    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    }