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.Beta;
025import com.google.common.annotations.GwtCompatible;
026import com.google.common.annotations.GwtIncompatible;
027import com.google.common.base.Converter;
028
029import java.io.Serializable;
030import java.util.AbstractList;
031import java.util.Arrays;
032import java.util.Collection;
033import java.util.Collections;
034import java.util.Comparator;
035import java.util.List;
036import java.util.RandomAccess;
037
038import javax.annotation.CheckForNull;
039
040/**
041 * Static utility methods pertaining to {@code int} primitives, that are not
042 * already found in either {@link Integer} or {@link Arrays}.
043 *
044 * <p>See the Guava User Guide article on <a href=
045 * "http://code.google.com/p/guava-libraries/wiki/PrimitivesExplained">
046 * primitive utilities</a>.
047 *
048 * @author Kevin Bourrillion
049 * @since 1.0
050 */
051@GwtCompatible(emulated = true)
052public final class Ints {
053  private Ints() {}
054
055  /**
056   * The number of bytes required to represent a primitive {@code int}
057   * value.
058   */
059  public static final int BYTES = Integer.SIZE / Byte.SIZE;
060
061  /**
062   * The largest power of two that can be represented as an {@code int}.
063   *
064   * @since 10.0
065   */
066  public static final int MAX_POWER_OF_TWO = 1 << (Integer.SIZE - 2);
067
068  /**
069   * Returns a hash code for {@code value}; equal to the result of invoking
070   * {@code ((Integer) value).hashCode()}.
071   *
072   * @param value a primitive {@code int} value
073   * @return a hash code for the value
074   */
075  public static int hashCode(int value) {
076    return value;
077  }
078
079  /**
080   * Returns the {@code int} value that is equal to {@code value}, if possible.
081   *
082   * @param value any value in the range of the {@code int} type
083   * @return the {@code int} value that equals {@code value}
084   * @throws IllegalArgumentException if {@code value} is greater than {@link
085   *     Integer#MAX_VALUE} or less than {@link Integer#MIN_VALUE}
086   */
087  public static int checkedCast(long value) {
088    int result = (int) value;
089    if (result != value) {
090      // don't use checkArgument here, to avoid boxing
091      throw new IllegalArgumentException("Out of range: " + value);
092    }
093    return result;
094  }
095
096  /**
097   * Returns the {@code int} nearest in value to {@code value}.
098   *
099   * @param value any {@code long} value
100   * @return the same value cast to {@code int} if it is in the range of the
101   *     {@code int} type, {@link Integer#MAX_VALUE} if it is too large,
102   *     or {@link Integer#MIN_VALUE} if it is too small
103   */
104  public static int saturatedCast(long value) {
105    if (value > Integer.MAX_VALUE) {
106      return Integer.MAX_VALUE;
107    }
108    if (value < Integer.MIN_VALUE) {
109      return Integer.MIN_VALUE;
110    }
111    return (int) value;
112  }
113
114  /**
115   * Compares the two specified {@code int} values. The sign of the value
116   * returned is the same as that of {@code ((Integer) a).compareTo(b)}.
117   *
118   * <p><b>Note:</b> projects using JDK 7 or later should use the equivalent
119   * {@link Integer#compare} method instead.
120   *
121   * @param a the first {@code int} to compare
122   * @param b the second {@code int} to compare
123   * @return a negative value if {@code a} is less than {@code b}; a positive
124   *     value if {@code a} is greater than {@code b}; or zero if they are equal
125   */
126  public static int compare(int a, int b) {
127    return (a < b) ? -1 : ((a > b) ? 1 : 0);
128  }
129
130  /**
131   * Returns {@code true} if {@code target} is present as an element anywhere in
132   * {@code array}.
133   *
134   * @param array an array of {@code int} values, possibly empty
135   * @param target a primitive {@code int} value
136   * @return {@code true} if {@code array[i] == target} for some value of {@code
137   *     i}
138   */
139  public static boolean contains(int[] array, int target) {
140    for (int value : array) {
141      if (value == target) {
142        return true;
143      }
144    }
145    return false;
146  }
147
148  /**
149   * Returns the index of the first appearance of the value {@code target} in
150   * {@code array}.
151   *
152   * @param array an array of {@code int} values, possibly empty
153   * @param target a primitive {@code int} value
154   * @return the least index {@code i} for which {@code array[i] == target}, or
155   *     {@code -1} if no such index exists.
156   */
157  public static int indexOf(int[] array, int target) {
158    return indexOf(array, target, 0, array.length);
159  }
160
161  // TODO(kevinb): consider making this public
162  private static int indexOf(
163      int[] array, int target, int start, int end) {
164    for (int i = start; i < end; i++) {
165      if (array[i] == target) {
166        return i;
167      }
168    }
169    return -1;
170  }
171
172  /**
173   * Returns the start position of the first occurrence of the specified {@code
174   * target} within {@code array}, or {@code -1} if there is no such occurrence.
175   *
176   * <p>More formally, returns the lowest index {@code i} such that {@code
177   * java.util.Arrays.copyOfRange(array, i, i + target.length)} contains exactly
178   * the same elements as {@code target}.
179   *
180   * @param array the array to search for the sequence {@code target}
181   * @param target the array to search for as a sub-sequence of {@code array}
182   */
183  public static int indexOf(int[] array, int[] target) {
184    checkNotNull(array, "array");
185    checkNotNull(target, "target");
186    if (target.length == 0) {
187      return 0;
188    }
189
190    outer:
191    for (int i = 0; i < array.length - target.length + 1; i++) {
192      for (int j = 0; j < target.length; j++) {
193        if (array[i + j] != target[j]) {
194          continue outer;
195        }
196      }
197      return i;
198    }
199    return -1;
200  }
201
202  /**
203   * Returns the index of the last appearance of the value {@code target} in
204   * {@code array}.
205   *
206   * @param array an array of {@code int} values, possibly empty
207   * @param target a primitive {@code int} value
208   * @return the greatest index {@code i} for which {@code array[i] == target},
209   *     or {@code -1} if no such index exists.
210   */
211  public static int lastIndexOf(int[] array, int target) {
212    return lastIndexOf(array, target, 0, array.length);
213  }
214
215  // TODO(kevinb): consider making this public
216  private static int lastIndexOf(
217      int[] array, int target, int start, int end) {
218    for (int i = end - 1; i >= start; i--) {
219      if (array[i] == target) {
220        return i;
221      }
222    }
223    return -1;
224  }
225
226  /**
227   * Returns the least value present in {@code array}.
228   *
229   * @param array a <i>nonempty</i> array of {@code int} values
230   * @return the value present in {@code array} that is less than or equal to
231   *     every other value in the array
232   * @throws IllegalArgumentException if {@code array} is empty
233   */
234  public static int min(int... array) {
235    checkArgument(array.length > 0);
236    int min = array[0];
237    for (int i = 1; i < array.length; i++) {
238      if (array[i] < min) {
239        min = array[i];
240      }
241    }
242    return min;
243  }
244
245  /**
246   * Returns the greatest value present in {@code array}.
247   *
248   * @param array a <i>nonempty</i> array of {@code int} values
249   * @return the value present in {@code array} that is greater than or equal to
250   *     every other value in the array
251   * @throws IllegalArgumentException if {@code array} is empty
252   */
253  public static int max(int... array) {
254    checkArgument(array.length > 0);
255    int max = array[0];
256    for (int i = 1; i < array.length; i++) {
257      if (array[i] > max) {
258        max = array[i];
259      }
260    }
261    return max;
262  }
263
264  /**
265   * Returns the values from each provided array combined into a single array.
266   * For example, {@code concat(new int[] {a, b}, new int[] {}, new
267   * int[] {c}} returns the array {@code {a, b, c}}.
268   *
269   * @param arrays zero or more {@code int} arrays
270   * @return a single array containing all the values from the source arrays, in
271   *     order
272   */
273  public static int[] concat(int[]... arrays) {
274    int length = 0;
275    for (int[] array : arrays) {
276      length += array.length;
277    }
278    int[] result = new int[length];
279    int pos = 0;
280    for (int[] array : arrays) {
281      System.arraycopy(array, 0, result, pos, array.length);
282      pos += array.length;
283    }
284    return result;
285  }
286
287  /**
288   * Returns a big-endian representation of {@code value} in a 4-element byte
289   * array; equivalent to {@code ByteBuffer.allocate(4).putInt(value).array()}.
290   * For example, the input value {@code 0x12131415} would yield the byte array
291   * {@code {0x12, 0x13, 0x14, 0x15}}.
292   *
293   * <p>If you need to convert and concatenate several values (possibly even of
294   * different types), use a shared {@link java.nio.ByteBuffer} instance, or use
295   * {@link com.google.common.io.ByteStreams#newDataOutput()} to get a growable
296   * buffer.
297   */
298  @GwtIncompatible("doesn't work")
299  public static byte[] toByteArray(int value) {
300    return new byte[] {
301        (byte) (value >> 24),
302        (byte) (value >> 16),
303        (byte) (value >> 8),
304        (byte) value};
305  }
306
307  /**
308   * Returns the {@code int} value whose big-endian representation is stored in
309   * the first 4 bytes of {@code bytes}; equivalent to {@code
310   * ByteBuffer.wrap(bytes).getInt()}. For example, the input byte array {@code
311   * {0x12, 0x13, 0x14, 0x15, 0x33}} would yield the {@code int} value {@code
312   * 0x12131415}.
313   *
314   * <p>Arguably, it's preferable to use {@link java.nio.ByteBuffer}; that
315   * library exposes much more flexibility at little cost in readability.
316   *
317   * @throws IllegalArgumentException if {@code bytes} has fewer than 4 elements
318   */
319  @GwtIncompatible("doesn't work")
320  public static int fromByteArray(byte[] bytes) {
321    checkArgument(bytes.length >= BYTES,
322        "array too small: %s < %s", bytes.length, BYTES);
323    return fromBytes(bytes[0], bytes[1], bytes[2], bytes[3]);
324  }
325
326  /**
327   * Returns the {@code int} value whose byte representation is the given 4
328   * bytes, in big-endian order; equivalent to {@code Ints.fromByteArray(new
329   * byte[] {b1, b2, b3, b4})}.
330   *
331   * @since 7.0
332   */
333  @GwtIncompatible("doesn't work")
334  public static int fromBytes(byte b1, byte b2, byte b3, byte b4) {
335    return b1 << 24 | (b2 & 0xFF) << 16 | (b3 & 0xFF) << 8 | (b4 & 0xFF);
336  }
337
338  private static final class IntConverter
339      extends Converter<String, Integer> implements Serializable {
340    static final IntConverter INSTANCE = new IntConverter();
341
342    @Override
343    protected Integer doForward(String value) {
344      return Integer.decode(value);
345    }
346
347    @Override
348    protected String doBackward(Integer value) {
349      return value.toString();
350    }
351
352    @Override
353    public String toString() {
354      return "Ints.stringConverter()";
355    }
356
357    private Object readResolve() {
358      return INSTANCE;
359    }
360    private static final long serialVersionUID = 1;
361  }
362
363  /**
364   * Returns a serializable converter object that converts between strings and
365   * integers using {@link Integer#decode} and {@link Integer#toString()}.
366   *
367   * @since 16.0
368   */
369  @Beta
370  public static Converter<String, Integer> stringConverter() {
371    return IntConverter.INSTANCE;
372  }
373
374  /**
375   * Returns an array containing the same values as {@code array}, but
376   * guaranteed to be of a specified minimum length. If {@code array} already
377   * has a length of at least {@code minLength}, it is returned directly.
378   * Otherwise, a new array of size {@code minLength + padding} is returned,
379   * containing the values of {@code array}, and zeroes in the remaining places.
380   *
381   * @param array the source array
382   * @param minLength the minimum length the returned array must guarantee
383   * @param padding an extra amount to "grow" the array by if growth is
384   *     necessary
385   * @throws IllegalArgumentException if {@code minLength} or {@code padding} is
386   *     negative
387   * @return an array containing the values of {@code array}, with guaranteed
388   *     minimum length {@code minLength}
389   */
390  public static int[] ensureCapacity(
391      int[] array, int minLength, int padding) {
392    checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
393    checkArgument(padding >= 0, "Invalid padding: %s", padding);
394    return (array.length < minLength)
395        ? copyOf(array, minLength + padding)
396        : array;
397  }
398
399  // Arrays.copyOf() requires Java 6
400  private static int[] copyOf(int[] original, int length) {
401    int[] copy = new int[length];
402    System.arraycopy(original, 0, copy, 0, Math.min(original.length, length));
403    return copy;
404  }
405
406  /**
407   * Returns a string containing the supplied {@code int} values separated
408   * by {@code separator}. For example, {@code join("-", 1, 2, 3)} returns
409   * the string {@code "1-2-3"}.
410   *
411   * @param separator the text that should appear between consecutive values in
412   *     the resulting string (but not at the start or end)
413   * @param array an array of {@code int} values, possibly empty
414   */
415  public static String join(String separator, int... array) {
416    checkNotNull(separator);
417    if (array.length == 0) {
418      return "";
419    }
420
421    // For pre-sizing a builder, just get the right order of magnitude
422    StringBuilder builder = new StringBuilder(array.length * 5);
423    builder.append(array[0]);
424    for (int i = 1; i < array.length; i++) {
425      builder.append(separator).append(array[i]);
426    }
427    return builder.toString();
428  }
429
430  /**
431   * Returns a comparator that compares two {@code int} arrays
432   * lexicographically. That is, it compares, using {@link
433   * #compare(int, int)}), the first pair of values that follow any
434   * common prefix, or when one array is a prefix of the other, treats the
435   * shorter array as the lesser. For example, {@code [] < [1] < [1, 2] < [2]}.
436   *
437   * <p>The returned comparator is inconsistent with {@link
438   * Object#equals(Object)} (since arrays support only identity equality), but
439   * it is consistent with {@link Arrays#equals(int[], int[])}.
440   *
441   * @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order">
442   *     Lexicographical order article at Wikipedia</a>
443   * @since 2.0
444   */
445  public static Comparator<int[]> lexicographicalComparator() {
446    return LexicographicalComparator.INSTANCE;
447  }
448
449  private enum LexicographicalComparator implements Comparator<int[]> {
450    INSTANCE;
451
452    @Override
453    public int compare(int[] left, int[] right) {
454      int minLength = Math.min(left.length, right.length);
455      for (int i = 0; i < minLength; i++) {
456        int result = Ints.compare(left[i], right[i]);
457        if (result != 0) {
458          return result;
459        }
460      }
461      return left.length - right.length;
462    }
463  }
464
465  /**
466   * Returns an array containing each value of {@code collection}, converted to
467   * a {@code int} value in the manner of {@link Number#intValue}.
468   *
469   * <p>Elements are copied from the argument collection as if by {@code
470   * collection.toArray()}.  Calling this method is as thread-safe as calling
471   * that method.
472   *
473   * @param collection a collection of {@code Number} instances
474   * @return an array containing the same values as {@code collection}, in the
475   *     same order, converted to primitives
476   * @throws NullPointerException if {@code collection} or any of its elements
477   *     is null
478   * @since 1.0 (parameter was {@code Collection<Integer>} before 12.0)
479   */
480  public static int[] toArray(Collection<? extends Number> collection) {
481    if (collection instanceof IntArrayAsList) {
482      return ((IntArrayAsList) collection).toIntArray();
483    }
484
485    Object[] boxedArray = collection.toArray();
486    int len = boxedArray.length;
487    int[] array = new int[len];
488    for (int i = 0; i < len; i++) {
489      // checkNotNull for GWT (do not optimize)
490      array[i] = ((Number) checkNotNull(boxedArray[i])).intValue();
491    }
492    return array;
493  }
494
495  /**
496   * Returns a fixed-size list backed by the specified array, similar to {@link
497   * Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)},
498   * but any attempt to set a value to {@code null} will result in a {@link
499   * NullPointerException}.
500   *
501   * <p>The returned list maintains the values, but not the identities, of
502   * {@code Integer} objects written to or read from it.  For example, whether
503   * {@code list.get(0) == list.get(0)} is true for the returned list is
504   * unspecified.
505   *
506   * @param backingArray the array to back the list
507   * @return a list view of the array
508   */
509  public static List<Integer> asList(int... backingArray) {
510    if (backingArray.length == 0) {
511      return Collections.emptyList();
512    }
513    return new IntArrayAsList(backingArray);
514  }
515
516  @GwtCompatible
517  private static class IntArrayAsList extends AbstractList<Integer>
518      implements RandomAccess, Serializable {
519    final int[] array;
520    final int start;
521    final int end;
522
523    IntArrayAsList(int[] array) {
524      this(array, 0, array.length);
525    }
526
527    IntArrayAsList(int[] array, int start, int end) {
528      this.array = array;
529      this.start = start;
530      this.end = end;
531    }
532
533    @Override public int size() {
534      return end - start;
535    }
536
537    @Override public boolean isEmpty() {
538      return false;
539    }
540
541    @Override public Integer get(int index) {
542      checkElementIndex(index, size());
543      return array[start + index];
544    }
545
546    @Override public boolean contains(Object target) {
547      // Overridden to prevent a ton of boxing
548      return (target instanceof Integer)
549          && Ints.indexOf(array, (Integer) target, start, end) != -1;
550    }
551
552    @Override public int indexOf(Object target) {
553      // Overridden to prevent a ton of boxing
554      if (target instanceof Integer) {
555        int i = Ints.indexOf(array, (Integer) target, start, end);
556        if (i >= 0) {
557          return i - start;
558        }
559      }
560      return -1;
561    }
562
563    @Override public int lastIndexOf(Object target) {
564      // Overridden to prevent a ton of boxing
565      if (target instanceof Integer) {
566        int i = Ints.lastIndexOf(array, (Integer) target, start, end);
567        if (i >= 0) {
568          return i - start;
569        }
570      }
571      return -1;
572    }
573
574    @Override public Integer set(int index, Integer element) {
575      checkElementIndex(index, size());
576      int oldValue = array[start + index];
577      // checkNotNull for GWT (do not optimize)
578      array[start + index] = checkNotNull(element);
579      return oldValue;
580    }
581
582    @Override public List<Integer> subList(int fromIndex, int toIndex) {
583      int size = size();
584      checkPositionIndexes(fromIndex, toIndex, size);
585      if (fromIndex == toIndex) {
586        return Collections.emptyList();
587      }
588      return new IntArrayAsList(array, start + fromIndex, start + toIndex);
589    }
590
591    @Override public boolean equals(Object object) {
592      if (object == this) {
593        return true;
594      }
595      if (object instanceof IntArrayAsList) {
596        IntArrayAsList that = (IntArrayAsList) object;
597        int size = size();
598        if (that.size() != size) {
599          return false;
600        }
601        for (int i = 0; i < size; i++) {
602          if (array[start + i] != that.array[that.start + i]) {
603            return false;
604          }
605        }
606        return true;
607      }
608      return super.equals(object);
609    }
610
611    @Override public int hashCode() {
612      int result = 1;
613      for (int i = start; i < end; i++) {
614        result = 31 * result + Ints.hashCode(array[i]);
615      }
616      return result;
617    }
618
619    @Override public String toString() {
620      StringBuilder builder = new StringBuilder(size() * 5);
621      builder.append('[').append(array[start]);
622      for (int i = start + 1; i < end; i++) {
623        builder.append(", ").append(array[i]);
624      }
625      return builder.append(']').toString();
626    }
627
628    int[] toIntArray() {
629      // Arrays.copyOfRange() is not available under GWT
630      int size = size();
631      int[] result = new int[size];
632      System.arraycopy(array, start, result, 0, size);
633      return result;
634    }
635
636    private static final long serialVersionUID = 0;
637  }
638
639  private static final byte[] asciiDigits = new byte[128];
640
641  static {
642    Arrays.fill(asciiDigits, (byte) -1);
643    for (int i = 0; i <= 9; i++) {
644      asciiDigits['0' + i] = (byte) i;
645    }
646    for (int i = 0; i <= 26; i++) {
647      asciiDigits['A' + i] = (byte) (10 + i);
648      asciiDigits['a' + i] = (byte) (10 + i);
649    }
650  }
651
652  private static int digit(char c) {
653    return (c < 128) ? asciiDigits[c] : -1;
654  }
655
656  /**
657   * Parses the specified string as a signed decimal integer value. The ASCII
658   * character {@code '-'} (<code>'&#92;u002D'</code>) is recognized as the
659   * minus sign.
660   *
661   * <p>Unlike {@link Integer#parseInt(String)}, this method returns
662   * {@code null} instead of throwing an exception if parsing fails.
663   * Additionally, this method only accepts ASCII digits, and returns
664   * {@code null} if non-ASCII digits are present in the string.
665   *
666   * <p>Note that strings prefixed with ASCII {@code '+'} are rejected, even
667   * under JDK 7, despite the change to {@link Integer#parseInt(String)} for
668   * that version.
669   *
670   * @param string the string representation of an integer value
671   * @return the integer value represented by {@code string}, or {@code null} if
672   *     {@code string} has a length of zero or cannot be parsed as an integer
673   *     value
674   * @since 11.0
675   */
676  @Beta
677  @CheckForNull
678  @GwtIncompatible("TODO")
679  public static Integer tryParse(String string) {
680    return tryParse(string, 10);
681  }
682
683  /**
684   * Parses the specified string as a signed integer value using the specified
685   * radix. The ASCII character {@code '-'} (<code>'&#92;u002D'</code>) is
686   * recognized as the minus sign.
687   *
688   * <p>Unlike {@link Integer#parseInt(String, int)}, this method returns
689   * {@code null} instead of throwing an exception if parsing fails.
690   * Additionally, this method only accepts ASCII digits, and returns
691   * {@code null} if non-ASCII digits are present in the string.
692   *
693   * <p>Note that strings prefixed with ASCII {@code '+'} are rejected, even
694   * under JDK 7, despite the change to {@link Integer#parseInt(String, int)}
695   * for that version.
696   *
697   * @param string the string representation of an integer value
698   * @param radix the radix to use when parsing
699   * @return the integer value represented by {@code string} using
700   *     {@code radix}, or {@code null} if {@code string} has a length of zero
701   *     or cannot be parsed as an integer value
702   * @throws IllegalArgumentException if {@code radix < Character.MIN_RADIX} or
703   *     {@code radix > Character.MAX_RADIX}
704   */
705  @CheckForNull
706  @GwtIncompatible("TODO") static Integer tryParse(
707      String string, int radix) {
708    if (checkNotNull(string).isEmpty()) {
709      return null;
710    }
711    if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX) {
712      throw new IllegalArgumentException(
713          "radix must be between MIN_RADIX and MAX_RADIX but was " + radix);
714    }
715    boolean negative = string.charAt(0) == '-';
716    int index = negative ? 1 : 0;
717    if (index == string.length()) {
718      return null;
719    }
720    int digit = digit(string.charAt(index++));
721    if (digit < 0 || digit >= radix) {
722      return null;
723    }
724    int accum = -digit;
725
726    int cap = Integer.MIN_VALUE / radix;
727
728    while (index < string.length()) {
729      digit = digit(string.charAt(index++));
730      if (digit < 0 || digit >= radix || accum < cap) {
731        return null;
732      }
733      accum *= radix;
734      if (accum < Integer.MIN_VALUE + digit) {
735        return null;
736      }
737      accum -= digit;
738    }
739
740    if (negative) {
741      return accum;
742    } else if (accum == Integer.MIN_VALUE) {
743      return null;
744    } else {
745      return -accum;
746    }
747  }
748}