Update #0 - First Release

sources/main/java/com/google/common/primitives/SignedBytes.java

@@ -0,0 +1,208 @@
+/*
+ * Copyright (C) 2009 The Guava Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.common.primitives;
+
+import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.common.base.Preconditions.checkNotNull;
+
+import java.util.Comparator;
+
+import com.google.common.annotations.GwtCompatible;
+
+/**
+ * Static utility methods pertaining to {@code byte} primitives that interpret
+ * values as signed. The corresponding methods that treat the values as unsigned
+ * are found in {@link UnsignedBytes}, and the methods for which signedness is
+ * not an issue are in {@link Bytes}.
+ * 
+ * <p>
+ * See the Guava User Guide article on
+ * <a href= "http://code.google.com/p/guava-libraries/wiki/PrimitivesExplained">
+ * primitive utilities</a>.
+ *
+ * @author Kevin Bourrillion
+ * @since 1.0
+ */
+// TODO(kevinb): how to prevent warning on UnsignedBytes when building GWT
+// javadoc?
+@GwtCompatible
+public final class SignedBytes {
+	private SignedBytes() {
+	}
+
+	/**
+	 * The largest power of two that can be represented as a signed {@code byte}.
+	 *
+	 * @since 10.0
+	 */
+	public static final byte MAX_POWER_OF_TWO = 1 << 6;
+
+	/**
+	 * Returns the {@code byte} value that is equal to {@code value}, if possible.
+	 *
+	 * @param value any value in the range of the {@code byte} type
+	 * @return the {@code byte} value that equals {@code value}
+	 * @throws IllegalArgumentException if {@code value} is greater than
+	 *                                  {@link Byte#MAX_VALUE} or less than
+	 *                                  {@link Byte#MIN_VALUE}
+	 */
+	public static byte checkedCast(long value) {
+		byte result = (byte) value;
+		if (result != value) {
+			// don't use checkArgument here, to avoid boxing
+			throw new IllegalArgumentException("Out of range: " + value);
+		}
+		return result;
+	}
+
+	/**
+	 * Returns the {@code byte} nearest in value to {@code value}.
+	 *
+	 * @param value any {@code long} value
+	 * @return the same value cast to {@code byte} if it is in the range of the
+	 *         {@code byte} type, {@link Byte#MAX_VALUE} if it is too large, or
+	 *         {@link Byte#MIN_VALUE} if it is too small
+	 */
+	public static byte saturatedCast(long value) {
+		if (value > Byte.MAX_VALUE) {
+			return Byte.MAX_VALUE;
+		}
+		if (value < Byte.MIN_VALUE) {
+			return Byte.MIN_VALUE;
+		}
+		return (byte) value;
+	}
+
+	/**
+	 * Compares the two specified {@code byte} values. The sign of the value
+	 * returned is the same as that of {@code ((Byte) a).compareTo(b)}.
+	 *
+	 * <p>
+	 * <b>Note:</b> this method behaves identically to the JDK 7 method
+	 * {@link Byte#compare}.
+	 *
+	 * @param a the first {@code byte} to compare
+	 * @param b the second {@code byte} to compare
+	 * @return a negative value if {@code a} is less than {@code b}; a positive
+	 *         value if {@code a} is greater than {@code b}; or zero if they are
+	 *         equal
+	 */
+	// TODO(kevinb): if Ints.compare etc. are ever removed, *maybe* remove this
+	// one too, which would leave compare methods only on the Unsigned* classes.
+	public static int compare(byte a, byte b) {
+		return a - b; // safe due to restricted range
+	}
+
+	/**
+	 * Returns the least value present in {@code array}.
+	 *
+	 * @param array a <i>nonempty</i> array of {@code byte} values
+	 * @return the value present in {@code array} that is less than or equal to
+	 *         every other value in the array
+	 * @throws IllegalArgumentException if {@code array} is empty
+	 */
+	public static byte min(byte... array) {
+		checkArgument(array.length > 0);
+		byte min = array[0];
+		for (int i = 1; i < array.length; i++) {
+			if (array[i] < min) {
+				min = array[i];
+			}
+		}
+		return min;
+	}
+
+	/**
+	 * Returns the greatest value present in {@code array}.
+	 *
+	 * @param array a <i>nonempty</i> array of {@code byte} values
+	 * @return the value present in {@code array} that is greater than or equal to
+	 *         every other value in the array
+	 * @throws IllegalArgumentException if {@code array} is empty
+	 */
+	public static byte max(byte... array) {
+		checkArgument(array.length > 0);
+		byte max = array[0];
+		for (int i = 1; i < array.length; i++) {
+			if (array[i] > max) {
+				max = array[i];
+			}
+		}
+		return max;
+	}
+
+	/**
+	 * Returns a string containing the supplied {@code byte} values separated by
+	 * {@code separator}. For example, {@code join(":", 0x01, 0x02, -0x01)} returns
+	 * the string {@code "1:2:-1"}.
+	 *
+	 * @param separator the text that should appear between consecutive values in
+	 *                  the resulting string (but not at the start or end)
+	 * @param array     an array of {@code byte} values, possibly empty
+	 */
+	public static String join(String separator, byte... array) {
+		checkNotNull(separator);
+		if (array.length == 0) {
+			return "";
+		}
+
+		// For pre-sizing a builder, just get the right order of magnitude
+		StringBuilder builder = new StringBuilder(array.length * 5);
+		builder.append(array[0]);
+		for (int i = 1; i < array.length; i++) {
+			builder.append(separator).append(array[i]);
+		}
+		return builder.toString();
+	}
+
+	/**
+	 * Returns a comparator that compares two {@code byte} arrays lexicographically.
+	 * That is, it compares, using {@link #compare(byte, byte)}), the first pair of
+	 * values that follow any common prefix, or when one array is a prefix of the
+	 * other, treats the shorter array as the lesser. For example,
+	 * {@code [] < [0x01] < [0x01, 0x80] <
+	 * [0x01, 0x7F] < [0x02]}. Values are treated as signed.
+	 *
+	 * <p>
+	 * The returned comparator is inconsistent with {@link Object#equals(Object)}
+	 * (since arrays support only identity equality), but it is consistent with
+	 * {@link java.util.Arrays#equals(byte[], byte[])}.
+	 *
+	 * @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order">
+	 *      Lexicographical order article at Wikipedia</a>
+	 * @since 2.0
+	 */
+	public static Comparator<byte[]> lexicographicalComparator() {
+		return LexicographicalComparator.INSTANCE;
+	}
+
+	private enum LexicographicalComparator implements Comparator<byte[]> {
+		INSTANCE;
+
+		@Override
+		public int compare(byte[] left, byte[] right) {
+			int minLength = Math.min(left.length, right.length);
+			for (int i = 0; i < minLength; i++) {
+				int result = SignedBytes.compare(left[i], right[i]);
+				if (result != 0) {
+					return result;
+				}
+			}
+			return left.length - right.length;
+		}
+	}
+}