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 the JDK 7 method {@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 // TODO(kevinb): if Ints.compare etc. are ever removed, *maybe* remove this 092 // one too, which would leave compare methods only on the Unsigned* classes. 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 every other value in 102 * 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 every other value 121 * 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 by {@code separator}. 137 * For example, {@code join(":", 0x01, 0x02, -0x01)} returns the string {@code "1:2:-1"}. 138 * 139 * @param separator the text that should appear between consecutive values in the resulting string 140 * (but not at the start or end) 141 * @param array an array of {@code byte} values, possibly empty 142 */ 143 public static String join(String separator, byte... array) { 144 checkNotNull(separator); 145 if (array.length == 0) { 146 return ""; 147 } 148 149 // For pre-sizing a builder, just get the right order of magnitude 150 StringBuilder builder = new StringBuilder(array.length * 5); 151 builder.append(array[0]); 152 for (int i = 1; i < array.length; i++) { 153 builder.append(separator).append(array[i]); 154 } 155 return builder.toString(); 156 } 157 158 /** 159 * Returns a comparator that compares two {@code byte} arrays <a 160 * href="http://en.wikipedia.org/wiki/Lexicographical_order">lexicographically</a>. That is, it 161 * compares, using {@link #compare(byte, byte)}), the first pair of values that follow any common 162 * prefix, or when one array is a prefix of the other, treats the shorter array as the lesser. For 163 * example, {@code [] < [0x01] < [0x01, 0x80] < [0x01, 0x7F] < [0x02]}. Values are treated as 164 * signed. 165 * 166 * <p>The returned comparator is inconsistent with {@link Object#equals(Object)} (since arrays 167 * support only identity equality), but it is consistent with {@link 168 * java.util.Arrays#equals(byte[], byte[])}. 169 * 170 * @since 2.0 171 */ 172 public static Comparator<byte[]> lexicographicalComparator() { 173 return LexicographicalComparator.INSTANCE; 174 } 175 176 private enum LexicographicalComparator implements Comparator<byte[]> { 177 INSTANCE; 178 179 @Override 180 public int compare(byte[] left, byte[] right) { 181 int minLength = Math.min(left.length, right.length); 182 for (int i = 0; i < minLength; i++) { 183 int result = SignedBytes.compare(left[i], right[i]); 184 if (result != 0) { 185 return result; 186 } 187 } 188 return left.length - right.length; 189 } 190 191 @Override 192 public String toString() { 193 return "SignedBytes.lexicographicalComparator()"; 194 } 195 } 196 197 /** 198 * Sorts the elements of {@code array} in descending order. 199 * 200 * @since 23.1 201 */ 202 public static void sortDescending(byte[] array) { 203 checkNotNull(array); 204 sortDescending(array, 0, array.length); 205 } 206 207 /** 208 * Sorts the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex} 209 * exclusive in descending order. 210 * 211 * @since 23.1 212 */ 213 public static void sortDescending(byte[] array, int fromIndex, int toIndex) { 214 checkNotNull(array); 215 checkPositionIndexes(fromIndex, toIndex, array.length); 216 Arrays.sort(array, fromIndex, toIndex); 217 Bytes.reverse(array, fromIndex, toIndex); 218 } 219}