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    }