1/*
2 * Copyright (C) 2009 The Guava Authors
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.google.common.primitives;
18
19import static com.google.common.base.Preconditions.checkArgument;
20import static com.google.common.base.Preconditions.checkNotNull;
21
22import com.google.common.annotations.Beta;
23import com.google.common.annotations.VisibleForTesting;
24
25import java.util.Comparator;
26
27/**
28 * Static utility methods pertaining to {@code byte} primitives that interpret
29 * values as <i>unsigned</i> (that is, any negative value {@code b} is treated
30 * as the positive value {@code 256 + b}). The corresponding methods that treat
31 * the values as signed are found in {@link SignedBytes}, and the methods for
32 * which signedness is not an issue are in {@link Bytes}.
33 *
34 * <p>See the Guava User Guide article on <a href=
35 * "http://code.google.com/p/guava-libraries/wiki/PrimitivesExplained">
36 * primitive utilities</a>.
37 *
38 * @author Kevin Bourrillion
39 * @author Martin Buchholz
40 * @author Hiroshi Yamauchi
41 * @author Louis Wasserman
42 * @since 1.0
43 */
44public final class UnsignedBytes {
45  private UnsignedBytes() {}
46
47  /**
48   * The largest power of two that can be represented as an unsigned {@code
49   * byte}.
50   *
51   * @since 10.0
52   */
53  public static final byte MAX_POWER_OF_TWO = (byte) 0x80;
54
55  /**
56   * The largest value that fits into an unsigned byte.
57   *
58   * @since 13.0
59   */
60  public static final byte MAX_VALUE = (byte) 0xFF;
61
62  private static final int UNSIGNED_MASK = 0xFF;
63
64  /**
65   * Returns the value of the given byte as an integer, when treated as
66   * unsigned. That is, returns {@code value + 256} if {@code value} is
67   * negative; {@code value} itself otherwise.
68   *
69   * @since 6.0
70   */
71  public static int toInt(byte value) {
72    return value & UNSIGNED_MASK;
73  }
74
75  /**
76   * Returns the {@code byte} value that, when treated as unsigned, is equal to
77   * {@code value}, if possible.
78   *
79   * @param value a value between 0 and 255 inclusive
80   * @return the {@code byte} value that, when treated as unsigned, equals
81   *     {@code value}
82   * @throws IllegalArgumentException if {@code value} is negative or greater
83   *     than 255
84   */
85  public static byte checkedCast(long value) {
86    if ((value >> Byte.SIZE) != 0) {
87      // don't use checkArgument here, to avoid boxing
88      throw new IllegalArgumentException("Out of range: " + value);
89    }
90    return (byte) value;
91  }
92
93  /**
94   * Returns the {@code byte} value that, when treated as unsigned, is nearest
95   * in value to {@code value}.
96   *
97   * @param value any {@code long} value
98   * @return {@code (byte) 255} if {@code value >= 255}, {@code (byte) 0} if
99   *     {@code value <= 0}, and {@code value} cast to {@code byte} otherwise
100   */
101  public static byte saturatedCast(long value) {
102    if (value > toInt(MAX_VALUE)) {
103      return MAX_VALUE; // -1
104    }
105    if (value < 0) {
106      return (byte) 0;
107    }
108    return (byte) value;
109  }
110
111  /**
112   * Compares the two specified {@code byte} values, treating them as unsigned
113   * values between 0 and 255 inclusive. For example, {@code (byte) -127} is
114   * considered greater than {@code (byte) 127} because it is seen as having
115   * the value of positive {@code 129}.
116   *
117   * @param a the first {@code byte} to compare
118   * @param b the second {@code byte} to compare
119   * @return a negative value if {@code a} is less than {@code b}; a positive
120   *     value if {@code a} is greater than {@code b}; or zero if they are equal
121   */
122  public static int compare(byte a, byte b) {
123    return toInt(a) - toInt(b);
124  }
125
126  /**
127   * Returns the least value present in {@code array}.
128   *
129   * @param array a <i>nonempty</i> array of {@code byte} values
130   * @return the value present in {@code array} that is less than or equal to
131   *     every other value in the array
132   * @throws IllegalArgumentException if {@code array} is empty
133   */
134  public static byte min(byte... array) {
135    checkArgument(array.length > 0);
136    int min = toInt(array[0]);
137    for (int i = 1; i < array.length; i++) {
138      int next = toInt(array[i]);
139      if (next < min) {
140        min = next;
141      }
142    }
143    return (byte) min;
144  }
145
146  /**
147   * Returns the greatest value present in {@code array}.
148   *
149   * @param array a <i>nonempty</i> array of {@code byte} values
150   * @return the value present in {@code array} that is greater than or equal
151   *     to every other value in the array
152   * @throws IllegalArgumentException if {@code array} is empty
153   */
154  public static byte max(byte... array) {
155    checkArgument(array.length > 0);
156    int max = toInt(array[0]);
157    for (int i = 1; i < array.length; i++) {
158      int next = toInt(array[i]);
159      if (next > max) {
160        max = next;
161      }
162    }
163    return (byte) max;
164  }
165
166  /**
167   * Returns a string representation of x, where x is treated as unsigned.
168   *
169   * @since 13.0
170   */
171  @Beta
172  public static String toString(byte x) {
173    return toString(x, 10);
174  }
175
176  /**
177   * Returns a string representation of {@code x} for the given radix, where {@code x} is treated
178   * as unsigned.
179   *
180   * @param x the value to convert to a string.
181   * @param radix the radix to use while working with {@code x}
182   * @throws IllegalArgumentException if {@code radix} is not between {@link Character#MIN_RADIX}
183   *         and {@link Character#MAX_RADIX}.
184   * @since 13.0
185   */
186  @Beta
187  public static String toString(byte x, int radix) {
188    checkArgument(radix >= Character.MIN_RADIX && radix <= Character.MAX_RADIX,
189        "radix (%s) must be between Character.MIN_RADIX and Character.MAX_RADIX", radix);
190    // Benchmarks indicate this is probably not worth optimizing.
191    return Integer.toString(toInt(x), radix);
192  }
193
194  /**
195   * Returns the unsigned {@code byte} value represented by the given decimal string.
196   *
197   * @throws NumberFormatException if the string does not contain a valid unsigned {@code byte}
198   *         value
199   * @throws NullPointerException if {@code s} is null
200   *         (in contrast to {@link Byte#parseByte(String)})
201   * @since 13.0
202   */
203  @Beta
204  public static byte parseUnsignedByte(String string) {
205    return parseUnsignedByte(string, 10);
206  }
207
208  /**
209   * Returns the unsigned {@code byte} value represented by a string with the given radix.
210   *
211   * @param string the string containing the unsigned {@code byte} representation to be parsed.
212   * @param radix the radix to use while parsing {@code string}
213   * @throws NumberFormatException if the string does not contain a valid unsigned {@code byte}
214   *         with the given radix, or if {@code radix} is not between {@link Character#MIN_RADIX}
215   *         and {@link Character#MAX_RADIX}.
216   * @throws NullPointerException if {@code s} is null
217   *         (in contrast to {@link Byte#parseByte(String)})
218   * @since 13.0
219   */
220  @Beta
221  public static byte parseUnsignedByte(String string, int radix) {
222    int parse = Integer.parseInt(checkNotNull(string), radix);
223    // We need to throw a NumberFormatException, so we have to duplicate checkedCast. =(
224    if (parse >> Byte.SIZE == 0) {
225      return (byte) parse;
226    } else {
227      throw new NumberFormatException("out of range: " + parse);
228    }
229  }
230
231  /**
232   * Returns a string containing the supplied {@code byte} values separated by
233   * {@code separator}. For example, {@code join(":", (byte) 1, (byte) 2,
234   * (byte) 255)} returns the string {@code "1:2:255"}.
235   *
236   * @param separator the text that should appear between consecutive values in
237   *     the resulting string (but not at the start or end)
238   * @param array an array of {@code byte} values, possibly empty
239   */
240  public static String join(String separator, byte... array) {
241    checkNotNull(separator);
242    if (array.length == 0) {
243      return "";
244    }
245
246    // For pre-sizing a builder, just get the right order of magnitude
247    StringBuilder builder = new StringBuilder(array.length * (3 + separator.length()));
248    builder.append(toInt(array[0]));
249    for (int i = 1; i < array.length; i++) {
250      builder.append(separator).append(toString(array[i]));
251    }
252    return builder.toString();
253  }
254
255  /**
256   * Returns a comparator that compares two {@code byte} arrays
257   * lexicographically. That is, it compares, using {@link
258   * #compare(byte, byte)}), the first pair of values that follow any common
259   * prefix, or when one array is a prefix of the other, treats the shorter
260   * array as the lesser. For example, {@code [] < [0x01] < [0x01, 0x7F] <
261   * [0x01, 0x80] < [0x02]}. Values are treated as unsigned.
262   *
263   * <p>The returned comparator is inconsistent with {@link
264   * Object#equals(Object)} (since arrays support only identity equality), but
265   * it is consistent with {@link java.util.Arrays#equals(byte[], byte[])}.
266   *
267   * @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order">
268   *     Lexicographical order article at Wikipedia</a>
269   * @since 2.0
270   */
271  public static Comparator<byte[]> lexicographicalComparator() {
272    return LexicographicalComparatorHolder.BEST_COMPARATOR;
273  }
274
275  @VisibleForTesting
276  static Comparator<byte[]> lexicographicalComparatorJavaImpl() {
277    return LexicographicalComparatorHolder.PureJavaComparator.INSTANCE;
278  }
279
280  /**
281   * Provides a pure Java lexicographical comparator implementation.
282   */
283  @VisibleForTesting
284  static class LexicographicalComparatorHolder {
285
286    static final Comparator<byte[]> BEST_COMPARATOR = lexicographicalComparatorJavaImpl();
287
288    enum PureJavaComparator implements Comparator<byte[]> {
289      INSTANCE;
290
291      @Override public int compare(byte[] left, byte[] right) {
292        int minLength = Math.min(left.length, right.length);
293        for (int i = 0; i < minLength; i++) {
294          int result = UnsignedBytes.compare(left[i], right[i]);
295          if (result != 0) {
296            return result;
297          }
298        }
299        return left.length - right.length;
300      }
301    }
302  }
303}
304