117 lines
4.0 KiB
Java
117 lines
4.0 KiB
Java
/*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The ASF licenses this file to You under the Apache License, Version 2.0
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* (the "License"); you may not use this file except in compliance with
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* the License. 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.frostwire.jlibtorrent;
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/**
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* Converts hexadecimal Strings.
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*/
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final class Hex {
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private Hex() {
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}
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/**
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* Used to build output as Hex
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*/
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private static final char[] DIGITS_LOWER =
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{'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
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/**
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* Converts an array of characters representing hexadecimal values into an array of bytes of those same values. The
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* returned array will be half the length of the passed array, as it takes two characters to represent any given
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* byte. An exception is thrown if the passed char array has an odd number of elements.
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*
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* @param data An array of characters containing hexadecimal digits
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* @return A byte array containing binary data decoded from the supplied char array.
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*/
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public static byte[] decode(final char[] data) {
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final int len = data.length;
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final byte[] out = new byte[len >> 1];
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// two characters form the hex value.
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for (int i = 0, j = 0; j < len; i++) {
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int f = toDigit(data[j], j) << 4;
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j++;
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f = f | toDigit(data[j], j);
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j++;
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out[i] = (byte) (f & 0xFF);
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}
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return out;
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}
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public static byte[] decode(String data) {
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return decode(data.toCharArray());
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}
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/**
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* Converts an array of bytes into an array of characters representing the hexadecimal values of each byte in order.
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* The returned array will be double the length of the passed array, as it takes two characters to represent any
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* given byte.
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*
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* @param data
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* a byte[] to convert to Hex characters
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* @return A char[] containing hexadecimal characters
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*/
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public static String encode(final byte[] data) {
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return new String(encode(data, DIGITS_LOWER));
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}
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/**
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* Converts an array of bytes into an array of characters representing the hexadecimal values of each byte in order.
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* The returned array will be double the length of the passed array, as it takes two characters to represent any
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* given byte.
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*
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* @param data
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* a byte[] to convert to Hex characters
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* @param toDigits
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* the output alphabet
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* @return A char[] containing hexadecimal characters
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* @since 1.4
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*/
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private static char[] encode(final byte[] data, final char[] toDigits) {
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final int l = data.length;
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final char[] out = new char[l << 1];
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// two characters form the hex value.
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for (int i = 0, j = 0; i < l; i++) {
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out[j++] = toDigits[(0xF0 & data[i]) >>> 4];
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out[j++] = toDigits[0x0F & data[i]];
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}
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return out;
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}
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/**
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* Converts a hexadecimal character to an integer.
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*
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* @param ch
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* A character to convert to an integer digit
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* @param index
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* The index of the character in the source
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* @return An integer
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*/
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private static int toDigit(final char ch, final int index) {
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final int digit = Character.digit(ch, 16);
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if (digit == -1) {
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throw new IllegalArgumentException("Illegal hexadecimal character " + ch + " at index " + index);
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}
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return digit;
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}
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}
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