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
050@ElementTypesAreNonnullByDefault
051public final class UnsignedInts {
052  static final long INT_MASK = 0xffffffffL;
053
054  private UnsignedInts() {}
055
056  static int flip(int value) {
057    return value ^ Integer.MIN_VALUE;
058  }
059
060  /**
061   * Compares the two specified {@code int} values, treating them as unsigned values between {@code
062   * 0} and {@code 2^32 - 1} inclusive.
063   *
064   * <p><b>Java 8 users:</b> use {@link Integer#compareUnsigned(int, int)} instead.
065   *
066   * @param a the first unsigned {@code int} to compare
067   * @param b the second unsigned {@code int} to compare
068   * @return a negative value if {@code a} is less than {@code b}; a positive value if {@code a} is
069   *     greater than {@code b}; or zero if they are equal
070   */
071  public static int compare(int a, int b) {
072    return Ints.compare(flip(a), flip(b));
073  }
074
075  /**
076   * Returns the value of the given {@code int} as a {@code long}, when treated as unsigned.
077   *
078   * <p><b>Java 8 users:</b> use {@link Integer#toUnsignedLong(int)} instead.
079   */
080  public static long toLong(int value) {
081    return value & INT_MASK;
082  }
083
084  /**
085   * Returns the {@code int} value that, when treated as unsigned, is equal to {@code value}, if
086   * possible.
087   *
088   * @param value a value between 0 and 2<sup>32</sup>-1 inclusive
089   * @return the {@code int} value that, when treated as unsigned, equals {@code value}
090   * @throws IllegalArgumentException if {@code value} is negative or greater than or equal to
091   *     2<sup>32</sup>
092   * @since 21.0
093   */
094  public static int checkedCast(long value) {
095    checkArgument((value >> Integer.SIZE) == 0, "out of range: %s", value);
096    return (int) value;
097  }
098
099  /**
100   * Returns the {@code int} value that, when treated as unsigned, is nearest in value to {@code
101   * value}.
102   *
103   * @param value any {@code long} value
104   * @return {@code 2^32 - 1} if {@code value >= 2^32}, {@code 0} if {@code value <= 0}, and {@code
105   *     value} cast to {@code int} otherwise
106   * @since 21.0
107   */
108  public static int saturatedCast(long value) {
109    if (value <= 0) {
110      return 0;
111    } else if (value >= (1L << 32)) {
112      return -1;
113    } else {
114      return (int) value;
115    }
116  }
117
118  /**
119   * Returns the least value present in {@code array}, treating values as unsigned.
120   *
121   * @param array a <i>nonempty</i> array of unsigned {@code int} values
122   * @return the value present in {@code array} that is less than or equal to every other value in
123   *     the array according to {@link #compare}
124   * @throws IllegalArgumentException if {@code array} is empty
125   */
126  public static int min(int... array) {
127    checkArgument(array.length > 0);
128    int min = flip(array[0]);
129    for (int i = 1; i < array.length; i++) {
130      int next = flip(array[i]);
131      if (next < min) {
132        min = next;
133      }
134    }
135    return flip(min);
136  }
137
138  /**
139   * Returns the greatest value present in {@code array}, treating values as unsigned.
140   *
141   * @param array a <i>nonempty</i> array of unsigned {@code int} values
142   * @return the value present in {@code array} that is greater than or equal to every other value
143   *     in the array according to {@link #compare}
144   * @throws IllegalArgumentException if {@code array} is empty
145   */
146  public static int max(int... array) {
147    checkArgument(array.length > 0);
148    int max = flip(array[0]);
149    for (int i = 1; i < array.length; i++) {
150      int next = flip(array[i]);
151      if (next > max) {
152        max = next;
153      }
154    }
155    return flip(max);
156  }
157
158  /**
159   * Returns a string containing the supplied unsigned {@code int} values separated by {@code
160   * separator}. For example, {@code join("-", 1, 2, 3)} returns the string {@code "1-2-3"}.
161   *
162   * @param separator the text that should appear between consecutive values in the resulting string
163   *     (but not at the start or end)
164   * @param array an array of unsigned {@code int} values, possibly empty
165   */
166  public static String join(String separator, int... array) {
167    checkNotNull(separator);
168    if (array.length == 0) {
169      return "";
170    }
171
172    // For pre-sizing a builder, just get the right order of magnitude
173    StringBuilder builder = new StringBuilder(array.length * 5);
174    builder.append(toString(array[0]));
175    for (int i = 1; i < array.length; i++) {
176      builder.append(separator).append(toString(array[i]));
177    }
178    return builder.toString();
179  }
180
181  /**
182   * Returns a comparator that compares two arrays of unsigned {@code int} values <a
183   * href="http://en.wikipedia.org/wiki/Lexicographical_order">lexicographically</a>. That is, it
184   * compares, using {@link #compare(int, int)}), the first pair of values that follow any common
185   * prefix, or when one array is a prefix of the other, treats the shorter array as the lesser. For
186   * example, {@code [] < [1] < [1, 2] < [2] < [1 << 31]}.
187   *
188   * <p>The returned comparator is inconsistent with {@link Object#equals(Object)} (since arrays
189   * support only identity equality), but it is consistent with {@link Arrays#equals(int[], int[])}.
190   */
191  public static Comparator<int[]> lexicographicalComparator() {
192    return LexicographicalComparator.INSTANCE;
193  }
194
195  enum LexicographicalComparator implements Comparator<int[]> {
196    INSTANCE;
197
198    @Override
199    public int compare(int[] left, int[] right) {
200      int minLength = Math.min(left.length, right.length);
201      for (int i = 0; i < minLength; i++) {
202        if (left[i] != right[i]) {
203          return UnsignedInts.compare(left[i], right[i]);
204        }
205      }
206      return left.length - right.length;
207    }
208
209    @Override
210    public String toString() {
211      return "UnsignedInts.lexicographicalComparator()";
212    }
213  }
214
215  /**
216   * Sorts the array, treating its elements as unsigned 32-bit integers.
217   *
218   * @since 23.1
219   */
220  public static void sort(int[] array) {
221    checkNotNull(array);
222    sort(array, 0, array.length);
223  }
224
225  /**
226   * Sorts the array between {@code fromIndex} inclusive and {@code toIndex} exclusive, treating its
227   * elements as unsigned 32-bit integers.
228   *
229   * @since 23.1
230   */
231  public static void sort(int[] array, int fromIndex, int toIndex) {
232    checkNotNull(array);
233    checkPositionIndexes(fromIndex, toIndex, array.length);
234    for (int i = fromIndex; i < toIndex; i++) {
235      array[i] = flip(array[i]);
236    }
237    Arrays.sort(array, fromIndex, toIndex);
238    for (int i = fromIndex; i < toIndex; i++) {
239      array[i] = flip(array[i]);
240    }
241  }
242
243  /**
244   * Sorts the elements of {@code array} in descending order, interpreting them as unsigned 32-bit
245   * integers.
246   *
247   * @since 23.1
248   */
249  public static void sortDescending(int[] array) {
250    checkNotNull(array);
251    sortDescending(array, 0, array.length);
252  }
253
254  /**
255   * Sorts the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex}
256   * exclusive in descending order, interpreting them as unsigned 32-bit integers.
257   *
258   * @since 23.1
259   */
260  public static void sortDescending(int[] array, int fromIndex, int toIndex) {
261    checkNotNull(array);
262    checkPositionIndexes(fromIndex, toIndex, array.length);
263    for (int i = fromIndex; i < toIndex; i++) {
264      array[i] ^= Integer.MAX_VALUE;
265    }
266    Arrays.sort(array, fromIndex, toIndex);
267    for (int i = fromIndex; i < toIndex; i++) {
268      array[i] ^= Integer.MAX_VALUE;
269    }
270  }
271
272  /**
273   * Returns dividend / divisor, where the dividend and divisor are treated as unsigned 32-bit
274   * quantities.
275   *
276   * <p><b>Java 8 users:</b> use {@link Integer#divideUnsigned(int, int)} instead.
277   *
278   * @param dividend the dividend (numerator)
279   * @param divisor the divisor (denominator)
280   * @throws ArithmeticException if divisor is 0
281   */
282  public static int divide(int dividend, int divisor) {
283    return (int) (toLong(dividend) / toLong(divisor));
284  }
285
286  /**
287   * Returns dividend % divisor, where the dividend and divisor are treated as unsigned 32-bit
288   * quantities.
289   *
290   * <p><b>Java 8 users:</b> use {@link Integer#remainderUnsigned(int, int)} instead.
291   *
292   * @param dividend the dividend (numerator)
293   * @param divisor the divisor (denominator)
294   * @throws ArithmeticException if divisor is 0
295   */
296  public static int remainder(int dividend, int divisor) {
297    return (int) (toLong(dividend) % toLong(divisor));
298  }
299
300  /**
301   * Returns the unsigned {@code int} value represented by the given string.
302   *
303   * <p>Accepts a decimal, hexadecimal, or octal number given by specifying the following prefix:
304   *
305   * <ul>
306   *   <li>{@code 0x}<i>HexDigits</i>
307   *   <li>{@code 0X}<i>HexDigits</i>
308   *   <li>{@code #}<i>HexDigits</i>
309   *   <li>{@code 0}<i>OctalDigits</i>
310   * </ul>
311   *
312   * @throws NumberFormatException if the string does not contain a valid unsigned {@code int} value
313   * @since 13.0
314   */
315  @CanIgnoreReturnValue
316  public static int decode(String stringValue) {
317    ParseRequest request = ParseRequest.fromString(stringValue);
318
319    try {
320      return parseUnsignedInt(request.rawValue, request.radix);
321    } catch (NumberFormatException e) {
322      NumberFormatException decodeException =
323          new NumberFormatException("Error parsing value: " + stringValue);
324      decodeException.initCause(e);
325      throw decodeException;
326    }
327  }
328
329  /**
330   * Returns the unsigned {@code int} value represented by the given decimal string.
331   *
332   * <p><b>Java 8 users:</b> use {@link Integer#parseUnsignedInt(String)} instead.
333   *
334   * @throws NumberFormatException if the string does not contain a valid unsigned {@code int} value
335   * @throws NullPointerException if {@code s} is null (in contrast to {@link
336   *     Integer#parseInt(String)})
337   */
338  @CanIgnoreReturnValue
339  public static int parseUnsignedInt(String s) {
340    return parseUnsignedInt(s, 10);
341  }
342
343  /**
344   * Returns the unsigned {@code int} value represented by a string with the given radix.
345   *
346   * <p><b>Java 8 users:</b> use {@link Integer#parseUnsignedInt(String, int)} instead.
347   *
348   * @param string the string containing the unsigned integer representation to be parsed.
349   * @param radix the radix to use while parsing {@code s}; must be between {@link
350   *     Character#MIN_RADIX} and {@link Character#MAX_RADIX}.
351   * @throws NumberFormatException if the string does not contain a valid unsigned {@code int}, or
352   *     if supplied radix is invalid.
353   * @throws NullPointerException if {@code s} is null (in contrast to {@link
354   *     Integer#parseInt(String)})
355   */
356  @CanIgnoreReturnValue
357  public static int parseUnsignedInt(String string, int radix) {
358    checkNotNull(string);
359    long result = Long.parseLong(string, radix);
360    if ((result & INT_MASK) != result) {
361      throw new NumberFormatException(
362          "Input " + string + " in base " + radix + " is not in the range of an unsigned integer");
363    }
364    return (int) result;
365  }
366
367  /**
368   * Returns a string representation of x, where x is treated as unsigned.
369   *
370   * <p><b>Java 8 users:</b> use {@link Integer#toUnsignedString(int)} instead.
371   */
372  public static String toString(int x) {
373    return toString(x, 10);
374  }
375
376  /**
377   * Returns a string representation of {@code x} for the given radix, where {@code x} is treated as
378   * unsigned.
379   *
380   * <p><b>Java 8 users:</b> use {@link Integer#toUnsignedString(int, int)} instead.
381   *
382   * @param x the value to convert to a string.
383   * @param radix the radix to use while working with {@code x}
384   * @throws IllegalArgumentException if {@code radix} is not between {@link Character#MIN_RADIX}
385   *     and {@link Character#MAX_RADIX}.
386   */
387  public static String toString(int x, int radix) {
388    long asLong = x & INT_MASK;
389    return Long.toString(asLong, radix);
390  }
391}