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;
019import static com.google.common.base.Preconditions.checkPositionIndexes;
020
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 {@code
029 * 2^32 + x}). The methods for which signedness is not an issue are in {@link Ints}, as well as
030 * 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 <a
041 * 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@GwtCompatible
048@ElementTypesAreNonnullByDefault
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 {@code
060   * 0} and {@code 2^32 - 1} inclusive.
061   *
062   * <p><b>Java 8 users:</b> use {@link Integer#compareUnsigned(int, int)} instead.
063   *
064   * @param a the first unsigned {@code int} to compare
065   * @param b the second unsigned {@code int} to compare
066   * @return a negative value if {@code a} is less than {@code b}; a positive value if {@code a} is
067   *     greater than {@code b}; or zero if they are equal
068   */
069  public static int compare(int a, int b) {
070    return Ints.compare(flip(a), flip(b));
071  }
072
073  /**
074   * Returns the value of the given {@code int} as a {@code long}, when treated as unsigned.
075   *
076   * <p><b>Java 8 users:</b> use {@link Integer#toUnsignedLong(int)} instead.
077   */
078  public static long toLong(int value) {
079    return value & INT_MASK;
080  }
081
082  /**
083   * Returns the {@code int} value that, when treated as unsigned, is equal to {@code value}, if
084   * possible.
085   *
086   * @param value a value between 0 and 2<sup>32</sup>-1 inclusive
087   * @return the {@code int} value that, when treated as unsigned, equals {@code value}
088   * @throws IllegalArgumentException if {@code value} is negative or greater than or equal to
089   *     2<sup>32</sup>
090   * @since 21.0
091   */
092  public static int checkedCast(long value) {
093    checkArgument((value >> Integer.SIZE) == 0, "out of range: %s", value);
094    return (int) value;
095  }
096
097  /**
098   * Returns the {@code int} value that, when treated as unsigned, is nearest in value to {@code
099   * value}.
100   *
101   * @param value any {@code long} value
102   * @return {@code 2^32 - 1} if {@code value >= 2^32}, {@code 0} if {@code value <= 0}, and {@code
103   *     value} cast to {@code int} otherwise
104   * @since 21.0
105   */
106  public static int saturatedCast(long value) {
107    if (value <= 0) {
108      return 0;
109    } else if (value >= (1L << 32)) {
110      return -1;
111    } else {
112      return (int) value;
113    }
114  }
115
116  /**
117   * Returns the least value present in {@code array}, treating values as unsigned.
118   *
119   * @param array a <i>nonempty</i> array of unsigned {@code int} values
120   * @return the value present in {@code array} that is less than or equal to every other value in
121   *     the array according to {@link #compare}
122   * @throws IllegalArgumentException if {@code array} is empty
123   */
124  public static int min(int... array) {
125    checkArgument(array.length > 0);
126    int min = flip(array[0]);
127    for (int i = 1; i < array.length; i++) {
128      int next = flip(array[i]);
129      if (next < min) {
130        min = next;
131      }
132    }
133    return flip(min);
134  }
135
136  /**
137   * Returns the greatest value present in {@code array}, treating values as unsigned.
138   *
139   * @param array a <i>nonempty</i> array of unsigned {@code int} values
140   * @return the value present in {@code array} that is greater than or equal to every other value
141   *     in the array according to {@link #compare}
142   * @throws IllegalArgumentException if {@code array} is empty
143   */
144  public static int max(int... array) {
145    checkArgument(array.length > 0);
146    int max = flip(array[0]);
147    for (int i = 1; i < array.length; i++) {
148      int next = flip(array[i]);
149      if (next > max) {
150        max = next;
151      }
152    }
153    return flip(max);
154  }
155
156  /**
157   * Returns a string containing the supplied unsigned {@code int} values separated by {@code
158   * separator}. For example, {@code join("-", 1, 2, 3)} returns the string {@code "1-2-3"}.
159   *
160   * @param separator the text that should appear between consecutive values in the resulting string
161   *     (but not at the start or end)
162   * @param array an array of unsigned {@code int} values, possibly empty
163   */
164  public static String join(String separator, int... array) {
165    checkNotNull(separator);
166    if (array.length == 0) {
167      return "";
168    }
169
170    // For pre-sizing a builder, just get the right order of magnitude
171    StringBuilder builder = new StringBuilder(array.length * 5);
172    builder.append(toString(array[0]));
173    for (int i = 1; i < array.length; i++) {
174      builder.append(separator).append(toString(array[i]));
175    }
176    return builder.toString();
177  }
178
179  /**
180   * Returns a comparator that compares two arrays of unsigned {@code int} values <a
181   * href="http://en.wikipedia.org/wiki/Lexicographical_order">lexicographically</a>. That is, it
182   * compares, using {@link #compare(int, int)}), the first pair of values that follow any common
183   * prefix, or when one array is a prefix of the other, treats the shorter array as the lesser. For
184   * example, {@code [] < [1] < [1, 2] < [2] < [1 << 31]}.
185   *
186   * <p>The returned comparator is inconsistent with {@link Object#equals(Object)} (since arrays
187   * support only identity equality), but it is consistent with {@link Arrays#equals(int[], int[])}.
188   */
189  public static Comparator<int[]> lexicographicalComparator() {
190    return LexicographicalComparator.INSTANCE;
191  }
192
193  enum LexicographicalComparator implements Comparator<int[]> {
194    INSTANCE;
195
196    @Override
197    public int compare(int[] left, int[] right) {
198      int minLength = Math.min(left.length, right.length);
199      for (int i = 0; i < minLength; i++) {
200        if (left[i] != right[i]) {
201          return UnsignedInts.compare(left[i], right[i]);
202        }
203      }
204      return left.length - right.length;
205    }
206
207    @Override
208    public String toString() {
209      return "UnsignedInts.lexicographicalComparator()";
210    }
211  }
212
213  /**
214   * Sorts the array, treating its elements as unsigned 32-bit integers.
215   *
216   * @since 23.1
217   */
218  public static void sort(int[] array) {
219    checkNotNull(array);
220    sort(array, 0, array.length);
221  }
222
223  /**
224   * Sorts the array between {@code fromIndex} inclusive and {@code toIndex} exclusive, treating its
225   * elements as unsigned 32-bit integers.
226   *
227   * @since 23.1
228   */
229  public static void sort(int[] array, int fromIndex, int toIndex) {
230    checkNotNull(array);
231    checkPositionIndexes(fromIndex, toIndex, array.length);
232    for (int i = fromIndex; i < toIndex; i++) {
233      array[i] = flip(array[i]);
234    }
235    Arrays.sort(array, fromIndex, toIndex);
236    for (int i = fromIndex; i < toIndex; i++) {
237      array[i] = flip(array[i]);
238    }
239  }
240
241  /**
242   * Sorts the elements of {@code array} in descending order, interpreting them as unsigned 32-bit
243   * integers.
244   *
245   * @since 23.1
246   */
247  public static void sortDescending(int[] array) {
248    checkNotNull(array);
249    sortDescending(array, 0, array.length);
250  }
251
252  /**
253   * Sorts the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex}
254   * exclusive in descending order, interpreting them as unsigned 32-bit integers.
255   *
256   * @since 23.1
257   */
258  public static void sortDescending(int[] array, int fromIndex, int toIndex) {
259    checkNotNull(array);
260    checkPositionIndexes(fromIndex, toIndex, array.length);
261    for (int i = fromIndex; i < toIndex; i++) {
262      array[i] ^= Integer.MAX_VALUE;
263    }
264    Arrays.sort(array, fromIndex, toIndex);
265    for (int i = fromIndex; i < toIndex; i++) {
266      array[i] ^= Integer.MAX_VALUE;
267    }
268  }
269
270  /**
271   * Returns dividend / divisor, where the dividend and divisor are treated as unsigned 32-bit
272   * quantities.
273   *
274   * <p><b>Java 8 users:</b> use {@link Integer#divideUnsigned(int, int)} instead.
275   *
276   * @param dividend the dividend (numerator)
277   * @param divisor the divisor (denominator)
278   * @throws ArithmeticException if divisor is 0
279   */
280  public static int divide(int dividend, int divisor) {
281    return (int) (toLong(dividend) / toLong(divisor));
282  }
283
284  /**
285   * Returns dividend % divisor, where the dividend and divisor are treated as unsigned 32-bit
286   * quantities.
287   *
288   * <p><b>Java 8 users:</b> use {@link Integer#remainderUnsigned(int, int)} instead.
289   *
290   * @param dividend the dividend (numerator)
291   * @param divisor the divisor (denominator)
292   * @throws ArithmeticException if divisor is 0
293   */
294  public static int remainder(int dividend, int divisor) {
295    return (int) (toLong(dividend) % toLong(divisor));
296  }
297
298  /**
299   * Returns the unsigned {@code int} value represented by the given string.
300   *
301   * <p>Accepts a decimal, hexadecimal, or octal number given by specifying the following prefix:
302   *
303   * <ul>
304   *   <li>{@code 0x}<i>HexDigits</i>
305   *   <li>{@code 0X}<i>HexDigits</i>
306   *   <li>{@code #}<i>HexDigits</i>
307   *   <li>{@code 0}<i>OctalDigits</i>
308   * </ul>
309   *
310   * @throws NumberFormatException if the string does not contain a valid unsigned {@code int} value
311   * @since 13.0
312   */
313  @CanIgnoreReturnValue
314  public static int decode(String stringValue) {
315    ParseRequest request = ParseRequest.fromString(stringValue);
316
317    try {
318      return parseUnsignedInt(request.rawValue, request.radix);
319    } catch (NumberFormatException e) {
320      NumberFormatException decodeException =
321          new NumberFormatException("Error parsing value: " + stringValue);
322      decodeException.initCause(e);
323      throw decodeException;
324    }
325  }
326
327  /**
328   * Returns the unsigned {@code int} value represented by the given decimal string.
329   *
330   * <p><b>Java 8 users:</b> use {@link Integer#parseUnsignedInt(String)} instead.
331   *
332   * @throws NumberFormatException if the string does not contain a valid unsigned {@code int} value
333   * @throws NullPointerException if {@code s} is null (in contrast to {@link
334   *     Integer#parseInt(String)})
335   */
336  @CanIgnoreReturnValue
337  public static int parseUnsignedInt(String s) {
338    return parseUnsignedInt(s, 10);
339  }
340
341  /**
342   * Returns the unsigned {@code int} value represented by a string with the given radix.
343   *
344   * <p><b>Java 8 users:</b> use {@link Integer#parseUnsignedInt(String, int)} instead.
345   *
346   * @param string the string containing the unsigned integer representation to be parsed.
347   * @param radix the radix to use while parsing {@code s}; must be between {@link
348   *     Character#MIN_RADIX} and {@link Character#MAX_RADIX}.
349   * @throws NumberFormatException if the string does not contain a valid unsigned {@code int}, or
350   *     if supplied radix is invalid.
351   * @throws NullPointerException if {@code s} is null (in contrast to {@link
352   *     Integer#parseInt(String)})
353   */
354  @CanIgnoreReturnValue
355  public static int parseUnsignedInt(String string, int radix) {
356    checkNotNull(string);
357    long result = Long.parseLong(string, radix);
358    if ((result & INT_MASK) != result) {
359      throw new NumberFormatException(
360          "Input " + string + " in base " + radix + " is not in the range of an unsigned integer");
361    }
362    return (int) result;
363  }
364
365  /**
366   * Returns a string representation of x, where x is treated as unsigned.
367   *
368   * <p><b>Java 8 users:</b> use {@link Integer#toUnsignedString(int)} instead.
369   */
370  public static String toString(int x) {
371    return toString(x, 10);
372  }
373
374  /**
375   * Returns a string representation of {@code x} for the given radix, where {@code x} is treated as
376   * unsigned.
377   *
378   * <p><b>Java 8 users:</b> use {@link Integer#toUnsignedString(int, int)} instead.
379   *
380   * @param x the value to convert to a string.
381   * @param radix the radix to use while working with {@code x}
382   * @throws IllegalArgumentException if {@code radix} is not between {@link Character#MIN_RADIX}
383   *     and {@link Character#MAX_RADIX}.
384   */
385  public static String toString(int x, int radix) {
386    long asLong = x & INT_MASK;
387    return Long.toString(asLong, radix);
388  }
389}