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