1 /* 2 * Copyright (C) 2009 The Guava Authors 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.google.common.primitives; 18 19 import static com.google.common.base.Preconditions.checkArgument; 20 import static com.google.common.base.Preconditions.checkNotNull; 21 22 import com.google.common.annotations.GwtCompatible; 23 24 import java.util.Comparator; 25 26 /** 27 * Static utility methods pertaining to {@code byte} primitives that 28 * interpret values as signed. The corresponding methods that treat the values 29 * as unsigned are found in {@link UnsignedBytes}, and the methods for which 30 * signedness is not an issue are in {@link Bytes}. 31 * 32 * @author Kevin Bourrillion 33 * @since 1.0 34 */ 35 // TODO(kevinb): how to prevent warning on UnsignedBytes when building GWT 36 // javadoc? 37 @GwtCompatible 38 public final class SignedBytes { 39 private SignedBytes() {} 40 41 /** 42 * The largest power of two that can be represented as a signed {@code byte}. 43 * 44 * @since 10.0 45 */ 46 public static final byte MAX_POWER_OF_TWO = 1 << 6; 47 48 /** 49 * Returns the {@code byte} value that is equal to {@code value}, if possible. 50 * 51 * @param value any value in the range of the {@code byte} type 52 * @return the {@code byte} value that equals {@code value} 53 * @throws IllegalArgumentException if {@code value} is greater than {@link 54 * Byte#MAX_VALUE} or less than {@link Byte#MIN_VALUE} 55 */ 56 public static byte checkedCast(long value) { 57 byte result = (byte) value; 58 checkArgument(result == value, "Out of range: %s", value); 59 return result; 60 } 61 62 /** 63 * Returns the {@code byte} nearest in value to {@code value}. 64 * 65 * @param value any {@code long} value 66 * @return the same value cast to {@code byte} if it is in the range of the 67 * {@code byte} type, {@link Byte#MAX_VALUE} if it is too large, 68 * or {@link Byte#MIN_VALUE} if it is too small 69 */ 70 public static byte saturatedCast(long value) { 71 if (value > Byte.MAX_VALUE) { 72 return Byte.MAX_VALUE; 73 } 74 if (value < Byte.MIN_VALUE) { 75 return Byte.MIN_VALUE; 76 } 77 return (byte) value; 78 } 79 80 /** 81 * Compares the two specified {@code byte} values. The sign of the value 82 * returned is the same as that of {@code ((Byte) a).compareTo(b)}. 83 * 84 * @param a the first {@code byte} to compare 85 * @param b the second {@code byte} to compare 86 * @return a negative value if {@code a} is less than {@code b}; a positive 87 * value if {@code a} is greater than {@code b}; or zero if they are equal 88 */ 89 public static int compare(byte a, byte b) { 90 return a - b; // safe due to restricted range 91 } 92 93 /** 94 * Returns the least value present in {@code array}. 95 * 96 * @param array a <i>nonempty</i> array of {@code byte} values 97 * @return the value present in {@code array} that is less than or equal to 98 * every other value in the array 99 * @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 } 191
