398 lines
12 KiB
Java
398 lines
12 KiB
Java
/*
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* Copyright (C) 2008 The Guava Authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.google.common.primitives;
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import static com.google.common.base.Preconditions.checkArgument;
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import static com.google.common.base.Preconditions.checkElementIndex;
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import static com.google.common.base.Preconditions.checkNotNull;
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import static com.google.common.base.Preconditions.checkPositionIndexes;
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import java.io.Serializable;
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import java.util.AbstractList;
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import java.util.Arrays;
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import java.util.Collection;
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import java.util.Collections;
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import java.util.List;
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import java.util.RandomAccess;
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import com.google.common.annotations.GwtCompatible;
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/**
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* Static utility methods pertaining to {@code byte} primitives, that are not
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* already found in either {@link Byte} or {@link Arrays}, <i>and interpret
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* bytes as neither signed nor unsigned</i>. The methods which specifically
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* treat bytes as signed or unsigned are found in {@link SignedBytes} and
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* {@link UnsignedBytes}.
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*
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* <p>
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* See the Guava User Guide article on
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* <a href= "http://code.google.com/p/guava-libraries/wiki/PrimitivesExplained">
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* primitive utilities</a>.
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*
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* @author Kevin Bourrillion
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* @since 1.0
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*/
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// TODO(kevinb): how to prevent warning on UnsignedBytes when building GWT
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// javadoc?
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@GwtCompatible
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public final class Bytes {
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private Bytes() {
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}
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/**
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* Returns a hash code for {@code value}; equal to the result of invoking
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* {@code ((Byte) value).hashCode()}.
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*
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* @param value a primitive {@code byte} value
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* @return a hash code for the value
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*/
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public static int hashCode(byte value) {
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return value;
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}
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/**
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* Returns {@code true} if {@code target} is present as an element anywhere in
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* {@code array}.
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*
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* @param array an array of {@code byte} values, possibly empty
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* @param target a primitive {@code byte} value
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* @return {@code true} if {@code array[i] == target} for some value of {@code
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* i}
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*/
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public static boolean contains(byte[] array, byte target) {
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for (byte value : array) {
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if (value == target) {
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return true;
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}
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}
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return false;
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}
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/**
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* Returns the index of the first appearance of the value {@code target} in
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* {@code array}.
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*
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* @param array an array of {@code byte} values, possibly empty
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* @param target a primitive {@code byte} value
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* @return the least index {@code i} for which {@code array[i] == target}, or
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* {@code -1} if no such index exists.
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*/
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public static int indexOf(byte[] array, byte target) {
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return indexOf(array, target, 0, array.length);
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}
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// TODO(kevinb): consider making this public
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private static int indexOf(byte[] array, byte target, int start, int end) {
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for (int i = start; i < end; i++) {
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if (array[i] == target) {
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return i;
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}
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}
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return -1;
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}
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/**
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* Returns the start position of the first occurrence of the specified {@code
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* target} within {@code array}, or {@code -1} if there is no such occurrence.
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*
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* <p>
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* More formally, returns the lowest index {@code i} such that {@code
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* java.util.Arrays.copyOfRange(array, i, i + target.length)} contains exactly
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* the same elements as {@code target}.
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*
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* @param array the array to search for the sequence {@code target}
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* @param target the array to search for as a sub-sequence of {@code array}
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*/
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public static int indexOf(byte[] array, byte[] target) {
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checkNotNull(array, "array");
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checkNotNull(target, "target");
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if (target.length == 0) {
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return 0;
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}
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outer: for (int i = 0; i < array.length - target.length + 1; i++) {
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for (int j = 0; j < target.length; j++) {
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if (array[i + j] != target[j]) {
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continue outer;
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}
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}
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return i;
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}
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return -1;
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}
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/**
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* Returns the index of the last appearance of the value {@code target} in
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* {@code array}.
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*
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* @param array an array of {@code byte} values, possibly empty
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* @param target a primitive {@code byte} value
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* @return the greatest index {@code i} for which {@code array[i] == target}, or
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* {@code -1} if no such index exists.
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*/
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public static int lastIndexOf(byte[] array, byte target) {
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return lastIndexOf(array, target, 0, array.length);
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}
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// TODO(kevinb): consider making this public
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private static int lastIndexOf(byte[] array, byte target, int start, int end) {
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for (int i = end - 1; i >= start; i--) {
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if (array[i] == target) {
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return i;
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}
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}
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return -1;
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}
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/**
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* Returns the values from each provided array combined into a single array. For
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* example, {@code concat(new byte[] {a, b}, new byte[] {}, new byte[] {c}}
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* returns the array {@code {a, b, c}}.
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*
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* @param arrays zero or more {@code byte} arrays
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* @return a single array containing all the values from the source arrays, in
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* order
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*/
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public static byte[] concat(byte[]... arrays) {
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int length = 0;
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for (byte[] array : arrays) {
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length += array.length;
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}
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byte[] result = new byte[length];
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int pos = 0;
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for (byte[] array : arrays) {
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System.arraycopy(array, 0, result, pos, array.length);
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pos += array.length;
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}
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return result;
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}
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/**
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* Returns an array containing the same values as {@code array}, but guaranteed
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* to be of a specified minimum length. If {@code array} already has a length of
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* at least {@code minLength}, it is returned directly. Otherwise, a new array
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* of size {@code minLength + padding} is returned, containing the values of
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* {@code array}, and zeroes in the remaining places.
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*
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* @param array the source array
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* @param minLength the minimum length the returned array must guarantee
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* @param padding an extra amount to "grow" the array by if growth is
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* necessary
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* @throws IllegalArgumentException if {@code minLength} or {@code padding} is
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* negative
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* @return an array containing the values of {@code array}, with guaranteed
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* minimum length {@code minLength}
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*/
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public static byte[] ensureCapacity(byte[] array, int minLength, int padding) {
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checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
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checkArgument(padding >= 0, "Invalid padding: %s", padding);
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return (array.length < minLength) ? copyOf(array, minLength + padding) : array;
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}
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// Arrays.copyOf() requires Java 6
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private static byte[] copyOf(byte[] original, int length) {
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byte[] copy = new byte[length];
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System.arraycopy(original, 0, copy, 0, Math.min(original.length, length));
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return copy;
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}
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/**
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* Returns an array containing each value of {@code collection}, converted to a
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* {@code byte} value in the manner of {@link Number#byteValue}.
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*
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* <p>
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* Elements are copied from the argument collection as if by {@code
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* collection.toArray()}. Calling this method is as thread-safe as calling that
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* method.
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*
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* @param collection a collection of {@code Number} instances
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* @return an array containing the same values as {@code collection}, in the
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* same order, converted to primitives
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* @throws NullPointerException if {@code collection} or any of its elements is
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* null
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* @since 1.0 (parameter was {@code Collection<Byte>} before 12.0)
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*/
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public static byte[] toArray(Collection<? extends Number> collection) {
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if (collection instanceof ByteArrayAsList) {
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return ((ByteArrayAsList) collection).toByteArray();
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}
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Object[] boxedArray = collection.toArray();
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int len = boxedArray.length;
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byte[] array = new byte[len];
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for (int i = 0; i < len; i++) {
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// checkNotNull for GWT (do not optimize)
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array[i] = ((Number) checkNotNull(boxedArray[i])).byteValue();
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}
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return array;
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}
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/**
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* Returns a fixed-size list backed by the specified array, similar to
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* {@link Arrays#asList(Object[])}. The list supports
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* {@link List#set(int, Object)}, but any attempt to set a value to {@code null}
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* will result in a {@link NullPointerException}.
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*
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* <p>
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* The returned list maintains the values, but not the identities, of
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* {@code Byte} objects written to or read from it. For example, whether
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* {@code list.get(0) == list.get(0)} is true for the returned list is
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* unspecified.
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*
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* @param backingArray the array to back the list
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* @return a list view of the array
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*/
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public static List<Byte> asList(byte... backingArray) {
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if (backingArray.length == 0) {
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return Collections.emptyList();
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}
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return new ByteArrayAsList(backingArray);
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}
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@GwtCompatible
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private static class ByteArrayAsList extends AbstractList<Byte> implements RandomAccess, Serializable {
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final byte[] array;
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final int start;
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final int end;
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ByteArrayAsList(byte[] array) {
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this(array, 0, array.length);
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}
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ByteArrayAsList(byte[] array, int start, int end) {
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this.array = array;
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this.start = start;
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this.end = end;
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}
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@Override
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public int size() {
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return end - start;
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}
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@Override
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public boolean isEmpty() {
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return false;
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}
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@Override
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public Byte get(int index) {
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checkElementIndex(index, size());
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return array[start + index];
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}
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@Override
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public boolean contains(Object target) {
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// Overridden to prevent a ton of boxing
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return (target instanceof Byte) && Bytes.indexOf(array, (Byte) target, start, end) != -1;
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}
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@Override
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public int indexOf(Object target) {
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// Overridden to prevent a ton of boxing
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if (target instanceof Byte) {
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int i = Bytes.indexOf(array, (Byte) target, start, end);
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if (i >= 0) {
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return i - start;
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}
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}
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return -1;
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}
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@Override
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public int lastIndexOf(Object target) {
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// Overridden to prevent a ton of boxing
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if (target instanceof Byte) {
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int i = Bytes.lastIndexOf(array, (Byte) target, start, end);
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if (i >= 0) {
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return i - start;
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}
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}
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return -1;
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}
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@Override
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public Byte set(int index, Byte element) {
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checkElementIndex(index, size());
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byte oldValue = array[start + index];
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// checkNotNull for GWT (do not optimize)
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array[start + index] = checkNotNull(element);
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return oldValue;
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}
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@Override
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public List<Byte> subList(int fromIndex, int toIndex) {
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int size = size();
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checkPositionIndexes(fromIndex, toIndex, size);
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if (fromIndex == toIndex) {
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return Collections.emptyList();
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}
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return new ByteArrayAsList(array, start + fromIndex, start + toIndex);
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}
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@Override
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public boolean equals(Object object) {
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if (object == this) {
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return true;
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}
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if (object instanceof ByteArrayAsList) {
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ByteArrayAsList that = (ByteArrayAsList) object;
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int size = size();
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if (that.size() != size) {
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return false;
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}
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for (int i = 0; i < size; i++) {
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if (array[start + i] != that.array[that.start + i]) {
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return false;
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}
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}
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return true;
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}
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return super.equals(object);
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}
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@Override
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public int hashCode() {
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int result = 1;
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for (int i = start; i < end; i++) {
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result = 31 * result + Bytes.hashCode(array[i]);
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}
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return result;
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}
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@Override
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public String toString() {
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StringBuilder builder = new StringBuilder(size() * 5);
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builder.append('[').append(array[start]);
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for (int i = start + 1; i < end; i++) {
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builder.append(", ").append(array[i]);
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}
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return builder.append(']').toString();
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}
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byte[] toByteArray() {
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// Arrays.copyOfRange() is not available under GWT
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int size = size();
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byte[] result = new byte[size];
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System.arraycopy(array, start, result, 0, size);
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return result;
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}
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private static final long serialVersionUID = 0;
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}
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}
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