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