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
017 package com.google.common.primitives;
018
019 import static com.google.common.base.Preconditions.checkArgument;
020 import static com.google.common.base.Preconditions.checkElementIndex;
021 import static com.google.common.base.Preconditions.checkNotNull;
022 import static com.google.common.base.Preconditions.checkPositionIndexes;
023
024 import com.google.common.annotations.GwtCompatible;
025
026 import java.io.Serializable;
027 import java.util.AbstractList;
028 import java.util.Arrays;
029 import java.util.Collection;
030 import java.util.Collections;
031 import java.util.List;
032 import java.util.RandomAccess;
033
034 /**
035 * Static utility methods pertaining to {@code byte} primitives, that are not
036 * already found in either {@link Byte} or {@link Arrays}, <i>and interpret
037 * bytes as neither signed nor unsigned</i>. The methods which specifically
038 * treat bytes as signed or unsigned are found in {@link SignedBytes} and {@link
039 * UnsignedBytes}.
040 *
041 * @author Kevin Bourrillion
042 * @since 1
043 */
044 @GwtCompatible
045 public final class Bytes {
046 private Bytes() {}
047
048 /**
049 * Returns a hash code for {@code value}; equal to the result of invoking
050 * {@code ((Byte) value).hashCode()}.
051 *
052 * @param value a primitive {@code byte} value
053 * @return a hash code for the value
054 */
055 public static int hashCode(byte value) {
056 return value;
057 }
058
059 /**
060 * Returns {@code true} if {@code target} is present as an element anywhere in
061 * {@code array}.
062 *
063 * @param array an array of {@code byte} values, possibly empty
064 * @param target a primitive {@code byte} value
065 * @return {@code true} if {@code array[i] == target} for some value of {@code
066 * i}
067 */
068 public static boolean contains(byte[] array, byte target) {
069 for (byte value : array) {
070 if (value == target) {
071 return true;
072 }
073 }
074 return false;
075 }
076
077 /**
078 * Returns the index of the first appearance of the value {@code target} in
079 * {@code array}.
080 *
081 * @param array an array of {@code byte} values, possibly empty
082 * @param target a primitive {@code byte} value
083 * @return the least index {@code i} for which {@code array[i] == target}, or
084 * {@code -1} if no such index exists.
085 */
086 public static int indexOf(byte[] array, byte target) {
087 return indexOf(array, target, 0, array.length);
088 }
089
090 // TODO(kevinb): consider making this public
091 private static int indexOf(
092 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
103 * target} within {@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
106 * java.util.Arrays.copyOfRange(array, i, i + target.length)} contains exactly
107 * the same elements as {@code target}.
108 *
109 * @param array the array to search for the sequence {@code target}
110 * @param target the array to search for as a sub-sequence of {@code array}
111 */
112 public static int indexOf(byte[] array, byte[] target) {
113 checkNotNull(array, "array");
114 checkNotNull(target, "target");
115 if (target.length == 0) {
116 return 0;
117 }
118
119 outer:
120 for (int i = 0; i < array.length - target.length + 1; i++) {
121 for (int j = 0; j < target.length; j++) {
122 if (array[i + j] != target[j]) {
123 continue outer;
124 }
125 }
126 return i;
127 }
128 return -1;
129 }
130
131 /**
132 * Returns the index of the last appearance of the value {@code target} in
133 * {@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},
138 * or {@code -1} if no 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(
146 byte[] array, byte target, int start, int end) {
147 for (int i = end - 1; i >= start; i--) {
148 if (array[i] == target) {
149 return i;
150 }
151 }
152 return -1;
153 }
154
155 /**
156 * Returns the values from each provided array combined into a single array.
157 * For example, {@code concat(new byte[] {a, b}, new byte[] {}, new
158 * byte[] {c}} returns the array {@code {a, b, c}}.
159 *
160 * @param arrays zero or more {@code byte} arrays
161 * @return a single array containing all the values from the source arrays, in
162 * order
163 */
164 public static byte[] concat(byte[]... arrays) {
165 int length = 0;
166 for (byte[] array : arrays) {
167 length += array.length;
168 }
169 byte[] result = new byte[length];
170 int pos = 0;
171 for (byte[] array : arrays) {
172 System.arraycopy(array, 0, result, pos, array.length);
173 pos += array.length;
174 }
175 return result;
176 }
177
178 /**
179 * Returns an array containing the same values as {@code array}, but
180 * guaranteed to be of a specified minimum length. If {@code array} already
181 * has a length of at least {@code minLength}, it is returned directly.
182 * Otherwise, a new array of size {@code minLength + padding} is returned,
183 * containing the values of {@code array}, and zeroes in the remaining places.
184 *
185 * @param array the source array
186 * @param minLength the minimum length the returned array must guarantee
187 * @param padding an extra amount to "grow" the array by if growth is
188 * necessary
189 * @throws IllegalArgumentException if {@code minLength} or {@code padding} is
190 * negative
191 * @return an array containing the values of {@code array}, with guaranteed
192 * minimum length {@code minLength}
193 */
194 public static byte[] ensureCapacity(
195 byte[] array, int minLength, int padding) {
196 checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
197 checkArgument(padding >= 0, "Invalid padding: %s", padding);
198 return (array.length < minLength)
199 ? copyOf(array, minLength + padding)
200 : array;
201 }
202
203 // Arrays.copyOf() requires Java 6
204 private static byte[] copyOf(byte[] original, int length) {
205 byte[] copy = new byte[length];
206 System.arraycopy(original, 0, copy, 0, Math.min(original.length, length));
207 return copy;
208 }
209
210 /**
211 * Copies a collection of {@code Byte} instances into a new array of
212 * primitive {@code byte} values.
213 *
214 * <p>Elements are copied from the argument collection as if by {@code
215 * collection.toArray()}. Calling this method is as thread-safe as calling
216 * that method.
217 *
218 * @param collection a collection of {@code Byte} objects
219 * @return an array containing the same values as {@code collection}, in the
220 * same order, converted to primitives
221 * @throws NullPointerException if {@code collection} or any of its elements
222 * is null
223 */
224 public static byte[] toArray(Collection<Byte> collection) {
225 if (collection instanceof ByteArrayAsList) {
226 return ((ByteArrayAsList) collection).toByteArray();
227 }
228
229 Object[] boxedArray = collection.toArray();
230 int len = boxedArray.length;
231 byte[] array = new byte[len];
232 for (int i = 0; i < len; i++) {
233 array[i] = (Byte) boxedArray[i];
234 }
235 return array;
236 }
237
238 /**
239 * Returns a fixed-size list backed by the specified array, similar to {@link
240 * Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)},
241 * but any attempt to set a value to {@code null} will result in a {@link
242 * NullPointerException}.
243 *
244 * <p>The returned list maintains the values, but not the identities, of
245 * {@code Byte} objects written to or read from it. For example, whether
246 * {@code list.get(0) == list.get(0)} is true for the returned list is
247 * unspecified.
248 *
249 * @param backingArray the array to back the list
250 * @return a list view of the array
251 */
252 public static List<Byte> asList(byte... backingArray) {
253 if (backingArray.length == 0) {
254 return Collections.emptyList();
255 }
256 return new ByteArrayAsList(backingArray);
257 }
258
259 @GwtCompatible
260 private static class ByteArrayAsList extends AbstractList<Byte>
261 implements RandomAccess, Serializable {
262 final byte[] array;
263 final int start;
264 final int end;
265
266 ByteArrayAsList(byte[] array) {
267 this(array, 0, array.length);
268 }
269
270 ByteArrayAsList(byte[] array, int start, int end) {
271 this.array = array;
272 this.start = start;
273 this.end = end;
274 }
275
276 @Override public int size() {
277 return end - start;
278 }
279
280 @Override public boolean isEmpty() {
281 return false;
282 }
283
284 @Override public Byte get(int index) {
285 checkElementIndex(index, size());
286 return array[start + index];
287 }
288
289 @Override public boolean contains(Object target) {
290 // Overridden to prevent a ton of boxing
291 return (target instanceof Byte)
292 && Bytes.indexOf(array, (Byte) target, start, end) != -1;
293 }
294
295 @Override public int indexOf(Object target) {
296 // Overridden to prevent a ton of boxing
297 if (target instanceof Byte) {
298 int i = Bytes.indexOf(array, (Byte) target, start, end);
299 if (i >= 0) {
300 return i - start;
301 }
302 }
303 return -1;
304 }
305
306 @Override public int lastIndexOf(Object target) {
307 // Overridden to prevent a ton of boxing
308 if (target instanceof Byte) {
309 int i = Bytes.lastIndexOf(array, (Byte) target, start, end);
310 if (i >= 0) {
311 return i - start;
312 }
313 }
314 return -1;
315 }
316
317 @Override public Byte set(int index, Byte element) {
318 checkElementIndex(index, size());
319 byte oldValue = array[start + index];
320 array[start + index] = element;
321 return oldValue;
322 }
323
324 @Override public List<Byte> subList(int fromIndex, int toIndex) {
325 int size = size();
326 checkPositionIndexes(fromIndex, toIndex, size);
327 if (fromIndex == toIndex) {
328 return Collections.emptyList();
329 }
330 return new ByteArrayAsList(array, start + fromIndex, start + toIndex);
331 }
332
333 @Override public boolean equals(Object object) {
334 if (object == this) {
335 return true;
336 }
337 if (object instanceof ByteArrayAsList) {
338 ByteArrayAsList that = (ByteArrayAsList) object;
339 int size = size();
340 if (that.size() != size) {
341 return false;
342 }
343 for (int i = 0; i < size; i++) {
344 if (array[start + i] != that.array[that.start + i]) {
345 return false;
346 }
347 }
348 return true;
349 }
350 return super.equals(object);
351 }
352
353 @Override public int hashCode() {
354 int result = 1;
355 for (int i = start; i < end; i++) {
356 result = 31 * result + Bytes.hashCode(array[i]);
357 }
358 return result;
359 }
360
361 @Override public String toString() {
362 StringBuilder builder = new StringBuilder(size() * 5);
363 builder.append('[').append(array[start]);
364 for (int i = start + 1; i < end; i++) {
365 builder.append(", ").append(array[i]);
366 }
367 return builder.append(']').toString();
368 }
369
370 byte[] toByteArray() {
371 // Arrays.copyOfRange() requires Java 6
372 int size = size();
373 byte[] result = new byte[size];
374 System.arraycopy(array, start, result, 0, size);
375 return result;
376 }
377
378 private static final long serialVersionUID = 0;
379 }
380 }