001/* 002 * Copyright (C) 2011 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; 019 020import com.google.common.annotations.Beta; 021import com.google.common.annotations.GwtCompatible; 022import com.google.errorprone.annotations.CanIgnoreReturnValue; 023import java.util.Arrays; 024import java.util.Comparator; 025 026/** 027 * Static utility methods pertaining to {@code int} primitives that interpret values as 028 * <i>unsigned</i> (that is, any negative value {@code x} is treated as the positive value 029 * {@code 2^32 + x}). The methods for which signedness is not an issue are in {@link Ints}, as well 030 * as signed versions of methods for which signedness is an issue. 031 * 032 * <p>In addition, this class provides several static methods for converting an {@code int} to a 033 * {@code String} and a {@code String} to an {@code int} that treat the {@code int} as an unsigned 034 * number. 035 * 036 * <p>Users of these utilities must be <i>extremely careful</i> not to mix up signed and unsigned 037 * {@code int} values. When possible, it is recommended that the {@link UnsignedInteger} wrapper 038 * class be used, at a small efficiency penalty, to enforce the distinction in the type system. 039 * 040 * <p>See the Guava User Guide article on 041 * <a href="https://github.com/google/guava/wiki/PrimitivesExplained#unsigned-support">unsigned 042 * primitive utilities</a>. 043 * 044 * @author Louis Wasserman 045 * @since 11.0 046 */ 047@Beta 048@GwtCompatible 049public final class UnsignedInts { 050 static final long INT_MASK = 0xffffffffL; 051 052 private UnsignedInts() {} 053 054 static int flip(int value) { 055 return value ^ Integer.MIN_VALUE; 056 } 057 058 /** 059 * Compares the two specified {@code int} values, treating them as unsigned values between 060 * {@code 0} and {@code 2^32 - 1} inclusive. 061 * 062 * @param a the first unsigned {@code int} to compare 063 * @param b the second unsigned {@code int} to compare 064 * @return a negative value if {@code a} is less than {@code b}; a positive value if {@code a} is 065 * greater than {@code b}; or zero if they are equal 066 */ 067 public static int compare(int a, int b) { 068 return Ints.compare(flip(a), flip(b)); 069 } 070 071 /** 072 * Returns the value of the given {@code int} as a {@code long}, when treated as unsigned. 073 */ 074 public static long toLong(int value) { 075 return value & INT_MASK; 076 } 077 078 /** 079 * Returns the {@code int} value that, when treated as unsigned, is equal to {@code value}, if 080 * possible. 081 * 082 * @param value a value between 0 and 2<sup>32</sup>-1 inclusive 083 * @return the {@code int} value that, when treated as unsigned, equals {@code value} 084 * @throws IllegalArgumentException if {@code value} is negative or greater than or equal to 085 * 2<sup>32</sup> 086 * @since 21.0 087 */ 088 public static int checkedCast(long value) { 089 checkArgument((value >> Integer.SIZE) == 0, "out of range: %s", value); 090 return (int) value; 091 } 092 093 /** 094 * Returns the {@code int} value that, when treated as unsigned, is nearest in value to 095 * {@code value}. 096 * 097 * @param value any {@code long} value 098 * @return {@code 2^32 - 1} if {@code value >= 2^32}, {@code 0} if {@code value <= 0}, and 099 * {@code value} cast to {@code int} otherwise 100 * @since 21.0 101 */ 102 public static int saturatedCast(long value) { 103 if (value <= 0) { 104 return 0; 105 } else if (value >= (1L << 32)) { 106 return -1; 107 } else { 108 return (int) value; 109 } 110 } 111 112 /** 113 * Returns the least value present in {@code array}, treating values as unsigned. 114 * 115 * @param array a <i>nonempty</i> array of unsigned {@code int} values 116 * @return the value present in {@code array} that is less than or equal to every other value in 117 * the array according to {@link #compare} 118 * @throws IllegalArgumentException if {@code array} is empty 119 */ 120 public static int min(int... array) { 121 checkArgument(array.length > 0); 122 int min = flip(array[0]); 123 for (int i = 1; i < array.length; i++) { 124 int next = flip(array[i]); 125 if (next < min) { 126 min = next; 127 } 128 } 129 return flip(min); 130 } 131 132 /** 133 * Returns the greatest value present in {@code array}, treating values as unsigned. 134 * 135 * @param array a <i>nonempty</i> array of unsigned {@code int} values 136 * @return the value present in {@code array} that is greater than or equal to every other value 137 * in the array according to {@link #compare} 138 * @throws IllegalArgumentException if {@code array} is empty 139 */ 140 public static int max(int... array) { 141 checkArgument(array.length > 0); 142 int max = flip(array[0]); 143 for (int i = 1; i < array.length; i++) { 144 int next = flip(array[i]); 145 if (next > max) { 146 max = next; 147 } 148 } 149 return flip(max); 150 } 151 152 /** 153 * Returns a string containing the supplied unsigned {@code int} values separated by 154 * {@code separator}. For example, {@code join("-", 1, 2, 3)} returns the string {@code "1-2-3"}. 155 * 156 * @param separator the text that should appear between consecutive values in the resulting string 157 * (but not at the start or end) 158 * @param array an array of unsigned {@code int} values, possibly empty 159 */ 160 public static String join(String separator, int... array) { 161 checkNotNull(separator); 162 if (array.length == 0) { 163 return ""; 164 } 165 166 // For pre-sizing a builder, just get the right order of magnitude 167 StringBuilder builder = new StringBuilder(array.length * 5); 168 builder.append(toString(array[0])); 169 for (int i = 1; i < array.length; i++) { 170 builder.append(separator).append(toString(array[i])); 171 } 172 return builder.toString(); 173 } 174 175 /** 176 * Returns a comparator that compares two arrays of unsigned {@code int} values <a 177 * href="http://en.wikipedia.org/wiki/Lexicographical_order">lexicographically</a>. That is, it 178 * compares, using {@link #compare(int, int)}), the first pair of values that follow any common 179 * prefix, or when one array is a prefix of the other, treats the shorter array as the lesser. For 180 * example, {@code [] < [1] < [1, 2] < [2] < [1 << 31]}. 181 * 182 * <p>The returned comparator is inconsistent with {@link Object#equals(Object)} (since arrays 183 * support only identity equality), but it is consistent with {@link Arrays#equals(int[], int[])}. 184 */ 185 public static Comparator<int[]> lexicographicalComparator() { 186 return LexicographicalComparator.INSTANCE; 187 } 188 189 enum LexicographicalComparator implements Comparator<int[]> { 190 INSTANCE; 191 192 @Override 193 public int compare(int[] left, int[] right) { 194 int minLength = Math.min(left.length, right.length); 195 for (int i = 0; i < minLength; i++) { 196 if (left[i] != right[i]) { 197 return UnsignedInts.compare(left[i], right[i]); 198 } 199 } 200 return left.length - right.length; 201 } 202 203 @Override 204 public String toString() { 205 return "UnsignedInts.lexicographicalComparator()"; 206 } 207 } 208 209 /** 210 * Returns dividend / divisor, where the dividend and divisor are treated as unsigned 32-bit 211 * quantities. 212 * 213 * @param dividend the dividend (numerator) 214 * @param divisor the divisor (denominator) 215 * @throws ArithmeticException if divisor is 0 216 */ 217 public static int divide(int dividend, int divisor) { 218 return (int) (toLong(dividend) / toLong(divisor)); 219 } 220 221 /** 222 * Returns dividend % divisor, where the dividend and divisor are treated as unsigned 32-bit 223 * quantities. 224 * 225 * @param dividend the dividend (numerator) 226 * @param divisor the divisor (denominator) 227 * @throws ArithmeticException if divisor is 0 228 */ 229 public static int remainder(int dividend, int divisor) { 230 return (int) (toLong(dividend) % toLong(divisor)); 231 } 232 233 /** 234 * Returns the unsigned {@code int} value represented by the given string. 235 * 236 * Accepts a decimal, hexadecimal, or octal number given by specifying the following prefix: 237 * 238 * <ul> 239 * <li>{@code 0x}<i>HexDigits</i> 240 * <li>{@code 0X}<i>HexDigits</i> 241 * <li>{@code #}<i>HexDigits</i> 242 * <li>{@code 0}<i>OctalDigits</i> 243 * </ul> 244 * 245 * @throws NumberFormatException if the string does not contain a valid unsigned {@code int} value 246 * @since 13.0 247 */ 248 @CanIgnoreReturnValue 249 public static int decode(String stringValue) { 250 ParseRequest request = ParseRequest.fromString(stringValue); 251 252 try { 253 return parseUnsignedInt(request.rawValue, request.radix); 254 } catch (NumberFormatException e) { 255 NumberFormatException decodeException = 256 new NumberFormatException("Error parsing value: " + stringValue); 257 decodeException.initCause(e); 258 throw decodeException; 259 } 260 } 261 262 /** 263 * Returns the unsigned {@code int} value represented by the given decimal string. 264 * 265 * @throws NumberFormatException if the string does not contain a valid unsigned {@code int} value 266 * @throws NullPointerException if {@code s} is null (in contrast to 267 * {@link Integer#parseInt(String)}) 268 */ 269 @CanIgnoreReturnValue 270 public static int parseUnsignedInt(String s) { 271 return parseUnsignedInt(s, 10); 272 } 273 274 /** 275 * Returns the unsigned {@code int} value represented by a string with the given radix. 276 * 277 * @param string the string containing the unsigned integer representation to be parsed. 278 * @param radix the radix to use while parsing {@code s}; must be between 279 * {@link Character#MIN_RADIX} and {@link Character#MAX_RADIX}. 280 * @throws NumberFormatException if the string does not contain a valid unsigned {@code int}, or 281 * if supplied radix is invalid. 282 * @throws NullPointerException if {@code s} is null (in contrast to 283 * {@link Integer#parseInt(String)}) 284 */ 285 @CanIgnoreReturnValue 286 public static int parseUnsignedInt(String string, int radix) { 287 checkNotNull(string); 288 long result = Long.parseLong(string, radix); 289 if ((result & INT_MASK) != result) { 290 throw new NumberFormatException( 291 "Input " + string + " in base " + radix + " is not in the range of an unsigned integer"); 292 } 293 return (int) result; 294 } 295 296 /** 297 * Returns a string representation of x, where x is treated as unsigned. 298 */ 299 public static String toString(int x) { 300 return toString(x, 10); 301 } 302 303 /** 304 * Returns a string representation of {@code x} for the given radix, where {@code x} is treated as 305 * unsigned. 306 * 307 * @param x the value to convert to a string. 308 * @param radix the radix to use while working with {@code x} 309 * @throws IllegalArgumentException if {@code radix} is not between {@link Character#MIN_RADIX} 310 * and {@link Character#MAX_RADIX}. 311 */ 312 public static String toString(int x, int radix) { 313 long asLong = x & INT_MASK; 314 return Long.toString(asLong, radix); 315 } 316}