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 int} primitives, that are not
038 * already found in either {@link Integer} or {@link Arrays}.
039 *
040 * @author Kevin Bourrillion
041 * @since 1
042 */
043@GwtCompatible(emulated = true)
044public final class Ints {
045  private Ints() {}
046
047  /**
048   * The number of bytes required to represent a primitive {@code int}
049   * value.
050   */
051  public static final int BYTES = Integer.SIZE / Byte.SIZE;
052
053  /**
054   * Returns a hash code for {@code value}; equal to the result of invoking
055   * {@code ((Integer) value).hashCode()}.
056   *
057   * @param value a primitive {@code int} value
058   * @return a hash code for the value
059   */
060  public static int hashCode(int value) {
061    return value;
062  }
063
064  /**
065   * Returns the {@code int} value that is equal to {@code value}, if possible.
066   *
067   * @param value any value in the range of the {@code int} type
068   * @return the {@code int} value that equals {@code value}
069   * @throws IllegalArgumentException if {@code value} is greater than {@link
070   *     Integer#MAX_VALUE} or less than {@link Integer#MIN_VALUE}
071   */
072  public static int checkedCast(long value) {
073    int result = (int) value;
074    checkArgument(result == value, "Out of range: %s", value);
075    return result;
076  }
077
078  /**
079   * Returns the {@code int} nearest in value to {@code value}.
080   *
081   * @param value any {@code long} value
082   * @return the same value cast to {@code int} if it is in the range of the
083   *     {@code int} type, {@link Integer#MAX_VALUE} if it is too large,
084   *     or {@link Integer#MIN_VALUE} if it is too small
085   */
086  public static int saturatedCast(long value) {
087    if (value > Integer.MAX_VALUE) {
088      return Integer.MAX_VALUE;
089    }
090    if (value < Integer.MIN_VALUE) {
091      return Integer.MIN_VALUE;
092    }
093    return (int) value;
094  }
095
096  /**
097   * Compares the two specified {@code int} values. The sign of the value
098   * returned is the same as that of {@code ((Integer) a).compareTo(b)}.
099   *
100   * @param a the first {@code int} to compare
101   * @param b the second {@code int} to compare
102   * @return a negative value if {@code a} is less than {@code b}; a positive
103   *     value if {@code a} is greater than {@code b}; or zero if they are equal
104   */
105  public static int compare(int a, int b) {
106    return (a < b) ? -1 : ((a > b) ? 1 : 0);
107  }
108
109  /**
110   * Returns {@code true} if {@code target} is present as an element anywhere in
111   * {@code array}.
112   *
113   * @param array an array of {@code int} values, possibly empty
114   * @param target a primitive {@code int} value
115   * @return {@code true} if {@code array[i] == target} for some value of {@code
116   *     i}
117   */
118  public static boolean contains(int[] array, int target) {
119    for (int value : array) {
120      if (value == target) {
121        return true;
122      }
123    }
124    return false;
125  }
126
127  /**
128   * Returns the index of the first appearance of the value {@code target} in
129   * {@code array}.
130   *
131   * @param array an array of {@code int} values, possibly empty
132   * @param target a primitive {@code int} value
133   * @return the least index {@code i} for which {@code array[i] == target}, or
134   *     {@code -1} if no such index exists.
135   */
136  public static int indexOf(int[] array, int target) {
137    return indexOf(array, target, 0, array.length);
138  }
139
140  // TODO(kevinb): consider making this public
141  private static int indexOf(
142      int[] array, int target, int start, int end) {
143    for (int i = start; i < end; i++) {
144      if (array[i] == target) {
145        return i;
146      }
147    }
148    return -1;
149  }
150
151  /**
152   * Returns the start position of the first occurrence of the specified {@code
153   * target} within {@code array}, or {@code -1} if there is no such occurrence.
154   *
155   * <p>More formally, returns the lowest index {@code i} such that {@code
156   * java.util.Arrays.copyOfRange(array, i, i + target.length)} contains exactly
157   * the same elements as {@code target}.
158   *
159   * @param array the array to search for the sequence {@code target}
160   * @param target the array to search for as a sub-sequence of {@code array}
161   */
162  public static int indexOf(int[] array, int[] target) {
163    checkNotNull(array, "array");
164    checkNotNull(target, "target");
165    if (target.length == 0) {
166      return 0;
167    }
168
169    outer:
170    for (int i = 0; i < array.length - target.length + 1; i++) {
171      for (int j = 0; j < target.length; j++) {
172        if (array[i + j] != target[j]) {
173          continue outer;
174        }
175      }
176      return i;
177    }
178    return -1;
179  }
180
181  /**
182   * Returns the index of the last appearance of the value {@code target} in
183   * {@code array}.
184   *
185   * @param array an array of {@code int} values, possibly empty
186   * @param target a primitive {@code int} value
187   * @return the greatest index {@code i} for which {@code array[i] == target},
188   *     or {@code -1} if no such index exists.
189   */
190  public static int lastIndexOf(int[] array, int target) {
191    return lastIndexOf(array, target, 0, array.length);
192  }
193
194  // TODO(kevinb): consider making this public
195  private static int lastIndexOf(
196      int[] array, int target, int start, int end) {
197    for (int i = end - 1; i >= start; i--) {
198      if (array[i] == target) {
199        return i;
200      }
201    }
202    return -1;
203  }
204
205  /**
206   * Returns the least value present in {@code array}.
207   *
208   * @param array a <i>nonempty</i> array of {@code int} values
209   * @return the value present in {@code array} that is less than or equal to
210   *     every other value in the array
211   * @throws IllegalArgumentException if {@code array} is empty
212   */
213  public static int min(int... array) {
214    checkArgument(array.length > 0);
215    int min = array[0];
216    for (int i = 1; i < array.length; i++) {
217      if (array[i] < min) {
218        min = array[i];
219      }
220    }
221    return min;
222  }
223
224  /**
225   * Returns the greatest value present in {@code array}.
226   *
227   * @param array a <i>nonempty</i> array of {@code int} values
228   * @return the value present in {@code array} that is greater than or equal to
229   *     every other value in the array
230   * @throws IllegalArgumentException if {@code array} is empty
231   */
232  public static int max(int... array) {
233    checkArgument(array.length > 0);
234    int max = array[0];
235    for (int i = 1; i < array.length; i++) {
236      if (array[i] > max) {
237        max = array[i];
238      }
239    }
240    return max;
241  }
242
243  /**
244   * Returns the values from each provided array combined into a single array.
245   * For example, {@code concat(new int[] {a, b}, new int[] {}, new
246   * int[] {c}} returns the array {@code {a, b, c}}.
247   *
248   * @param arrays zero or more {@code int} arrays
249   * @return a single array containing all the values from the source arrays, in
250   *     order
251   */
252  public static int[] concat(int[]... arrays) {
253    int length = 0;
254    for (int[] array : arrays) {
255      length += array.length;
256    }
257    int[] result = new int[length];
258    int pos = 0;
259    for (int[] array : arrays) {
260      System.arraycopy(array, 0, result, pos, array.length);
261      pos += array.length;
262    }
263    return result;
264  }
265
266  /**
267   * Returns a big-endian representation of {@code value} in a 4-element byte
268   * array; equivalent to {@code ByteBuffer.allocate(4).putInt(value).array()}.
269   * For example, the input value {@code 0x12131415} would yield the byte array
270   * {@code {0x12, 0x13, 0x14, 0x15}}.
271   *
272   * <p>If you need to convert and concatenate several values (possibly even of
273   * different types), use a shared {@link java.nio.ByteBuffer} instance, or use
274   * {@link com.google.common.io.ByteStreams#newDataOutput()} to get a growable
275   * buffer.
276   */
277  @GwtIncompatible("doesn't work")
278  public static byte[] toByteArray(int value) {
279    return new byte[] {
280        (byte) (value >> 24),
281        (byte) (value >> 16),
282        (byte) (value >> 8),
283        (byte) value};
284  }
285
286  /**
287   * Returns the {@code int} value whose big-endian representation is stored in
288   * the first 4 bytes of {@code bytes}; equivalent to {@code
289   * ByteBuffer.wrap(bytes).getInt()}. For example, the input byte array {@code
290   * {0x12, 0x13, 0x14, 0x15, 0x33}} would yield the {@code int} value {@code
291   * 0x12131415}.
292   *
293   * <p>Arguably, it's preferable to use {@link java.nio.ByteBuffer}; that
294   * library exposes much more flexibility at little cost in readability.
295   *
296   * @throws IllegalArgumentException if {@code bytes} has fewer than 4 elements
297   */
298  @GwtIncompatible("doesn't work")
299  public static int fromByteArray(byte[] bytes) {
300    checkArgument(bytes.length >= BYTES,
301        "array too small: %s < %s", bytes.length, BYTES);
302    return fromBytes(bytes[0], bytes[1], bytes[2], bytes[3]);
303  }
304
305  /**
306   * Returns the {@code int} value whose byte representation is the given 4
307   * bytes, in big-endian order; equivalent to {@code Ints.fromByteArray(new
308   * byte[] {b1, b2, b3, b4})}.
309   *
310   * @since 7
311   */
312  @GwtIncompatible("doesn't work")
313  public static int fromBytes(byte b1, byte b2, byte b3, byte b4) {
314    return b1 << 24 | (b2 & 0xFF) << 16 | (b3 & 0xFF) << 8 | (b4 & 0xFF);
315  }
316
317  /**
318   * Returns an array containing the same values as {@code array}, but
319   * guaranteed to be of a specified minimum length. If {@code array} already
320   * has a length of at least {@code minLength}, it is returned directly.
321   * Otherwise, a new array of size {@code minLength + padding} is returned,
322   * containing the values of {@code array}, and zeroes in the remaining places.
323   *
324   * @param array the source array
325   * @param minLength the minimum length the returned array must guarantee
326   * @param padding an extra amount to "grow" the array by if growth is
327   *     necessary
328   * @throws IllegalArgumentException if {@code minLength} or {@code padding} is
329   *     negative
330   * @return an array containing the values of {@code array}, with guaranteed
331   *     minimum length {@code minLength}
332   */
333  public static int[] ensureCapacity(
334      int[] array, int minLength, int padding) {
335    checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
336    checkArgument(padding >= 0, "Invalid padding: %s", padding);
337    return (array.length < minLength)
338        ? copyOf(array, minLength + padding)
339        : array;
340  }
341
342  // Arrays.copyOf() requires Java 6
343  private static int[] copyOf(int[] original, int length) {
344    int[] copy = new int[length];
345    System.arraycopy(original, 0, copy, 0, Math.min(original.length, length));
346    return copy;
347  }
348
349  /**
350   * Returns a string containing the supplied {@code int} values separated
351   * by {@code separator}. For example, {@code join("-", 1, 2, 3)} returns
352   * the string {@code "1-2-3"}.
353   *
354   * @param separator the text that should appear between consecutive values in
355   *     the resulting string (but not at the start or end)
356   * @param array an array of {@code int} values, possibly empty
357   */
358  public static String join(String separator, int... array) {
359    checkNotNull(separator);
360    if (array.length == 0) {
361      return "";
362    }
363
364    // For pre-sizing a builder, just get the right order of magnitude
365    StringBuilder builder = new StringBuilder(array.length * 5);
366    builder.append(array[0]);
367    for (int i = 1; i < array.length; i++) {
368      builder.append(separator).append(array[i]);
369    }
370    return builder.toString();
371  }
372
373  /**
374   * Returns a comparator that compares two {@code int} arrays
375   * lexicographically. That is, it compares, using {@link
376   * #compare(int, int)}), the first pair of values that follow any
377   * common prefix, or when one array is a prefix of the other, treats the
378   * shorter array as the lesser. For example, {@code [] < [1] < [1, 2] < [2]}.
379   *
380   * <p>The returned comparator is inconsistent with {@link
381   * Object#equals(Object)} (since arrays support only identity equality), but
382   * it is consistent with {@link Arrays#equals(int[], int[])}.
383   *
384   * @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order">
385   *     Lexicographical order article at Wikipedia</a>
386   * @since 2
387   */
388  public static Comparator<int[]> lexicographicalComparator() {
389    return LexicographicalComparator.INSTANCE;
390  }
391
392  private enum LexicographicalComparator implements Comparator<int[]> {
393    INSTANCE;
394
395    @Override
396    public int compare(int[] left, int[] right) {
397      int minLength = Math.min(left.length, right.length);
398      for (int i = 0; i < minLength; i++) {
399        int result = Ints.compare(left[i], right[i]);
400        if (result != 0) {
401          return result;
402        }
403      }
404      return left.length - right.length;
405    }
406  }
407
408  /**
409   * Copies a collection of {@code Integer} instances into a new array of
410   * primitive {@code int} values.
411   *
412   * <p>Elements are copied from the argument collection as if by {@code
413   * collection.toArray()}.  Calling this method is as thread-safe as calling
414   * that method.
415   *
416   * @param collection a collection of {@code Integer} objects
417   * @return an array containing the same values as {@code collection}, in the
418   *     same order, converted to primitives
419   * @throws NullPointerException if {@code collection} or any of its elements
420   *     is null
421   */
422  public static int[] toArray(Collection<Integer> collection) {
423    if (collection instanceof IntArrayAsList) {
424      return ((IntArrayAsList) collection).toIntArray();
425    }
426
427    Object[] boxedArray = collection.toArray();
428    int len = boxedArray.length;
429    int[] array = new int[len];
430    for (int i = 0; i < len; i++) {
431      array[i] = (Integer) boxedArray[i];
432    }
433    return array;
434  }
435
436  /**
437   * Returns a fixed-size list backed by the specified array, similar to {@link
438   * Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)},
439   * but any attempt to set a value to {@code null} will result in a {@link
440   * NullPointerException}.
441   *
442   * <p>The returned list maintains the values, but not the identities, of
443   * {@code Integer} objects written to or read from it.  For example, whether
444   * {@code list.get(0) == list.get(0)} is true for the returned list is
445   * unspecified.
446   *
447   * @param backingArray the array to back the list
448   * @return a list view of the array
449   */
450  public static List<Integer> asList(int... backingArray) {
451    if (backingArray.length == 0) {
452      return Collections.emptyList();
453    }
454    return new IntArrayAsList(backingArray);
455  }
456
457  @GwtCompatible
458  private static class IntArrayAsList extends AbstractList<Integer>
459      implements RandomAccess, Serializable {
460    final int[] array;
461    final int start;
462    final int end;
463
464    IntArrayAsList(int[] array) {
465      this(array, 0, array.length);
466    }
467
468    IntArrayAsList(int[] array, int start, int end) {
469      this.array = array;
470      this.start = start;
471      this.end = end;
472    }
473
474    @Override public int size() {
475      return end - start;
476    }
477
478    @Override public boolean isEmpty() {
479      return false;
480    }
481
482    @Override public Integer get(int index) {
483      checkElementIndex(index, size());
484      return array[start + index];
485    }
486
487    @Override public boolean contains(Object target) {
488      // Overridden to prevent a ton of boxing
489      return (target instanceof Integer)
490          && Ints.indexOf(array, (Integer) target, start, end) != -1;
491    }
492
493    @Override public int indexOf(Object target) {
494      // Overridden to prevent a ton of boxing
495      if (target instanceof Integer) {
496        int i = Ints.indexOf(array, (Integer) target, start, end);
497        if (i >= 0) {
498          return i - start;
499        }
500      }
501      return -1;
502    }
503
504    @Override public int lastIndexOf(Object target) {
505      // Overridden to prevent a ton of boxing
506      if (target instanceof Integer) {
507        int i = Ints.lastIndexOf(array, (Integer) target, start, end);
508        if (i >= 0) {
509          return i - start;
510        }
511      }
512      return -1;
513    }
514
515    @Override public Integer set(int index, Integer element) {
516      checkElementIndex(index, size());
517      int oldValue = array[start + index];
518      array[start + index] = element;
519      return oldValue;
520    }
521
522    @Override public List<Integer> subList(int fromIndex, int toIndex) {
523      int size = size();
524      checkPositionIndexes(fromIndex, toIndex, size);
525      if (fromIndex == toIndex) {
526        return Collections.emptyList();
527      }
528      return new IntArrayAsList(array, start + fromIndex, start + toIndex);
529    }
530
531    @Override public boolean equals(Object object) {
532      if (object == this) {
533        return true;
534      }
535      if (object instanceof IntArrayAsList) {
536        IntArrayAsList that = (IntArrayAsList) object;
537        int size = size();
538        if (that.size() != size) {
539          return false;
540        }
541        for (int i = 0; i < size; i++) {
542          if (array[start + i] != that.array[that.start + i]) {
543            return false;
544          }
545        }
546        return true;
547      }
548      return super.equals(object);
549    }
550
551    @Override public int hashCode() {
552      int result = 1;
553      for (int i = start; i < end; i++) {
554        result = 31 * result + Ints.hashCode(array[i]);
555      }
556      return result;
557    }
558
559    @Override public String toString() {
560      StringBuilder builder = new StringBuilder(size() * 5);
561      builder.append('[').append(array[start]);
562      for (int i = start + 1; i < end; i++) {
563        builder.append(", ").append(array[i]);
564      }
565      return builder.append(']').toString();
566    }
567
568    int[] toIntArray() {
569      // Arrays.copyOfRange() requires Java 6
570      int size = size();
571      int[] result = new int[size];
572      System.arraycopy(array, start, result, 0, size);
573      return result;
574    }
575
576    private static final long serialVersionUID = 0;
577  }
578}