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 javax.annotation.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
039 * <a 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
052   * {@code ((Byte) 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
069   *     i}
070   */
071  public static boolean contains(byte[] array, byte target) {
072    for (byte value : array) {
073      if (value == target) {
074        return true;
075      }
076    }
077    return false;
078  }
079
080  /**
081   * Returns the index of the first appearance of the value {@code target} in {@code array}.
082   *
083   * @param array an array of {@code byte} values, possibly empty
084   * @param target a primitive {@code byte} value
085   * @return the least index {@code i} for which {@code array[i] == target}, or {@code -1} if no
086   *     such index exists.
087   */
088  public static int indexOf(byte[] array, byte target) {
089    return indexOf(array, target, 0, array.length);
090  }
091
092  // TODO(kevinb): consider making this public
093  private static int indexOf(byte[] array, byte target, int start, int end) {
094    for (int i = start; i < end; i++) {
095      if (array[i] == target) {
096        return i;
097      }
098    }
099    return -1;
100  }
101
102  /**
103   * Returns the start position of the first occurrence of the specified {@code
104   * target} within {@code array}, or {@code -1} if there is no such occurrence.
105   *
106   * <p>More formally, returns the lowest index {@code i} such that
107   * {@code Arrays.copyOfRange(array, i, i + target.length)} contains exactly the same elements as
108   * {@code target}.
109   *
110   * @param array the array to search for the sequence {@code target}
111   * @param target the array to search for as a sub-sequence of {@code array}
112   */
113  public static int indexOf(byte[] array, byte[] target) {
114    checkNotNull(array, "array");
115    checkNotNull(target, "target");
116    if (target.length == 0) {
117      return 0;
118    }
119
120    outer:
121    for (int i = 0; i < array.length - target.length + 1; i++) {
122      for (int j = 0; j < target.length; j++) {
123        if (array[i + j] != target[j]) {
124          continue outer;
125        }
126      }
127      return i;
128    }
129    return -1;
130  }
131
132  /**
133   * Returns the index of the last appearance of the value {@code target} in {@code array}.
134   *
135   * @param array an array of {@code byte} values, possibly empty
136   * @param target a primitive {@code byte} value
137   * @return the greatest index {@code i} for which {@code array[i] == target}, or {@code -1} if no
138   *     such index exists.
139   */
140  public static int lastIndexOf(byte[] array, byte target) {
141    return lastIndexOf(array, target, 0, array.length);
142  }
143
144  // TODO(kevinb): consider making this public
145  private static int lastIndexOf(byte[] array, byte target, int start, int end) {
146    for (int i = end - 1; i >= start; i--) {
147      if (array[i] == target) {
148        return i;
149      }
150    }
151    return -1;
152  }
153
154  /**
155   * Returns the values from each provided array combined into a single array. For example,
156   * {@code concat(new byte[] {a, b}, new byte[] {}, new byte[] {c}} returns the array {@code {a, b,
157   * c}}.
158   *
159   * @param arrays zero or more {@code byte} arrays
160   * @return a single array containing all the values from the source arrays, in order
161   */
162  public static byte[] concat(byte[]... arrays) {
163    int length = 0;
164    for (byte[] array : arrays) {
165      length += array.length;
166    }
167    byte[] result = new byte[length];
168    int pos = 0;
169    for (byte[] array : arrays) {
170      System.arraycopy(array, 0, result, pos, array.length);
171      pos += array.length;
172    }
173    return result;
174  }
175
176  /**
177   * Returns an array containing the same values as {@code array}, but guaranteed to be of a
178   * specified minimum length. If {@code array} already has a length of at least {@code minLength},
179   * it is returned directly. Otherwise, a new array of size {@code minLength + padding} is
180   * returned, containing the values of {@code array}, and zeroes in the remaining places.
181   *
182   * @param array the source array
183   * @param minLength the minimum length the returned array must guarantee
184   * @param padding an extra amount to "grow" the array by if growth is necessary
185   * @throws IllegalArgumentException if {@code minLength} or {@code padding} is negative
186   * @return an array containing the values of {@code array}, with guaranteed minimum length
187   *     {@code minLength}
188   */
189  public static byte[] ensureCapacity(byte[] array, int minLength, int padding) {
190    checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
191    checkArgument(padding >= 0, "Invalid padding: %s", padding);
192    return (array.length < minLength) ? Arrays.copyOf(array, minLength + padding) : array;
193  }
194
195  /**
196   * Returns an array containing each value of {@code collection}, converted to a {@code byte} value
197   * in the manner of {@link Number#byteValue}.
198   *
199   * <p>Elements are copied from the argument collection as if by {@code
200   * collection.toArray()}. Calling this method is as thread-safe as calling that method.
201   *
202   * @param collection a collection of {@code Number} instances
203   * @return an array containing the same values as {@code collection}, in the same order, converted
204   *     to primitives
205   * @throws NullPointerException if {@code collection} or any of its elements is null
206   * @since 1.0 (parameter was {@code Collection<Byte>} before 12.0)
207   */
208  public static byte[] toArray(Collection<? extends Number> collection) {
209    if (collection instanceof ByteArrayAsList) {
210      return ((ByteArrayAsList) collection).toByteArray();
211    }
212
213    Object[] boxedArray = collection.toArray();
214    int len = boxedArray.length;
215    byte[] array = new byte[len];
216    for (int i = 0; i < len; i++) {
217      // checkNotNull for GWT (do not optimize)
218      array[i] = ((Number) checkNotNull(boxedArray[i])).byteValue();
219    }
220    return array;
221  }
222
223  /**
224   * Returns a fixed-size list backed by the specified array, similar to
225   * {@link Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)}, but any
226   * attempt to set a value to {@code null} will result in a {@link NullPointerException}.
227   *
228   * <p>The returned list maintains the values, but not the identities, of {@code Byte} objects
229   * written to or read from it. For example, whether {@code list.get(0) == list.get(0)} is true for
230   * the returned list is unspecified.
231   *
232   * @param backingArray the array to back the list
233   * @return a list view of the array
234   */
235  public static List<Byte> asList(byte... backingArray) {
236    if (backingArray.length == 0) {
237      return Collections.emptyList();
238    }
239    return new ByteArrayAsList(backingArray);
240  }
241
242  @GwtCompatible
243  private static class ByteArrayAsList extends AbstractList<Byte>
244      implements RandomAccess, Serializable {
245    final byte[] array;
246    final int start;
247    final int end;
248
249    ByteArrayAsList(byte[] array) {
250      this(array, 0, array.length);
251    }
252
253    ByteArrayAsList(byte[] array, int start, int end) {
254      this.array = array;
255      this.start = start;
256      this.end = end;
257    }
258
259    @Override
260    public int size() {
261      return end - start;
262    }
263
264    @Override
265    public boolean isEmpty() {
266      return false;
267    }
268
269    @Override
270    public Byte get(int index) {
271      checkElementIndex(index, size());
272      return array[start + index];
273    }
274
275    @Override
276    public boolean contains(Object target) {
277      // Overridden to prevent a ton of boxing
278      return (target instanceof Byte) && Bytes.indexOf(array, (Byte) target, start, end) != -1;
279    }
280
281    @Override
282    public int indexOf(Object target) {
283      // Overridden to prevent a ton of boxing
284      if (target instanceof Byte) {
285        int i = Bytes.indexOf(array, (Byte) target, start, end);
286        if (i >= 0) {
287          return i - start;
288        }
289      }
290      return -1;
291    }
292
293    @Override
294    public int lastIndexOf(Object target) {
295      // Overridden to prevent a ton of boxing
296      if (target instanceof Byte) {
297        int i = Bytes.lastIndexOf(array, (Byte) target, start, end);
298        if (i >= 0) {
299          return i - start;
300        }
301      }
302      return -1;
303    }
304
305    @Override
306    public Byte set(int index, Byte element) {
307      checkElementIndex(index, size());
308      byte oldValue = array[start + index];
309      // checkNotNull for GWT (do not optimize)
310      array[start + index] = checkNotNull(element);
311      return oldValue;
312    }
313
314    @Override
315    public List<Byte> subList(int fromIndex, int toIndex) {
316      int size = size();
317      checkPositionIndexes(fromIndex, toIndex, size);
318      if (fromIndex == toIndex) {
319        return Collections.emptyList();
320      }
321      return new ByteArrayAsList(array, start + fromIndex, start + toIndex);
322    }
323
324    @Override
325    public boolean equals(@Nullable Object object) {
326      if (object == this) {
327        return true;
328      }
329      if (object instanceof ByteArrayAsList) {
330        ByteArrayAsList that = (ByteArrayAsList) object;
331        int size = size();
332        if (that.size() != size) {
333          return false;
334        }
335        for (int i = 0; i < size; i++) {
336          if (array[start + i] != that.array[that.start + i]) {
337            return false;
338          }
339        }
340        return true;
341      }
342      return super.equals(object);
343    }
344
345    @Override
346    public int hashCode() {
347      int result = 1;
348      for (int i = start; i < end; i++) {
349        result = 31 * result + Bytes.hashCode(array[i]);
350      }
351      return result;
352    }
353
354    @Override
355    public String toString() {
356      StringBuilder builder = new StringBuilder(size() * 5);
357      builder.append('[').append(array[start]);
358      for (int i = start + 1; i < end; i++) {
359        builder.append(", ").append(array[i]);
360      }
361      return builder.append(']').toString();
362    }
363
364    byte[] toByteArray() {
365      // Arrays.copyOfRange() is not available under GWT
366      int size = size();
367      byte[] result = new byte[size];
368      System.arraycopy(array, start, result, 0, size);
369      return result;
370    }
371
372    private static final long serialVersionUID = 0;
373  }
374}