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 least value present in {@code array}, treating values as unsigned.
080   *
081   * @param array a <i>nonempty</i> array of unsigned {@code int} values
082   * @return the value present in {@code array} that is less than or equal to every other value in
083   *     the array according to {@link #compare}
084   * @throws IllegalArgumentException if {@code array} is empty
085   */
086  public static int min(int... array) {
087    checkArgument(array.length > 0);
088    int min = flip(array[0]);
089    for (int i = 1; i < array.length; i++) {
090      int next = flip(array[i]);
091      if (next < min) {
092        min = next;
093      }
094    }
095    return flip(min);
096  }
097
098  /**
099   * Returns the greatest value present in {@code array}, treating values as unsigned.
100   *
101   * @param array a <i>nonempty</i> array of unsigned {@code int} values
102   * @return the value present in {@code array} that is greater than or equal to every other value
103   *     in the array according to {@link #compare}
104   * @throws IllegalArgumentException if {@code array} is empty
105   */
106  public static int max(int... array) {
107    checkArgument(array.length > 0);
108    int max = flip(array[0]);
109    for (int i = 1; i < array.length; i++) {
110      int next = flip(array[i]);
111      if (next > max) {
112        max = next;
113      }
114    }
115    return flip(max);
116  }
117
118  /**
119   * Returns a string containing the supplied unsigned {@code int} values separated by
120   * {@code separator}. For example, {@code join("-", 1, 2, 3)} returns the string {@code "1-2-3"}.
121   *
122   * @param separator the text that should appear between consecutive values in the resulting string
123   *     (but not at the start or end)
124   * @param array an array of unsigned {@code int} values, possibly empty
125   */
126  public static String join(String separator, int... array) {
127    checkNotNull(separator);
128    if (array.length == 0) {
129      return "";
130    }
131
132    // For pre-sizing a builder, just get the right order of magnitude
133    StringBuilder builder = new StringBuilder(array.length * 5);
134    builder.append(toString(array[0]));
135    for (int i = 1; i < array.length; i++) {
136      builder.append(separator).append(toString(array[i]));
137    }
138    return builder.toString();
139  }
140
141  /**
142   * Returns a comparator that compares two arrays of unsigned {@code int} values <a
143   * href="http://en.wikipedia.org/wiki/Lexicographical_order">lexicographically</a>. That is, it
144   * compares, using {@link #compare(int, int)}), the first pair of values that follow any common
145   * prefix, or when one array is a prefix of the other, treats the shorter array as the lesser. For
146   * example, {@code [] < [1] < [1, 2] < [2] < [1 << 31]}.
147   *
148   * <p>The returned comparator is inconsistent with {@link Object#equals(Object)} (since arrays
149   * support only identity equality), but it is consistent with {@link Arrays#equals(int[], int[])}.
150   */
151  public static Comparator<int[]> lexicographicalComparator() {
152    return LexicographicalComparator.INSTANCE;
153  }
154
155  enum LexicographicalComparator implements Comparator<int[]> {
156    INSTANCE;
157
158    @Override
159    public int compare(int[] left, int[] right) {
160      int minLength = Math.min(left.length, right.length);
161      for (int i = 0; i < minLength; i++) {
162        if (left[i] != right[i]) {
163          return UnsignedInts.compare(left[i], right[i]);
164        }
165      }
166      return left.length - right.length;
167    }
168
169    @Override
170    public String toString() {
171      return "UnsignedInts.lexicographicalComparator()";
172    }
173  }
174
175  /**
176   * Returns dividend / divisor, where the dividend and divisor are treated as unsigned 32-bit
177   * quantities.
178   *
179   * @param dividend the dividend (numerator)
180   * @param divisor the divisor (denominator)
181   * @throws ArithmeticException if divisor is 0
182   */
183  public static int divide(int dividend, int divisor) {
184    return (int) (toLong(dividend) / toLong(divisor));
185  }
186
187  /**
188   * Returns dividend % divisor, where the dividend and divisor are treated as unsigned 32-bit
189   * quantities.
190   *
191   * @param dividend the dividend (numerator)
192   * @param divisor the divisor (denominator)
193   * @throws ArithmeticException if divisor is 0
194   */
195  public static int remainder(int dividend, int divisor) {
196    return (int) (toLong(dividend) % toLong(divisor));
197  }
198
199  /**
200   * Returns the unsigned {@code int} value represented by the given string.
201   *
202   * Accepts a decimal, hexadecimal, or octal number given by specifying the following prefix:
203   *
204   * <ul>
205   * <li>{@code 0x}<i>HexDigits</i>
206   * <li>{@code 0X}<i>HexDigits</i>
207   * <li>{@code #}<i>HexDigits</i>
208   * <li>{@code 0}<i>OctalDigits</i>
209   * </ul>
210   *
211   * @throws NumberFormatException if the string does not contain a valid unsigned {@code int} value
212   * @since 13.0
213   */
214  @CanIgnoreReturnValue
215  public static int decode(String stringValue) {
216    ParseRequest request = ParseRequest.fromString(stringValue);
217
218    try {
219      return parseUnsignedInt(request.rawValue, request.radix);
220    } catch (NumberFormatException e) {
221      NumberFormatException decodeException =
222          new NumberFormatException("Error parsing value: " + stringValue);
223      decodeException.initCause(e);
224      throw decodeException;
225    }
226  }
227
228  /**
229   * Returns the unsigned {@code int} value represented by the given decimal string.
230   *
231   * @throws NumberFormatException if the string does not contain a valid unsigned {@code int} value
232   * @throws NullPointerException if {@code s} is null (in contrast to
233   *     {@link Integer#parseInt(String)})
234   */
235  @CanIgnoreReturnValue
236  public static int parseUnsignedInt(String s) {
237    return parseUnsignedInt(s, 10);
238  }
239
240  /**
241   * Returns the unsigned {@code int} value represented by a string with the given radix.
242   *
243   * @param string the string containing the unsigned integer representation to be parsed.
244   * @param radix the radix to use while parsing {@code s}; must be between
245   *     {@link Character#MIN_RADIX} and {@link Character#MAX_RADIX}.
246   * @throws NumberFormatException if the string does not contain a valid unsigned {@code int}, or
247   *     if supplied radix is invalid.
248   * @throws NullPointerException if {@code s} is null (in contrast to
249   *     {@link Integer#parseInt(String)})
250   */
251  @CanIgnoreReturnValue
252  public static int parseUnsignedInt(String string, int radix) {
253    checkNotNull(string);
254    long result = Long.parseLong(string, radix);
255    if ((result & INT_MASK) != result) {
256      throw new NumberFormatException(
257          "Input " + string + " in base " + radix + " is not in the range of an unsigned integer");
258    }
259    return (int) result;
260  }
261
262  /**
263   * Returns a string representation of x, where x is treated as unsigned.
264   */
265  public static String toString(int x) {
266    return toString(x, 10);
267  }
268
269  /**
270   * Returns a string representation of {@code x} for the given radix, where {@code x} is treated as
271   * unsigned.
272   *
273   * @param x the value to convert to a string.
274   * @param radix the radix to use while working with {@code x}
275   * @throws IllegalArgumentException if {@code radix} is not between {@link Character#MIN_RADIX}
276   *     and {@link Character#MAX_RADIX}.
277   */
278  public static String toString(int x, int radix) {
279    long asLong = x & INT_MASK;
280    return Long.toString(asLong, radix);
281  }
282}