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 * <p>See the Guava User Guide article on <a href=
033 * "http://code.google.com/p/guava-libraries/wiki/PrimitivesExplained">
034 * primitive utilities</a>.
035 *
036 * @author Kevin Bourrillion
037 * @since 1.0
038 */
039 // TODO(kevinb): how to prevent warning on UnsignedBytes when building GWT
040 // javadoc?
041 @GwtCompatible
042 public final class SignedBytes {
043 private SignedBytes() {}
044
045 /**
046 * The largest power of two that can be represented as a signed {@code byte}.
047 *
048 * @since 10.0
049 */
050 public static final byte MAX_POWER_OF_TWO = 1 << 6;
051
052 /**
053 * Returns the {@code byte} value that is equal to {@code value}, if possible.
054 *
055 * @param value any value in the range of the {@code byte} type
056 * @return the {@code byte} value that equals {@code value}
057 * @throws IllegalArgumentException if {@code value} is greater than {@link
058 * Byte#MAX_VALUE} or less than {@link Byte#MIN_VALUE}
059 */
060 public static byte checkedCast(long value) {
061 byte result = (byte) value;
062 checkArgument(result == value, "Out of range: %s", value);
063 return result;
064 }
065
066 /**
067 * Returns the {@code byte} nearest in value to {@code value}.
068 *
069 * @param value any {@code long} value
070 * @return the same value cast to {@code byte} if it is in the range of the
071 * {@code byte} type, {@link Byte#MAX_VALUE} if it is too large,
072 * or {@link Byte#MIN_VALUE} if it is too small
073 */
074 public static byte saturatedCast(long value) {
075 if (value > Byte.MAX_VALUE) {
076 return Byte.MAX_VALUE;
077 }
078 if (value < Byte.MIN_VALUE) {
079 return Byte.MIN_VALUE;
080 }
081 return (byte) value;
082 }
083
084 /**
085 * Compares the two specified {@code byte} values. The sign of the value
086 * returned is the same as that of {@code ((Byte) a).compareTo(b)}.
087 *
088 * @param a the first {@code byte} to compare
089 * @param b the second {@code byte} to compare
090 * @return a negative value if {@code a} is less than {@code b}; a positive
091 * value if {@code a} is greater than {@code b}; or zero if they are equal
092 */
093 public static int compare(byte a, byte b) {
094 return a - b; // safe due to restricted range
095 }
096
097 /**
098 * Returns the least value present in {@code array}.
099 *
100 * @param array a <i>nonempty</i> array of {@code byte} values
101 * @return the value present in {@code array} that is less than or equal to
102 * every other value in the array
103 * @throws IllegalArgumentException if {@code array} is empty
104 */
105 public static byte min(byte... array) {
106 checkArgument(array.length > 0);
107 byte min = array[0];
108 for (int i = 1; i < array.length; i++) {
109 if (array[i] < min) {
110 min = array[i];
111 }
112 }
113 return min;
114 }
115
116 /**
117 * Returns the greatest value present in {@code array}.
118 *
119 * @param array a <i>nonempty</i> array of {@code byte} values
120 * @return the value present in {@code array} that is greater than or equal to
121 * every other value in the array
122 * @throws IllegalArgumentException if {@code array} is empty
123 */
124 public static byte max(byte... array) {
125 checkArgument(array.length > 0);
126 byte max = array[0];
127 for (int i = 1; i < array.length; i++) {
128 if (array[i] > max) {
129 max = array[i];
130 }
131 }
132 return max;
133 }
134
135 /**
136 * Returns a string containing the supplied {@code byte} values separated
137 * by {@code separator}. For example, {@code join(":", 0x01, 0x02, -0x01)}
138 * returns the string {@code "1:2:-1"}.
139 *
140 * @param separator the text that should appear between consecutive values in
141 * the resulting string (but not at the start or end)
142 * @param array an array of {@code byte} values, possibly empty
143 */
144 public static String join(String separator, byte... array) {
145 checkNotNull(separator);
146 if (array.length == 0) {
147 return "";
148 }
149
150 // For pre-sizing a builder, just get the right order of magnitude
151 StringBuilder builder = new StringBuilder(array.length * 5);
152 builder.append(array[0]);
153 for (int i = 1; i < array.length; i++) {
154 builder.append(separator).append(array[i]);
155 }
156 return builder.toString();
157 }
158
159 /**
160 * Returns a comparator that compares two {@code byte} arrays
161 * lexicographically. That is, it compares, using {@link
162 * #compare(byte, byte)}), the first pair of values that follow any common
163 * prefix, or when one array is a prefix of the other, treats the shorter
164 * array as the lesser. For example, {@code [] < [0x01] < [0x01, 0x80] <
165 * [0x01, 0x7F] < [0x02]}. Values are treated as signed.
166 *
167 * <p>The returned comparator is inconsistent with {@link
168 * Object#equals(Object)} (since arrays support only identity equality), but
169 * it is consistent with {@link java.util.Arrays#equals(byte[], byte[])}.
170 *
171 * @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order">
172 * Lexicographical order article at Wikipedia</a>
173 * @since 2.0
174 */
175 public static Comparator<byte[]> lexicographicalComparator() {
176 return LexicographicalComparator.INSTANCE;
177 }
178
179 private enum LexicographicalComparator implements Comparator<byte[]> {
180 INSTANCE;
181
182 @Override
183 public int compare(byte[] left, byte[] right) {
184 int minLength = Math.min(left.length, right.length);
185 for (int i = 0; i < minLength; i++) {
186 int result = SignedBytes.compare(left[i], right[i]);
187 if (result != 0) {
188 return result;
189 }
190 }
191 return left.length - right.length;
192 }
193 }
194 }