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except 005 * in compliance with the License. You may obtain a copy of the License at 006 * 007 * http://www.apache.org/licenses/LICENSE-2.0 008 * 009 * Unless required by applicable law or agreed to in writing, software distributed under the License 010 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express 011 * or implied. See the License for the specific language governing permissions and limitations under 012 * the License. 013 */ 014 015package com.google.common.primitives; 016 017import static com.google.common.base.Preconditions.checkArgument; 018import static com.google.common.base.Preconditions.checkNotNull; 019 020import com.google.common.annotations.Beta; 021import com.google.common.annotations.GwtCompatible; 022import com.google.common.base.Preconditions; 023import com.google.errorprone.annotations.CanIgnoreReturnValue; 024import com.google.errorprone.annotations.CheckReturnValue; 025import com.google.errorprone.annotations.Immutable; 026import java.io.Serializable; 027import java.util.AbstractList; 028import java.util.Arrays; 029import java.util.Collection; 030import java.util.List; 031import java.util.RandomAccess; 032import java.util.Spliterator; 033import java.util.Spliterators; 034import java.util.function.LongConsumer; 035import java.util.stream.LongStream; 036import org.checkerframework.checker.nullness.compatqual.NullableDecl; 037 038/** 039 * An immutable array of {@code long} values, with an API resembling {@link List}. 040 * 041 * <p>Advantages compared to {@code long[]}: 042 * 043 * <ul> 044 * <li>All the many well-known advantages of immutability (read <i>Effective Java</i>, second 045 * edition, Item 15). 046 * <li>Has the value-based (not identity-based) {@link #equals}, {@link #hashCode}, and {@link 047 * #toString} behavior you expect. 048 * <li>Offers useful operations beyond just {@code get} and {@code length}, so you don't have to 049 * hunt through classes like {@link Arrays} and {@link Longs} for them. 050 * <li>Supports a copy-free {@link #subArray} view, so methods that accept this type don't need to 051 * add overloads that accept start and end indexes. 052 * <li>Can be streamed without "breaking the chain": {@code foo.getBarLongs().stream()...}. 053 * <li>Access to all collection-based utilities via {@link #asList} (though at the cost of 054 * allocating garbage). 055 * </ul> 056 * 057 * <p>Disadvantages compared to {@code long[]}: 058 * 059 * <ul> 060 * <li>Memory footprint has a fixed overhead (about 24 bytes per instance). 061 * <li><i>Some</i> construction use cases force the data to be copied (though several construction 062 * APIs are offered that don't). 063 * <li>Can't be passed directly to methods that expect {@code long[]} (though the most common 064 * utilities do have replacements here). 065 * <li>Dependency on {@code com.google.common} / Guava. 066 * </ul> 067 * 068 * <p>Advantages compared to {@link com.google.common.collect.ImmutableList ImmutableList}{@code 069 * <Long>}: 070 * 071 * <ul> 072 * <li>Improved memory compactness and locality. 073 * <li>Can be queried without allocating garbage. 074 * <li>Access to {@code LongStream} features (like {@link LongStream#sum}) using {@code stream()} 075 * instead of the awkward {@code stream().mapToLong(v -> v)}. 076 * </ul> 077 * 078 * <p>Disadvantages compared to {@code ImmutableList<Long>}: 079 * 080 * <ul> 081 * <li>Can't be passed directly to methods that expect {@code Iterable}, {@code Collection}, or 082 * {@code List} (though the most common utilities do have replacements here, and there is a 083 * lazy {@link #asList} view). 084 * </ul> 085 * 086 * @since 22.0 087 */ 088@Beta 089@GwtCompatible 090@Immutable 091public final class ImmutableLongArray implements Serializable { 092 private static final ImmutableLongArray EMPTY = new ImmutableLongArray(new long[0]); 093 094 /** Returns the empty array. */ 095 public static ImmutableLongArray of() { 096 return EMPTY; 097 } 098 099 /** Returns an immutable array containing a single value. */ 100 public static ImmutableLongArray of(long e0) { 101 return new ImmutableLongArray(new long[] {e0}); 102 } 103 104 /** Returns an immutable array containing the given values, in order. */ 105 public static ImmutableLongArray of(long e0, long e1) { 106 return new ImmutableLongArray(new long[] {e0, e1}); 107 } 108 109 /** Returns an immutable array containing the given values, in order. */ 110 public static ImmutableLongArray of(long e0, long e1, long e2) { 111 return new ImmutableLongArray(new long[] {e0, e1, e2}); 112 } 113 114 /** Returns an immutable array containing the given values, in order. */ 115 public static ImmutableLongArray of(long e0, long e1, long e2, long e3) { 116 return new ImmutableLongArray(new long[] {e0, e1, e2, e3}); 117 } 118 119 /** Returns an immutable array containing the given values, in order. */ 120 public static ImmutableLongArray of(long e0, long e1, long e2, long e3, long e4) { 121 return new ImmutableLongArray(new long[] {e0, e1, e2, e3, e4}); 122 } 123 124 /** Returns an immutable array containing the given values, in order. */ 125 public static ImmutableLongArray of(long e0, long e1, long e2, long e3, long e4, long e5) { 126 return new ImmutableLongArray(new long[] {e0, e1, e2, e3, e4, e5}); 127 } 128 129 // TODO(kevinb): go up to 11? 130 131 /** Returns an immutable array containing the given values, in order. */ 132 // Use (first, rest) so that `of(someLongArray)` won't compile (they should use copyOf), which is 133 // okay since we have to copy the just-created array anyway. 134 public static ImmutableLongArray of(long first, long... rest) { 135 long[] array = new long[rest.length + 1]; 136 array[0] = first; 137 System.arraycopy(rest, 0, array, 1, rest.length); 138 return new ImmutableLongArray(array); 139 } 140 141 /** Returns an immutable array containing the given values, in order. */ 142 public static ImmutableLongArray copyOf(long[] values) { 143 return values.length == 0 144 ? EMPTY 145 : new ImmutableLongArray(Arrays.copyOf(values, values.length)); 146 } 147 148 /** Returns an immutable array containing the given values, in order. */ 149 public static ImmutableLongArray copyOf(Collection<Long> values) { 150 return values.isEmpty() ? EMPTY : new ImmutableLongArray(Longs.toArray(values)); 151 } 152 153 /** 154 * Returns an immutable array containing the given values, in order. 155 * 156 * <p><b>Performance note:</b> this method delegates to {@link #copyOf(Collection)} if {@code 157 * values} is a {@link Collection}. Otherwise it creates a {@link #builder} and uses {@link 158 * Builder#addAll(Iterable)}, with all the performance implications associated with that. 159 */ 160 public static ImmutableLongArray copyOf(Iterable<Long> values) { 161 if (values instanceof Collection) { 162 return copyOf((Collection<Long>) values); 163 } 164 return builder().addAll(values).build(); 165 } 166 167 /** Returns an immutable array containing all the values from {@code stream}, in order. */ 168 public static ImmutableLongArray copyOf(LongStream stream) { 169 // Note this uses very different growth behavior from copyOf(Iterable) and the builder. 170 long[] array = stream.toArray(); 171 return (array.length == 0) ? EMPTY : new ImmutableLongArray(array); 172 } 173 174 /** 175 * Returns a new, empty builder for {@link ImmutableLongArray} instances, sized to hold up to 176 * {@code initialCapacity} values without resizing. The returned builder is not thread-safe. 177 * 178 * <p><b>Performance note:</b> When feasible, {@code initialCapacity} should be the exact number 179 * of values that will be added, if that knowledge is readily available. It is better to guess a 180 * value slightly too high than slightly too low. If the value is not exact, the {@link 181 * ImmutableLongArray} that is built will very likely occupy more memory than strictly necessary; 182 * to trim memory usage, build using {@code builder.build().trimmed()}. 183 */ 184 public static Builder builder(int initialCapacity) { 185 checkArgument(initialCapacity >= 0, "Invalid initialCapacity: %s", initialCapacity); 186 return new Builder(initialCapacity); 187 } 188 189 /** 190 * Returns a new, empty builder for {@link ImmutableLongArray} instances, with a default initial 191 * capacity. The returned builder is not thread-safe. 192 * 193 * <p><b>Performance note:</b> The {@link ImmutableLongArray} that is built will very likely 194 * occupy more memory than necessary; to trim memory usage, build using {@code 195 * builder.build().trimmed()}. 196 */ 197 public static Builder builder() { 198 return new Builder(10); 199 } 200 201 /** 202 * A builder for {@link ImmutableLongArray} instances; obtained using {@link 203 * ImmutableLongArray#builder}. 204 */ 205 @CanIgnoreReturnValue 206 public static final class Builder { 207 private long[] array; 208 private int count = 0; // <= array.length 209 210 Builder(int initialCapacity) { 211 array = new long[initialCapacity]; 212 } 213 214 /** 215 * Appends {@code value} to the end of the values the built {@link ImmutableLongArray} will 216 * contain. 217 */ 218 public Builder add(long value) { 219 ensureRoomFor(1); 220 array[count] = value; 221 count += 1; 222 return this; 223 } 224 225 /** 226 * Appends {@code values}, in order, to the end of the values the built {@link 227 * ImmutableLongArray} will contain. 228 */ 229 public Builder addAll(long[] values) { 230 ensureRoomFor(values.length); 231 System.arraycopy(values, 0, array, count, values.length); 232 count += values.length; 233 return this; 234 } 235 236 /** 237 * Appends {@code values}, in order, to the end of the values the built {@link 238 * ImmutableLongArray} will contain. 239 */ 240 public Builder addAll(Iterable<Long> values) { 241 if (values instanceof Collection) { 242 return addAll((Collection<Long>) values); 243 } 244 for (Long value : values) { 245 add(value); 246 } 247 return this; 248 } 249 250 /** 251 * Appends {@code values}, in order, to the end of the values the built {@link 252 * ImmutableLongArray} will contain. 253 */ 254 public Builder addAll(Collection<Long> values) { 255 ensureRoomFor(values.size()); 256 for (Long value : values) { 257 array[count++] = value; 258 } 259 return this; 260 } 261 262 /** 263 * Appends all values from {@code stream}, in order, to the end of the values the built {@link 264 * ImmutableLongArray} will contain. 265 */ 266 public Builder addAll(LongStream stream) { 267 Spliterator.OfLong spliterator = stream.spliterator(); 268 long size = spliterator.getExactSizeIfKnown(); 269 if (size > 0) { // known *and* nonempty 270 ensureRoomFor(Ints.saturatedCast(size)); 271 } 272 spliterator.forEachRemaining((LongConsumer) this::add); 273 return this; 274 } 275 276 /** 277 * Appends {@code values}, in order, to the end of the values the built {@link 278 * ImmutableLongArray} will contain. 279 */ 280 public Builder addAll(ImmutableLongArray values) { 281 ensureRoomFor(values.length()); 282 System.arraycopy(values.array, values.start, array, count, values.length()); 283 count += values.length(); 284 return this; 285 } 286 287 private void ensureRoomFor(int numberToAdd) { 288 int newCount = count + numberToAdd; // TODO(kevinb): check overflow now? 289 if (newCount > array.length) { 290 long[] newArray = new long[expandedCapacity(array.length, newCount)]; 291 System.arraycopy(array, 0, newArray, 0, count); 292 this.array = newArray; 293 } 294 } 295 296 // Unfortunately this is pasted from ImmutableCollection.Builder. 297 private static int expandedCapacity(int oldCapacity, int minCapacity) { 298 if (minCapacity < 0) { 299 throw new AssertionError("cannot store more than MAX_VALUE elements"); 300 } 301 // careful of overflow! 302 int newCapacity = oldCapacity + (oldCapacity >> 1) + 1; 303 if (newCapacity < minCapacity) { 304 newCapacity = Integer.highestOneBit(minCapacity - 1) << 1; 305 } 306 if (newCapacity < 0) { 307 newCapacity = Integer.MAX_VALUE; // guaranteed to be >= newCapacity 308 } 309 return newCapacity; 310 } 311 312 /** 313 * Returns a new immutable array. The builder can continue to be used after this call, to append 314 * more values and build again. 315 * 316 * <p><b>Performance note:</b> the returned array is backed by the same array as the builder, so 317 * no data is copied as part of this step, but this may occupy more memory than strictly 318 * necessary. To copy the data to a right-sized backing array, use {@code .build().trimmed()}. 319 */ 320 @CheckReturnValue 321 public ImmutableLongArray build() { 322 return count == 0 ? EMPTY : new ImmutableLongArray(array, 0, count); 323 } 324 } 325 326 // Instance stuff here 327 328 // The array is never mutated after storing in this field and the construction strategies ensure 329 // it doesn't escape this class 330 @SuppressWarnings("Immutable") 331 private final long[] array; 332 333 /* 334 * TODO(kevinb): evaluate the trade-offs of going bimorphic to save these two fields from most 335 * instances. Note that the instances that would get smaller are the right set to care about 336 * optimizing, because the rest have the option of calling `trimmed`. 337 */ 338 339 private final transient int start; // it happens that we only serialize instances where this is 0 340 private final int end; // exclusive 341 342 private ImmutableLongArray(long[] array) { 343 this(array, 0, array.length); 344 } 345 346 private ImmutableLongArray(long[] array, int start, int end) { 347 this.array = array; 348 this.start = start; 349 this.end = end; 350 } 351 352 /** Returns the number of values in this array. */ 353 public int length() { 354 return end - start; 355 } 356 357 /** Returns {@code true} if there are no values in this array ({@link #length} is zero). */ 358 public boolean isEmpty() { 359 return end == start; 360 } 361 362 /** 363 * Returns the {@code long} value present at the given index. 364 * 365 * @throws IndexOutOfBoundsException if {@code index} is negative, or greater than or equal to 366 * {@link #length} 367 */ 368 public long get(int index) { 369 Preconditions.checkElementIndex(index, length()); 370 return array[start + index]; 371 } 372 373 /** 374 * Returns the smallest index for which {@link #get} returns {@code target}, or {@code -1} if no 375 * such index exists. Equivalent to {@code asList().indexOf(target)}. 376 */ 377 public int indexOf(long target) { 378 for (int i = start; i < end; i++) { 379 if (array[i] == target) { 380 return i - start; 381 } 382 } 383 return -1; 384 } 385 386 /** 387 * Returns the largest index for which {@link #get} returns {@code target}, or {@code -1} if no 388 * such index exists. Equivalent to {@code asList().lastIndexOf(target)}. 389 */ 390 public int lastIndexOf(long target) { 391 for (int i = end - 1; i >= start; i--) { 392 if (array[i] == target) { 393 return i - start; 394 } 395 } 396 return -1; 397 } 398 399 /** 400 * Returns {@code true} if {@code target} is present at any index in this array. Equivalent to 401 * {@code asList().contains(target)}. 402 */ 403 public boolean contains(long target) { 404 return indexOf(target) >= 0; 405 } 406 407 /** Invokes {@code consumer} for each value contained in this array, in order. */ 408 public void forEach(LongConsumer consumer) { 409 checkNotNull(consumer); 410 for (int i = start; i < end; i++) { 411 consumer.accept(array[i]); 412 } 413 } 414 415 /** Returns a stream over the values in this array, in order. */ 416 public LongStream stream() { 417 return Arrays.stream(array, start, end); 418 } 419 420 /** Returns a new, mutable copy of this array's values, as a primitive {@code long[]}. */ 421 public long[] toArray() { 422 return Arrays.copyOfRange(array, start, end); 423 } 424 425 /** 426 * Returns a new immutable array containing the values in the specified range. 427 * 428 * <p><b>Performance note:</b> The returned array has the same full memory footprint as this one 429 * does (no actual copying is performed). To reduce memory usage, use {@code subArray(start, 430 * end).trimmed()}. 431 */ 432 public ImmutableLongArray subArray(int startIndex, int endIndex) { 433 Preconditions.checkPositionIndexes(startIndex, endIndex, length()); 434 return startIndex == endIndex 435 ? EMPTY 436 : new ImmutableLongArray(array, start + startIndex, start + endIndex); 437 } 438 439 private Spliterator.OfLong spliterator() { 440 return Spliterators.spliterator(array, start, end, Spliterator.IMMUTABLE | Spliterator.ORDERED); 441 } 442 443 /** 444 * Returns an immutable <i>view</i> of this array's values as a {@code List}; note that {@code 445 * long} values are boxed into {@link Long} instances on demand, which can be very expensive. The 446 * returned list should be used once and discarded. For any usages beyond that, pass the returned 447 * list to {@link com.google.common.collect.ImmutableList#copyOf(Collection) ImmutableList.copyOf} 448 * and use that list instead. 449 */ 450 public List<Long> asList() { 451 /* 452 * Typically we cache this kind of thing, but much repeated use of this view is a performance 453 * anti-pattern anyway. If we cache, then everyone pays a price in memory footprint even if 454 * they never use this method. 455 */ 456 return new AsList(this); 457 } 458 459 static class AsList extends AbstractList<Long> implements RandomAccess, Serializable { 460 private final ImmutableLongArray parent; 461 462 private AsList(ImmutableLongArray parent) { 463 this.parent = parent; 464 } 465 466 // inherit: isEmpty, containsAll, toArray x2, iterator, listIterator, stream, forEach, mutations 467 468 @Override 469 public int size() { 470 return parent.length(); 471 } 472 473 @Override 474 public Long get(int index) { 475 return parent.get(index); 476 } 477 478 @Override 479 public boolean contains(Object target) { 480 return indexOf(target) >= 0; 481 } 482 483 @Override 484 public int indexOf(Object target) { 485 return target instanceof Long ? parent.indexOf((Long) target) : -1; 486 } 487 488 @Override 489 public int lastIndexOf(Object target) { 490 return target instanceof Long ? parent.lastIndexOf((Long) target) : -1; 491 } 492 493 @Override 494 public List<Long> subList(int fromIndex, int toIndex) { 495 return parent.subArray(fromIndex, toIndex).asList(); 496 } 497 498 // The default List spliterator is not efficiently splittable 499 @Override 500 public Spliterator<Long> spliterator() { 501 return parent.spliterator(); 502 } 503 504 @Override 505 public boolean equals(@NullableDecl Object object) { 506 if (object instanceof AsList) { 507 AsList that = (AsList) object; 508 return this.parent.equals(that.parent); 509 } 510 // We could delegate to super now but it would still box too much 511 if (!(object instanceof List)) { 512 return false; 513 } 514 List<?> that = (List<?>) object; 515 if (this.size() != that.size()) { 516 return false; 517 } 518 int i = parent.start; 519 // Since `that` is very likely RandomAccess we could avoid allocating this iterator... 520 for (Object element : that) { 521 if (!(element instanceof Long) || parent.array[i++] != (Long) element) { 522 return false; 523 } 524 } 525 return true; 526 } 527 528 // Because we happen to use the same formula. If that changes, just don't override this. 529 @Override 530 public int hashCode() { 531 return parent.hashCode(); 532 } 533 534 @Override 535 public String toString() { 536 return parent.toString(); 537 } 538 } 539 540 /** 541 * Returns {@code true} if {@code object} is an {@code ImmutableLongArray} containing the same 542 * values as this one, in the same order. 543 */ 544 @Override 545 public boolean equals(@NullableDecl Object object) { 546 if (object == this) { 547 return true; 548 } 549 if (!(object instanceof ImmutableLongArray)) { 550 return false; 551 } 552 ImmutableLongArray that = (ImmutableLongArray) object; 553 if (this.length() != that.length()) { 554 return false; 555 } 556 for (int i = 0; i < length(); i++) { 557 if (this.get(i) != that.get(i)) { 558 return false; 559 } 560 } 561 return true; 562 } 563 564 /** Returns an unspecified hash code for the contents of this immutable array. */ 565 @Override 566 public int hashCode() { 567 int hash = 1; 568 for (int i = start; i < end; i++) { 569 hash *= 31; 570 hash += Longs.hashCode(array[i]); 571 } 572 return hash; 573 } 574 575 /** 576 * Returns a string representation of this array in the same form as {@link 577 * Arrays#toString(long[])}, for example {@code "[1, 2, 3]"}. 578 */ 579 @Override 580 public String toString() { 581 if (isEmpty()) { 582 return "[]"; 583 } 584 StringBuilder builder = new StringBuilder(length() * 5); // rough estimate is fine 585 builder.append('[').append(array[start]); 586 587 for (int i = start + 1; i < end; i++) { 588 builder.append(", ").append(array[i]); 589 } 590 builder.append(']'); 591 return builder.toString(); 592 } 593 594 /** 595 * Returns an immutable array containing the same values as {@code this} array. This is logically 596 * a no-op, and in some circumstances {@code this} itself is returned. However, if this instance 597 * is a {@link #subArray} view of a larger array, this method will copy only the appropriate range 598 * of values, resulting in an equivalent array with a smaller memory footprint. 599 */ 600 public ImmutableLongArray trimmed() { 601 return isPartialView() ? new ImmutableLongArray(toArray()) : this; 602 } 603 604 private boolean isPartialView() { 605 return start > 0 || end < array.length; 606 } 607 608 Object writeReplace() { 609 return trimmed(); 610 } 611 612 Object readResolve() { 613 return isEmpty() ? EMPTY : this; 614 } 615}