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.Beta;
022import com.google.common.annotations.GwtCompatible;
023import com.google.errorprone.annotations.CanIgnoreReturnValue;
024import java.util.Arrays;
025import java.util.Comparator;
026
027/**
028 * Static utility methods pertaining to {@code int} primitives that interpret values as
029 * <i>unsigned</i> (that is, any negative value {@code x} is treated as the positive value {@code
030 * 2^32 + x}). The methods for which signedness is not an issue are in {@link Ints}, as well as
031 * signed versions of methods for which signedness is an issue.
032 *
033 * <p>In addition, this class provides several static methods for converting an {@code int} to a
034 * {@code String} and a {@code String} to an {@code int} that treat the {@code int} as an unsigned
035 * number.
036 *
037 * <p>Users of these utilities must be <i>extremely careful</i> not to mix up signed and unsigned
038 * {@code int} values. When possible, it is recommended that the {@link UnsignedInteger} wrapper
039 * class be used, at a small efficiency penalty, to enforce the distinction in the type system.
040 *
041 * <p>See the Guava User Guide article on <a
042 * href="https://github.com/google/guava/wiki/PrimitivesExplained#unsigned-support">unsigned
043 * primitive utilities</a>.
044 *
045 * @author Louis Wasserman
046 * @since 11.0
047 */
048@Beta
049@GwtCompatible
050public final class UnsignedInts {
051  static final long INT_MASK = 0xffffffffL;
052
053  private UnsignedInts() {}
054
055  static int flip(int value) {
056    return value ^ Integer.MIN_VALUE;
057  }
058
059  /**
060   * Compares the two specified {@code int} values, treating them as unsigned values between {@code
061   * 0} and {@code 2^32 - 1} inclusive.
062   *
063   * <p><b>Java 8 users:</b> use {@link Integer#compareUnsigned(int, int)} instead.
064   *
065   * @param a the first unsigned {@code int} to compare
066   * @param b the second unsigned {@code int} to compare
067   * @return a negative value if {@code a} is less than {@code b}; a positive value if {@code a} is
068   *     greater than {@code b}; or zero if they are equal
069   */
070  public static int compare(int a, int b) {
071    return Ints.compare(flip(a), flip(b));
072  }
073
074  /**
075   * Returns the value of the given {@code int} as a {@code long}, when treated as unsigned.
076   *
077   * <p><b>Java 8 users:</b> use {@link Integer#toUnsignedLong(int)} instead.
078   */
079  public static long toLong(int value) {
080    return value & INT_MASK;
081  }
082
083  /**
084   * Returns the {@code int} value that, when treated as unsigned, is equal to {@code value}, if
085   * possible.
086   *
087   * @param value a value between 0 and 2<sup>32</sup>-1 inclusive
088   * @return the {@code int} value that, when treated as unsigned, equals {@code value}
089   * @throws IllegalArgumentException if {@code value} is negative or greater than or equal to
090   *     2<sup>32</sup>
091   * @since 21.0
092   */
093  public static int checkedCast(long value) {
094    checkArgument((value >> Integer.SIZE) == 0, "out of range: %s", value);
095    return (int) value;
096  }
097
098  /**
099   * Returns the {@code int} value that, when treated as unsigned, is nearest in value to {@code
100   * value}.
101   *
102   * @param value any {@code long} value
103   * @return {@code 2^32 - 1} if {@code value >= 2^32}, {@code 0} if {@code value <= 0}, and {@code
104   *     value} cast to {@code int} otherwise
105   * @since 21.0
106   */
107  public static int saturatedCast(long value) {
108    if (value <= 0) {
109      return 0;
110    } else if (value >= (1L << 32)) {
111      return -1;
112    } else {
113      return (int) value;
114    }
115  }
116
117  /**
118   * Returns the least value present in {@code array}, treating values as unsigned.
119   *
120   * @param array a <i>nonempty</i> array of unsigned {@code int} values
121   * @return the value present in {@code array} that is less than or equal to every other value in
122   *     the array according to {@link #compare}
123   * @throws IllegalArgumentException if {@code array} is empty
124   */
125  public static int min(int... array) {
126    checkArgument(array.length > 0);
127    int min = flip(array[0]);
128    for (int i = 1; i < array.length; i++) {
129      int next = flip(array[i]);
130      if (next < min) {
131        min = next;
132      }
133    }
134    return flip(min);
135  }
136
137  /**
138   * Returns the greatest value present in {@code array}, treating values as unsigned.
139   *
140   * @param array a <i>nonempty</i> array of unsigned {@code int} values
141   * @return the value present in {@code array} that is greater than or equal to every other value
142   *     in the array according to {@link #compare}
143   * @throws IllegalArgumentException if {@code array} is empty
144   */
145  public static int max(int... array) {
146    checkArgument(array.length > 0);
147    int max = flip(array[0]);
148    for (int i = 1; i < array.length; i++) {
149      int next = flip(array[i]);
150      if (next > max) {
151        max = next;
152      }
153    }
154    return flip(max);
155  }
156
157  /**
158   * Returns a string containing the supplied unsigned {@code int} values separated by {@code
159   * separator}. For example, {@code join("-", 1, 2, 3)} returns the string {@code "1-2-3"}.
160   *
161   * @param separator the text that should appear between consecutive values in the resulting string
162   *     (but not at the start or end)
163   * @param array an array of unsigned {@code int} values, possibly empty
164   */
165  public static String join(String separator, int... array) {
166    checkNotNull(separator);
167    if (array.length == 0) {
168      return "";
169    }
170
171    // For pre-sizing a builder, just get the right order of magnitude
172    StringBuilder builder = new StringBuilder(array.length * 5);
173    builder.append(toString(array[0]));
174    for (int i = 1; i < array.length; i++) {
175      builder.append(separator).append(toString(array[i]));
176    }
177    return builder.toString();
178  }
179
180  /**
181   * Returns a comparator that compares two arrays of unsigned {@code int} values <a
182   * href="http://en.wikipedia.org/wiki/Lexicographical_order">lexicographically</a>. That is, it
183   * compares, using {@link #compare(int, int)}), the first pair of values that follow any common
184   * prefix, or when one array is a prefix of the other, treats the shorter array as the lesser. For
185   * example, {@code [] < [1] < [1, 2] < [2] < [1 << 31]}.
186   *
187   * <p>The returned comparator is inconsistent with {@link Object#equals(Object)} (since arrays
188   * support only identity equality), but it is consistent with {@link Arrays#equals(int[], int[])}.
189   */
190  public static Comparator<int[]> lexicographicalComparator() {
191    return LexicographicalComparator.INSTANCE;
192  }
193
194  enum LexicographicalComparator implements Comparator<int[]> {
195    INSTANCE;
196
197    @Override
198    public int compare(int[] left, int[] right) {
199      int minLength = Math.min(left.length, right.length);
200      for (int i = 0; i < minLength; i++) {
201        if (left[i] != right[i]) {
202          return UnsignedInts.compare(left[i], right[i]);
203        }
204      }
205      return left.length - right.length;
206    }
207
208    @Override
209    public String toString() {
210      return "UnsignedInts.lexicographicalComparator()";
211    }
212  }
213
214  /**
215   * Sorts the array, treating its elements as unsigned 32-bit integers.
216   *
217   * @since 23.1
218   */
219  public static void sort(int[] array) {
220    checkNotNull(array);
221    sort(array, 0, array.length);
222  }
223
224  /**
225   * Sorts the array between {@code fromIndex} inclusive and {@code toIndex} exclusive, treating its
226   * elements as unsigned 32-bit integers.
227   *
228   * @since 23.1
229   */
230  public static void sort(int[] array, int fromIndex, int toIndex) {
231    checkNotNull(array);
232    checkPositionIndexes(fromIndex, toIndex, array.length);
233    for (int i = fromIndex; i < toIndex; i++) {
234      array[i] = flip(array[i]);
235    }
236    Arrays.sort(array, fromIndex, toIndex);
237    for (int i = fromIndex; i < toIndex; i++) {
238      array[i] = flip(array[i]);
239    }
240  }
241
242  /**
243   * Sorts the elements of {@code array} in descending order, interpreting them as unsigned 32-bit
244   * integers.
245   *
246   * @since 23.1
247   */
248  public static void sortDescending(int[] array) {
249    checkNotNull(array);
250    sortDescending(array, 0, array.length);
251  }
252
253  /**
254   * Sorts the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex}
255   * exclusive in descending order, interpreting them as unsigned 32-bit integers.
256   *
257   * @since 23.1
258   */
259  public static void sortDescending(int[] array, int fromIndex, int toIndex) {
260    checkNotNull(array);
261    checkPositionIndexes(fromIndex, toIndex, array.length);
262    for (int i = fromIndex; i < toIndex; i++) {
263      array[i] ^= Integer.MAX_VALUE;
264    }
265    Arrays.sort(array, fromIndex, toIndex);
266    for (int i = fromIndex; i < toIndex; i++) {
267      array[i] ^= Integer.MAX_VALUE;
268    }
269  }
270
271  /**
272   * Returns dividend / divisor, where the dividend and divisor are treated as unsigned 32-bit
273   * quantities.
274   *
275   * <p><b>Java 8 users:</b> use {@link Integer#divideUnsigned(int, int)} instead.
276   *
277   * @param dividend the dividend (numerator)
278   * @param divisor the divisor (denominator)
279   * @throws ArithmeticException if divisor is 0
280   */
281  public static int divide(int dividend, int divisor) {
282    return (int) (toLong(dividend) / toLong(divisor));
283  }
284
285  /**
286   * Returns dividend % divisor, where the dividend and divisor are treated as unsigned 32-bit
287   * quantities.
288   *
289   * <p><b>Java 8 users:</b> use {@link Integer#remainderUnsigned(int, int)} instead.
290   *
291   * @param dividend the dividend (numerator)
292   * @param divisor the divisor (denominator)
293   * @throws ArithmeticException if divisor is 0
294   */
295  public static int remainder(int dividend, int divisor) {
296    return (int) (toLong(dividend) % toLong(divisor));
297  }
298
299  /**
300   * Returns the unsigned {@code int} value represented by the given string.
301   *
302   * <p>Accepts a decimal, hexadecimal, or octal number given by specifying the following prefix:
303   *
304   * <ul>
305   *   <li>{@code 0x}<i>HexDigits</i>
306   *   <li>{@code 0X}<i>HexDigits</i>
307   *   <li>{@code #}<i>HexDigits</i>
308   *   <li>{@code 0}<i>OctalDigits</i>
309   * </ul>
310   *
311   * @throws NumberFormatException if the string does not contain a valid unsigned {@code int} value
312   * @since 13.0
313   */
314  @CanIgnoreReturnValue
315  public static int decode(String stringValue) {
316    ParseRequest request = ParseRequest.fromString(stringValue);
317
318    try {
319      return parseUnsignedInt(request.rawValue, request.radix);
320    } catch (NumberFormatException e) {
321      NumberFormatException decodeException =
322          new NumberFormatException("Error parsing value: " + stringValue);
323      decodeException.initCause(e);
324      throw decodeException;
325    }
326  }
327
328  /**
329   * Returns the unsigned {@code int} value represented by the given decimal string.
330   *
331   * <p><b>Java 8 users:</b> use {@link Integer#parseUnsignedInt(String)} instead.
332   *
333   * @throws NumberFormatException if the string does not contain a valid unsigned {@code int} value
334   * @throws NullPointerException if {@code s} is null (in contrast to {@link
335   *     Integer#parseInt(String)})
336   */
337  @CanIgnoreReturnValue
338  public static int parseUnsignedInt(String s) {
339    return parseUnsignedInt(s, 10);
340  }
341
342  /**
343   * Returns the unsigned {@code int} value represented by a string with the given radix.
344   *
345   * <p><b>Java 8 users:</b> use {@link Integer#parseUnsignedInt(String, int)} instead.
346   *
347   * @param string the string containing the unsigned integer representation to be parsed.
348   * @param radix the radix to use while parsing {@code s}; must be between {@link
349   *     Character#MIN_RADIX} and {@link Character#MAX_RADIX}.
350   * @throws NumberFormatException if the string does not contain a valid unsigned {@code int}, or
351   *     if supplied radix is invalid.
352   * @throws NullPointerException if {@code s} is null (in contrast to {@link
353   *     Integer#parseInt(String)})
354   */
355  @CanIgnoreReturnValue
356  public static int parseUnsignedInt(String string, int radix) {
357    checkNotNull(string);
358    long result = Long.parseLong(string, radix);
359    if ((result & INT_MASK) != result) {
360      throw new NumberFormatException(
361          "Input " + string + " in base " + radix + " is not in the range of an unsigned integer");
362    }
363    return (int) result;
364  }
365
366  /**
367   * Returns a string representation of x, where x is treated as unsigned.
368   *
369   * <p><b>Java 8 users:</b> use {@link Integer#toUnsignedString(int)} instead.
370   */
371  public static String toString(int x) {
372    return toString(x, 10);
373  }
374
375  /**
376   * Returns a string representation of {@code x} for the given radix, where {@code x} is treated as
377   * unsigned.
378   *
379   * <p><b>Java 8 users:</b> use {@link Integer#toUnsignedString(int, int)} instead.
380   *
381   * @param x the value to convert to a string.
382   * @param radix the radix to use while working with {@code x}
383   * @throws IllegalArgumentException if {@code radix} is not between {@link Character#MIN_RADIX}
384   *     and {@link Character#MAX_RADIX}.
385   */
386  public static String toString(int x, int radix) {
387    long asLong = x & INT_MASK;
388    return Long.toString(asLong, radix);
389  }
390}