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 char} primitives, that are not
038 * already found in either {@link Character} or {@link Arrays}.
039 *
040 * <p>All the operations in this class treat {@code char} values strictly
041 * numerically; they are neither Unicode-aware nor locale-dependent.
042 *
043 * <p>See the Guava User Guide article on <a href=
044 * "http://code.google.com/p/guava-libraries/wiki/PrimitivesExplained">
045 * primitive utilities</a>.
046 *
047 * @author Kevin Bourrillion
048 * @since 1.0
049 */
050@GwtCompatible(emulated = true)
051public final class Chars {
052  private Chars() {}
053
054  /**
055   * The number of bytes required to represent a primitive {@code char}
056   * value.
057   */
058  public static final int BYTES = Character.SIZE / Byte.SIZE;
059
060  /**
061   * Returns a hash code for {@code value}; equal to the result of invoking
062   * {@code ((Character) value).hashCode()}.
063   *
064   * @param value a primitive {@code char} value
065   * @return a hash code for the value
066   */
067  public static int hashCode(char value) {
068    return value;
069  }
070
071  /**
072   * Returns the {@code char} value that is equal to {@code value}, if possible.
073   *
074   * @param value any value in the range of the {@code char} type
075   * @return the {@code char} value that equals {@code value}
076   * @throws IllegalArgumentException if {@code value} is greater than {@link
077   *     Character#MAX_VALUE} or less than {@link Character#MIN_VALUE}
078   */
079  public static char checkedCast(long value) {
080    char result = (char) value;
081    if (result != value) {
082      // don't use checkArgument here, to avoid boxing
083      throw new IllegalArgumentException("Out of range: " + value);
084    }
085    return result;
086  }
087
088  /**
089   * Returns the {@code char} nearest in value to {@code value}.
090   *
091   * @param value any {@code long} value
092   * @return the same value cast to {@code char} if it is in the range of the
093   *     {@code char} type, {@link Character#MAX_VALUE} if it is too large,
094   *     or {@link Character#MIN_VALUE} if it is too small
095   */
096  public static char saturatedCast(long value) {
097    if (value > Character.MAX_VALUE) {
098      return Character.MAX_VALUE;
099    }
100    if (value < Character.MIN_VALUE) {
101      return Character.MIN_VALUE;
102    }
103    return (char) value;
104  }
105
106  /**
107   * Compares the two specified {@code char} values. The sign of the value
108   * returned is the same as that of {@code ((Character) a).compareTo(b)}.
109   *
110   * <p><b>Note:</b> projects using JDK 7 or later should use the equivalent
111   * {@link Character#compare} method instead.
112   *
113   * @param a the first {@code char} to compare
114   * @param b the second {@code char} to compare
115   * @return a negative value if {@code a} is less than {@code b}; a positive
116   *     value if {@code a} is greater than {@code b}; or zero if they are equal
117   */
118  // TODO(kevinb): if JDK 6 ever becomes a non-concern, remove this
119  public static int compare(char a, char b) {
120    return a - b; // safe due to restricted range
121  }
122
123  /**
124   * Returns {@code true} if {@code target} is present as an element anywhere in
125   * {@code array}.
126   *
127   * @param array an array of {@code char} values, possibly empty
128   * @param target a primitive {@code char} value
129   * @return {@code true} if {@code array[i] == target} for some value of {@code
130   *     i}
131   */
132  public static boolean contains(char[] array, char target) {
133    for (char value : array) {
134      if (value == target) {
135        return true;
136      }
137    }
138    return false;
139  }
140
141  /**
142   * Returns the index of the first appearance of the value {@code target} in
143   * {@code array}.
144   *
145   * @param array an array of {@code char} values, possibly empty
146   * @param target a primitive {@code char} value
147   * @return the least index {@code i} for which {@code array[i] == target}, or
148   *     {@code -1} if no such index exists.
149   */
150  public static int indexOf(char[] array, char target) {
151    return indexOf(array, target, 0, array.length);
152  }
153
154  // TODO(kevinb): consider making this public
155  private static int indexOf(
156      char[] array, char target, int start, int end) {
157    for (int i = start; i < end; i++) {
158      if (array[i] == target) {
159        return i;
160      }
161    }
162    return -1;
163  }
164
165  /**
166   * Returns the start position of the first occurrence of the specified {@code
167   * target} within {@code array}, or {@code -1} if there is no such occurrence.
168   *
169   * <p>More formally, returns the lowest index {@code i} such that {@code
170   * java.util.Arrays.copyOfRange(array, i, i + target.length)} contains exactly
171   * the same elements as {@code target}.
172   *
173   * @param array the array to search for the sequence {@code target}
174   * @param target the array to search for as a sub-sequence of {@code array}
175   */
176  public static int indexOf(char[] array, char[] target) {
177    checkNotNull(array, "array");
178    checkNotNull(target, "target");
179    if (target.length == 0) {
180      return 0;
181    }
182
183    outer:
184    for (int i = 0; i < array.length - target.length + 1; i++) {
185      for (int j = 0; j < target.length; j++) {
186        if (array[i + j] != target[j]) {
187          continue outer;
188        }
189      }
190      return i;
191    }
192    return -1;
193  }
194
195  /**
196   * Returns the index of the last appearance of the value {@code target} in
197   * {@code array}.
198   *
199   * @param array an array of {@code char} values, possibly empty
200   * @param target a primitive {@code char} value
201   * @return the greatest index {@code i} for which {@code array[i] == target},
202   *     or {@code -1} if no such index exists.
203   */
204  public static int lastIndexOf(char[] array, char target) {
205    return lastIndexOf(array, target, 0, array.length);
206  }
207
208  // TODO(kevinb): consider making this public
209  private static int lastIndexOf(
210      char[] array, char target, int start, int end) {
211    for (int i = end - 1; i >= start; i--) {
212      if (array[i] == target) {
213        return i;
214      }
215    }
216    return -1;
217  }
218
219  /**
220   * Returns the least value present in {@code array}.
221   *
222   * @param array a <i>nonempty</i> array of {@code char} values
223   * @return the value present in {@code array} that is less than or equal to
224   *     every other value in the array
225   * @throws IllegalArgumentException if {@code array} is empty
226   */
227  public static char min(char... array) {
228    checkArgument(array.length > 0);
229    char min = array[0];
230    for (int i = 1; i < array.length; i++) {
231      if (array[i] < min) {
232        min = array[i];
233      }
234    }
235    return min;
236  }
237
238  /**
239   * Returns the greatest value present in {@code array}.
240   *
241   * @param array a <i>nonempty</i> array of {@code char} values
242   * @return the value present in {@code array} that is greater than or equal to
243   *     every other value in the array
244   * @throws IllegalArgumentException if {@code array} is empty
245   */
246  public static char max(char... array) {
247    checkArgument(array.length > 0);
248    char max = array[0];
249    for (int i = 1; i < array.length; i++) {
250      if (array[i] > max) {
251        max = array[i];
252      }
253    }
254    return max;
255  }
256
257  /**
258   * Returns the values from each provided array combined into a single array.
259   * For example, {@code concat(new char[] {a, b}, new char[] {}, new
260   * char[] {c}} returns the array {@code {a, b, c}}.
261   *
262   * @param arrays zero or more {@code char} arrays
263   * @return a single array containing all the values from the source arrays, in
264   *     order
265   */
266  public static char[] concat(char[]... arrays) {
267    int length = 0;
268    for (char[] array : arrays) {
269      length += array.length;
270    }
271    char[] result = new char[length];
272    int pos = 0;
273    for (char[] array : arrays) {
274      System.arraycopy(array, 0, result, pos, array.length);
275      pos += array.length;
276    }
277    return result;
278  }
279
280  /**
281   * Returns a big-endian representation of {@code value} in a 2-element byte
282   * array; equivalent to {@code
283   * ByteBuffer.allocate(2).putChar(value).array()}.  For example, the input
284   * value {@code '\\u5432'} would yield the byte array {@code {0x54, 0x32}}.
285   *
286   * <p>If you need to convert and concatenate several values (possibly even of
287   * different types), use a shared {@link java.nio.ByteBuffer} instance, or use
288   * {@link com.google.common.io.ByteStreams#newDataOutput()} to get a growable
289   * buffer.
290   */
291  @GwtIncompatible("doesn't work")
292  public static byte[] toByteArray(char value) {
293    return new byte[] {
294        (byte) (value >> 8),
295        (byte) value};
296  }
297
298  /**
299   * Returns the {@code char} value whose big-endian representation is
300   * stored in the first 2 bytes of {@code bytes}; equivalent to {@code
301   * ByteBuffer.wrap(bytes).getChar()}. For example, the input byte array
302   * {@code {0x54, 0x32}} would yield the {@code char} value {@code '\\u5432'}.
303   *
304   * <p>Arguably, it's preferable to use {@link java.nio.ByteBuffer}; that
305   * library exposes much more flexibility at little cost in readability.
306   *
307   * @throws IllegalArgumentException if {@code bytes} has fewer than 2
308   *     elements
309   */
310  @GwtIncompatible("doesn't work")
311  public static char fromByteArray(byte[] bytes) {
312    checkArgument(bytes.length >= BYTES,
313        "array too small: %s < %s", bytes.length, BYTES);
314    return fromBytes(bytes[0], bytes[1]);
315  }
316
317  /**
318   * Returns the {@code char} value whose byte representation is the given 2
319   * bytes, in big-endian order; equivalent to {@code Chars.fromByteArray(new
320   * byte[] {b1, b2})}.
321   *
322   * @since 7.0
323   */
324  @GwtIncompatible("doesn't work")
325  public static char fromBytes(byte b1, byte b2) {
326    return (char) ((b1 << 8) | (b2 & 0xFF));
327  }
328
329  /**
330   * Returns an array containing the same values as {@code array}, but
331   * guaranteed to be of a specified minimum length. If {@code array} already
332   * has a length of at least {@code minLength}, it is returned directly.
333   * Otherwise, a new array of size {@code minLength + padding} is returned,
334   * containing the values of {@code array}, and zeroes in the remaining places.
335   *
336   * @param array the source array
337   * @param minLength the minimum length the returned array must guarantee
338   * @param padding an extra amount to "grow" the array by if growth is
339   *     necessary
340   * @throws IllegalArgumentException if {@code minLength} or {@code padding} is
341   *     negative
342   * @return an array containing the values of {@code array}, with guaranteed
343   *     minimum length {@code minLength}
344   */
345  public static char[] ensureCapacity(
346      char[] array, int minLength, int padding) {
347    checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
348    checkArgument(padding >= 0, "Invalid padding: %s", padding);
349    return (array.length < minLength)
350        ? copyOf(array, minLength + padding)
351        : array;
352  }
353
354  // Arrays.copyOf() requires Java 6
355  private static char[] copyOf(char[] original, int length) {
356    char[] copy = new char[length];
357    System.arraycopy(original, 0, copy, 0, Math.min(original.length, length));
358    return copy;
359  }
360
361  /**
362   * Returns a string containing the supplied {@code char} values separated
363   * by {@code separator}. For example, {@code join("-", '1', '2', '3')} returns
364   * the string {@code "1-2-3"}.
365   *
366   * @param separator the text that should appear between consecutive values in
367   *     the resulting string (but not at the start or end)
368   * @param array an array of {@code char} values, possibly empty
369   */
370  public static String join(String separator, char... array) {
371    checkNotNull(separator);
372    int len = array.length;
373    if (len == 0) {
374      return "";
375    }
376
377    StringBuilder builder
378        = new StringBuilder(len + separator.length() * (len - 1));
379    builder.append(array[0]);
380    for (int i = 1; i < len; i++) {
381      builder.append(separator).append(array[i]);
382    }
383    return builder.toString();
384  }
385
386  /**
387   * Returns a comparator that compares two {@code char} arrays
388   * lexicographically. That is, it compares, using {@link
389   * #compare(char, char)}), the first pair of values that follow any
390   * common prefix, or when one array is a prefix of the other, treats the
391   * shorter array as the lesser. For example,
392   * {@code [] < ['a'] < ['a', 'b'] < ['b']}.
393   *
394   * <p>The returned comparator is inconsistent with {@link
395   * Object#equals(Object)} (since arrays support only identity equality), but
396   * it is consistent with {@link Arrays#equals(char[], char[])}.
397   *
398   * @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order">
399   *     Lexicographical order article at Wikipedia</a>
400   * @since 2.0
401   */
402  public static Comparator<char[]> lexicographicalComparator() {
403    return LexicographicalComparator.INSTANCE;
404  }
405
406  private enum LexicographicalComparator implements Comparator<char[]> {
407    INSTANCE;
408
409    @Override
410    public int compare(char[] left, char[] right) {
411      int minLength = Math.min(left.length, right.length);
412      for (int i = 0; i < minLength; i++) {
413        int result = Chars.compare(left[i], right[i]);
414        if (result != 0) {
415          return result;
416        }
417      }
418      return left.length - right.length;
419    }
420  }
421
422  /**
423   * Copies a collection of {@code Character} instances into a new array of
424   * primitive {@code char} values.
425   *
426   * <p>Elements are copied from the argument collection as if by {@code
427   * collection.toArray()}.  Calling this method is as thread-safe as calling
428   * that method.
429   *
430   * @param collection a collection of {@code Character} objects
431   * @return an array containing the same values as {@code collection}, in the
432   *     same order, converted to primitives
433   * @throws NullPointerException if {@code collection} or any of its elements
434   *     is null
435   */
436  public static char[] toArray(Collection<Character> collection) {
437    if (collection instanceof CharArrayAsList) {
438      return ((CharArrayAsList) collection).toCharArray();
439    }
440
441    Object[] boxedArray = collection.toArray();
442    int len = boxedArray.length;
443    char[] array = new char[len];
444    for (int i = 0; i < len; i++) {
445      // checkNotNull for GWT (do not optimize)
446      array[i] = (Character) checkNotNull(boxedArray[i]);
447    }
448    return array;
449  }
450
451  /**
452   * Returns a fixed-size list backed by the specified array, similar to {@link
453   * Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)},
454   * but any attempt to set a value to {@code null} will result in a {@link
455   * NullPointerException}.
456   *
457   * <p>The returned list maintains the values, but not the identities, of
458   * {@code Character} objects written to or read from it.  For example, whether
459   * {@code list.get(0) == list.get(0)} is true for the returned list is
460   * unspecified.
461   *
462   * @param backingArray the array to back the list
463   * @return a list view of the array
464   */
465  public static List<Character> asList(char... backingArray) {
466    if (backingArray.length == 0) {
467      return Collections.emptyList();
468    }
469    return new CharArrayAsList(backingArray);
470  }
471
472  @GwtCompatible
473  private static class CharArrayAsList extends AbstractList<Character>
474      implements RandomAccess, Serializable {
475    final char[] array;
476    final int start;
477    final int end;
478
479    CharArrayAsList(char[] array) {
480      this(array, 0, array.length);
481    }
482
483    CharArrayAsList(char[] array, int start, int end) {
484      this.array = array;
485      this.start = start;
486      this.end = end;
487    }
488
489    @Override public int size() {
490      return end - start;
491    }
492
493    @Override public boolean isEmpty() {
494      return false;
495    }
496
497    @Override public Character get(int index) {
498      checkElementIndex(index, size());
499      return array[start + index];
500    }
501
502    @Override public boolean contains(Object target) {
503      // Overridden to prevent a ton of boxing
504      return (target instanceof Character)
505          && Chars.indexOf(array, (Character) target, start, end) != -1;
506    }
507
508    @Override public int indexOf(Object target) {
509      // Overridden to prevent a ton of boxing
510      if (target instanceof Character) {
511        int i = Chars.indexOf(array, (Character) target, start, end);
512        if (i >= 0) {
513          return i - start;
514        }
515      }
516      return -1;
517    }
518
519    @Override public int lastIndexOf(Object target) {
520      // Overridden to prevent a ton of boxing
521      if (target instanceof Character) {
522        int i = Chars.lastIndexOf(array, (Character) target, start, end);
523        if (i >= 0) {
524          return i - start;
525        }
526      }
527      return -1;
528    }
529
530    @Override public Character set(int index, Character element) {
531      checkElementIndex(index, size());
532      char oldValue = array[start + index];
533      // checkNotNull for GWT (do not optimize)
534      array[start + index] = checkNotNull(element);
535      return oldValue;
536    }
537
538    @Override public List<Character> subList(int fromIndex, int toIndex) {
539      int size = size();
540      checkPositionIndexes(fromIndex, toIndex, size);
541      if (fromIndex == toIndex) {
542        return Collections.emptyList();
543      }
544      return new CharArrayAsList(array, start + fromIndex, start + toIndex);
545    }
546
547    @Override public boolean equals(Object object) {
548      if (object == this) {
549        return true;
550      }
551      if (object instanceof CharArrayAsList) {
552        CharArrayAsList that = (CharArrayAsList) object;
553        int size = size();
554        if (that.size() != size) {
555          return false;
556        }
557        for (int i = 0; i < size; i++) {
558          if (array[start + i] != that.array[that.start + i]) {
559            return false;
560          }
561        }
562        return true;
563      }
564      return super.equals(object);
565    }
566
567    @Override public int hashCode() {
568      int result = 1;
569      for (int i = start; i < end; i++) {
570        result = 31 * result + Chars.hashCode(array[i]);
571      }
572      return result;
573    }
574
575    @Override public String toString() {
576      StringBuilder builder = new StringBuilder(size() * 3);
577      builder.append('[').append(array[start]);
578      for (int i = start + 1; i < end; i++) {
579        builder.append(", ").append(array[i]);
580      }
581      return builder.append(']').toString();
582    }
583
584    char[] toCharArray() {
585      // Arrays.copyOfRange() is not available under GWT
586      int size = size();
587      char[] result = new char[size];
588      System.arraycopy(array, start, result, 0, size);
589      return result;
590    }
591
592    private static final long serialVersionUID = 0;
593  }
594}