001/*
002 * Copyright (C) 2008 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package com.google.common.primitives;
018
019import static com.google.common.base.Preconditions.checkArgument;
020import static com.google.common.base.Preconditions.checkElementIndex;
021import static com.google.common.base.Preconditions.checkNotNull;
022import static com.google.common.base.Preconditions.checkPositionIndexes;
023
024import com.google.common.annotations.GwtCompatible;
025import com.google.common.annotations.GwtIncompatible;
026
027import java.io.Serializable;
028import java.util.AbstractList;
029import java.util.Arrays;
030import java.util.Collection;
031import java.util.Collections;
032import java.util.Comparator;
033import java.util.List;
034import java.util.RandomAccess;
035
036/**
037 * Static utility methods pertaining to {@code long} primitives, that are not
038 * already found in either {@link Long} or {@link Arrays}.
039 *
040 * @author Kevin Bourrillion
041 * @since 1
042 */
043@GwtCompatible(emulated = true)
044public 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   * Returns a hash code for {@code value}; equal to the result of invoking
055   * {@code ((Long) value).hashCode()}.
056   *
057   * @param value a primitive {@code long} value
058   * @return a hash code for the value
059   */
060  public static int hashCode(long value) {
061    return (int) (value ^ (value >>> 32));
062  }
063
064  /**
065   * Compares the two specified {@code long} values. The sign of the value
066   * returned is the same as that of {@code ((Long) a).compareTo(b)}.
067   *
068   * @param a the first {@code long} to compare
069   * @param b the second {@code long} to compare
070   * @return a negative value if {@code a} is less than {@code b}; a positive
071   *     value if {@code a} is greater than {@code b}; or zero if they are equal
072   */
073  public static int compare(long a, long b) {
074    return (a < b) ? -1 : ((a > b) ? 1 : 0);
075  }
076
077  /**
078   * Returns {@code true} if {@code target} is present as an element anywhere in
079   * {@code array}.
080   *
081   * @param array an array of {@code long} values, possibly empty
082   * @param target a primitive {@code long} value
083   * @return {@code true} if {@code array[i] == target} for some value of {@code
084   *     i}
085   */
086  public static boolean contains(long[] array, long target) {
087    for (long value : array) {
088      if (value == target) {
089        return true;
090      }
091    }
092    return false;
093  }
094
095  /**
096   * Returns the index of the first appearance of the value {@code target} in
097   * {@code array}.
098   *
099   * @param array an array of {@code long} values, possibly empty
100   * @param target a primitive {@code long} value
101   * @return the least index {@code i} for which {@code array[i] == target}, or
102   *     {@code -1} if no such index exists.
103   */
104  public static int indexOf(long[] array, long target) {
105    return indexOf(array, target, 0, array.length);
106  }
107
108  // TODO(kevinb): consider making this public
109  private static int indexOf(
110      long[] array, long target, int start, int end) {
111    for (int i = start; i < end; i++) {
112      if (array[i] == target) {
113        return i;
114      }
115    }
116    return -1;
117  }
118
119  /**
120   * Returns the start position of the first occurrence of the specified {@code
121   * target} within {@code array}, or {@code -1} if there is no such occurrence.
122   *
123   * <p>More formally, returns the lowest index {@code i} such that {@code
124   * java.util.Arrays.copyOfRange(array, i, i + target.length)} contains exactly
125   * the same elements as {@code target}.
126   *
127   * @param array the array to search for the sequence {@code target}
128   * @param target the array to search for as a sub-sequence of {@code array}
129   */
130  public static int indexOf(long[] array, long[] target) {
131    checkNotNull(array, "array");
132    checkNotNull(target, "target");
133    if (target.length == 0) {
134      return 0;
135    }
136
137    outer:
138    for (int i = 0; i < array.length - target.length + 1; i++) {
139      for (int j = 0; j < target.length; j++) {
140        if (array[i + j] != target[j]) {
141          continue outer;
142        }
143      }
144      return i;
145    }
146    return -1;
147  }
148
149  /**
150   * Returns the index of the last appearance of the value {@code target} in
151   * {@code array}.
152   *
153   * @param array an array of {@code long} values, possibly empty
154   * @param target a primitive {@code long} value
155   * @return the greatest index {@code i} for which {@code array[i] == target},
156   *     or {@code -1} if no such index exists.
157   */
158  public static int lastIndexOf(long[] array, long target) {
159    return lastIndexOf(array, target, 0, array.length);
160  }
161
162  // TODO(kevinb): consider making this public
163  private static int lastIndexOf(
164      long[] array, long target, int start, int end) {
165    for (int i = end - 1; i >= start; i--) {
166      if (array[i] == target) {
167        return i;
168      }
169    }
170    return -1;
171  }
172
173  /**
174   * Returns the least value present in {@code array}.
175   *
176   * @param array a <i>nonempty</i> array of {@code long} values
177   * @return the value present in {@code array} that is less than or equal to
178   *     every other value in the array
179   * @throws IllegalArgumentException if {@code array} is empty
180   */
181  public static long min(long... array) {
182    checkArgument(array.length > 0);
183    long min = array[0];
184    for (int i = 1; i < array.length; i++) {
185      if (array[i] < min) {
186        min = array[i];
187      }
188    }
189    return min;
190  }
191
192  /**
193   * Returns the greatest value present in {@code array}.
194   *
195   * @param array a <i>nonempty</i> array of {@code long} values
196   * @return the value present in {@code array} that is greater than or equal to
197   *     every other value in the array
198   * @throws IllegalArgumentException if {@code array} is empty
199   */
200  public static long max(long... array) {
201    checkArgument(array.length > 0);
202    long max = array[0];
203    for (int i = 1; i < array.length; i++) {
204      if (array[i] > max) {
205        max = array[i];
206      }
207    }
208    return max;
209  }
210
211  /**
212   * Returns the values from each provided array combined into a single array.
213   * For example, {@code concat(new long[] {a, b}, new long[] {}, new
214   * long[] {c}} returns the array {@code {a, b, c}}.
215   *
216   * @param arrays zero or more {@code long} arrays
217   * @return a single array containing all the values from the source arrays, in
218   *     order
219   */
220  public static long[] concat(long[]... arrays) {
221    int length = 0;
222    for (long[] array : arrays) {
223      length += array.length;
224    }
225    long[] result = new long[length];
226    int pos = 0;
227    for (long[] array : arrays) {
228      System.arraycopy(array, 0, result, pos, array.length);
229      pos += array.length;
230    }
231    return result;
232  }
233
234  /**
235   * Returns a big-endian representation of {@code value} in an 8-element byte
236   * array; equivalent to {@code ByteBuffer.allocate(8).putLong(value).array()}.
237   * For example, the input value {@code 0x1213141516171819L} would yield the
238   * byte array {@code {0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19}}.
239   *
240   * <p>If you need to convert and concatenate several values (possibly even of
241   * different types), use a shared {@link java.nio.ByteBuffer} instance, or use
242   * {@link com.google.common.io.ByteStreams#newDataOutput()} to get a growable
243   * buffer.
244   */
245  @GwtIncompatible("doesn't work")
246  public static byte[] toByteArray(long value) {
247    return new byte[] {
248        (byte) (value >> 56),
249        (byte) (value >> 48),
250        (byte) (value >> 40),
251        (byte) (value >> 32),
252        (byte) (value >> 24),
253        (byte) (value >> 16),
254        (byte) (value >> 8),
255        (byte) value};
256  }
257
258  /**
259   * Returns the {@code long} value whose big-endian representation is
260   * stored in the first 8 bytes of {@code bytes}; equivalent to {@code
261   * ByteBuffer.wrap(bytes).getLong()}. For example, the input byte array
262   * {@code {0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19}} would yield the
263   * {@code long} value {@code 0x1213141516171819L}.
264   *
265   * <p>Arguably, it's preferable to use {@link java.nio.ByteBuffer}; that
266   * library exposes much more flexibility at little cost in readability.
267   *
268   * @throws IllegalArgumentException if {@code bytes} has fewer than 8
269   *     elements
270   */
271  @GwtIncompatible("doesn't work")
272  public static long fromByteArray(byte[] bytes) {
273    checkArgument(bytes.length >= BYTES,
274        "array too small: %s < %s", bytes.length, BYTES);
275    return fromBytes(bytes[0], bytes[1], bytes[2], bytes[3], 
276        bytes[4], bytes[5], bytes[6], bytes[7]) ;
277  }
278
279  /**
280   * Returns the {@code long} value whose byte representation is the given 8
281   * bytes, in big-endian order; equivalent to {@code Longs.fromByteArray(new
282   * byte[] {b1, b2, b3, b4, b5, b6, b7, b8})}.
283   *
284   * @since 7
285   */
286  @GwtIncompatible("doesn't work")
287  public static long fromBytes(byte b1, byte b2, byte b3, byte b4,
288      byte b5, byte b6, byte b7, byte b8) {
289    return (b1 & 0xFFL) << 56
290        | (b2 & 0xFFL) << 48
291        | (b3 & 0xFFL) << 40
292        | (b4 & 0xFFL) << 32
293        | (b5 & 0xFFL) << 24
294        | (b6 & 0xFFL) << 16
295        | (b7 & 0xFFL) << 8
296        | (b8 & 0xFFL);
297  }
298
299  /**
300   * Returns an array containing the same values as {@code array}, but
301   * guaranteed to be of a specified minimum length. If {@code array} already
302   * has a length of at least {@code minLength}, it is returned directly.
303   * Otherwise, a new array of size {@code minLength + padding} is returned,
304   * containing the values of {@code array}, and zeroes in the remaining places.
305   *
306   * @param array the source array
307   * @param minLength the minimum length the returned array must guarantee
308   * @param padding an extra amount to "grow" the array by if growth is
309   *     necessary
310   * @throws IllegalArgumentException if {@code minLength} or {@code padding} is
311   *     negative
312   * @return an array containing the values of {@code array}, with guaranteed
313   *     minimum length {@code minLength}
314   */
315  public static long[] ensureCapacity(
316      long[] array, int minLength, int padding) {
317    checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
318    checkArgument(padding >= 0, "Invalid padding: %s", padding);
319    return (array.length < minLength)
320        ? copyOf(array, minLength + padding)
321        : array;
322  }
323
324  // Arrays.copyOf() requires Java 6
325  private static long[] copyOf(long[] original, int length) {
326    long[] copy = new long[length];
327    System.arraycopy(original, 0, copy, 0, Math.min(original.length, length));
328    return copy;
329  }
330
331  /**
332   * Returns a string containing the supplied {@code long} values separated
333   * by {@code separator}. For example, {@code join("-", 1L, 2L, 3L)} returns
334   * the string {@code "1-2-3"}.
335   *
336   * @param separator the text that should appear between consecutive values in
337   *     the resulting string (but not at the start or end)
338   * @param array an array of {@code long} values, possibly empty
339   */
340  public static String join(String separator, long... array) {
341    checkNotNull(separator);
342    if (array.length == 0) {
343      return "";
344    }
345
346    // For pre-sizing a builder, just get the right order of magnitude
347    StringBuilder builder = new StringBuilder(array.length * 10);
348    builder.append(array[0]);
349    for (int i = 1; i < array.length; i++) {
350      builder.append(separator).append(array[i]);
351    }
352    return builder.toString();
353  }
354
355  /**
356   * Returns a comparator that compares two {@code long} arrays
357   * lexicographically. That is, it compares, using {@link
358   * #compare(long, long)}), the first pair of values that follow any
359   * common prefix, or when one array is a prefix of the other, treats the
360   * shorter array as the lesser. For example,
361   * {@code [] < [1L] < [1L, 2L] < [2L]}.
362   *
363   * <p>The returned comparator is inconsistent with {@link
364   * Object#equals(Object)} (since arrays support only identity equality), but
365   * it is consistent with {@link Arrays#equals(long[], long[])}.
366   *
367   * @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order">
368   *     Lexicographical order article at Wikipedia</a>
369   * @since 2
370   */
371  public static Comparator<long[]> lexicographicalComparator() {
372    return LexicographicalComparator.INSTANCE;
373  }
374
375  private enum LexicographicalComparator implements Comparator<long[]> {
376    INSTANCE;
377
378    @Override
379    public int compare(long[] left, long[] right) {
380      int minLength = Math.min(left.length, right.length);
381      for (int i = 0; i < minLength; i++) {
382        int result = Longs.compare(left[i], right[i]);
383        if (result != 0) {
384          return result;
385        }
386      }
387      return left.length - right.length;
388    }
389  }
390
391  /**
392   * Copies a collection of {@code Long} instances into a new array of
393   * primitive {@code long} values.
394   *
395   * <p>Elements are copied from the argument collection as if by {@code
396   * collection.toArray()}.  Calling this method is as thread-safe as calling
397   * that method.
398   *
399   * @param collection a collection of {@code Long} objects
400   * @return an array containing the same values as {@code collection}, in the
401   *     same order, converted to primitives
402   * @throws NullPointerException if {@code collection} or any of its elements
403   *     is null
404   */
405  public static long[] toArray(Collection<Long> collection) {
406    if (collection instanceof LongArrayAsList) {
407      return ((LongArrayAsList) collection).toLongArray();
408    }
409
410    Object[] boxedArray = collection.toArray();
411    int len = boxedArray.length;
412    long[] array = new long[len];
413    for (int i = 0; i < len; i++) {
414      array[i] = (Long) boxedArray[i];
415    }
416    return array;
417  }
418
419  /**
420   * Returns a fixed-size list backed by the specified array, similar to {@link
421   * Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)},
422   * but any attempt to set a value to {@code null} will result in a {@link
423   * NullPointerException}.
424   *
425   * <p>The returned list maintains the values, but not the identities, of
426   * {@code Long} objects written to or read from it.  For example, whether
427   * {@code list.get(0) == list.get(0)} is true for the returned list is
428   * unspecified.
429   *
430   * @param backingArray the array to back the list
431   * @return a list view of the array
432   */
433  public static List<Long> asList(long... backingArray) {
434    if (backingArray.length == 0) {
435      return Collections.emptyList();
436    }
437    return new LongArrayAsList(backingArray);
438  }
439
440  @GwtCompatible
441  private static class LongArrayAsList extends AbstractList<Long>
442      implements RandomAccess, Serializable {
443    final long[] array;
444    final int start;
445    final int end;
446
447    LongArrayAsList(long[] array) {
448      this(array, 0, array.length);
449    }
450
451    LongArrayAsList(long[] array, int start, int end) {
452      this.array = array;
453      this.start = start;
454      this.end = end;
455    }
456
457    @Override public int size() {
458      return end - start;
459    }
460
461    @Override public boolean isEmpty() {
462      return false;
463    }
464
465    @Override public Long get(int index) {
466      checkElementIndex(index, size());
467      return array[start + index];
468    }
469
470    @Override public boolean contains(Object target) {
471      // Overridden to prevent a ton of boxing
472      return (target instanceof Long)
473          && Longs.indexOf(array, (Long) target, start, end) != -1;
474    }
475
476    @Override public int indexOf(Object target) {
477      // Overridden to prevent a ton of boxing
478      if (target instanceof Long) {
479        int i = Longs.indexOf(array, (Long) target, start, end);
480        if (i >= 0) {
481          return i - start;
482        }
483      }
484      return -1;
485    }
486
487    @Override public int lastIndexOf(Object target) {
488      // Overridden to prevent a ton of boxing
489      if (target instanceof Long) {
490        int i = Longs.lastIndexOf(array, (Long) target, start, end);
491        if (i >= 0) {
492          return i - start;
493        }
494      }
495      return -1;
496    }
497
498    @Override public Long set(int index, Long element) {
499      checkElementIndex(index, size());
500      long oldValue = array[start + index];
501      array[start + index] = element;
502      return oldValue;
503    }
504
505    @Override public List<Long> subList(int fromIndex, int toIndex) {
506      int size = size();
507      checkPositionIndexes(fromIndex, toIndex, size);
508      if (fromIndex == toIndex) {
509        return Collections.emptyList();
510      }
511      return new LongArrayAsList(array, start + fromIndex, start + toIndex);
512    }
513
514    @Override public boolean equals(Object object) {
515      if (object == this) {
516        return true;
517      }
518      if (object instanceof LongArrayAsList) {
519        LongArrayAsList that = (LongArrayAsList) object;
520        int size = size();
521        if (that.size() != size) {
522          return false;
523        }
524        for (int i = 0; i < size; i++) {
525          if (array[start + i] != that.array[that.start + i]) {
526            return false;
527          }
528        }
529        return true;
530      }
531      return super.equals(object);
532    }
533
534    @Override public int hashCode() {
535      int result = 1;
536      for (int i = start; i < end; i++) {
537        result = 31 * result + Longs.hashCode(array[i]);
538      }
539      return result;
540    }
541
542    @Override public String toString() {
543      StringBuilder builder = new StringBuilder(size() * 10);
544      builder.append('[').append(array[start]);
545      for (int i = start + 1; i < end; i++) {
546        builder.append(", ").append(array[i]);
547      }
548      return builder.append(']').toString();
549    }
550
551    long[] toLongArray() {
552      // Arrays.copyOfRange() requires Java 6
553      int size = size();
554      long[] result = new long[size];
555      System.arraycopy(array, start, result, 0, size);
556      return result;
557    }
558
559    private static final long serialVersionUID = 0;
560  }
561}