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‎.gitignore‎

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*.class
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# Mobile Tools for Java (J2ME)
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.mtj.tmp/
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# Package Files #
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*.jar
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*.war
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*.ear
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build/**
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dist/**
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.idea/**
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# virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
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hs_err_pid*

‎LICENSE‎

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MIT License
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Copyright (c) 2016 Multiformats
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Copyright (c) 2015 Ian Preston
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to deal

‎README.md‎

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# java-multihash
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A Java implementation of Multihash
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## Usage
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Multihash m = Multihash.fromBase58("QmatmE9msSfkKxoffpHwNLNKgwZG8eT9Bud6YoPab52vpy");
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## Compilation
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To compile just run ant.

‎build.xml‎

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<project name="java-multihash" default="dist" basedir=".">
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<description>
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Java Multihash
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</description>
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<property name="src" location="src"/>
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<property name="build" location="build"/>
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<property name="dist" location="dist"/>
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<path id="dep.runtime">
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<fileset dir="./lib">
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<include name="**/*.jar" />
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</fileset>
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</path>
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<target name="init">
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<mkdir dir="${build}"/>
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</target>
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<target name="compile" depends="init" description="compile the source">
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<javac includeantruntime="false" srcdir="${src}" destdir="${build}" debug="true" debuglevel="lines,vars,source">
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<classpath>
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<fileset dir="lib">
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<include name="**/*.jar" />
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</fileset>
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</classpath>
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</javac>
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</target>
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<target name="dist" depends="compile" description="generate the distribution">
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<mkdir dir="${dist}/lib"/>
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<copy todir="${dist}/lib">
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<fileset dir="lib"/>
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</copy>
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<manifestclasspath property="manifest_cp" jarfile="myjar.jar">
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<classpath refid="dep.runtime" />
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</manifestclasspath>
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<jar jarfile="${dist}/Multihash.jar" basedir="${build}">
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<manifest>
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<attribute name="Class-Path" value="${manifest_cp}"/>
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</manifest>
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<fileset dir=".">
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<include name="**/ui/**"/>
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<exclude name="out/**"/>
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<exclude name="ui/doppio/**"/>
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<exclude name="ui/PeergosServer.jar"/>
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</fileset>
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</jar>
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<copy todir=".">
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<fileset file="${dist}/Multihash.jar"/>
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</copy>
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</target>
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<target name="test" depends="compile,dist">
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<junit printsummary="yes" fork="true" haltonfailure="yes">
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<jvmarg value="-Xmx1g"/>
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<classpath>
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<pathelement location="lib/junit-4.11.jar" />
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<pathelement location="lib/hamcrest-core-1.3.jar" />
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<pathelement location="Multihash.jar" />
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</classpath>
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<test name="org.ipfs.api.MultihashTests" haltonfailure="yes">
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<formatter type="plain"/>
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<formatter type="xml"/>
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</test>
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</junit>
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</target>
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<target name="clean" description="clean up">
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<delete dir="${build}"/>
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<delete dir="${dist}"/>
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</target>
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</project>

‎lib/hamcrest-core-1.3.jar‎

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‎lib/junit-4.12.jar‎

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‎src/main/java/org/ipfs/api/Base58.java‎

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package org.ipfs.api;
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/**
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* Copyright 2011 Google Inc.
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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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import java.math.BigInteger;
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/**
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* A custom form of base58 is used to encode BitCoin addresses. Note that this is not the same base58 as used by
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* Flickr, which you may see reference to around the internet.<p>
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*
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* Satoshi says: why base-58 instead of standard base-64 encoding?<p>
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*
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* <ul>
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* <li>Don't want 0OIl characters that look the same in some fonts and
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* could be used to create visually identical looking account numbers.</li>
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* <li>A string with non-alphanumeric characters is not as easily accepted as an account number.</li>
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* <li>E-mail usually won't line-break if there's no punctuation to break at.</li>
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* <li>Doubleclicking selects the whole number as one word if it's all alphanumeric.</li>
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* </ul>
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*/
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public class Base58 {
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private static final String ALPHABET = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";
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private static final BigInteger BASE = BigInteger.valueOf(58);
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public static String encode(byte[] input) {
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// TODO: This could be a lot more efficient.
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BigInteger bi = new BigInteger(1, input);
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StringBuffer s = new StringBuffer();
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while (bi.compareTo(BASE) >= 0) {
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BigInteger mod = bi.mod(BASE);
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s.insert(0, ALPHABET.charAt(mod.intValue()));
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bi = bi.subtract(mod).divide(BASE);
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}
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s.insert(0, ALPHABET.charAt(bi.intValue()));
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// Convert leading zeros too.
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for (byte anInput : input) {
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if (anInput == 0)
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s.insert(0, ALPHABET.charAt(0));
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else
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break;
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}
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return s.toString();
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}
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public static byte[] decode(String input) {
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byte[] bytes = decodeToBigInteger(input).toByteArray();
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// We may have got one more byte than we wanted, if the high bit of the next-to-last byte was not zero. This
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// is because BigIntegers are represented with twos-compliment notation, thus if the high bit of the last
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// byte happens to be 1 another 8 zero bits will be added to ensure the number parses as positive. Detect
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// that case here and chop it off.
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boolean stripSignByte = bytes.length > 1 && bytes[0] == 0 && bytes[1] < 0;
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// Count the leading zeros, if any.
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int leadingZeros = 0;
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for (int i = 0; input.charAt(i) == ALPHABET.charAt(0); i++) {
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leadingZeros++;
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}
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// Now cut/pad correctly. Java 6 has a convenience for this, but Android can't use it.
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byte[] tmp = new byte[bytes.length - (stripSignByte ? 1 : 0) + leadingZeros];
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System.arraycopy(bytes, stripSignByte ? 1 : 0, tmp, leadingZeros, tmp.length - leadingZeros);
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return tmp;
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}
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public static BigInteger decodeToBigInteger(String input) {
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BigInteger bi = BigInteger.valueOf(0);
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// Work backwards through the string.
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for (int i = input.length() - 1; i >= 0; i--) {
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int alphaIndex = ALPHABET.indexOf(input.charAt(i));
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if (alphaIndex == -1) {
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throw new IllegalStateException("Illegal character " + input.charAt(i) + " at " + i);
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}
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bi = bi.add(BigInteger.valueOf(alphaIndex).multiply(BASE.pow(input.length() - 1 - i)));
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}
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return bi;
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}
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}

‎src/main/java/org/ipfs/api/Multihash.java‎

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package org.ipfs.api;
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import java.io.*;
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import java.util.*;
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public class Multihash {
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public enum Type {
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sha1(0x11, 20),
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sha2_256(0x12, 32),
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sha2_512(0x13, 64),
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sha3(0x14, 64),
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blake2b(0x40, 64),
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blake2s(0x41, 32);
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public int index, length;
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Type(int index, int length) {
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this.index = index;
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this.length = length;
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}
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private static Map<Integer, Type> lookup = new TreeMap<>();
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static {
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for (Type t: Type.values())
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lookup.put(t.index, t);
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}
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public static Type lookup(int t) {
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if (!lookup.containsKey(t))
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throw new IllegalStateException("Unknown Multihash type: "+t);
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return lookup.get(t);
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}
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}
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public final Type type;
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private final byte[] hash;
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public Multihash(Type type, byte[] hash) {
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if (hash.length > 127)
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throw new IllegalStateException("Unsupported hash size: "+hash.length);
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if (hash.length != type.length)
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throw new IllegalStateException("Incorrect hash length: " + hash.length + " != "+type.length);
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this.type = type;
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this.hash = hash;
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}
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public Multihash(byte[] multihash) {
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this(Type.lookup(multihash[0] & 0xff), Arrays.copyOfRange(multihash, 2, multihash.length));
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}
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public byte[] toBytes() {
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byte[] res = new byte[hash.length+2];
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res[0] = (byte)type.index;
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res[1] = (byte)hash.length;
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System.arraycopy(hash, 0, res, 2, hash.length);
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return res;
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}
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public void serialize(DataOutput dout) throws IOException {
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dout.write(toBytes());
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}
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public static Multihash deserialize(DataInput din) throws IOException {
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int type = din.readUnsignedByte();
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int len = din.readUnsignedByte();
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Type t = Type.lookup(type);
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byte[] hash = new byte[len];
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din.readFully(hash);
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return new Multihash(t, hash);
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}
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@Override
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public String toString() {
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return toBase58();
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}
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@Override
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public boolean equals(Object o) {
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if (!(o instanceof Multihash))
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return false;
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return type == ((Multihash) o).type && Arrays.equals(hash, ((Multihash) o).hash);
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}
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@Override
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public int hashCode() {
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return Arrays.hashCode(hash) ^ type.hashCode();
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}
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public String toHex() {
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StringBuilder res = new StringBuilder();
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for (byte b: toBytes())
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res.append(String.format("%x", b&0xff));
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return res.toString();
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}
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public String toBase58() {
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return Base58.encode(toBytes());
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}
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public static Multihash fromHex(String hex) {
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if (hex.length() % 2 != 0)
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throw new IllegalStateException("Uneven number of hex digits!");
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ByteArrayOutputStream bout = new ByteArrayOutputStream();
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for (int i=0; i < hex.length()-1; i+= 2)
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bout.write(Integer.valueOf(hex.substring(i, i+2), 16));
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return new Multihash(bout.toByteArray());
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}
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public static Multihash fromBase58(String base58) {
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return new Multihash(Base58.decode(base58));
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}
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}

‎src/test/java/org/ipfs/api/MultihashTests.java‎

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package org.ipfs.api;
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import org.junit.*;
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import java.util.*;
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public class MultihashTests {
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@Test
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public void base58Test() {
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List<String> examples = Arrays.asList("QmPZ9gcCEpqKTo6aq61g2nXGUhM4iCL3ewB6LDXZCtioEB",
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"QmatmE9msSfkKxoffpHwNLNKgwZG8eT9Bud6YoPab52vpy");
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for (String example: examples) {
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byte[] output = Base58.decode(example);
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String encoded = Base58.encode(output);
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if (!encoded.equals(encoded))
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throw new IllegalStateException("Incorrect base58! " + example + " => " + encoded);
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}
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}
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}

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