001 /*
002 * Copyright (C) 2008 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017 package com.google.common.primitives;
018
019 import static com.google.common.base.Preconditions.checkArgument;
020 import static com.google.common.base.Preconditions.checkElementIndex;
021 import static com.google.common.base.Preconditions.checkNotNull;
022 import static com.google.common.base.Preconditions.checkPositionIndexes;
023
024 import com.google.common.annotations.GwtCompatible;
025 import com.google.common.annotations.GwtIncompatible;
026
027 import java.io.Serializable;
028 import java.util.AbstractList;
029 import java.util.Arrays;
030 import java.util.Collection;
031 import java.util.Collections;
032 import java.util.Comparator;
033 import java.util.List;
034 import java.util.RandomAccess;
035
036 /**
037 * Static utility methods pertaining to {@code long} primitives, that are not
038 * already found in either {@link Long} or {@link Arrays}.
039 *
040 * <p>See the Guava User Guide article on <a href=
041 * "http://code.google.com/p/guava-libraries/wiki/PrimitivesExplained">
042 * primitive utilities</a>.
043 *
044 * @author Kevin Bourrillion
045 * @since 1.0
046 */
047 @GwtCompatible(emulated = true)
048 public final class Longs {
049 private Longs() {}
050
051 /**
052 * The number of bytes required to represent a primitive {@code long}
053 * value.
054 */
055 public static final int BYTES = Long.SIZE / Byte.SIZE;
056
057 /**
058 * The largest power of two that can be represented as a {@code long}.
059 *
060 * @since 10.0
061 */
062 public static final long MAX_POWER_OF_TWO = 1L << (Long.SIZE - 2);
063
064 /**
065 * Returns a hash code for {@code value}; equal to the result of invoking
066 * {@code ((Long) value).hashCode()}.
067 *
068 * <p>This method always return the value specified by {@link
069 * Long#hashCode()} in java, which might be different from
070 * {@code ((Long) value).hashCode()} in GWT because {@link Long#hashCode()}
071 * in GWT does not obey the JRE contract.
072 *
073 * @param value a primitive {@code long} value
074 * @return a hash code for the value
075 */
076 public static int hashCode(long value) {
077 return (int) (value ^ (value >>> 32));
078 }
079
080 /**
081 * Compares the two specified {@code long} values. The sign of the value
082 * returned is the same as that of {@code ((Long) a).compareTo(b)}.
083 *
084 * @param a the first {@code long} to compare
085 * @param b the second {@code long} to compare
086 * @return a negative value if {@code a} is less than {@code b}; a positive
087 * value if {@code a} is greater than {@code b}; or zero if they are equal
088 */
089 public static int compare(long a, long b) {
090 return (a < b) ? -1 : ((a > b) ? 1 : 0);
091 }
092
093 /**
094 * Returns {@code true} if {@code target} is present as an element anywhere in
095 * {@code array}.
096 *
097 * @param array an array of {@code long} values, possibly empty
098 * @param target a primitive {@code long} value
099 * @return {@code true} if {@code array[i] == target} for some value of {@code
100 * i}
101 */
102 public static boolean contains(long[] array, long target) {
103 for (long value : array) {
104 if (value == target) {
105 return true;
106 }
107 }
108 return false;
109 }
110
111 /**
112 * Returns the index of the first appearance of the value {@code target} in
113 * {@code array}.
114 *
115 * @param array an array of {@code long} values, possibly empty
116 * @param target a primitive {@code long} value
117 * @return the least index {@code i} for which {@code array[i] == target}, or
118 * {@code -1} if no such index exists.
119 */
120 public static int indexOf(long[] array, long target) {
121 return indexOf(array, target, 0, array.length);
122 }
123
124 // TODO(kevinb): consider making this public
125 private static int indexOf(
126 long[] array, long target, int start, int end) {
127 for (int i = start; i < end; i++) {
128 if (array[i] == target) {
129 return i;
130 }
131 }
132 return -1;
133 }
134
135 /**
136 * Returns the start position of the first occurrence of the specified {@code
137 * target} within {@code array}, or {@code -1} if there is no such occurrence.
138 *
139 * <p>More formally, returns the lowest index {@code i} such that {@code
140 * java.util.Arrays.copyOfRange(array, i, i + target.length)} contains exactly
141 * the same elements as {@code target}.
142 *
143 * @param array the array to search for the sequence {@code target}
144 * @param target the array to search for as a sub-sequence of {@code array}
145 */
146 public static int indexOf(long[] array, long[] target) {
147 checkNotNull(array, "array");
148 checkNotNull(target, "target");
149 if (target.length == 0) {
150 return 0;
151 }
152
153 outer:
154 for (int i = 0; i < array.length - target.length + 1; i++) {
155 for (int j = 0; j < target.length; j++) {
156 if (array[i + j] != target[j]) {
157 continue outer;
158 }
159 }
160 return i;
161 }
162 return -1;
163 }
164
165 /**
166 * Returns the index of the last appearance of the value {@code target} in
167 * {@code array}.
168 *
169 * @param array an array of {@code long} values, possibly empty
170 * @param target a primitive {@code long} value
171 * @return the greatest index {@code i} for which {@code array[i] == target},
172 * or {@code -1} if no such index exists.
173 */
174 public static int lastIndexOf(long[] array, long target) {
175 return lastIndexOf(array, target, 0, array.length);
176 }
177
178 // TODO(kevinb): consider making this public
179 private static int lastIndexOf(
180 long[] array, long target, int start, int end) {
181 for (int i = end - 1; i >= start; i--) {
182 if (array[i] == target) {
183 return i;
184 }
185 }
186 return -1;
187 }
188
189 /**
190 * Returns the least value present in {@code array}.
191 *
192 * @param array a <i>nonempty</i> array of {@code long} values
193 * @return the value present in {@code array} that is less than or equal to
194 * every other value in the array
195 * @throws IllegalArgumentException if {@code array} is empty
196 */
197 public static long min(long... array) {
198 checkArgument(array.length > 0);
199 long min = array[0];
200 for (int i = 1; i < array.length; i++) {
201 if (array[i] < min) {
202 min = array[i];
203 }
204 }
205 return min;
206 }
207
208 /**
209 * Returns the greatest value present in {@code array}.
210 *
211 * @param array a <i>nonempty</i> array of {@code long} values
212 * @return the value present in {@code array} that is greater than or equal to
213 * every other value in the array
214 * @throws IllegalArgumentException if {@code array} is empty
215 */
216 public static long max(long... array) {
217 checkArgument(array.length > 0);
218 long max = array[0];
219 for (int i = 1; i < array.length; i++) {
220 if (array[i] > max) {
221 max = array[i];
222 }
223 }
224 return max;
225 }
226
227 /**
228 * Returns the values from each provided array combined into a single array.
229 * For example, {@code concat(new long[] {a, b}, new long[] {}, new
230 * long[] {c}} returns the array {@code {a, b, c}}.
231 *
232 * @param arrays zero or more {@code long} arrays
233 * @return a single array containing all the values from the source arrays, in
234 * order
235 */
236 public static long[] concat(long[]... arrays) {
237 int length = 0;
238 for (long[] array : arrays) {
239 length += array.length;
240 }
241 long[] result = new long[length];
242 int pos = 0;
243 for (long[] array : arrays) {
244 System.arraycopy(array, 0, result, pos, array.length);
245 pos += array.length;
246 }
247 return result;
248 }
249
250 /**
251 * Returns a big-endian representation of {@code value} in an 8-element byte
252 * array; equivalent to {@code ByteBuffer.allocate(8).putLong(value).array()}.
253 * For example, the input value {@code 0x1213141516171819L} would yield the
254 * byte array {@code {0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19}}.
255 *
256 * <p>If you need to convert and concatenate several values (possibly even of
257 * different types), use a shared {@link java.nio.ByteBuffer} instance, or use
258 * {@link com.google.common.io.ByteStreams#newDataOutput()} to get a growable
259 * buffer.
260 */
261 @GwtIncompatible("doesn't work")
262 public static byte[] toByteArray(long value) {
263 return new byte[] {
264 (byte) (value >> 56),
265 (byte) (value >> 48),
266 (byte) (value >> 40),
267 (byte) (value >> 32),
268 (byte) (value >> 24),
269 (byte) (value >> 16),
270 (byte) (value >> 8),
271 (byte) value};
272 }
273
274 /**
275 * Returns the {@code long} value whose big-endian representation is
276 * stored in the first 8 bytes of {@code bytes}; equivalent to {@code
277 * ByteBuffer.wrap(bytes).getLong()}. For example, the input byte array
278 * {@code {0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19}} would yield the
279 * {@code long} value {@code 0x1213141516171819L}.
280 *
281 * <p>Arguably, it's preferable to use {@link java.nio.ByteBuffer}; that
282 * library exposes much more flexibility at little cost in readability.
283 *
284 * @throws IllegalArgumentException if {@code bytes} has fewer than 8
285 * elements
286 */
287 @GwtIncompatible("doesn't work")
288 public static long fromByteArray(byte[] bytes) {
289 checkArgument(bytes.length >= BYTES,
290 "array too small: %s < %s", bytes.length, BYTES);
291 return fromBytes(bytes[0], bytes[1], bytes[2], bytes[3],
292 bytes[4], bytes[5], bytes[6], bytes[7]) ;
293 }
294
295 /**
296 * Returns the {@code long} value whose byte representation is the given 8
297 * bytes, in big-endian order; equivalent to {@code Longs.fromByteArray(new
298 * byte[] {b1, b2, b3, b4, b5, b6, b7, b8})}.
299 *
300 * @since 7.0
301 */
302 @GwtIncompatible("doesn't work")
303 public static long fromBytes(byte b1, byte b2, byte b3, byte b4,
304 byte b5, byte b6, byte b7, byte b8) {
305 return (b1 & 0xFFL) << 56
306 | (b2 & 0xFFL) << 48
307 | (b3 & 0xFFL) << 40
308 | (b4 & 0xFFL) << 32
309 | (b5 & 0xFFL) << 24
310 | (b6 & 0xFFL) << 16
311 | (b7 & 0xFFL) << 8
312 | (b8 & 0xFFL);
313 }
314
315 /**
316 * Returns an array containing the same values as {@code array}, but
317 * guaranteed to be of a specified minimum length. If {@code array} already
318 * has a length of at least {@code minLength}, it is returned directly.
319 * Otherwise, a new array of size {@code minLength + padding} is returned,
320 * containing the values of {@code array}, and zeroes in the remaining places.
321 *
322 * @param array the source array
323 * @param minLength the minimum length the returned array must guarantee
324 * @param padding an extra amount to "grow" the array by if growth is
325 * necessary
326 * @throws IllegalArgumentException if {@code minLength} or {@code padding} is
327 * negative
328 * @return an array containing the values of {@code array}, with guaranteed
329 * minimum length {@code minLength}
330 */
331 public static long[] ensureCapacity(
332 long[] array, int minLength, int padding) {
333 checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
334 checkArgument(padding >= 0, "Invalid padding: %s", padding);
335 return (array.length < minLength)
336 ? copyOf(array, minLength + padding)
337 : array;
338 }
339
340 // Arrays.copyOf() requires Java 6
341 private static long[] copyOf(long[] original, int length) {
342 long[] copy = new long[length];
343 System.arraycopy(original, 0, copy, 0, Math.min(original.length, length));
344 return copy;
345 }
346
347 /**
348 * Returns a string containing the supplied {@code long} values separated
349 * by {@code separator}. For example, {@code join("-", 1L, 2L, 3L)} returns
350 * the string {@code "1-2-3"}.
351 *
352 * @param separator the text that should appear between consecutive values in
353 * the resulting string (but not at the start or end)
354 * @param array an array of {@code long} values, possibly empty
355 */
356 public static String join(String separator, long... array) {
357 checkNotNull(separator);
358 if (array.length == 0) {
359 return "";
360 }
361
362 // For pre-sizing a builder, just get the right order of magnitude
363 StringBuilder builder = new StringBuilder(array.length * 10);
364 builder.append(array[0]);
365 for (int i = 1; i < array.length; i++) {
366 builder.append(separator).append(array[i]);
367 }
368 return builder.toString();
369 }
370
371 /**
372 * Returns a comparator that compares two {@code long} arrays
373 * lexicographically. That is, it compares, using {@link
374 * #compare(long, long)}), the first pair of values that follow any
375 * common prefix, or when one array is a prefix of the other, treats the
376 * shorter array as the lesser. For example,
377 * {@code [] < [1L] < [1L, 2L] < [2L]}.
378 *
379 * <p>The returned comparator is inconsistent with {@link
380 * Object#equals(Object)} (since arrays support only identity equality), but
381 * it is consistent with {@link Arrays#equals(long[], long[])}.
382 *
383 * @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order">
384 * Lexicographical order article at Wikipedia</a>
385 * @since 2.0
386 */
387 public static Comparator<long[]> lexicographicalComparator() {
388 return LexicographicalComparator.INSTANCE;
389 }
390
391 private enum LexicographicalComparator implements Comparator<long[]> {
392 INSTANCE;
393
394 @Override
395 public int compare(long[] left, long[] right) {
396 int minLength = Math.min(left.length, right.length);
397 for (int i = 0; i < minLength; i++) {
398 int result = Longs.compare(left[i], right[i]);
399 if (result != 0) {
400 return result;
401 }
402 }
403 return left.length - right.length;
404 }
405 }
406
407 /**
408 * Returns an array containing each value of {@code collection}, converted to
409 * a {@code long} value in the manner of {@link Number#longValue}.
410 *
411 * <p>Elements are copied from the argument collection as if by {@code
412 * collection.toArray()}. Calling this method is as thread-safe as calling
413 * that method.
414 *
415 * @param collection a collection of {@code Number} instances
416 * @return an array containing the same values as {@code collection}, in the
417 * same order, converted to primitives
418 * @throws NullPointerException if {@code collection} or any of its elements
419 * is null
420 * @since 1.0 (parameter was {@code Collection<Long>} before 12.0)
421 */
422 public static long[] toArray(Collection<? extends Number> collection) {
423 if (collection instanceof LongArrayAsList) {
424 return ((LongArrayAsList) collection).toLongArray();
425 }
426
427 Object[] boxedArray = collection.toArray();
428 int len = boxedArray.length;
429 long[] array = new long[len];
430 for (int i = 0; i < len; i++) {
431 // checkNotNull for GWT (do not optimize)
432 array[i] = ((Number) checkNotNull(boxedArray[i])).longValue();
433 }
434 return array;
435 }
436
437 /**
438 * Returns a fixed-size list backed by the specified array, similar to {@link
439 * Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)},
440 * but any attempt to set a value to {@code null} will result in a {@link
441 * NullPointerException}.
442 *
443 * <p>The returned list maintains the values, but not the identities, of
444 * {@code Long} objects written to or read from it. For example, whether
445 * {@code list.get(0) == list.get(0)} is true for the returned list is
446 * unspecified.
447 *
448 * @param backingArray the array to back the list
449 * @return a list view of the array
450 */
451 public static List<Long> asList(long... backingArray) {
452 if (backingArray.length == 0) {
453 return Collections.emptyList();
454 }
455 return new LongArrayAsList(backingArray);
456 }
457
458 @GwtCompatible
459 private static class LongArrayAsList extends AbstractList<Long>
460 implements RandomAccess, Serializable {
461 final long[] array;
462 final int start;
463 final int end;
464
465 LongArrayAsList(long[] array) {
466 this(array, 0, array.length);
467 }
468
469 LongArrayAsList(long[] array, int start, int end) {
470 this.array = array;
471 this.start = start;
472 this.end = end;
473 }
474
475 @Override public int size() {
476 return end - start;
477 }
478
479 @Override public boolean isEmpty() {
480 return false;
481 }
482
483 @Override public Long get(int index) {
484 checkElementIndex(index, size());
485 return array[start + index];
486 }
487
488 @Override public boolean contains(Object target) {
489 // Overridden to prevent a ton of boxing
490 return (target instanceof Long)
491 && Longs.indexOf(array, (Long) target, start, end) != -1;
492 }
493
494 @Override public int indexOf(Object target) {
495 // Overridden to prevent a ton of boxing
496 if (target instanceof Long) {
497 int i = Longs.indexOf(array, (Long) target, start, end);
498 if (i >= 0) {
499 return i - start;
500 }
501 }
502 return -1;
503 }
504
505 @Override public int lastIndexOf(Object target) {
506 // Overridden to prevent a ton of boxing
507 if (target instanceof Long) {
508 int i = Longs.lastIndexOf(array, (Long) target, start, end);
509 if (i >= 0) {
510 return i - start;
511 }
512 }
513 return -1;
514 }
515
516 @Override public Long set(int index, Long element) {
517 checkElementIndex(index, size());
518 long oldValue = array[start + index];
519 array[start + index] = checkNotNull(element); // checkNotNull for GWT (do not optimize)
520 return oldValue;
521 }
522
523 @Override public List<Long> subList(int fromIndex, int toIndex) {
524 int size = size();
525 checkPositionIndexes(fromIndex, toIndex, size);
526 if (fromIndex == toIndex) {
527 return Collections.emptyList();
528 }
529 return new LongArrayAsList(array, start + fromIndex, start + toIndex);
530 }
531
532 @Override public boolean equals(Object object) {
533 if (object == this) {
534 return true;
535 }
536 if (object instanceof LongArrayAsList) {
537 LongArrayAsList that = (LongArrayAsList) object;
538 int size = size();
539 if (that.size() != size) {
540 return false;
541 }
542 for (int i = 0; i < size; i++) {
543 if (array[start + i] != that.array[that.start + i]) {
544 return false;
545 }
546 }
547 return true;
548 }
549 return super.equals(object);
550 }
551
552 @Override public int hashCode() {
553 int result = 1;
554 for (int i = start; i < end; i++) {
555 result = 31 * result + Longs.hashCode(array[i]);
556 }
557 return result;
558 }
559
560 @Override public String toString() {
561 StringBuilder builder = new StringBuilder(size() * 10);
562 builder.append('[').append(array[start]);
563 for (int i = start + 1; i < end; i++) {
564 builder.append(", ").append(array[i]);
565 }
566 return builder.append(']').toString();
567 }
568
569 long[] toLongArray() {
570 // Arrays.copyOfRange() requires Java 6
571 int size = size();
572 long[] result = new long[size];
573 System.arraycopy(array, start, result, 0, size);
574 return result;
575 }
576
577 private static final long serialVersionUID = 0;
578 }
579 }