001/*
002 * Copyright (C) 2009 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package com.google.common.primitives;
018
019import static com.google.common.base.Preconditions.checkArgument;
020import static com.google.common.base.Preconditions.checkNotNull;
021
022import com.google.common.annotations.GwtCompatible;
023
024import java.util.Comparator;
025
026/**
027 * Static utility methods pertaining to {@code byte} primitives that
028 * interpret values as signed. The corresponding methods that treat the values
029 * as unsigned are found in {@link UnsignedBytes}, and the methods for which
030 * signedness is not an issue are in {@link Bytes}.
031 *
032 * @author Kevin Bourrillion
033 * @since 1
034 */
035@GwtCompatible
036public final class SignedBytes {
037  private SignedBytes() {}
038
039  /**
040   * Returns the {@code byte} value that is equal to {@code value}, if possible.
041   *
042   * @param value any value in the range of the {@code byte} type
043   * @return the {@code byte} value that equals {@code value}
044   * @throws IllegalArgumentException if {@code value} is greater than {@link
045   *     Byte#MAX_VALUE} or less than {@link Byte#MIN_VALUE}
046   */
047  public static byte checkedCast(long value) {
048    byte result = (byte) value;
049    checkArgument(result == value, "Out of range: %s", value);
050    return result;
051  }
052
053  /**
054   * Returns the {@code byte} nearest in value to {@code value}.
055   *
056   * @param value any {@code long} value
057   * @return the same value cast to {@code byte} if it is in the range of the
058   *     {@code byte} type, {@link Byte#MAX_VALUE} if it is too large,
059   *     or {@link Byte#MIN_VALUE} if it is too small
060   */
061  public static byte saturatedCast(long value) {
062    if (value > Byte.MAX_VALUE) {
063      return Byte.MAX_VALUE;
064    }
065    if (value < Byte.MIN_VALUE) {
066      return Byte.MIN_VALUE;
067    }
068    return (byte) value;
069  }
070
071  /**
072   * Compares the two specified {@code byte} values. The sign of the value
073   * returned is the same as that of {@code ((Byte) a).compareTo(b)}.
074   *
075   * @param a the first {@code byte} to compare
076   * @param b the second {@code byte} to compare
077   * @return a negative value if {@code a} is less than {@code b}; a positive
078   *     value if {@code a} is greater than {@code b}; or zero if they are equal
079   */
080  public static int compare(byte a, byte b) {
081    return a - b; // safe due to restricted range
082  }
083
084  /**
085   * Returns the least value present in {@code array}.
086   *
087   * @param array a <i>nonempty</i> array of {@code byte} values
088   * @return the value present in {@code array} that is less than or equal to
089   *     every other value in the array
090   * @throws IllegalArgumentException if {@code array} is empty
091   */
092  public static byte min(byte... array) {
093    checkArgument(array.length > 0);
094    byte min = array[0];
095    for (int i = 1; i < array.length; i++) {
096      if (array[i] < min) {
097        min = array[i];
098      }
099    }
100    return min;
101  }
102
103  /**
104   * Returns the greatest value present in {@code array}.
105   *
106   * @param array a <i>nonempty</i> array of {@code byte} values
107   * @return the value present in {@code array} that is greater than or equal to
108   *     every other value in the array
109   * @throws IllegalArgumentException if {@code array} is empty
110   */
111  public static byte max(byte... array) {
112    checkArgument(array.length > 0);
113    byte max = array[0];
114    for (int i = 1; i < array.length; i++) {
115      if (array[i] > max) {
116        max = array[i];
117      }
118    }
119    return max;
120  }
121
122  /**
123   * Returns a string containing the supplied {@code byte} values separated
124   * by {@code separator}. For example, {@code join(":", 0x01, 0x02, -0x01)}
125   * returns the string {@code "1:2:-1"}.
126   *
127   * @param separator the text that should appear between consecutive values in
128   *     the resulting string (but not at the start or end)
129   * @param array an array of {@code byte} values, possibly empty
130   */
131  public static String join(String separator, byte... array) {
132    checkNotNull(separator);
133    if (array.length == 0) {
134      return "";
135    }
136
137    // For pre-sizing a builder, just get the right order of magnitude
138    StringBuilder builder = new StringBuilder(array.length * 5);
139    builder.append(array[0]);
140    for (int i = 1; i < array.length; i++) {
141      builder.append(separator).append(array[i]);
142    }
143    return builder.toString();
144  }
145
146  /**
147   * Returns a comparator that compares two {@code byte} arrays
148   * lexicographically. That is, it compares, using {@link
149   * #compare(byte, byte)}), the first pair of values that follow any common
150   * prefix, or when one array is a prefix of the other, treats the shorter
151   * array as the lesser. For example, {@code [] < [0x01] < [0x01, 0x80] <
152   * [0x01, 0x7F] < [0x02]}. Values are treated as signed.
153   *
154   * <p>The returned comparator is inconsistent with {@link
155   * Object#equals(Object)} (since arrays support only identity equality), but
156   * it is consistent with {@link java.util.Arrays#equals(byte[], byte[])}.
157   *
158   * @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order">
159   *     Lexicographical order article at Wikipedia</a>
160   * @since 2
161   */
162  public static Comparator<byte[]> lexicographicalComparator() {
163    return LexicographicalComparator.INSTANCE;
164  }
165
166  private enum LexicographicalComparator implements Comparator<byte[]> {
167    INSTANCE;
168
169    @Override
170    public int compare(byte[] left, byte[] right) {
171      int minLength = Math.min(left.length, right.length);
172      for (int i = 0; i < minLength; i++) {
173        int result = SignedBytes.compare(left[i], right[i]);
174        if (result != 0) {
175          return result;
176        }
177      }
178      return left.length - right.length;
179    }
180  }
181}