001/* 002 * Copyright (C) 2009 The Guava Authors 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except 005 * in compliance with the License. You may obtain a copy of the License at 006 * 007 * http://www.apache.org/licenses/LICENSE-2.0 008 * 009 * Unless required by applicable law or agreed to in writing, software distributed under the License 010 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express 011 * or implied. See the License for the specific language governing permissions and limitations under 012 * the License. 013 */ 014 015package com.google.common.primitives; 016 017import static com.google.common.base.Preconditions.checkArgument; 018import static com.google.common.base.Preconditions.checkNotNull; 019import static com.google.common.base.Preconditions.checkPositionIndexes; 020 021import com.google.common.annotations.GwtCompatible; 022import java.util.Arrays; 023import java.util.Comparator; 024 025/** 026 * Static utility methods pertaining to {@code byte} primitives that interpret values as signed. The 027 * corresponding methods that treat the values as unsigned are found in {@link UnsignedBytes}, and 028 * the methods for which signedness is not an issue are in {@link Bytes}. 029 * 030 * <p>See the Guava User Guide article on <a 031 * href="https://github.com/google/guava/wiki/PrimitivesExplained">primitive utilities</a>. 032 * 033 * @author Kevin Bourrillion 034 * @since 1.0 035 */ 036// TODO(kevinb): how to prevent warning on UnsignedBytes when building GWT 037// javadoc? 038@GwtCompatible 039public final class SignedBytes { 040 private SignedBytes() {} 041 042 /** 043 * The largest power of two that can be represented as a signed {@code byte}. 044 * 045 * @since 10.0 046 */ 047 public static final byte MAX_POWER_OF_TWO = 1 << 6; 048 049 /** 050 * Returns the {@code byte} value that is equal to {@code value}, if possible. 051 * 052 * @param value any value in the range of the {@code byte} type 053 * @return the {@code byte} value that equals {@code value} 054 * @throws IllegalArgumentException if {@code value} is greater than {@link Byte#MAX_VALUE} or 055 * less than {@link Byte#MIN_VALUE} 056 */ 057 public static byte checkedCast(long value) { 058 byte result = (byte) value; 059 checkArgument(result == value, "Out of range: %s", value); 060 return result; 061 } 062 063 /** 064 * Returns the {@code byte} nearest in value to {@code value}. 065 * 066 * @param value any {@code long} value 067 * @return the same value cast to {@code byte} if it is in the range of the {@code byte} type, 068 * {@link Byte#MAX_VALUE} if it is too large, 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 returned is the same as 082 * that of {@code ((Byte) a).compareTo(b)}. 083 * 084 * <p><b>Note:</b> this method behaves identically to {@link Byte#compare}. 085 * 086 * @param a the first {@code byte} to compare 087 * @param b the second {@code byte} to compare 088 * @return a negative value if {@code a} is less than {@code b}; a positive value if {@code a} is 089 * greater than {@code b}; or zero if they are equal 090 */ 091 public static int compare(byte a, byte b) { 092 return Byte.compare(a, b); 093 } 094 095 /** 096 * Returns the least value present in {@code array}. 097 * 098 * @param array a <i>nonempty</i> array of {@code byte} values 099 * @return the value present in {@code array} that is less than or equal to every other value in 100 * the array 101 * @throws IllegalArgumentException if {@code array} is empty 102 */ 103 public static byte min(byte... array) { 104 checkArgument(array.length > 0); 105 byte min = array[0]; 106 for (int i = 1; i < array.length; i++) { 107 if (array[i] < min) { 108 min = array[i]; 109 } 110 } 111 return min; 112 } 113 114 /** 115 * Returns the greatest value present in {@code array}. 116 * 117 * @param array a <i>nonempty</i> array of {@code byte} values 118 * @return the value present in {@code array} that is greater than or equal to every other value 119 * in the array 120 * @throws IllegalArgumentException if {@code array} is empty 121 */ 122 public static byte max(byte... array) { 123 checkArgument(array.length > 0); 124 byte max = array[0]; 125 for (int i = 1; i < array.length; i++) { 126 if (array[i] > max) { 127 max = array[i]; 128 } 129 } 130 return max; 131 } 132 133 /** 134 * Returns a string containing the supplied {@code byte} values separated by {@code separator}. 135 * For example, {@code join(":", 0x01, 0x02, -0x01)} returns the string {@code "1:2:-1"}. 136 * 137 * @param separator the text that should appear between consecutive values in the resulting string 138 * (but not at the start or end) 139 * @param array an array of {@code byte} values, possibly empty 140 */ 141 public static String join(String separator, byte... array) { 142 checkNotNull(separator); 143 if (array.length == 0) { 144 return ""; 145 } 146 147 // For pre-sizing a builder, just get the right order of magnitude 148 StringBuilder builder = new StringBuilder(array.length * 5); 149 builder.append(array[0]); 150 for (int i = 1; i < array.length; i++) { 151 builder.append(separator).append(array[i]); 152 } 153 return builder.toString(); 154 } 155 156 /** 157 * Returns a comparator that compares two {@code byte} arrays <a 158 * href="http://en.wikipedia.org/wiki/Lexicographical_order">lexicographically</a>. That is, it 159 * compares, using {@link #compare(byte, byte)}), the first pair of values that follow any common 160 * prefix, or when one array is a prefix of the other, treats the shorter array as the lesser. For 161 * example, {@code [] < [0x01] < [0x01, 0x80] < [0x01, 0x7F] < [0x02]}. Values are treated as 162 * signed. 163 * 164 * <p>The returned comparator is inconsistent with {@link Object#equals(Object)} (since arrays 165 * support only identity equality), but it is consistent with {@link 166 * java.util.Arrays#equals(byte[], byte[])}. 167 * 168 * @since 2.0 169 */ 170 public static Comparator<byte[]> lexicographicalComparator() { 171 return LexicographicalComparator.INSTANCE; 172 } 173 174 private enum LexicographicalComparator implements Comparator<byte[]> { 175 INSTANCE; 176 177 @Override 178 public int compare(byte[] left, byte[] right) { 179 int minLength = Math.min(left.length, right.length); 180 for (int i = 0; i < minLength; i++) { 181 int result = Byte.compare(left[i], right[i]); 182 if (result != 0) { 183 return result; 184 } 185 } 186 return left.length - right.length; 187 } 188 189 @Override 190 public String toString() { 191 return "SignedBytes.lexicographicalComparator()"; 192 } 193 } 194 195 /** 196 * Sorts the elements of {@code array} in descending order. 197 * 198 * @since 23.1 199 */ 200 public static void sortDescending(byte[] array) { 201 checkNotNull(array); 202 sortDescending(array, 0, array.length); 203 } 204 205 /** 206 * Sorts the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex} 207 * exclusive in descending order. 208 * 209 * @since 23.1 210 */ 211 public static void sortDescending(byte[] array, int fromIndex, int toIndex) { 212 checkNotNull(array); 213 checkPositionIndexes(fromIndex, toIndex, array.length); 214 Arrays.sort(array, fromIndex, toIndex); 215 Bytes.reverse(array, fromIndex, toIndex); 216 } 217}