001 /*
002 * Copyright (C) 2009 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.checkNotNull;
021
022 import com.google.common.annotations.GwtCompatible;
023
024 import java.util.Comparator;
025
026 /**
027 * Static utility methods pertaining to {@code byte} primitives that
028 * interpret values as signed. The corresponding methods that treat the values
029 * as unsigned are found in {@link UnsignedBytes}, and the methods for which
030 * signedness is not an issue are in {@link Bytes}.
031 *
032 * @author Kevin Bourrillion
033 * @since 1.0
034 */
035 // TODO(kevinb): how to prevent warning on UnsignedBytes when building GWT
036 // javadoc?
037 @GwtCompatible
038 public final class SignedBytes {
039 private SignedBytes() {}
040
041 /**
042 * The largest power of two that can be represented as a signed {@code byte}.
043 *
044 * @since 10.0
045 */
046 public static final byte MAX_POWER_OF_TWO = 1 << 6;
047
048 /**
049 * Returns the {@code byte} value that is equal to {@code value}, if possible.
050 *
051 * @param value any value in the range of the {@code byte} type
052 * @return the {@code byte} value that equals {@code value}
053 * @throws IllegalArgumentException if {@code value} is greater than {@link
054 * Byte#MAX_VALUE} or less than {@link Byte#MIN_VALUE}
055 */
056 public static byte checkedCast(long value) {
057 byte result = (byte) value;
058 checkArgument(result == value, "Out of range: %s", value);
059 return result;
060 }
061
062 /**
063 * Returns the {@code byte} nearest in value to {@code value}.
064 *
065 * @param value any {@code long} value
066 * @return the same value cast to {@code byte} if it is in the range of the
067 * {@code byte} type, {@link Byte#MAX_VALUE} if it is too large,
068 * or {@link Byte#MIN_VALUE} if it is too small
069 */
070 public static byte saturatedCast(long value) {
071 if (value > Byte.MAX_VALUE) {
072 return Byte.MAX_VALUE;
073 }
074 if (value < Byte.MIN_VALUE) {
075 return Byte.MIN_VALUE;
076 }
077 return (byte) value;
078 }
079
080 /**
081 * Compares the two specified {@code byte} values. The sign of the value
082 * returned is the same as that of {@code ((Byte) a).compareTo(b)}.
083 *
084 * @param a the first {@code byte} to compare
085 * @param b the second {@code byte} to compare
086 * @return a negative value if {@code a} is less than {@code b}; a positive
087 * value if {@code a} is greater than {@code b}; or zero if they are equal
088 */
089 public static int compare(byte a, byte b) {
090 return a - b; // safe due to restricted range
091 }
092
093 /**
094 * Returns the least value present in {@code array}.
095 *
096 * @param array a <i>nonempty</i> array of {@code byte} values
097 * @return the value present in {@code array} that is less than or equal to
098 * every other value in the array
099 * @throws IllegalArgumentException if {@code array} is empty
100 */
101 public static byte min(byte... array) {
102 checkArgument(array.length > 0);
103 byte min = array[0];
104 for (int i = 1; i < array.length; i++) {
105 if (array[i] < min) {
106 min = array[i];
107 }
108 }
109 return min;
110 }
111
112 /**
113 * Returns the greatest value present in {@code array}.
114 *
115 * @param array a <i>nonempty</i> array of {@code byte} values
116 * @return the value present in {@code array} that is greater than or equal to
117 * every other value in the array
118 * @throws IllegalArgumentException if {@code array} is empty
119 */
120 public static byte max(byte... array) {
121 checkArgument(array.length > 0);
122 byte max = array[0];
123 for (int i = 1; i < array.length; i++) {
124 if (array[i] > max) {
125 max = array[i];
126 }
127 }
128 return max;
129 }
130
131 /**
132 * Returns a string containing the supplied {@code byte} values separated
133 * by {@code separator}. For example, {@code join(":", 0x01, 0x02, -0x01)}
134 * returns the string {@code "1:2:-1"}.
135 *
136 * @param separator the text that should appear between consecutive values in
137 * the resulting string (but not at the start or end)
138 * @param array an array of {@code byte} values, possibly empty
139 */
140 public static String join(String separator, byte... array) {
141 checkNotNull(separator);
142 if (array.length == 0) {
143 return "";
144 }
145
146 // For pre-sizing a builder, just get the right order of magnitude
147 StringBuilder builder = new StringBuilder(array.length * 5);
148 builder.append(array[0]);
149 for (int i = 1; i < array.length; i++) {
150 builder.append(separator).append(array[i]);
151 }
152 return builder.toString();
153 }
154
155 /**
156 * Returns a comparator that compares two {@code byte} arrays
157 * lexicographically. That is, it compares, using {@link
158 * #compare(byte, byte)}), the first pair of values that follow any common
159 * prefix, or when one array is a prefix of the other, treats the shorter
160 * array as the lesser. For example, {@code [] < [0x01] < [0x01, 0x80] <
161 * [0x01, 0x7F] < [0x02]}. Values are treated as signed.
162 *
163 * <p>The returned comparator is inconsistent with {@link
164 * Object#equals(Object)} (since arrays support only identity equality), but
165 * it is consistent with {@link java.util.Arrays#equals(byte[], byte[])}.
166 *
167 * @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order">
168 * Lexicographical order article at Wikipedia</a>
169 * @since 2.0
170 */
171 public static Comparator<byte[]> lexicographicalComparator() {
172 return LexicographicalComparator.INSTANCE;
173 }
174
175 private enum LexicographicalComparator implements Comparator<byte[]> {
176 INSTANCE;
177
178 @Override
179 public int compare(byte[] left, byte[] right) {
180 int minLength = Math.min(left.length, right.length);
181 for (int i = 0; i < minLength; i++) {
182 int result = SignedBytes.compare(left[i], right[i]);
183 if (result != 0) {
184 return result;
185 }
186 }
187 return left.length - right.length;
188 }
189 }
190 }