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