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 039@ElementTypesAreNonnullByDefault 040public final class SignedBytes { 041 private SignedBytes() {} 042 043 /** 044 * The largest power of two that can be represented as a signed {@code byte}. 045 * 046 * @since 10.0 047 */ 048 public static final byte MAX_POWER_OF_TWO = 1 << 6; 049 050 /** 051 * Returns the {@code byte} value that is equal to {@code value}, if possible. 052 * 053 * @param value any value in the range of the {@code byte} type 054 * @return the {@code byte} value that equals {@code value} 055 * @throws IllegalArgumentException if {@code value} is greater than {@link Byte#MAX_VALUE} or 056 * less than {@link Byte#MIN_VALUE} 057 */ 058 public static byte checkedCast(long value) { 059 byte result = (byte) value; 060 checkArgument(result == value, "Out of range: %s", value); 061 return result; 062 } 063 064 /** 065 * Returns the {@code byte} nearest in value to {@code value}. 066 * 067 * @param value any {@code long} value 068 * @return the same value cast to {@code byte} if it is in the range of the {@code byte} type, 069 * {@link Byte#MAX_VALUE} if it is too large, or {@link Byte#MIN_VALUE} if it is too small 070 */ 071 public static byte saturatedCast(long value) { 072 if (value > Byte.MAX_VALUE) { 073 return Byte.MAX_VALUE; 074 } 075 if (value < Byte.MIN_VALUE) { 076 return Byte.MIN_VALUE; 077 } 078 return (byte) value; 079 } 080 081 /** 082 * Compares the two specified {@code byte} values. The sign of the value returned is the same as 083 * that of {@code ((Byte) a).compareTo(b)}. 084 * 085 * <p><b>Note:</b> this method behaves identically to the JDK 7 method {@link Byte#compare}. 086 * 087 * @param a the first {@code byte} to compare 088 * @param b the second {@code byte} to compare 089 * @return a negative value if {@code a} is less than {@code b}; a positive value if {@code a} is 090 * greater than {@code b}; or zero if they are equal 091 */ 092 // TODO(kevinb): if Ints.compare etc. are ever removed, *maybe* remove this 093 // one too, which would leave compare methods only on the Unsigned* classes. 094 public static int compare(byte a, byte b) { 095 return a - b; // safe due to restricted range 096 } 097 098 /** 099 * Returns the least value present in {@code array}. 100 * 101 * @param array a <i>nonempty</i> array of {@code byte} values 102 * @return the value present in {@code array} that is less than or equal to every other value in 103 * the array 104 * @throws IllegalArgumentException if {@code array} is empty 105 */ 106 public static byte min(byte... array) { 107 checkArgument(array.length > 0); 108 byte min = array[0]; 109 for (int i = 1; i < array.length; i++) { 110 if (array[i] < min) { 111 min = array[i]; 112 } 113 } 114 return min; 115 } 116 117 /** 118 * Returns the greatest value present in {@code array}. 119 * 120 * @param array a <i>nonempty</i> array of {@code byte} values 121 * @return the value present in {@code array} that is greater than or equal to every other value 122 * in the array 123 * @throws IllegalArgumentException if {@code array} is empty 124 */ 125 public static byte max(byte... array) { 126 checkArgument(array.length > 0); 127 byte max = array[0]; 128 for (int i = 1; i < array.length; i++) { 129 if (array[i] > max) { 130 max = array[i]; 131 } 132 } 133 return max; 134 } 135 136 /** 137 * Returns a string containing the supplied {@code byte} values separated by {@code separator}. 138 * For example, {@code join(":", 0x01, 0x02, -0x01)} returns the string {@code "1:2:-1"}. 139 * 140 * @param separator the text that should appear between consecutive values in the resulting string 141 * (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 <a 161 * href="http://en.wikipedia.org/wiki/Lexicographical_order">lexicographically</a>. That is, it 162 * compares, using {@link #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 array as the lesser. For 164 * example, {@code [] < [0x01] < [0x01, 0x80] < [0x01, 0x7F] < [0x02]}. Values are treated as 165 * signed. 166 * 167 * <p>The returned comparator is inconsistent with {@link Object#equals(Object)} (since arrays 168 * support only identity equality), but it is consistent with {@link 169 * java.util.Arrays#equals(byte[], byte[])}. 170 * 171 * @since 2.0 172 */ 173 public static Comparator<byte[]> lexicographicalComparator() { 174 return LexicographicalComparator.INSTANCE; 175 } 176 177 private enum LexicographicalComparator implements Comparator<byte[]> { 178 INSTANCE; 179 180 @Override 181 public int compare(byte[] left, byte[] right) { 182 int minLength = Math.min(left.length, right.length); 183 for (int i = 0; i < minLength; i++) { 184 int result = SignedBytes.compare(left[i], right[i]); 185 if (result != 0) { 186 return result; 187 } 188 } 189 return left.length - right.length; 190 } 191 192 @Override 193 public String toString() { 194 return "SignedBytes.lexicographicalComparator()"; 195 } 196 } 197 198 /** 199 * Sorts the elements of {@code array} in descending order. 200 * 201 * @since 23.1 202 */ 203 public static void sortDescending(byte[] array) { 204 checkNotNull(array); 205 sortDescending(array, 0, array.length); 206 } 207 208 /** 209 * Sorts the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex} 210 * exclusive in descending order. 211 * 212 * @since 23.1 213 */ 214 public static void sortDescending(byte[] array, int fromIndex, int toIndex) { 215 checkNotNull(array); 216 checkPositionIndexes(fromIndex, toIndex, array.length); 217 Arrays.sort(array, fromIndex, toIndex); 218 Bytes.reverse(array, fromIndex, toIndex); 219 } 220}