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/*
* Copyright www.jingtum.com Inc.
*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.jingtum.core.encodings.base58;
import com.jingtum.core.utils.HashUtils;
import java.io.UnsupportedEncodingException;
import java.util.Arrays;
public class B58 {
private int[] mIndexes;
private char[] mAlphabet;
public B58(String alphabet) {
setAlphabet(alphabet);
buildIndexes();
}
private void setAlphabet(String alphabet) {
mAlphabet = alphabet.toCharArray();
}
private void buildIndexes() {
mIndexes = new int[128];
for (int i = 0; i < mIndexes.length; i++) {
mIndexes[i] = -1;
}
for (int i = 0; i < mAlphabet.length; i++) {
mIndexes[mAlphabet[i]] = i;
}
}
public String encodeToStringChecked(byte[] input, int version) {
try {
return new String(encodeToBytesChecked(input, version), "US-ASCII");
} catch (UnsupportedEncodingException e) {
throw new RuntimeException(e); // Cannot happen.
}
}
public byte[] encodeToBytesChecked(byte[] input, int version) {
byte[] buffer = new byte[input.length + 1];
buffer[0] = (byte) version;
System.arraycopy(input, 0, buffer, 1, input.length);
byte[] checkSum = copyOfRange(HashUtils.doubleDigest(buffer), 0, 4);
byte[] output = new byte[buffer.length + checkSum.length];
System.arraycopy(buffer, 0, output, 0, buffer.length);
System.arraycopy(checkSum, 0, output, buffer.length, checkSum.length);
return encodeToBytes(output);
}
/**
* Encodes the given bytes in base58. No checksum is appended.
*/
public byte[] encodeToBytes(byte[] input) {
if (input.length == 0) {
return new byte[0];
}
input = copyOfRange(input, 0, input.length);
// Count leading zeroes.
int zeroCount = 0;
while (zeroCount < input.length && input[zeroCount] == 0) {
++zeroCount;
}
// The actual encoding.
byte[] temp = new byte[input.length * 2];
int j = temp.length;
int startAt = zeroCount;
while (startAt < input.length) {
byte mod = divmod58(input, startAt);
if (input[startAt] == 0) {
++startAt;
}
temp[--j] = (byte) mAlphabet[mod];
}
// Strip extra '1' if there are some after decoding.
while (j < temp.length && temp[j] == mAlphabet[0]) {
++j;
}
// Add as many leading '1' as there were leading zeros.
while (--zeroCount >= 0) {
temp[--j] = (byte) mAlphabet[0];
}
byte[] output;
output = copyOfRange(temp, j, temp.length);
return output;
}
public byte[] decode(String input) throws EncodingFormatException {
if (input.length() == 0) {
return new byte[0];
}
byte[] input58 = new byte[input.length()];
// Transform the String to a base58 byte sequence
for (int i = 0; i < input.length(); ++i) {
char c = input.charAt(i);
int digit58 = -1;
if (c >= 0 && c < 128) {
digit58 = mIndexes[c];
}
if (digit58 < 0) {
throw new EncodingFormatException("Illegal character " + c + " at " + i);
}
input58[i] = (byte) digit58;
}
// Count leading zeroes
int zeroCount = 0;
while (zeroCount < input58.length && input58[zeroCount] == 0) {
++zeroCount;
}
// The encoding
byte[] temp = new byte[input.length()];
int j = temp.length;
int startAt = zeroCount;
while (startAt < input58.length) {
byte mod = divmod256(input58, startAt);
if (input58[startAt] == 0) {
++startAt;
}
temp[--j] = mod;
}
// Do no add extra leading zeroes, move j to first non null byte.
while (j < temp.length && temp[j] == 0) {
++j;
}
return copyOfRange(temp, j - zeroCount, temp.length);
}
/**
* Uses the checksum in the last 4 bytes of the decoded data to verify the rest are correct. The checksum is
* removed from the returned data.
*
* @throws EncodingFormatException if the input is not baseFields 58 or the checksum does not validate.
*/
public byte[] decodeChecked(String input, int version) throws EncodingFormatException {
byte buffer[] = decode(input);
if (buffer.length < 4)
throw new EncodingFormatException("Input too short");
byte actualVersion = buffer[0];
if (actualVersion != version) {
throw new EncodingFormatException("Bro, version is wrong yo");
}
byte[] toHash = copyOfRange(buffer, 0, buffer.length - 4);
byte[] hashed = copyOfRange(HashUtils.doubleDigest(toHash), 0, 4);
byte[] checksum = copyOfRange(buffer, buffer.length - 4, buffer.length);
if (!Arrays.equals(checksum, hashed))
throw new EncodingFormatException("Checksum does not validate");
return copyOfRange(buffer, 1, buffer.length - 4);
}
//
// number -> number / 58, returns number % 58
//
private byte divmod58(byte[] number, int startAt) {
int remainder = 0;
for (int i = startAt; i < number.length; i++) {
int digit256 = (int) number[i] & 0xFF;
int temp = remainder * 256 + digit256;
number[i] = (byte) (temp / 58);
remainder = temp % 58;
}
return (byte) remainder;
}
//
// number -> number / 256, returns number % 256
//
private byte divmod256(byte[] number58, int startAt) {
int remainder = 0;
for (int i = startAt; i < number58.length; i++) {
int digit58 = (int) number58[i] & 0xFF;
int temp = remainder * 58 + digit58;
number58[i] = (byte) (temp / 256);
remainder = temp % 256;
}
return (byte) remainder;
}
private byte[] copyOfRange(byte[] source, int from, int to) {
byte[] range = new byte[to - from];
System.arraycopy(source, from, range, 0, range.length);
return range;
}
}
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