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;
025
026import java.io.Serializable;
027import java.util.AbstractList;
028import java.util.Arrays;
029import java.util.Collection;
030import java.util.Collections;
031import java.util.Comparator;
032import java.util.List;
033import java.util.RandomAccess;
034
035/**
036 * Static utility methods pertaining to {@code long} primitives, that are not
037 * already found in either {@link Long} or {@link Arrays}.
038 *
039 * <p>See the Guava User Guide article on <a href=
040 * "http://code.google.com/p/guava-libraries/wiki/PrimitivesExplained">
041 * primitive utilities</a>.
042 *
043 * @author Kevin Bourrillion
044 * @since 1.0
045 */
046@GwtCompatible
047public final class Longs {
048  private Longs() {}
049
050  /**
051   * The number of bytes required to represent a primitive {@code long}
052   * value.
053   */
054  public static final int BYTES = Long.SIZE / Byte.SIZE;
055
056  /**
057   * The largest power of two that can be represented as a {@code long}.
058   *
059   * @since 10.0
060   */
061  public static final long MAX_POWER_OF_TWO = 1L << (Long.SIZE - 2);
062
063  /**
064   * Returns a hash code for {@code value}; equal to the result of invoking
065   * {@code ((Long) value).hashCode()}.
066   *
067   * <p>This method always return the value specified by {@link
068   * Long#hashCode()} in java, which might be different from
069   * {@code ((Long) value).hashCode()} in GWT because {@link Long#hashCode()}
070   * in GWT does not obey the JRE contract.
071   *
072   * @param value a primitive {@code long} value
073   * @return a hash code for the value
074   */
075  public static int hashCode(long value) {
076    return (int) (value ^ (value >>> 32));
077  }
078
079  /**
080   * Compares the two specified {@code long} values. The sign of the value
081   * returned is the same as that of {@code ((Long) a).compareTo(b)}.
082   *
083   * @param a the first {@code long} to compare
084   * @param b the second {@code long} to compare
085   * @return a negative value if {@code a} is less than {@code b}; a positive
086   *     value if {@code a} is greater than {@code b}; or zero if they are equal
087   */
088  public static int compare(long a, long b) {
089    return (a < b) ? -1 : ((a > b) ? 1 : 0);
090  }
091
092  /**
093   * Returns {@code true} if {@code target} is present as an element anywhere in
094   * {@code array}.
095   *
096   * @param array an array of {@code long} values, possibly empty
097   * @param target a primitive {@code long} value
098   * @return {@code true} if {@code array[i] == target} for some value of {@code
099   *     i}
100   */
101  public static boolean contains(long[] array, long target) {
102    for (long value : array) {
103      if (value == target) {
104        return true;
105      }
106    }
107    return false;
108  }
109
110  /**
111   * Returns the index of the first appearance of the value {@code target} in
112   * {@code array}.
113   *
114   * @param array an array of {@code long} values, possibly empty
115   * @param target a primitive {@code long} value
116   * @return the least index {@code i} for which {@code array[i] == target}, or
117   *     {@code -1} if no such index exists.
118   */
119  public static int indexOf(long[] array, long target) {
120    return indexOf(array, target, 0, array.length);
121  }
122
123  // TODO(kevinb): consider making this public
124  private static int indexOf(
125      long[] array, long target, int start, int end) {
126    for (int i = start; i < end; i++) {
127      if (array[i] == target) {
128        return i;
129      }
130    }
131    return -1;
132  }
133
134  /**
135   * Returns the start position of the first occurrence of the specified {@code
136   * target} within {@code array}, or {@code -1} if there is no such occurrence.
137   *
138   * <p>More formally, returns the lowest index {@code i} such that {@code
139   * java.util.Arrays.copyOfRange(array, i, i + target.length)} contains exactly
140   * the same elements as {@code target}.
141   *
142   * @param array the array to search for the sequence {@code target}
143   * @param target the array to search for as a sub-sequence of {@code array}
144   */
145  public static int indexOf(long[] array, long[] target) {
146    checkNotNull(array, "array");
147    checkNotNull(target, "target");
148    if (target.length == 0) {
149      return 0;
150    }
151
152    outer:
153    for (int i = 0; i < array.length - target.length + 1; i++) {
154      for (int j = 0; j < target.length; j++) {
155        if (array[i + j] != target[j]) {
156          continue outer;
157        }
158      }
159      return i;
160    }
161    return -1;
162  }
163
164  /**
165   * Returns the index of the last appearance of the value {@code target} in
166   * {@code array}.
167   *
168   * @param array an array of {@code long} values, possibly empty
169   * @param target a primitive {@code long} value
170   * @return the greatest index {@code i} for which {@code array[i] == target},
171   *     or {@code -1} if no such index exists.
172   */
173  public static int lastIndexOf(long[] array, long target) {
174    return lastIndexOf(array, target, 0, array.length);
175  }
176
177  // TODO(kevinb): consider making this public
178  private static int lastIndexOf(
179      long[] array, long target, int start, int end) {
180    for (int i = end - 1; i >= start; i--) {
181      if (array[i] == target) {
182        return i;
183      }
184    }
185    return -1;
186  }
187
188  /**
189   * Returns the least value present in {@code array}.
190   *
191   * @param array a <i>nonempty</i> array of {@code long} values
192   * @return the value present in {@code array} that is less than or equal to
193   *     every other value in the array
194   * @throws IllegalArgumentException if {@code array} is empty
195   */
196  public static long min(long... array) {
197    checkArgument(array.length > 0);
198    long min = array[0];
199    for (int i = 1; i < array.length; i++) {
200      if (array[i] < min) {
201        min = array[i];
202      }
203    }
204    return min;
205  }
206
207  /**
208   * Returns the greatest value present in {@code array}.
209   *
210   * @param array a <i>nonempty</i> array of {@code long} values
211   * @return the value present in {@code array} that is greater than or equal to
212   *     every other value in the array
213   * @throws IllegalArgumentException if {@code array} is empty
214   */
215  public static long max(long... array) {
216    checkArgument(array.length > 0);
217    long max = array[0];
218    for (int i = 1; i < array.length; i++) {
219      if (array[i] > max) {
220        max = array[i];
221      }
222    }
223    return max;
224  }
225
226  /**
227   * Returns the values from each provided array combined into a single array.
228   * For example, {@code concat(new long[] {a, b}, new long[] {}, new
229   * long[] {c}} returns the array {@code {a, b, c}}.
230   *
231   * @param arrays zero or more {@code long} arrays
232   * @return a single array containing all the values from the source arrays, in
233   *     order
234   */
235  public static long[] concat(long[]... arrays) {
236    int length = 0;
237    for (long[] array : arrays) {
238      length += array.length;
239    }
240    long[] result = new long[length];
241    int pos = 0;
242    for (long[] array : arrays) {
243      System.arraycopy(array, 0, result, pos, array.length);
244      pos += array.length;
245    }
246    return result;
247  }
248
249  /**
250   * Returns a big-endian representation of {@code value} in an 8-element byte
251   * array; equivalent to {@code ByteBuffer.allocate(8).putLong(value).array()}.
252   * For example, the input value {@code 0x1213141516171819L} would yield the
253   * byte array {@code {0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19}}.
254   *
255   * <p>If you need to convert and concatenate several values (possibly even of
256   * different types), use a shared {@link java.nio.ByteBuffer} instance, or use
257   * {@link com.google.common.io.ByteStreams#newDataOutput()} to get a growable
258   * buffer.
259   */
260  public static byte[] toByteArray(long value) {
261    // Note that this code needs to stay compatible with GWT, which has known
262    // bugs when narrowing byte casts of long values occur.
263    byte[] result = new byte[8];
264    for (int i = 7; i >= 0; i--) {
265      result[i] = (byte) (value & 0xffL);
266      value >>= 8;
267    }
268    return result;
269  }
270
271  /**
272   * Returns the {@code long} value whose big-endian representation is
273   * stored in the first 8 bytes of {@code bytes}; equivalent to {@code
274   * ByteBuffer.wrap(bytes).getLong()}. For example, the input byte array
275   * {@code {0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19}} would yield the
276   * {@code long} value {@code 0x1213141516171819L}.
277   *
278   * <p>Arguably, it's preferable to use {@link java.nio.ByteBuffer}; that
279   * library exposes much more flexibility at little cost in readability.
280   *
281   * @throws IllegalArgumentException if {@code bytes} has fewer than 8
282   *     elements
283   */
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  public static long fromBytes(byte b1, byte b2, byte b3, byte b4,
299      byte b5, byte b6, byte b7, byte b8) {
300    return (b1 & 0xFFL) << 56
301        | (b2 & 0xFFL) << 48
302        | (b3 & 0xFFL) << 40
303        | (b4 & 0xFFL) << 32
304        | (b5 & 0xFFL) << 24
305        | (b6 & 0xFFL) << 16
306        | (b7 & 0xFFL) << 8
307        | (b8 & 0xFFL);
308  }
309
310  /**
311   * Returns an array containing the same values as {@code array}, but
312   * guaranteed to be of a specified minimum length. If {@code array} already
313   * has a length of at least {@code minLength}, it is returned directly.
314   * Otherwise, a new array of size {@code minLength + padding} is returned,
315   * containing the values of {@code array}, and zeroes in the remaining places.
316   *
317   * @param array the source array
318   * @param minLength the minimum length the returned array must guarantee
319   * @param padding an extra amount to "grow" the array by if growth is
320   *     necessary
321   * @throws IllegalArgumentException if {@code minLength} or {@code padding} is
322   *     negative
323   * @return an array containing the values of {@code array}, with guaranteed
324   *     minimum length {@code minLength}
325   */
326  public static long[] ensureCapacity(
327      long[] array, int minLength, int padding) {
328    checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
329    checkArgument(padding >= 0, "Invalid padding: %s", padding);
330    return (array.length < minLength)
331        ? copyOf(array, minLength + padding)
332        : array;
333  }
334
335  // Arrays.copyOf() requires Java 6
336  private static long[] copyOf(long[] original, int length) {
337    long[] copy = new long[length];
338    System.arraycopy(original, 0, copy, 0, Math.min(original.length, length));
339    return copy;
340  }
341
342  /**
343   * Returns a string containing the supplied {@code long} values separated
344   * by {@code separator}. For example, {@code join("-", 1L, 2L, 3L)} returns
345   * the string {@code "1-2-3"}.
346   *
347   * @param separator the text that should appear between consecutive values in
348   *     the resulting string (but not at the start or end)
349   * @param array an array of {@code long} values, possibly empty
350   */
351  public static String join(String separator, long... array) {
352    checkNotNull(separator);
353    if (array.length == 0) {
354      return "";
355    }
356
357    // For pre-sizing a builder, just get the right order of magnitude
358    StringBuilder builder = new StringBuilder(array.length * 10);
359    builder.append(array[0]);
360    for (int i = 1; i < array.length; i++) {
361      builder.append(separator).append(array[i]);
362    }
363    return builder.toString();
364  }
365
366  /**
367   * Returns a comparator that compares two {@code long} arrays
368   * lexicographically. That is, it compares, using {@link
369   * #compare(long, long)}), the first pair of values that follow any
370   * common prefix, or when one array is a prefix of the other, treats the
371   * shorter array as the lesser. For example,
372   * {@code [] < [1L] < [1L, 2L] < [2L]}.
373   *
374   * <p>The returned comparator is inconsistent with {@link
375   * Object#equals(Object)} (since arrays support only identity equality), but
376   * it is consistent with {@link Arrays#equals(long[], long[])}.
377   *
378   * @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order">
379   *     Lexicographical order article at Wikipedia</a>
380   * @since 2.0
381   */
382  public static Comparator<long[]> lexicographicalComparator() {
383    return LexicographicalComparator.INSTANCE;
384  }
385
386  private enum LexicographicalComparator implements Comparator<long[]> {
387    INSTANCE;
388
389    @Override
390    public int compare(long[] left, long[] right) {
391      int minLength = Math.min(left.length, right.length);
392      for (int i = 0; i < minLength; i++) {
393        int result = Longs.compare(left[i], right[i]);
394        if (result != 0) {
395          return result;
396        }
397      }
398      return left.length - right.length;
399    }
400  }
401
402  /**
403   * Returns an array containing each value of {@code collection}, converted to
404   * a {@code long} value in the manner of {@link Number#longValue}.
405   *
406   * <p>Elements are copied from the argument collection as if by {@code
407   * collection.toArray()}.  Calling this method is as thread-safe as calling
408   * that method.
409   *
410   * @param collection a collection of {@code Number} instances
411   * @return an array containing the same values as {@code collection}, in the
412   *     same order, converted to primitives
413   * @throws NullPointerException if {@code collection} or any of its elements
414   *     is null
415   * @since 1.0 (parameter was {@code Collection<Long>} before 12.0)
416   */
417  public static long[] toArray(Collection<? extends Number> 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] = ((Number) checkNotNull(boxedArray[i])).longValue();
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      // checkNotNull for GWT (do not optimize)
515      array[start + index] = checkNotNull(element);
516      return oldValue;
517    }
518
519    @Override public List<Long> subList(int fromIndex, int toIndex) {
520      int size = size();
521      checkPositionIndexes(fromIndex, toIndex, size);
522      if (fromIndex == toIndex) {
523        return Collections.emptyList();
524      }
525      return new LongArrayAsList(array, start + fromIndex, start + toIndex);
526    }
527
528    @Override public boolean equals(Object object) {
529      if (object == this) {
530        return true;
531      }
532      if (object instanceof LongArrayAsList) {
533        LongArrayAsList that = (LongArrayAsList) object;
534        int size = size();
535        if (that.size() != size) {
536          return false;
537        }
538        for (int i = 0; i < size; i++) {
539          if (array[start + i] != that.array[that.start + i]) {
540            return false;
541          }
542        }
543        return true;
544      }
545      return super.equals(object);
546    }
547
548    @Override public int hashCode() {
549      int result = 1;
550      for (int i = start; i < end; i++) {
551        result = 31 * result + Longs.hashCode(array[i]);
552      }
553      return result;
554    }
555
556    @Override public String toString() {
557      StringBuilder builder = new StringBuilder(size() * 10);
558      builder.append('[').append(array[start]);
559      for (int i = start + 1; i < end; i++) {
560        builder.append(", ").append(array[i]);
561      }
562      return builder.append(']').toString();
563    }
564
565    long[] toLongArray() {
566      // Arrays.copyOfRange() is not available under GWT
567      int size = size();
568      long[] result = new long[size];
569      System.arraycopy(array, start, result, 0, size);
570      return result;
571    }
572
573    private static final long serialVersionUID = 0;
574  }
575}