209 lines
6.7 KiB
Java
209 lines
6.7 KiB
Java
/*
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* Copyright (C) 2009 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.checkNotNull;
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import java.util.Comparator;
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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 interpret
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* values as signed. The corresponding methods that treat the values as unsigned
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* are found in {@link UnsignedBytes}, and the methods for which signedness is
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* not an issue are in {@link Bytes}.
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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 SignedBytes {
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private SignedBytes() {
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}
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/**
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* The largest power of two that can be represented as a signed {@code byte}.
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*
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* @since 10.0
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*/
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public static final byte MAX_POWER_OF_TWO = 1 << 6;
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/**
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* Returns the {@code byte} value that is equal to {@code value}, if possible.
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*
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* @param value any value in the range of the {@code byte} type
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* @return the {@code byte} value that equals {@code value}
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* @throws IllegalArgumentException if {@code value} is greater than
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* {@link Byte#MAX_VALUE} or less than
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* {@link Byte#MIN_VALUE}
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*/
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public static byte checkedCast(long value) {
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byte result = (byte) value;
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if (result != value) {
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// don't use checkArgument here, to avoid boxing
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throw new IllegalArgumentException("Out of range: " + value);
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}
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return result;
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}
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/**
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* Returns the {@code byte} nearest in value to {@code value}.
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*
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* @param value any {@code long} value
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* @return the same value cast to {@code byte} if it is in the range of the
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* {@code byte} type, {@link Byte#MAX_VALUE} if it is too large, or
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* {@link Byte#MIN_VALUE} if it is too small
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*/
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public static byte saturatedCast(long value) {
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if (value > Byte.MAX_VALUE) {
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return Byte.MAX_VALUE;
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}
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if (value < Byte.MIN_VALUE) {
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return Byte.MIN_VALUE;
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}
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return (byte) value;
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}
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/**
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* Compares the two specified {@code byte} values. The sign of the value
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* returned is the same as that of {@code ((Byte) a).compareTo(b)}.
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*
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* <p>
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* <b>Note:</b> this method behaves identically to the JDK 7 method
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* {@link Byte#compare}.
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*
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* @param a the first {@code byte} to compare
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* @param b the second {@code byte} to compare
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* @return a negative value if {@code a} is less than {@code b}; a positive
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* value if {@code a} is greater than {@code b}; or zero if they are
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* equal
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*/
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// TODO(kevinb): if Ints.compare etc. are ever removed, *maybe* remove this
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// one too, which would leave compare methods only on the Unsigned* classes.
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public static int compare(byte a, byte b) {
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return a - b; // safe due to restricted range
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}
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/**
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* Returns the least value present in {@code array}.
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*
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* @param array a <i>nonempty</i> array of {@code byte} values
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* @return the value present in {@code array} that is less than or equal to
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* every other value in the array
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* @throws IllegalArgumentException if {@code array} is empty
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*/
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public static byte min(byte... array) {
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checkArgument(array.length > 0);
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byte min = array[0];
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for (int i = 1; i < array.length; i++) {
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if (array[i] < min) {
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min = array[i];
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}
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}
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return min;
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}
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/**
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* Returns the greatest value present in {@code array}.
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*
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* @param array a <i>nonempty</i> array of {@code byte} values
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* @return the value present in {@code array} that is greater than or equal to
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* every other value in the array
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* @throws IllegalArgumentException if {@code array} is empty
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*/
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public static byte max(byte... array) {
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checkArgument(array.length > 0);
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byte max = array[0];
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for (int i = 1; i < array.length; i++) {
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if (array[i] > max) {
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max = array[i];
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}
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}
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return max;
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}
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/**
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* Returns a string containing the supplied {@code byte} values separated by
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* {@code separator}. For example, {@code join(":", 0x01, 0x02, -0x01)} returns
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* the string {@code "1:2:-1"}.
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*
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* @param separator the text that should appear between consecutive values in
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* the resulting string (but not at the start or end)
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* @param array an array of {@code byte} values, possibly empty
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*/
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public static String join(String separator, byte... array) {
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checkNotNull(separator);
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if (array.length == 0) {
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return "";
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}
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// For pre-sizing a builder, just get the right order of magnitude
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StringBuilder builder = new StringBuilder(array.length * 5);
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builder.append(array[0]);
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for (int i = 1; i < array.length; i++) {
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builder.append(separator).append(array[i]);
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}
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return builder.toString();
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}
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/**
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* Returns a comparator that compares two {@code byte} arrays lexicographically.
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* That is, it compares, using {@link #compare(byte, byte)}), the first pair of
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* values that follow any common prefix, or when one array is a prefix of the
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* other, treats the shorter array as the lesser. For example,
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* {@code [] < [0x01] < [0x01, 0x80] <
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* [0x01, 0x7F] < [0x02]}. Values are treated as signed.
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*
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* <p>
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* The returned comparator is inconsistent with {@link Object#equals(Object)}
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* (since arrays support only identity equality), but it is consistent with
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* {@link java.util.Arrays#equals(byte[], byte[])}.
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*
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* @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order">
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* Lexicographical order article at Wikipedia</a>
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* @since 2.0
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*/
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public static Comparator<byte[]> lexicographicalComparator() {
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return LexicographicalComparator.INSTANCE;
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}
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private enum LexicographicalComparator implements Comparator<byte[]> {
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INSTANCE;
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@Override
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public int compare(byte[] left, byte[] right) {
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int minLength = Math.min(left.length, right.length);
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for (int i = 0; i < minLength; i++) {
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int result = SignedBytes.compare(left[i], right[i]);
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if (result != 0) {
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return result;
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}
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}
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return left.length - right.length;
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}
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}
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}
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