001/*
002 * Copyright (C) 2008 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
005 * in compliance with the License. You may obtain a copy of the License at
006 *
007 * http://www.apache.org/licenses/LICENSE-2.0
008 *
009 * Unless required by applicable law or agreed to in writing, software distributed under the License
010 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
011 * or implied. See the License for the specific language governing permissions and limitations under
012 * the License.
013 */
014
015package com.google.common.primitives;
016
017import static com.google.common.base.Preconditions.checkArgument;
018import static com.google.common.base.Preconditions.checkElementIndex;
019import static com.google.common.base.Preconditions.checkNotNull;
020import static com.google.common.base.Preconditions.checkPositionIndexes;
021
022import com.google.common.annotations.GwtCompatible;
023import java.io.Serializable;
024import java.util.AbstractList;
025import java.util.Arrays;
026import java.util.Collection;
027import java.util.Collections;
028import java.util.List;
029import java.util.RandomAccess;
030import org.checkerframework.checker.nullness.qual.Nullable;
031
032/**
033 * Static utility methods pertaining to {@code byte} primitives, that are not already found in
034 * either {@link Byte} or {@link Arrays}, <i>and interpret bytes as neither signed nor unsigned</i>.
035 * The methods which specifically treat bytes as signed or unsigned are found in {@link SignedBytes}
036 * and {@link UnsignedBytes}.
037 *
038 * <p>See the Guava User Guide article on <a
039 * href="https://github.com/google/guava/wiki/PrimitivesExplained">primitive utilities</a>.
040 *
041 * @author Kevin Bourrillion
042 * @since 1.0
043 */
044// TODO(kevinb): how to prevent warning on UnsignedBytes when building GWT
045// javadoc?
046@GwtCompatible
047public final class Bytes {
048  private Bytes() {}
049
050  /**
051   * Returns a hash code for {@code value}; equal to the result of invoking {@code ((Byte)
052   * value).hashCode()}.
053   *
054   * <p><b>Java 8 users:</b> use {@link Byte#hashCode(byte)} instead.
055   *
056   * @param value a primitive {@code byte} value
057   * @return a hash code for the value
058   */
059  public static int hashCode(byte value) {
060    return value;
061  }
062
063  /**
064   * Returns {@code true} if {@code target} is present as an element anywhere in {@code array}.
065   *
066   * @param array an array of {@code byte} values, possibly empty
067   * @param target a primitive {@code byte} value
068   * @return {@code true} if {@code array[i] == target} for some value of {@code i}
069   */
070  public static boolean contains(byte[] array, byte target) {
071    for (byte value : array) {
072      if (value == target) {
073        return true;
074      }
075    }
076    return false;
077  }
078
079  /**
080   * Returns the index of the first appearance of the value {@code target} in {@code array}.
081   *
082   * @param array an array of {@code byte} values, possibly empty
083   * @param target a primitive {@code byte} value
084   * @return the least index {@code i} for which {@code array[i] == target}, or {@code -1} if no
085   *     such index exists.
086   */
087  public static int indexOf(byte[] array, byte target) {
088    return indexOf(array, target, 0, array.length);
089  }
090
091  // TODO(kevinb): consider making this public
092  private static int indexOf(byte[] array, byte target, int start, int end) {
093    for (int i = start; i < end; i++) {
094      if (array[i] == target) {
095        return i;
096      }
097    }
098    return -1;
099  }
100
101  /**
102   * Returns the start position of the first occurrence of the specified {@code target} within
103   * {@code array}, or {@code -1} if there is no such occurrence.
104   *
105   * <p>More formally, returns the lowest index {@code i} such that {@code Arrays.copyOfRange(array,
106   * i, i + target.length)} contains exactly the same elements as {@code target}.
107   *
108   * @param array the array to search for the sequence {@code target}
109   * @param target the array to search for as a sub-sequence of {@code array}
110   */
111  public static int indexOf(byte[] array, byte[] target) {
112    checkNotNull(array, "array");
113    checkNotNull(target, "target");
114    if (target.length == 0) {
115      return 0;
116    }
117
118    outer:
119    for (int i = 0; i < array.length - target.length + 1; i++) {
120      for (int j = 0; j < target.length; j++) {
121        if (array[i + j] != target[j]) {
122          continue outer;
123        }
124      }
125      return i;
126    }
127    return -1;
128  }
129
130  /**
131   * Returns the index of the last appearance of the value {@code target} in {@code array}.
132   *
133   * @param array an array of {@code byte} values, possibly empty
134   * @param target a primitive {@code byte} value
135   * @return the greatest index {@code i} for which {@code array[i] == target}, or {@code -1} if no
136   *     such index exists.
137   */
138  public static int lastIndexOf(byte[] array, byte target) {
139    return lastIndexOf(array, target, 0, array.length);
140  }
141
142  // TODO(kevinb): consider making this public
143  private static int lastIndexOf(byte[] array, byte target, int start, int end) {
144    for (int i = end - 1; i >= start; i--) {
145      if (array[i] == target) {
146        return i;
147      }
148    }
149    return -1;
150  }
151
152  /**
153   * Returns the values from each provided array combined into a single array. For example, {@code
154   * concat(new byte[] {a, b}, new byte[] {}, new byte[] {c}} returns the array {@code {a, b, c}}.
155   *
156   * @param arrays zero or more {@code byte} arrays
157   * @return a single array containing all the values from the source arrays, in order
158   */
159  public static byte[] concat(byte[]... arrays) {
160    int length = 0;
161    for (byte[] array : arrays) {
162      length += array.length;
163    }
164    byte[] result = new byte[length];
165    int pos = 0;
166    for (byte[] array : arrays) {
167      System.arraycopy(array, 0, result, pos, array.length);
168      pos += array.length;
169    }
170    return result;
171  }
172
173  /**
174   * Returns an array containing the same values as {@code array}, but guaranteed to be of a
175   * specified minimum length. If {@code array} already has a length of at least {@code minLength},
176   * it is returned directly. Otherwise, a new array of size {@code minLength + padding} is
177   * returned, containing the values of {@code array}, and zeroes in the remaining places.
178   *
179   * @param array the source array
180   * @param minLength the minimum length the returned array must guarantee
181   * @param padding an extra amount to "grow" the array by if growth is necessary
182   * @throws IllegalArgumentException if {@code minLength} or {@code padding} is negative
183   * @return an array containing the values of {@code array}, with guaranteed minimum length {@code
184   *     minLength}
185   */
186  public static byte[] ensureCapacity(byte[] array, int minLength, int padding) {
187    checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
188    checkArgument(padding >= 0, "Invalid padding: %s", padding);
189    return (array.length < minLength) ? Arrays.copyOf(array, minLength + padding) : array;
190  }
191
192  /**
193   * Returns an array containing each value of {@code collection}, converted to a {@code byte} value
194   * in the manner of {@link Number#byteValue}.
195   *
196   * <p>Elements are copied from the argument collection as if by {@code collection.toArray()}.
197   * Calling this method is as thread-safe as calling that method.
198   *
199   * @param collection a collection of {@code Number} instances
200   * @return an array containing the same values as {@code collection}, in the same order, converted
201   *     to primitives
202   * @throws NullPointerException if {@code collection} or any of its elements is null
203   * @since 1.0 (parameter was {@code Collection<Byte>} before 12.0)
204   */
205  public static byte[] toArray(Collection<? extends Number> collection) {
206    if (collection instanceof ByteArrayAsList) {
207      return ((ByteArrayAsList) collection).toByteArray();
208    }
209
210    Object[] boxedArray = collection.toArray();
211    int len = boxedArray.length;
212    byte[] array = new byte[len];
213    for (int i = 0; i < len; i++) {
214      // checkNotNull for GWT (do not optimize)
215      array[i] = ((Number) checkNotNull(boxedArray[i])).byteValue();
216    }
217    return array;
218  }
219
220  /**
221   * Returns a fixed-size list backed by the specified array, similar to {@link
222   * Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)}, but any attempt to
223   * set a value to {@code null} will result in a {@link NullPointerException}.
224   *
225   * <p>The returned list maintains the values, but not the identities, of {@code Byte} objects
226   * written to or read from it. For example, whether {@code list.get(0) == list.get(0)} is true for
227   * the returned list is unspecified.
228   *
229   * @param backingArray the array to back the list
230   * @return a list view of the array
231   */
232  public static List<Byte> asList(byte... backingArray) {
233    if (backingArray.length == 0) {
234      return Collections.emptyList();
235    }
236    return new ByteArrayAsList(backingArray);
237  }
238
239  @GwtCompatible
240  private static class ByteArrayAsList extends AbstractList<Byte>
241      implements RandomAccess, Serializable {
242    final byte[] array;
243    final int start;
244    final int end;
245
246    ByteArrayAsList(byte[] array) {
247      this(array, 0, array.length);
248    }
249
250    ByteArrayAsList(byte[] array, int start, int end) {
251      this.array = array;
252      this.start = start;
253      this.end = end;
254    }
255
256    @Override
257    public int size() {
258      return end - start;
259    }
260
261    @Override
262    public boolean isEmpty() {
263      return false;
264    }
265
266    @Override
267    public Byte get(int index) {
268      checkElementIndex(index, size());
269      return array[start + index];
270    }
271
272    @Override
273    public boolean contains(Object target) {
274      // Overridden to prevent a ton of boxing
275      return (target instanceof Byte) && Bytes.indexOf(array, (Byte) target, start, end) != -1;
276    }
277
278    @Override
279    public int indexOf(Object target) {
280      // Overridden to prevent a ton of boxing
281      if (target instanceof Byte) {
282        int i = Bytes.indexOf(array, (Byte) target, start, end);
283        if (i >= 0) {
284          return i - start;
285        }
286      }
287      return -1;
288    }
289
290    @Override
291    public int lastIndexOf(Object target) {
292      // Overridden to prevent a ton of boxing
293      if (target instanceof Byte) {
294        int i = Bytes.lastIndexOf(array, (Byte) target, start, end);
295        if (i >= 0) {
296          return i - start;
297        }
298      }
299      return -1;
300    }
301
302    @Override
303    public Byte set(int index, Byte element) {
304      checkElementIndex(index, size());
305      byte oldValue = array[start + index];
306      // checkNotNull for GWT (do not optimize)
307      array[start + index] = checkNotNull(element);
308      return oldValue;
309    }
310
311    @Override
312    public List<Byte> subList(int fromIndex, int toIndex) {
313      int size = size();
314      checkPositionIndexes(fromIndex, toIndex, size);
315      if (fromIndex == toIndex) {
316        return Collections.emptyList();
317      }
318      return new ByteArrayAsList(array, start + fromIndex, start + toIndex);
319    }
320
321    @Override
322    public boolean equals(@Nullable Object object) {
323      if (object == this) {
324        return true;
325      }
326      if (object instanceof ByteArrayAsList) {
327        ByteArrayAsList that = (ByteArrayAsList) object;
328        int size = size();
329        if (that.size() != size) {
330          return false;
331        }
332        for (int i = 0; i < size; i++) {
333          if (array[start + i] != that.array[that.start + i]) {
334            return false;
335          }
336        }
337        return true;
338      }
339      return super.equals(object);
340    }
341
342    @Override
343    public int hashCode() {
344      int result = 1;
345      for (int i = start; i < end; i++) {
346        result = 31 * result + Bytes.hashCode(array[i]);
347      }
348      return result;
349    }
350
351    @Override
352    public String toString() {
353      StringBuilder builder = new StringBuilder(size() * 5);
354      builder.append('[').append(array[start]);
355      for (int i = start + 1; i < end; i++) {
356        builder.append(", ").append(array[i]);
357      }
358      return builder.append(']').toString();
359    }
360
361    byte[] toByteArray() {
362      return Arrays.copyOfRange(array, start, end);
363    }
364
365    private static final long serialVersionUID = 0;
366  }
367
368  /**
369   * Reverses the elements of {@code array}. This is equivalent to {@code
370   * Collections.reverse(Bytes.asList(array))}, but is likely to be more efficient.
371   *
372   * @since 23.1
373   */
374  public static void reverse(byte[] array) {
375    checkNotNull(array);
376    reverse(array, 0, array.length);
377  }
378
379  /**
380   * Reverses the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex}
381   * exclusive. This is equivalent to {@code
382   * Collections.reverse(Bytes.asList(array).subList(fromIndex, toIndex))}, but is likely to be more
383   * efficient.
384   *
385   * @throws IndexOutOfBoundsException if {@code fromIndex < 0}, {@code toIndex > array.length}, or
386   *     {@code toIndex > fromIndex}
387   * @since 23.1
388   */
389  public static void reverse(byte[] array, int fromIndex, int toIndex) {
390    checkNotNull(array);
391    checkPositionIndexes(fromIndex, toIndex, array.length);
392    for (int i = fromIndex, j = toIndex - 1; i < j; i++, j--) {
393      byte tmp = array[i];
394      array[i] = array[j];
395      array[j] = tmp;
396    }
397  }
398}