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 * <p>See the Guava User Guide article on <a href= 33 * "http://code.google.com/p/guava-libraries/wiki/PrimitivesExplained"> 34 * primitive utilities</a>. 35 * 36 * @author Kevin Bourrillion 37 * @since 1.0 38 */ 39 // TODO(kevinb): how to prevent warning on UnsignedBytes when building GWT 40 // javadoc? 41 @GwtCompatible 42 public final class SignedBytes { 43 private SignedBytes() {} 44 45 /** 46 * The largest power of two that can be represented as a signed {@code byte}. 47 * 48 * @since 10.0 49 */ 50 public static final byte MAX_POWER_OF_TWO = 1 << 6; 51 52 /** 53 * Returns the {@code byte} value that is equal to {@code value}, if possible. 54 * 55 * @param value any value in the range of the {@code byte} type 56 * @return the {@code byte} value that equals {@code value} 57 * @throws IllegalArgumentException if {@code value} is greater than {@link 58 * Byte#MAX_VALUE} or less than {@link Byte#MIN_VALUE} 59 */ 60 public static byte checkedCast(long value) { 61 byte result = (byte) value; 62 if (result != value) { 63 // don't use checkArgument here, to avoid boxing 64 throw new IllegalArgumentException("Out of range: " + value); 65 } 66 return result; 67 } 68 69 /** 70 * Returns the {@code byte} nearest in value to {@code value}. 71 * 72 * @param value any {@code long} value 73 * @return the same value cast to {@code byte} if it is in the range of the 74 * {@code byte} type, {@link Byte#MAX_VALUE} if it is too large, 75 * or {@link Byte#MIN_VALUE} if it is too small 76 */ 77 public static byte saturatedCast(long value) { 78 if (value > Byte.MAX_VALUE) { 79 return Byte.MAX_VALUE; 80 } 81 if (value < Byte.MIN_VALUE) { 82 return Byte.MIN_VALUE; 83 } 84 return (byte) value; 85 } 86 87 /** 88 * Compares the two specified {@code byte} values. The sign of the value 89 * returned is the same as that of {@code ((Byte) a).compareTo(b)}. 90 * 91 * <p><b>Note:</b> this method behaves identically to the JDK 7 method {@link 92 * Byte#compare}. 93 * 94 * @param a the first {@code byte} to compare 95 * @param b the second {@code byte} to compare 96 * @return a negative value if {@code a} is less than {@code b}; a positive 97 * value if {@code a} is greater than {@code b}; or zero if they are equal 98 */ 99 // TODO(kevinb): if Ints.compare etc. are ever removed, *maybe* remove this 100 // one too, which would leave compare methods only on the Unsigned* classes. 101 public static int compare(byte a, byte b) { 102 return a - b; // safe due to restricted range 103 } 104 105 /** 106 * Returns the least value present in {@code array}. 107 * 108 * @param array a <i>nonempty</i> array of {@code byte} values 109 * @return the value present in {@code array} that is less than or equal to 110 * every other value in the array 111 * @throws IllegalArgumentException if {@code array} is empty 112 */ 113 public static byte min(byte... array) { 114 checkArgument(array.length > 0); 115 byte min = array[0]; 116 for (int i = 1; i < array.length; i++) { 117 if (array[i] < min) { 118 min = array[i]; 119 } 120 } 121 return min; 122 } 123 124 /** 125 * Returns the greatest value present in {@code array}. 126 * 127 * @param array a <i>nonempty</i> array of {@code byte} values 128 * @return the value present in {@code array} that is greater than or equal to 129 * every other value in the array 130 * @throws IllegalArgumentException if {@code array} is empty 131 */ 132 public static byte max(byte... array) { 133 checkArgument(array.length > 0); 134 byte max = array[0]; 135 for (int i = 1; i < array.length; i++) { 136 if (array[i] > max) { 137 max = array[i]; 138 } 139 } 140 return max; 141 } 142 143 /** 144 * Returns a string containing the supplied {@code byte} values separated 145 * by {@code separator}. For example, {@code join(":", 0x01, 0x02, -0x01)} 146 * returns the string {@code "1:2:-1"}. 147 * 148 * @param separator the text that should appear between consecutive values in 149 * the resulting string (but not at the start or end) 150 * @param array an array of {@code byte} values, possibly empty 151 */ 152 public static String join(String separator, byte... array) { 153 checkNotNull(separator); 154 if (array.length == 0) { 155 return ""; 156 } 157 158 // For pre-sizing a builder, just get the right order of magnitude 159 StringBuilder builder = new StringBuilder(array.length * 5); 160 builder.append(array[0]); 161 for (int i = 1; i < array.length; i++) { 162 builder.append(separator).append(array[i]); 163 } 164 return builder.toString(); 165 } 166 167 /** 168 * Returns a comparator that compares two {@code byte} arrays 169 * lexicographically. That is, it compares, using {@link 170 * #compare(byte, byte)}), the first pair of values that follow any common 171 * prefix, or when one array is a prefix of the other, treats the shorter 172 * array as the lesser. For example, {@code [] < [0x01] < [0x01, 0x80] < 173 * [0x01, 0x7F] < [0x02]}. Values are treated as signed. 174 * 175 * <p>The returned comparator is inconsistent with {@link 176 * Object#equals(Object)} (since arrays support only identity equality), but 177 * it is consistent with {@link java.util.Arrays#equals(byte[], byte[])}. 178 * 179 * @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order"> 180 * Lexicographical order article at Wikipedia</a> 181 * @since 2.0 182 */ 183 public static Comparator<byte[]> lexicographicalComparator() { 184 return LexicographicalComparator.INSTANCE; 185 } 186 187 private enum LexicographicalComparator implements Comparator<byte[]> { 188 INSTANCE; 189 190 @Override 191 public int compare(byte[] left, byte[] right) { 192 int minLength = Math.min(left.length, right.length); 193 for (int i = 0; i < minLength; i++) { 194 int result = SignedBytes.compare(left[i], right[i]); 195 if (result != 0) { 196 return result; 197 } 198 } 199 return left.length - right.length; 200 } 201 } 202 } 203
