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
017package com.google.common.primitives;
018
019import static com.google.common.base.Preconditions.checkArgument;
020import static com.google.common.base.Preconditions.checkElementIndex;
021import static com.google.common.base.Preconditions.checkNotNull;
022import static com.google.common.base.Preconditions.checkPositionIndexes;
023
024import com.google.common.annotations.GwtCompatible;
025import com.google.common.annotations.GwtIncompatible;
026
027import java.io.Serializable;
028import java.util.AbstractList;
029import java.util.Arrays;
030import java.util.Collection;
031import java.util.Collections;
032import java.util.Comparator;
033import java.util.List;
034import 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
042 */
043@GwtCompatible(emulated = true)
044public 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   * Returns a hash code for {@code value}; equal to the result of invoking
055   * {@code ((Short) value).hashCode()}.
056   *
057   * @param value a primitive {@code short} value
058   * @return a hash code for the value
059   */
060  public static int hashCode(short value) {
061    return value;
062  }
063
064  /**
065   * Returns the {@code short} value that is equal to {@code value}, if
066   * possible.
067   *
068   * @param value any value in the range of the {@code short} type
069   * @return the {@code short} value that equals {@code value}
070   * @throws IllegalArgumentException if {@code value} is greater than {@link
071   *     Short#MAX_VALUE} or less than {@link Short#MIN_VALUE}
072   */
073  public static short checkedCast(long value) {
074    short result = (short) value;
075    checkArgument(result == value, "Out of range: %s", value);
076    return result;
077  }
078
079  /**
080   * Returns the {@code short} nearest in value to {@code value}.
081   *
082   * @param value any {@code long} value
083   * @return the same value cast to {@code short} if it is in the range of the
084   *     {@code short} type, {@link Short#MAX_VALUE} if it is too large,
085   *     or {@link Short#MIN_VALUE} if it is too small
086   */
087  public static short saturatedCast(long value) {
088    if (value > Short.MAX_VALUE) {
089      return Short.MAX_VALUE;
090    }
091    if (value < Short.MIN_VALUE) {
092      return Short.MIN_VALUE;
093    }
094    return (short) value;
095  }
096
097  /**
098   * Compares the two specified {@code short} values. The sign of the value
099   * returned is the same as that of {@code ((Short) a).compareTo(b)}.
100   *
101   * @param a the first {@code short} to compare
102   * @param b the second {@code short} to compare
103   * @return a negative value if {@code a} is less than {@code b}; a positive
104   *     value if {@code a} is greater than {@code b}; or zero if they are equal
105   */
106  public static int compare(short a, short b) {
107    return a - b; // safe due to restricted range
108  }
109
110  /**
111   * Returns {@code true} if {@code target} is present as an element anywhere in
112   * {@code array}.
113   *
114   * @param array an array of {@code short} values, possibly empty
115   * @param target a primitive {@code short} value
116   * @return {@code true} if {@code array[i] == target} for some value of {@code
117   *     i}
118   */
119  public static boolean contains(short[] array, short target) {
120    for (short value : array) {
121      if (value == target) {
122        return true;
123      }
124    }
125    return false;
126  }
127
128  /**
129   * Returns the index of the first appearance of the value {@code target} in
130   * {@code array}.
131   *
132   * @param array an array of {@code short} values, possibly empty
133   * @param target a primitive {@code short} value
134   * @return the least index {@code i} for which {@code array[i] == target}, or
135   *     {@code -1} if no such index exists.
136   */
137  public static int indexOf(short[] array, short target) {
138    return indexOf(array, target, 0, array.length);
139  }
140
141  // TODO(kevinb): consider making this public
142  private static int indexOf(
143      short[] array, short target, int start, int end) {
144    for (int i = start; i < end; i++) {
145      if (array[i] == target) {
146        return i;
147      }
148    }
149    return -1;
150  }
151
152  /**
153   * Returns the start position of the first occurrence of the specified {@code
154   * target} within {@code array}, or {@code -1} if there is no such occurrence.
155   *
156   * <p>More formally, returns the lowest index {@code i} such that {@code
157   * java.util.Arrays.copyOfRange(array, i, i + target.length)} contains exactly
158   * the same elements as {@code target}.
159   *
160   * @param array the array to search for the sequence {@code target}
161   * @param target the array to search for as a sub-sequence of {@code array}
162   */
163  public static int indexOf(short[] array, short[] target) {
164    checkNotNull(array, "array");
165    checkNotNull(target, "target");
166    if (target.length == 0) {
167      return 0;
168    }
169
170    outer:
171    for (int i = 0; i < array.length - target.length + 1; i++) {
172      for (int j = 0; j < target.length; j++) {
173        if (array[i + j] != target[j]) {
174          continue outer;
175        }
176      }
177      return i;
178    }
179    return -1;
180  }
181
182  /**
183   * Returns the index of the last appearance of the value {@code target} in
184   * {@code array}.
185   *
186   * @param array an array of {@code short} values, possibly empty
187   * @param target a primitive {@code short} value
188   * @return the greatest index {@code i} for which {@code array[i] == target},
189   *     or {@code -1} if no such index exists.
190   */
191  public static int lastIndexOf(short[] array, short target) {
192    return lastIndexOf(array, target, 0, array.length);
193  }
194
195  // TODO(kevinb): consider making this public
196  private static int lastIndexOf(
197      short[] array, short target, int start, int end) {
198    for (int i = end - 1; i >= start; i--) {
199      if (array[i] == target) {
200        return i;
201      }
202    }
203    return -1;
204  }
205
206  /**
207   * Returns the least value present in {@code array}.
208   *
209   * @param array a <i>nonempty</i> array of {@code short} values
210   * @return the value present in {@code array} that is less than or equal to
211   *     every other value in the array
212   * @throws IllegalArgumentException if {@code array} is empty
213   */
214  public static short min(short... array) {
215    checkArgument(array.length > 0);
216    short min = array[0];
217    for (int i = 1; i < array.length; i++) {
218      if (array[i] < min) {
219        min = array[i];
220      }
221    }
222    return min;
223  }
224
225  /**
226   * Returns the greatest value present in {@code array}.
227   *
228   * @param array a <i>nonempty</i> array of {@code short} values
229   * @return the value present in {@code array} that is greater than or equal to
230   *     every other value in the array
231   * @throws IllegalArgumentException if {@code array} is empty
232   */
233  public static short max(short... array) {
234    checkArgument(array.length > 0);
235    short max = array[0];
236    for (int i = 1; i < array.length; i++) {
237      if (array[i] > max) {
238        max = array[i];
239      }
240    }
241    return max;
242  }
243
244  /**
245   * Returns the values from each provided array combined into a single array.
246   * For example, {@code concat(new short[] {a, b}, new short[] {}, new
247   * short[] {c}} returns the array {@code {a, b, c}}.
248   *
249   * @param arrays zero or more {@code short} arrays
250   * @return a single array containing all the values from the source arrays, in
251   *     order
252   */
253  public static short[] concat(short[]... arrays) {
254    int length = 0;
255    for (short[] array : arrays) {
256      length += array.length;
257    }
258    short[] result = new short[length];
259    int pos = 0;
260    for (short[] array : arrays) {
261      System.arraycopy(array, 0, result, pos, array.length);
262      pos += array.length;
263    }
264    return result;
265  }
266
267  /**
268   * Returns a big-endian representation of {@code value} in a 2-element byte
269   * array; equivalent to {@code
270   * ByteBuffer.allocate(2).putShort(value).array()}.  For example, the input
271   * value {@code (short) 0x1234} would yield the byte array {@code {0x12,
272   * 0x34}}.
273   *
274   * <p>If you need to convert and concatenate several values (possibly even of
275   * different types), use a shared {@link java.nio.ByteBuffer} instance, or use
276   * {@link com.google.common.io.ByteStreams#newDataOutput()} to get a growable
277   * buffer.
278   */
279  @GwtIncompatible("doesn't work")
280  public static byte[] toByteArray(short value) {
281    return new byte[] {
282        (byte) (value >> 8),
283        (byte) value};
284  }
285
286  /**
287   * Returns the {@code short} value whose big-endian representation is
288   * stored in the first 2 bytes of {@code bytes}; equivalent to {@code
289   * ByteBuffer.wrap(bytes).getShort()}. For example, the input byte array
290   * {@code {0x54, 0x32}} would yield the {@code short} value {@code 0x5432}.
291   *
292   * <p>Arguably, it's preferable to use {@link java.nio.ByteBuffer}; that
293   * library exposes much more flexibility at little cost in readability.
294   *
295   * @throws IllegalArgumentException if {@code bytes} has fewer than 2
296   *     elements
297   */
298  @GwtIncompatible("doesn't work")
299  public static short fromByteArray(byte[] bytes) {
300    checkArgument(bytes.length >= BYTES,
301        "array too small: %s < %s", bytes.length, BYTES);
302    return fromBytes(bytes[0], bytes[1]);
303  }
304
305  /**
306   * Returns the {@code short} value whose byte representation is the given 2
307   * bytes, in big-endian order; equivalent to {@code Shorts.fromByteArray(new
308   * byte[] {b1, b2})}.
309   *
310   * @since 7
311   */
312  @GwtIncompatible("doesn't work")
313  public static short fromBytes(byte b1, byte b2) {
314    return (short) ((b1 << 8) | (b2 & 0xFF));
315  }
316
317  /**
318   * Returns an array containing the same values as {@code array}, but
319   * guaranteed to be of a specified minimum length. If {@code array} already
320   * has a length of at least {@code minLength}, it is returned directly.
321   * Otherwise, a new array of size {@code minLength + padding} is returned,
322   * containing the values of {@code array}, and zeroes in the remaining places.
323   *
324   * @param array the source array
325   * @param minLength the minimum length the returned array must guarantee
326   * @param padding an extra amount to "grow" the array by if growth is
327   *     necessary
328   * @throws IllegalArgumentException if {@code minLength} or {@code padding} is
329   *     negative
330   * @return an array containing the values of {@code array}, with guaranteed
331   *     minimum length {@code minLength}
332   */
333  public static short[] ensureCapacity(
334      short[] array, int minLength, int padding) {
335    checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
336    checkArgument(padding >= 0, "Invalid padding: %s", padding);
337    return (array.length < minLength)
338        ? copyOf(array, minLength + padding)
339        : array;
340  }
341
342  // Arrays.copyOf() requires Java 6
343  private static short[] copyOf(short[] original, int length) {
344    short[] copy = new short[length];
345    System.arraycopy(original, 0, copy, 0, Math.min(original.length, length));
346    return copy;
347  }
348
349  /**
350   * Returns a string containing the supplied {@code short} values separated
351   * by {@code separator}. For example, {@code join("-", (short) 1, (short) 2,
352   * (short) 3)} returns the string {@code "1-2-3"}.
353   *
354   * @param separator the text that should appear between consecutive values in
355   *     the resulting string (but not at the start or end)
356   * @param array an array of {@code short} values, possibly empty
357   */
358  public static String join(String separator, short... array) {
359    checkNotNull(separator);
360    if (array.length == 0) {
361      return "";
362    }
363
364    // For pre-sizing a builder, just get the right order of magnitude
365    StringBuilder builder = new StringBuilder(array.length * 6);
366    builder.append(array[0]);
367    for (int i = 1; i < array.length; i++) {
368      builder.append(separator).append(array[i]);
369    }
370    return builder.toString();
371  }
372
373  /**
374   * Returns a comparator that compares two {@code short} arrays
375   * lexicographically. That is, it compares, using {@link
376   * #compare(short, short)}), the first pair of values that follow any
377   * common prefix, or when one array is a prefix of the other, treats the
378   * shorter array as the lesser. For example, {@code [] < [(short) 1] <
379   * [(short) 1, (short) 2] < [(short) 2]}.
380   *
381   * <p>The returned comparator is inconsistent with {@link
382   * Object#equals(Object)} (since arrays support only identity equality), but
383   * it is consistent with {@link Arrays#equals(short[], short[])}.
384   *
385   * @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order">
386   *     Lexicographical order article at Wikipedia</a>
387   * @since 2
388   */
389  public static Comparator<short[]> lexicographicalComparator() {
390    return LexicographicalComparator.INSTANCE;
391  }
392
393  private enum LexicographicalComparator implements Comparator<short[]> {
394    INSTANCE;
395
396    @Override
397    public int compare(short[] left, short[] right) {
398      int minLength = Math.min(left.length, right.length);
399      for (int i = 0; i < minLength; i++) {
400        int result = Shorts.compare(left[i], right[i]);
401        if (result != 0) {
402          return result;
403        }
404      }
405      return left.length - right.length;
406    }
407  }
408
409  /**
410   * Copies a collection of {@code Short} instances into a new array of
411   * primitive {@code short} values.
412   *
413   * <p>Elements are copied from the argument collection as if by {@code
414   * collection.toArray()}.  Calling this method is as thread-safe as calling
415   * that method.
416   *
417   * @param collection a collection of {@code Short} objects
418   * @return an array containing the same values as {@code collection}, in the
419   *     same order, converted to primitives
420   * @throws NullPointerException if {@code collection} or any of its elements
421   *     is null
422   */
423  public static short[] toArray(Collection<Short> collection) {
424    if (collection instanceof ShortArrayAsList) {
425      return ((ShortArrayAsList) collection).toShortArray();
426    }
427
428    Object[] boxedArray = collection.toArray();
429    int len = boxedArray.length;
430    short[] array = new short[len];
431    for (int i = 0; i < len; i++) {
432      array[i] = (Short) boxedArray[i];
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 Short} 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<Short> asList(short... backingArray) {
452    if (backingArray.length == 0) {
453      return Collections.emptyList();
454    }
455    return new ShortArrayAsList(backingArray);
456  }
457
458  @GwtCompatible
459  private static class ShortArrayAsList extends AbstractList<Short>
460      implements RandomAccess, Serializable {
461    final short[] array;
462    final int start;
463    final int end;
464
465    ShortArrayAsList(short[] array) {
466      this(array, 0, array.length);
467    }
468
469    ShortArrayAsList(short[] 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 Short 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 Short)
491          && Shorts.indexOf(array, (Short) 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 Short) {
497        int i = Shorts.indexOf(array, (Short) 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 Short) {
508        int i = Shorts.lastIndexOf(array, (Short) target, start, end);
509        if (i >= 0) {
510          return i - start;
511        }
512      }
513      return -1;
514    }
515
516    @Override public Short set(int index, Short element) {
517      checkElementIndex(index, size());
518      short oldValue = array[start + index];
519      array[start + index] = element;
520      return oldValue;
521    }
522
523    @Override public List<Short> 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 ShortArrayAsList(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 ShortArrayAsList) {
537        ShortArrayAsList that = (ShortArrayAsList) 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 + Shorts.hashCode(array[i]);
556      }
557      return result;
558    }
559
560    @Override public String toString() {
561      StringBuilder builder = new StringBuilder(size() * 6);
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    short[] toShortArray() {
570      // Arrays.copyOfRange() requires Java 6
571      int size = size();
572      short[] result = new short[size];
573      System.arraycopy(array, start, result, 0, size);
574      return result;
575    }
576
577    private static final long serialVersionUID = 0;
578  }
579}