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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 short} primitives, that are not
038 * already found in either {@link Short} or {@link Arrays}.
039 *
040 * @author Kevin Bourrillion
041 * @since 1.0
042 */
043 @GwtCompatible(emulated = true)
044 public final class Shorts {
045 private Shorts() {}
046
047 /**
048 * The number of bytes required to represent a primitive {@code short}
049 * value.
050 */
051 public static final int BYTES = Short.SIZE / Byte.SIZE;
052
053 /**
054 * The largest power of two that can be represented as a {@code short}.
055 *
056 * @since 10.0
057 */
058 public static final short MAX_POWER_OF_TWO = 1 << (Short.SIZE - 2);
059
060 /**
061 * Returns a hash code for {@code value}; equal to the result of invoking
062 * {@code ((Short) value).hashCode()}.
063 *
064 * @param value a primitive {@code short} value
065 * @return a hash code for the value
066 */
067 public static int hashCode(short value) {
068 return value;
069 }
070
071 /**
072 * Returns the {@code short} value that is equal to {@code value}, if
073 * possible.
074 *
075 * @param value any value in the range of the {@code short} type
076 * @return the {@code short} value that equals {@code value}
077 * @throws IllegalArgumentException if {@code value} is greater than {@link
078 * Short#MAX_VALUE} or less than {@link Short#MIN_VALUE}
079 */
080 public static short checkedCast(long value) {
081 short result = (short) value;
082 checkArgument(result == value, "Out of range: %s", value);
083 return result;
084 }
085
086 /**
087 * Returns the {@code short} nearest in value to {@code value}.
088 *
089 * @param value any {@code long} value
090 * @return the same value cast to {@code short} if it is in the range of the
091 * {@code short} type, {@link Short#MAX_VALUE} if it is too large,
092 * or {@link Short#MIN_VALUE} if it is too small
093 */
094 public static short saturatedCast(long value) {
095 if (value > Short.MAX_VALUE) {
096 return Short.MAX_VALUE;
097 }
098 if (value < Short.MIN_VALUE) {
099 return Short.MIN_VALUE;
100 }
101 return (short) value;
102 }
103
104 /**
105 * Compares the two specified {@code short} values. The sign of the value
106 * returned is the same as that of {@code ((Short) a).compareTo(b)}.
107 *
108 * @param a the first {@code short} to compare
109 * @param b the second {@code short} to compare
110 * @return a negative value if {@code a} is less than {@code b}; a positive
111 * value if {@code a} is greater than {@code b}; or zero if they are equal
112 */
113 public static int compare(short a, short b) {
114 return a - b; // safe due to restricted range
115 }
116
117 /**
118 * Returns {@code true} if {@code target} is present as an element anywhere in
119 * {@code array}.
120 *
121 * @param array an array of {@code short} values, possibly empty
122 * @param target a primitive {@code short} value
123 * @return {@code true} if {@code array[i] == target} for some value of {@code
124 * i}
125 */
126 public static boolean contains(short[] array, short target) {
127 for (short value : array) {
128 if (value == target) {
129 return true;
130 }
131 }
132 return false;
133 }
134
135 /**
136 * Returns the index of the first appearance of the value {@code target} in
137 * {@code array}.
138 *
139 * @param array an array of {@code short} values, possibly empty
140 * @param target a primitive {@code short} value
141 * @return the least index {@code i} for which {@code array[i] == target}, or
142 * {@code -1} if no such index exists.
143 */
144 public static int indexOf(short[] array, short target) {
145 return indexOf(array, target, 0, array.length);
146 }
147
148 // TODO(kevinb): consider making this public
149 private static int indexOf(
150 short[] array, short target, int start, int end) {
151 for (int i = start; i < end; i++) {
152 if (array[i] == target) {
153 return i;
154 }
155 }
156 return -1;
157 }
158
159 /**
160 * Returns the start position of the first occurrence of the specified {@code
161 * target} within {@code array}, or {@code -1} if there is no such occurrence.
162 *
163 * <p>More formally, returns the lowest index {@code i} such that {@code
164 * java.util.Arrays.copyOfRange(array, i, i + target.length)} contains exactly
165 * the same elements as {@code target}.
166 *
167 * @param array the array to search for the sequence {@code target}
168 * @param target the array to search for as a sub-sequence of {@code array}
169 */
170 public static int indexOf(short[] array, short[] target) {
171 checkNotNull(array, "array");
172 checkNotNull(target, "target");
173 if (target.length == 0) {
174 return 0;
175 }
176
177 outer:
178 for (int i = 0; i < array.length - target.length + 1; i++) {
179 for (int j = 0; j < target.length; j++) {
180 if (array[i + j] != target[j]) {
181 continue outer;
182 }
183 }
184 return i;
185 }
186 return -1;
187 }
188
189 /**
190 * Returns the index of the last appearance of the value {@code target} in
191 * {@code array}.
192 *
193 * @param array an array of {@code short} values, possibly empty
194 * @param target a primitive {@code short} value
195 * @return the greatest index {@code i} for which {@code array[i] == target},
196 * or {@code -1} if no such index exists.
197 */
198 public static int lastIndexOf(short[] array, short target) {
199 return lastIndexOf(array, target, 0, array.length);
200 }
201
202 // TODO(kevinb): consider making this public
203 private static int lastIndexOf(
204 short[] array, short target, int start, int end) {
205 for (int i = end - 1; i >= start; i--) {
206 if (array[i] == target) {
207 return i;
208 }
209 }
210 return -1;
211 }
212
213 /**
214 * Returns the least value present in {@code array}.
215 *
216 * @param array a <i>nonempty</i> array of {@code short} values
217 * @return the value present in {@code array} that is less than or equal to
218 * every other value in the array
219 * @throws IllegalArgumentException if {@code array} is empty
220 */
221 public static short min(short... array) {
222 checkArgument(array.length > 0);
223 short min = array[0];
224 for (int i = 1; i < array.length; i++) {
225 if (array[i] < min) {
226 min = array[i];
227 }
228 }
229 return min;
230 }
231
232 /**
233 * Returns the greatest value present in {@code array}.
234 *
235 * @param array a <i>nonempty</i> array of {@code short} values
236 * @return the value present in {@code array} that is greater than or equal to
237 * every other value in the array
238 * @throws IllegalArgumentException if {@code array} is empty
239 */
240 public static short max(short... array) {
241 checkArgument(array.length > 0);
242 short max = array[0];
243 for (int i = 1; i < array.length; i++) {
244 if (array[i] > max) {
245 max = array[i];
246 }
247 }
248 return max;
249 }
250
251 /**
252 * Returns the values from each provided array combined into a single array.
253 * For example, {@code concat(new short[] {a, b}, new short[] {}, new
254 * short[] {c}} returns the array {@code {a, b, c}}.
255 *
256 * @param arrays zero or more {@code short} arrays
257 * @return a single array containing all the values from the source arrays, in
258 * order
259 */
260 public static short[] concat(short[]... arrays) {
261 int length = 0;
262 for (short[] array : arrays) {
263 length += array.length;
264 }
265 short[] result = new short[length];
266 int pos = 0;
267 for (short[] array : arrays) {
268 System.arraycopy(array, 0, result, pos, array.length);
269 pos += array.length;
270 }
271 return result;
272 }
273
274 /**
275 * Returns a big-endian representation of {@code value} in a 2-element byte
276 * array; equivalent to {@code
277 * ByteBuffer.allocate(2).putShort(value).array()}. For example, the input
278 * value {@code (short) 0x1234} would yield the byte array {@code {0x12,
279 * 0x34}}.
280 *
281 * <p>If you need to convert and concatenate several values (possibly even of
282 * different types), use a shared {@link java.nio.ByteBuffer} instance, or use
283 * {@link com.google.common.io.ByteStreams#newDataOutput()} to get a growable
284 * buffer.
285 */
286 @GwtIncompatible("doesn't work")
287 public static byte[] toByteArray(short value) {
288 return new byte[] {
289 (byte) (value >> 8),
290 (byte) value};
291 }
292
293 /**
294 * Returns the {@code short} value whose big-endian representation is
295 * stored in the first 2 bytes of {@code bytes}; equivalent to {@code
296 * ByteBuffer.wrap(bytes).getShort()}. For example, the input byte array
297 * {@code {0x54, 0x32}} would yield the {@code short} value {@code 0x5432}.
298 *
299 * <p>Arguably, it's preferable to use {@link java.nio.ByteBuffer}; that
300 * library exposes much more flexibility at little cost in readability.
301 *
302 * @throws IllegalArgumentException if {@code bytes} has fewer than 2
303 * elements
304 */
305 @GwtIncompatible("doesn't work")
306 public static short fromByteArray(byte[] bytes) {
307 checkArgument(bytes.length >= BYTES,
308 "array too small: %s < %s", bytes.length, BYTES);
309 return fromBytes(bytes[0], bytes[1]);
310 }
311
312 /**
313 * Returns the {@code short} value whose byte representation is the given 2
314 * bytes, in big-endian order; equivalent to {@code Shorts.fromByteArray(new
315 * byte[] {b1, b2})}.
316 *
317 * @since 7.0
318 */
319 @GwtIncompatible("doesn't work")
320 public static short fromBytes(byte b1, byte b2) {
321 return (short) ((b1 << 8) | (b2 & 0xFF));
322 }
323
324 /**
325 * Returns an array containing the same values as {@code array}, but
326 * guaranteed to be of a specified minimum length. If {@code array} already
327 * has a length of at least {@code minLength}, it is returned directly.
328 * Otherwise, a new array of size {@code minLength + padding} is returned,
329 * containing the values of {@code array}, and zeroes in the remaining places.
330 *
331 * @param array the source array
332 * @param minLength the minimum length the returned array must guarantee
333 * @param padding an extra amount to "grow" the array by if growth is
334 * necessary
335 * @throws IllegalArgumentException if {@code minLength} or {@code padding} is
336 * negative
337 * @return an array containing the values of {@code array}, with guaranteed
338 * minimum length {@code minLength}
339 */
340 public static short[] ensureCapacity(
341 short[] array, int minLength, int padding) {
342 checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
343 checkArgument(padding >= 0, "Invalid padding: %s", padding);
344 return (array.length < minLength)
345 ? copyOf(array, minLength + padding)
346 : array;
347 }
348
349 // Arrays.copyOf() requires Java 6
350 private static short[] copyOf(short[] original, int length) {
351 short[] copy = new short[length];
352 System.arraycopy(original, 0, copy, 0, Math.min(original.length, length));
353 return copy;
354 }
355
356 /**
357 * Returns a string containing the supplied {@code short} values separated
358 * by {@code separator}. For example, {@code join("-", (short) 1, (short) 2,
359 * (short) 3)} returns the string {@code "1-2-3"}.
360 *
361 * @param separator the text that should appear between consecutive values in
362 * the resulting string (but not at the start or end)
363 * @param array an array of {@code short} values, possibly empty
364 */
365 public static String join(String separator, short... array) {
366 checkNotNull(separator);
367 if (array.length == 0) {
368 return "";
369 }
370
371 // For pre-sizing a builder, just get the right order of magnitude
372 StringBuilder builder = new StringBuilder(array.length * 6);
373 builder.append(array[0]);
374 for (int i = 1; i < array.length; i++) {
375 builder.append(separator).append(array[i]);
376 }
377 return builder.toString();
378 }
379
380 /**
381 * Returns a comparator that compares two {@code short} arrays
382 * lexicographically. That is, it compares, using {@link
383 * #compare(short, short)}), the first pair of values that follow any
384 * common prefix, or when one array is a prefix of the other, treats the
385 * shorter array as the lesser. For example, {@code [] < [(short) 1] <
386 * [(short) 1, (short) 2] < [(short) 2]}.
387 *
388 * <p>The returned comparator is inconsistent with {@link
389 * Object#equals(Object)} (since arrays support only identity equality), but
390 * it is consistent with {@link Arrays#equals(short[], short[])}.
391 *
392 * @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order">
393 * Lexicographical order article at Wikipedia</a>
394 * @since 2.0
395 */
396 public static Comparator<short[]> lexicographicalComparator() {
397 return LexicographicalComparator.INSTANCE;
398 }
399
400 private enum LexicographicalComparator implements Comparator<short[]> {
401 INSTANCE;
402
403 @Override
404 public int compare(short[] left, short[] right) {
405 int minLength = Math.min(left.length, right.length);
406 for (int i = 0; i < minLength; i++) {
407 int result = Shorts.compare(left[i], right[i]);
408 if (result != 0) {
409 return result;
410 }
411 }
412 return left.length - right.length;
413 }
414 }
415
416 /**
417 * Copies a collection of {@code Short} instances into a new array of
418 * primitive {@code short} values.
419 *
420 * <p>Elements are copied from the argument collection as if by {@code
421 * collection.toArray()}. Calling this method is as thread-safe as calling
422 * that method.
423 *
424 * @param collection a collection of {@code Short} objects
425 * @return an array containing the same values as {@code collection}, in the
426 * same order, converted to primitives
427 * @throws NullPointerException if {@code collection} or any of its elements
428 * is null
429 */
430 public static short[] toArray(Collection<Short> collection) {
431 if (collection instanceof ShortArrayAsList) {
432 return ((ShortArrayAsList) collection).toShortArray();
433 }
434
435 Object[] boxedArray = collection.toArray();
436 int len = boxedArray.length;
437 short[] array = new short[len];
438 for (int i = 0; i < len; i++) {
439 // checkNotNull for GWT (do not optimize)
440 array[i] = (Short) checkNotNull(boxedArray[i]);
441 }
442 return array;
443 }
444
445 /**
446 * Returns a fixed-size list backed by the specified array, similar to {@link
447 * Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)},
448 * but any attempt to set a value to {@code null} will result in a {@link
449 * NullPointerException}.
450 *
451 * <p>The returned list maintains the values, but not the identities, of
452 * {@code Short} objects written to or read from it. For example, whether
453 * {@code list.get(0) == list.get(0)} is true for the returned list is
454 * unspecified.
455 *
456 * @param backingArray the array to back the list
457 * @return a list view of the array
458 */
459 public static List<Short> asList(short... backingArray) {
460 if (backingArray.length == 0) {
461 return Collections.emptyList();
462 }
463 return new ShortArrayAsList(backingArray);
464 }
465
466 @GwtCompatible
467 private static class ShortArrayAsList extends AbstractList<Short>
468 implements RandomAccess, Serializable {
469 final short[] array;
470 final int start;
471 final int end;
472
473 ShortArrayAsList(short[] array) {
474 this(array, 0, array.length);
475 }
476
477 ShortArrayAsList(short[] array, int start, int end) {
478 this.array = array;
479 this.start = start;
480 this.end = end;
481 }
482
483 @Override public int size() {
484 return end - start;
485 }
486
487 @Override public boolean isEmpty() {
488 return false;
489 }
490
491 @Override public Short get(int index) {
492 checkElementIndex(index, size());
493 return array[start + index];
494 }
495
496 @Override public boolean contains(Object target) {
497 // Overridden to prevent a ton of boxing
498 return (target instanceof Short)
499 && Shorts.indexOf(array, (Short) target, start, end) != -1;
500 }
501
502 @Override public int indexOf(Object target) {
503 // Overridden to prevent a ton of boxing
504 if (target instanceof Short) {
505 int i = Shorts.indexOf(array, (Short) target, start, end);
506 if (i >= 0) {
507 return i - start;
508 }
509 }
510 return -1;
511 }
512
513 @Override public int lastIndexOf(Object target) {
514 // Overridden to prevent a ton of boxing
515 if (target instanceof Short) {
516 int i = Shorts.lastIndexOf(array, (Short) target, start, end);
517 if (i >= 0) {
518 return i - start;
519 }
520 }
521 return -1;
522 }
523
524 @Override public Short set(int index, Short element) {
525 checkElementIndex(index, size());
526 short oldValue = array[start + index];
527 array[start + index] = checkNotNull(element); // checkNotNull for GWT (do not optimize)
528 return oldValue;
529 }
530
531 @Override public List<Short> subList(int fromIndex, int toIndex) {
532 int size = size();
533 checkPositionIndexes(fromIndex, toIndex, size);
534 if (fromIndex == toIndex) {
535 return Collections.emptyList();
536 }
537 return new ShortArrayAsList(array, start + fromIndex, start + toIndex);
538 }
539
540 @Override public boolean equals(Object object) {
541 if (object == this) {
542 return true;
543 }
544 if (object instanceof ShortArrayAsList) {
545 ShortArrayAsList that = (ShortArrayAsList) object;
546 int size = size();
547 if (that.size() != size) {
548 return false;
549 }
550 for (int i = 0; i < size; i++) {
551 if (array[start + i] != that.array[that.start + i]) {
552 return false;
553 }
554 }
555 return true;
556 }
557 return super.equals(object);
558 }
559
560 @Override public int hashCode() {
561 int result = 1;
562 for (int i = start; i < end; i++) {
563 result = 31 * result + Shorts.hashCode(array[i]);
564 }
565 return result;
566 }
567
568 @Override public String toString() {
569 StringBuilder builder = new StringBuilder(size() * 6);
570 builder.append('[').append(array[start]);
571 for (int i = start + 1; i < end; i++) {
572 builder.append(", ").append(array[i]);
573 }
574 return builder.append(']').toString();
575 }
576
577 short[] toShortArray() {
578 // Arrays.copyOfRange() requires Java 6
579 int size = size();
580 short[] result = new short[size];
581 System.arraycopy(array, start, result, 0, size);
582 return result;
583 }
584
585 private static final long serialVersionUID = 0;
586 }
587 }
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