167 lines
5.0 KiB
Java
167 lines
5.0 KiB
Java
/*
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* Copyright 2011 Google Inc.
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* Copyright 2015 Christian Basler
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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 ch.dissem.bitmessage.utils;
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import ch.dissem.bitmessage.exception.AddressFormatException;
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import java.io.UnsupportedEncodingException;
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import static java.util.Arrays.copyOfRange;
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/**
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* Base58 encoder and decoder.
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*
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* @author Christian Basler: I removed some dependencies to the BitcoinJ code so it can be used here more easily.
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*/
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public class Base58 {
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private static final int[] INDEXES = new int[128];
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private static char[] ALPHABET = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz".toCharArray();
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static {
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for (int i = 0; i < INDEXES.length; i++) {
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INDEXES[i] = -1;
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}
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for (int i = 0; i < ALPHABET.length; i++) {
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INDEXES[ALPHABET[i]] = i;
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}
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}
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/**
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* Encodes the given bytes in base58. No checksum is appended.
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*
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* @param input to encode
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* @return base58 encoded input
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*/
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public static String encode(byte[] input) {
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if (input.length == 0) {
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return "";
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}
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input = copyOfRange(input, 0, input.length);
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// Count leading zeroes.
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int zeroCount = 0;
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while (zeroCount < input.length && input[zeroCount] == 0) {
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++zeroCount;
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}
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// The actual encoding.
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byte[] temp = new byte[input.length * 2];
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int j = temp.length;
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int startAt = zeroCount;
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while (startAt < input.length) {
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byte mod = divmod58(input, startAt);
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if (input[startAt] == 0) {
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++startAt;
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}
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temp[--j] = (byte) ALPHABET[mod];
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}
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// Strip extra '1' if there are some after decoding.
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while (j < temp.length && temp[j] == ALPHABET[0]) {
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++j;
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}
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// Add as many leading '1' as there were leading zeros.
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while (--zeroCount >= 0) {
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temp[--j] = (byte) ALPHABET[0];
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}
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byte[] output = copyOfRange(temp, j, temp.length);
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try {
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return new String(output, "US-ASCII");
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} catch (UnsupportedEncodingException e) {
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throw new RuntimeException(e); // Cannot happen.
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}
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}
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public static byte[] decode(String input) throws AddressFormatException {
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if (input.length() == 0) {
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return new byte[0];
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}
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byte[] input58 = new byte[input.length()];
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// Transform the String to a base58 byte sequence
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for (int i = 0; i < input.length(); ++i) {
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char c = input.charAt(i);
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int digit58 = -1;
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if (c >= 0 && c < 128) {
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digit58 = INDEXES[c];
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}
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if (digit58 < 0) {
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throw new AddressFormatException("Illegal character " + c + " at " + i);
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}
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input58[i] = (byte) digit58;
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}
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// Count leading zeroes
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int zeroCount = 0;
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while (zeroCount < input58.length && input58[zeroCount] == 0) {
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++zeroCount;
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}
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// The encoding
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byte[] temp = new byte[input.length()];
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int j = temp.length;
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int startAt = zeroCount;
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while (startAt < input58.length) {
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byte mod = divmod256(input58, startAt);
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if (input58[startAt] == 0) {
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++startAt;
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}
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temp[--j] = mod;
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}
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// Do no add extra leading zeroes, move j to first non null byte.
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while (j < temp.length && temp[j] == 0) {
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++j;
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}
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return copyOfRange(temp, j - zeroCount, temp.length);
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}
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//
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// number -> number / 58, returns number % 58
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//
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private static byte divmod58(byte[] number, int startAt) {
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int remainder = 0;
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for (int i = startAt; i < number.length; i++) {
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int digit256 = (int) number[i] & 0xFF;
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int temp = remainder * 256 + digit256;
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number[i] = (byte) (temp / 58);
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remainder = temp % 58;
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}
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return (byte) remainder;
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}
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//
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// number -> number / 256, returns number % 256
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//
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private static byte divmod256(byte[] number58, int startAt) {
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int remainder = 0;
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for (int i = startAt; i < number58.length; i++) {
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int digit58 = (int) number58[i] & 0xFF;
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int temp = remainder * 58 + digit58;
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number58[i] = (byte) (temp / 256);
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remainder = temp % 256;
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}
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return (byte) remainder;
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}
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} |