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
026 import java.io.Serializable;
027 import java.util.AbstractList;
028 import java.util.Arrays;
029 import java.util.Collection;
030 import java.util.Collections;
031 import java.util.Comparator;
032 import java.util.List;
033 import java.util.RandomAccess;
034
035 /**
036 * Static utility methods pertaining to {@code long} primitives, that are not
037 * already found in either {@link Long} or {@link Arrays}.
038 *
039 * <p>See the Guava User Guide article on <a href=
040 * "http://code.google.com/p/guava-libraries/wiki/PrimitivesExplained">
041 * primitive utilities</a>.
042 *
043 * @author Kevin Bourrillion
044 * @since 1.0
045 */
046 @GwtCompatible
047 public final class Longs {
048 private Longs() {}
049
050 /**
051 * The number of bytes required to represent a primitive {@code long}
052 * value.
053 */
054 public static final int BYTES = Long.SIZE / Byte.SIZE;
055
056 /**
057 * The largest power of two that can be represented as a {@code long}.
058 *
059 * @since 10.0
060 */
061 public static final long MAX_POWER_OF_TWO = 1L << (Long.SIZE - 2);
062
063 /**
064 * Returns a hash code for {@code value}; equal to the result of invoking
065 * {@code ((Long) value).hashCode()}.
066 *
067 * <p>This method always return the value specified by {@link
068 * Long#hashCode()} in java, which might be different from
069 * {@code ((Long) value).hashCode()} in GWT because {@link Long#hashCode()}
070 * in GWT does not obey the JRE contract.
071 *
072 * @param value a primitive {@code long} value
073 * @return a hash code for the value
074 */
075 public static int hashCode(long value) {
076 return (int) (value ^ (value >>> 32));
077 }
078
079 /**
080 * Compares the two specified {@code long} values. The sign of the value
081 * returned is the same as that of {@code ((Long) a).compareTo(b)}.
082 *
083 * @param a the first {@code long} to compare
084 * @param b the second {@code long} to compare
085 * @return a negative value if {@code a} is less than {@code b}; a positive
086 * value if {@code a} is greater than {@code b}; or zero if they are equal
087 */
088 public static int compare(long a, long b) {
089 return (a < b) ? -1 : ((a > b) ? 1 : 0);
090 }
091
092 /**
093 * Returns {@code true} if {@code target} is present as an element anywhere in
094 * {@code array}.
095 *
096 * @param array an array of {@code long} values, possibly empty
097 * @param target a primitive {@code long} value
098 * @return {@code true} if {@code array[i] == target} for some value of {@code
099 * i}
100 */
101 public static boolean contains(long[] array, long target) {
102 for (long value : array) {
103 if (value == target) {
104 return true;
105 }
106 }
107 return false;
108 }
109
110 /**
111 * Returns the index of the first appearance of the value {@code target} in
112 * {@code array}.
113 *
114 * @param array an array of {@code long} values, possibly empty
115 * @param target a primitive {@code long} value
116 * @return the least index {@code i} for which {@code array[i] == target}, or
117 * {@code -1} if no such index exists.
118 */
119 public static int indexOf(long[] array, long target) {
120 return indexOf(array, target, 0, array.length);
121 }
122
123 // TODO(kevinb): consider making this public
124 private static int indexOf(
125 long[] array, long target, int start, int end) {
126 for (int i = start; i < end; i++) {
127 if (array[i] == target) {
128 return i;
129 }
130 }
131 return -1;
132 }
133
134 /**
135 * Returns the start position of the first occurrence of the specified {@code
136 * target} within {@code array}, or {@code -1} if there is no such occurrence.
137 *
138 * <p>More formally, returns the lowest index {@code i} such that {@code
139 * java.util.Arrays.copyOfRange(array, i, i + target.length)} contains exactly
140 * the same elements as {@code target}.
141 *
142 * @param array the array to search for the sequence {@code target}
143 * @param target the array to search for as a sub-sequence of {@code array}
144 */
145 public static int indexOf(long[] array, long[] target) {
146 checkNotNull(array, "array");
147 checkNotNull(target, "target");
148 if (target.length == 0) {
149 return 0;
150 }
151
152 outer:
153 for (int i = 0; i < array.length - target.length + 1; i++) {
154 for (int j = 0; j < target.length; j++) {
155 if (array[i + j] != target[j]) {
156 continue outer;
157 }
158 }
159 return i;
160 }
161 return -1;
162 }
163
164 /**
165 * Returns the index of the last appearance of the value {@code target} in
166 * {@code array}.
167 *
168 * @param array an array of {@code long} values, possibly empty
169 * @param target a primitive {@code long} value
170 * @return the greatest index {@code i} for which {@code array[i] == target},
171 * or {@code -1} if no such index exists.
172 */
173 public static int lastIndexOf(long[] array, long target) {
174 return lastIndexOf(array, target, 0, array.length);
175 }
176
177 // TODO(kevinb): consider making this public
178 private static int lastIndexOf(
179 long[] array, long target, int start, int end) {
180 for (int i = end - 1; i >= start; i--) {
181 if (array[i] == target) {
182 return i;
183 }
184 }
185 return -1;
186 }
187
188 /**
189 * Returns the least value present in {@code array}.
190 *
191 * @param array a <i>nonempty</i> array of {@code long} values
192 * @return the value present in {@code array} that is less than or equal to
193 * every other value in the array
194 * @throws IllegalArgumentException if {@code array} is empty
195 */
196 public static long min(long... array) {
197 checkArgument(array.length > 0);
198 long min = array[0];
199 for (int i = 1; i < array.length; i++) {
200 if (array[i] < min) {
201 min = array[i];
202 }
203 }
204 return min;
205 }
206
207 /**
208 * Returns the greatest value present in {@code array}.
209 *
210 * @param array a <i>nonempty</i> array of {@code long} values
211 * @return the value present in {@code array} that is greater than or equal to
212 * every other value in the array
213 * @throws IllegalArgumentException if {@code array} is empty
214 */
215 public static long max(long... array) {
216 checkArgument(array.length > 0);
217 long max = array[0];
218 for (int i = 1; i < array.length; i++) {
219 if (array[i] > max) {
220 max = array[i];
221 }
222 }
223 return max;
224 }
225
226 /**
227 * Returns the values from each provided array combined into a single array.
228 * For example, {@code concat(new long[] {a, b}, new long[] {}, new
229 * long[] {c}} returns the array {@code {a, b, c}}.
230 *
231 * @param arrays zero or more {@code long} arrays
232 * @return a single array containing all the values from the source arrays, in
233 * order
234 */
235 public static long[] concat(long[]... arrays) {
236 int length = 0;
237 for (long[] array : arrays) {
238 length += array.length;
239 }
240 long[] result = new long[length];
241 int pos = 0;
242 for (long[] array : arrays) {
243 System.arraycopy(array, 0, result, pos, array.length);
244 pos += array.length;
245 }
246 return result;
247 }
248
249 /**
250 * Returns a big-endian representation of {@code value} in an 8-element byte
251 * array; equivalent to {@code ByteBuffer.allocate(8).putLong(value).array()}.
252 * For example, the input value {@code 0x1213141516171819L} would yield the
253 * byte array {@code {0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19}}.
254 *
255 * <p>If you need to convert and concatenate several values (possibly even of
256 * different types), use a shared {@link java.nio.ByteBuffer} instance, or use
257 * {@link com.google.common.io.ByteStreams#newDataOutput()} to get a growable
258 * buffer.
259 */
260 public static byte[] toByteArray(long value) {
261 // Note that this code needs to stay compatible with GWT, which has known
262 // bugs when narrowing byte casts of long values occur.
263 byte[] result = new byte[8];
264 for (int i = 7; i >= 0; i--) {
265 result[i] = (byte) (value & 0xffL);
266 value >>= 8;
267 }
268 return result;
269 }
270
271 /**
272 * Returns the {@code long} value whose big-endian representation is
273 * stored in the first 8 bytes of {@code bytes}; equivalent to {@code
274 * ByteBuffer.wrap(bytes).getLong()}. For example, the input byte array
275 * {@code {0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19}} would yield the
276 * {@code long} value {@code 0x1213141516171819L}.
277 *
278 * <p>Arguably, it's preferable to use {@link java.nio.ByteBuffer}; that
279 * library exposes much more flexibility at little cost in readability.
280 *
281 * @throws IllegalArgumentException if {@code bytes} has fewer than 8
282 * elements
283 */
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 public static long fromBytes(byte b1, byte b2, byte b3, byte b4,
299 byte b5, byte b6, byte b7, byte b8) {
300 return (b1 & 0xFFL) << 56
301 | (b2 & 0xFFL) << 48
302 | (b3 & 0xFFL) << 40
303 | (b4 & 0xFFL) << 32
304 | (b5 & 0xFFL) << 24
305 | (b6 & 0xFFL) << 16
306 | (b7 & 0xFFL) << 8
307 | (b8 & 0xFFL);
308 }
309
310 /**
311 * Returns an array containing the same values as {@code array}, but
312 * guaranteed to be of a specified minimum length. If {@code array} already
313 * has a length of at least {@code minLength}, it is returned directly.
314 * Otherwise, a new array of size {@code minLength + padding} is returned,
315 * containing the values of {@code array}, and zeroes in the remaining places.
316 *
317 * @param array the source array
318 * @param minLength the minimum length the returned array must guarantee
319 * @param padding an extra amount to "grow" the array by if growth is
320 * necessary
321 * @throws IllegalArgumentException if {@code minLength} or {@code padding} is
322 * negative
323 * @return an array containing the values of {@code array}, with guaranteed
324 * minimum length {@code minLength}
325 */
326 public static long[] ensureCapacity(
327 long[] array, int minLength, int padding) {
328 checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
329 checkArgument(padding >= 0, "Invalid padding: %s", padding);
330 return (array.length < minLength)
331 ? copyOf(array, minLength + padding)
332 : array;
333 }
334
335 // Arrays.copyOf() requires Java 6
336 private static long[] copyOf(long[] original, int length) {
337 long[] copy = new long[length];
338 System.arraycopy(original, 0, copy, 0, Math.min(original.length, length));
339 return copy;
340 }
341
342 /**
343 * Returns a string containing the supplied {@code long} values separated
344 * by {@code separator}. For example, {@code join("-", 1L, 2L, 3L)} returns
345 * the string {@code "1-2-3"}.
346 *
347 * @param separator the text that should appear between consecutive values in
348 * the resulting string (but not at the start or end)
349 * @param array an array of {@code long} values, possibly empty
350 */
351 public static String join(String separator, long... array) {
352 checkNotNull(separator);
353 if (array.length == 0) {
354 return "";
355 }
356
357 // For pre-sizing a builder, just get the right order of magnitude
358 StringBuilder builder = new StringBuilder(array.length * 10);
359 builder.append(array[0]);
360 for (int i = 1; i < array.length; i++) {
361 builder.append(separator).append(array[i]);
362 }
363 return builder.toString();
364 }
365
366 /**
367 * Returns a comparator that compares two {@code long} arrays
368 * lexicographically. That is, it compares, using {@link
369 * #compare(long, long)}), the first pair of values that follow any
370 * common prefix, or when one array is a prefix of the other, treats the
371 * shorter array as the lesser. For example,
372 * {@code [] < [1L] < [1L, 2L] < [2L]}.
373 *
374 * <p>The returned comparator is inconsistent with {@link
375 * Object#equals(Object)} (since arrays support only identity equality), but
376 * it is consistent with {@link Arrays#equals(long[], long[])}.
377 *
378 * @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order">
379 * Lexicographical order article at Wikipedia</a>
380 * @since 2.0
381 */
382 public static Comparator<long[]> lexicographicalComparator() {
383 return LexicographicalComparator.INSTANCE;
384 }
385
386 private enum LexicographicalComparator implements Comparator<long[]> {
387 INSTANCE;
388
389 @Override
390 public int compare(long[] left, long[] right) {
391 int minLength = Math.min(left.length, right.length);
392 for (int i = 0; i < minLength; i++) {
393 int result = Longs.compare(left[i], right[i]);
394 if (result != 0) {
395 return result;
396 }
397 }
398 return left.length - right.length;
399 }
400 }
401
402 /**
403 * Returns an array containing each value of {@code collection}, converted to
404 * a {@code long} value in the manner of {@link Number#longValue}.
405 *
406 * <p>Elements are copied from the argument collection as if by {@code
407 * collection.toArray()}. Calling this method is as thread-safe as calling
408 * that method.
409 *
410 * @param collection a collection of {@code Number} instances
411 * @return an array containing the same values as {@code collection}, in the
412 * same order, converted to primitives
413 * @throws NullPointerException if {@code collection} or any of its elements
414 * is null
415 * @since 1.0 (parameter was {@code Collection<Long>} before 12.0)
416 */
417 public static long[] toArray(Collection<? extends Number> 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] = ((Number) checkNotNull(boxedArray[i])).longValue();
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 // checkNotNull for GWT (do not optimize)
515 array[start + index] = checkNotNull(element);
516 return oldValue;
517 }
518
519 @Override public List<Long> subList(int fromIndex, int toIndex) {
520 int size = size();
521 checkPositionIndexes(fromIndex, toIndex, size);
522 if (fromIndex == toIndex) {
523 return Collections.emptyList();
524 }
525 return new LongArrayAsList(array, start + fromIndex, start + toIndex);
526 }
527
528 @Override public boolean equals(Object object) {
529 if (object == this) {
530 return true;
531 }
532 if (object instanceof LongArrayAsList) {
533 LongArrayAsList that = (LongArrayAsList) object;
534 int size = size();
535 if (that.size() != size) {
536 return false;
537 }
538 for (int i = 0; i < size; i++) {
539 if (array[start + i] != that.array[that.start + i]) {
540 return false;
541 }
542 }
543 return true;
544 }
545 return super.equals(object);
546 }
547
548 @Override public int hashCode() {
549 int result = 1;
550 for (int i = start; i < end; i++) {
551 result = 31 * result + Longs.hashCode(array[i]);
552 }
553 return result;
554 }
555
556 @Override public String toString() {
557 StringBuilder builder = new StringBuilder(size() * 10);
558 builder.append('[').append(array[start]);
559 for (int i = start + 1; i < end; i++) {
560 builder.append(", ").append(array[i]);
561 }
562 return builder.append(']').toString();
563 }
564
565 long[] toLongArray() {
566 // Arrays.copyOfRange() is not available under GWT
567 int size = size();
568 long[] result = new long[size];
569 System.arraycopy(array, start, result, 0, size);
570 return result;
571 }
572
573 private static final long serialVersionUID = 0;
574 }
575 }