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
010 * License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
011 * express or implied. See the License for the specific language governing permissions and
012 * limitations under the License.
013 */
014
015 package com.google.common.primitives;
016
017 import static com.google.common.base.Preconditions.checkArgument;
018 import static com.google.common.base.Preconditions.checkNotNull;
019
020 import java.util.Arrays;
021 import java.util.Comparator;
022
023 import com.google.common.annotations.Beta;
024 import com.google.common.annotations.GwtCompatible;
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 * @author Louis Wasserman
041 * @since 11.0
042 */
043 @Beta
044 @GwtCompatible
045 public final class UnsignedInts {
046 static final long INT_MASK = 0xffffffffL;
047
048 private UnsignedInts() {}
049
050 static int flip(int value) {
051 return value ^ Integer.MIN_VALUE;
052 }
053
054 /**
055 * Compares the two specified {@code int} values, treating them as unsigned values between
056 * {@code 0} and {@code 2^32 - 1} inclusive.
057 *
058 * @param a the first unsigned {@code int} to compare
059 * @param b the second unsigned {@code int} to compare
060 * @return a negative value if {@code a} is less than {@code b}; a positive value if {@code a} is
061 * greater than {@code b}; or zero if they are equal
062 */
063 public static int compare(int a, int b) {
064 return Ints.compare(flip(a), flip(b));
065 }
066
067 /**
068 * Returns the value of the given {@code int} as a {@code long}, when treated as unsigned.
069 */
070 public static long toLong(int value) {
071 return value & INT_MASK;
072 }
073
074 /**
075 * Returns the least value present in {@code array}, treating values as unsigned.
076 *
077 * @param array a <i>nonempty</i> array of unsigned {@code int} values
078 * @return the value present in {@code array} that is less than or equal to every other value in
079 * the array according to {@link #compare}
080 * @throws IllegalArgumentException if {@code array} is empty
081 */
082 public static int min(int... array) {
083 checkArgument(array.length > 0);
084 int min = flip(array[0]);
085 for (int i = 1; i < array.length; i++) {
086 int next = flip(array[i]);
087 if (next < min) {
088 min = next;
089 }
090 }
091 return flip(min);
092 }
093
094 /**
095 * Returns the greatest value present in {@code array}, treating values as unsigned.
096 *
097 * @param array a <i>nonempty</i> array of unsigned {@code int} values
098 * @return the value present in {@code array} that is greater than or equal to every other value
099 * in the array according to {@link #compare}
100 * @throws IllegalArgumentException if {@code array} is empty
101 */
102 public static int max(int... array) {
103 checkArgument(array.length > 0);
104 int max = flip(array[0]);
105 for (int i = 1; i < array.length; i++) {
106 int next = flip(array[i]);
107 if (next > max) {
108 max = next;
109 }
110 }
111 return flip(max);
112 }
113
114 /**
115 * Returns a string containing the supplied unsigned {@code int} values separated by
116 * {@code separator}. For example, {@code join("-", 1, 2, 3)} returns the string {@code "1-2-3"}.
117 *
118 * @param separator the text that should appear between consecutive values in the resulting
119 * string (but not at the start or end)
120 * @param array an array of unsigned {@code int} values, possibly empty
121 */
122 public static String join(String separator, int... array) {
123 checkNotNull(separator);
124 if (array.length == 0) {
125 return "";
126 }
127
128 // For pre-sizing a builder, just get the right order of magnitude
129 StringBuilder builder = new StringBuilder(array.length * 5);
130 builder.append(array[0]);
131 for (int i = 1; i < array.length; i++) {
132 builder.append(separator).append(toString(array[i]));
133 }
134 return builder.toString();
135 }
136
137 /**
138 * Returns a comparator that compares two arrays of unsigned {@code int} values lexicographically.
139 * That is, it compares, using {@link #compare(int, int)}), the first pair of values that follow
140 * any common prefix, or when one array is a prefix of the other, treats the shorter array as the
141 * lesser. For example, {@code [] < [1] < [1, 2] < [2] < [1 << 31]}.
142 *
143 * <p>The returned comparator is inconsistent with {@link Object#equals(Object)} (since arrays
144 * support only identity equality), but it is consistent with {@link Arrays#equals(int[], int[])}.
145 *
146 * @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order"> Lexicographical order
147 * article at Wikipedia</a>
148 */
149 public static Comparator<int[]> lexicographicalComparator() {
150 return LexicographicalComparator.INSTANCE;
151 }
152
153 enum LexicographicalComparator implements Comparator<int[]> {
154 INSTANCE;
155
156 @Override
157 public int compare(int[] left, int[] right) {
158 int minLength = Math.min(left.length, right.length);
159 for (int i = 0; i < minLength; i++) {
160 if (left[i] != right[i]) {
161 return UnsignedInts.compare(left[i], right[i]);
162 }
163 }
164 return left.length - right.length;
165 }
166 }
167
168 /**
169 * Returns dividend / divisor, where the dividend and divisor are treated as unsigned 32-bit
170 * quantities.
171 *
172 * @param dividend the dividend (numerator)
173 * @param divisor the divisor (denominator)
174 * @throws ArithmeticException if divisor is 0
175 */
176 public static int divide(int dividend, int divisor) {
177 return (int) (toLong(dividend) / toLong(divisor));
178 }
179
180 /**
181 * Returns dividend % divisor, where the dividend and divisor are treated as unsigned 32-bit
182 * quantities.
183 *
184 * @param dividend the dividend (numerator)
185 * @param divisor the divisor (denominator)
186 * @throws ArithmeticException if divisor is 0
187 */
188 public static int remainder(int dividend, int divisor) {
189 return (int) (toLong(dividend) % toLong(divisor));
190 }
191
192 /**
193 * Returns the unsigned {@code int} value represented by the given decimal string.
194 *
195 * @throws NumberFormatException if the string does not contain a valid unsigned integer, or if
196 * the value represented is too large to fit in an unsigned {@code int}.
197 * @throws NullPointerException if {@code s} is null
198 */
199 public static int parseUnsignedInt(String s) {
200 return parseUnsignedInt(s, 10);
201 }
202
203 /**
204 * Returns the unsigned {@code int} value represented by a string with the given radix.
205 *
206 * @param string the string containing the unsigned integer representation to be parsed.
207 * @param radix the radix to use while parsing {@code s}; must be between
208 * {@link Character#MIN_RADIX} and {@link Character#MAX_RADIX}.
209 * @throws NumberFormatException if the string does not contain a valid unsigned {@code int}, or
210 * if supplied radix is invalid.
211 */
212 public static int parseUnsignedInt(String string, int radix) {
213 checkNotNull(string);
214 long result = Long.parseLong(string, radix);
215 if ((result & INT_MASK) != result) {
216 throw new NumberFormatException("Input " + string + " in base " + radix
217 + " is not in the range of an unsigned integer");
218 }
219 return (int) result;
220 }
221
222 /**
223 * Returns a string representation of x, where x is treated as unsigned.
224 */
225 public static String toString(int x) {
226 return toString(x, 10);
227 }
228
229 /**
230 * Returns a string representation of {@code x} for the given radix, where {@code x} is treated
231 * as unsigned.
232 *
233 * @param x the value to convert to a string.
234 * @param radix the radix to use while working with {@code x}
235 * @throws IllegalArgumentException if {@code radix} is not between {@link Character#MIN_RADIX}
236 * and {@link Character#MAX_RADIX}.
237 */
238 public static String toString(int x, int radix) {
239 long asLong = x & INT_MASK;
240 return Long.toString(asLong, radix);
241 }
242 }