use of bitcoinj file

syncany-util/src/main/java/org/syncany/util/Base58.java

@@ -1,117 +1,233 @@
-/*
- * Syncany, www.syncany.org
- * Copyright (C) 2011-2014 Philipp C. Heckel <philipp.heckel@gmail.com> 
+/**
+ * Copyright 2011 Google Inc.
  *
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
+ * Licensed 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
  *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
+ *    http://www.apache.org/licenses/LICENSE-2.0
  *
- * You should have received a copy of the GNU General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ * 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 org.syncany.util;
 
+import java.io.UnsupportedEncodingException;
 import java.math.BigInteger;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.util.Arrays;
 
 /**
- * base58 encoding
- * @author Vincent Wiencek <vwiencek@gmail.com>
+ * <p>Base58 is a way to encode Bitcoin addresses as numbers and letters. Note that this is not the same base58 as used by
+ * Flickr, which you may see reference to around the internet.</p>
+ *
+ * <p>You may instead wish to work with {@link VersionedChecksummedBytes}, which adds support for testing the prefix
+ * and suffix bytes commonly found in addresses.</p>
+ *
+ * <p>Satoshi says: why base-58 instead of standard base-64 encoding?<p>
+ *
+ * <ul>
+ * <li>Don't want 0OIl characters that look the same in some fonts and
+ *     could be used to create visually identical looking account numbers.</li>
+ * <li>A string with non-alphanumeric characters is not as easily accepted as an account number.</li>
+ * <li>E-mail usually won't line-break if there's no punctuation to break at.</li>
+ * <li>Doubleclicking selects the whole number as one word if it's all alphanumeric.</li>
+ * </ul>
  */
 public class Base58 {
+    public static final char[] ALPHABET = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz".toCharArray();
+    private static final int[] INDEXES = new int[128];
+    private static final MessageDigest digest;
+    static {
+        try {
+            digest = MessageDigest.getInstance("SHA-256");
+        } catch (NoSuchAlgorithmException e) {
+            throw new RuntimeException(e);  // Can't happen.
+        }
+    }
+
+    static {
+        for (int i = 0; i < INDEXES.length; i++) {
+            INDEXES[i] = -1;
+        }
+        for (int i = 0; i < ALPHABET.length; i++) {
+            INDEXES[ALPHABET[i]] = i;
+        }
+    }
+
+    /** Encodes the given bytes in base58. No checksum is appended. */
+    public static String encode(byte[] input) {
+        if (input.length == 0) {
+            return "";
+        }       
+        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) ALPHABET[mod];
+        }
+
+        // Strip extra '1' if there are some after decoding.
+        while (j < temp.length && temp[j] == ALPHABET[0]) {
+            ++j;
+        }
+        // Add as many leading '1' as there were leading zeros.
+        while (--zeroCount >= 0) {
+            temp[--j] = (byte) ALPHABET[0];
+        }
+
+        byte[] output = copyOfRange(temp, j, temp.length);
+        try {
+            return new String(output, "US-ASCII");
+        } catch (UnsupportedEncodingException e) {
+            throw new RuntimeException(e);  // Cannot happen.
+        }
+    }
+
+    public static byte[] decode(String input) {
+        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 = INDEXES[c];
+            }
+            if (digit58 < 0) {
+                throw new RuntimeException("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);
+    }
+
+    public static BigInteger decodeToBigInteger(String input) {
+        return new BigInteger(1, decode(input));
+    }
+
+    /**
+     * 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.
+     *
+     */
+    public static byte[] decodeChecked(String input) {
+        byte tmp [] = decode(input);
+        if (tmp.length < 4)
+            throw new RuntimeException("Input too short");
+        byte[] bytes = copyOfRange(tmp, 0, tmp.length - 4);
+        byte[] checksum = copyOfRange(tmp, tmp.length - 4, tmp.length);
+
+        tmp = doubleDigest(bytes);
+        byte[] hash = copyOfRange(tmp, 0, 4);
+        if (!Arrays.equals(checksum, hash)) 
+            throw new RuntimeException("Checksum does not validate");
+
+        return bytes;
+    }
+
+    /**
+     * See {@link Utils#doubleDigest(byte[], int, int)}.
+     */
+    public static byte[] doubleDigest(byte[] input) {
+        return doubleDigest(input, 0, input.length);
+    }
+
+    /**
+     * Calculates the SHA-256 hash of the given byte range, and then hashes the resulting hash again. This is
+     * standard procedure in Bitcoin. The resulting hash is in big endian form.
+     */
+    public static byte[] doubleDigest(byte[] input, int offset, int length) {
+        synchronized (digest) {
+            digest.reset();
+            digest.update(input, offset, length);
+            byte[] first = digest.digest();
+            return digest.digest(first);
+        }
+    }
+
+    //
+    // number -> number / 58, returns number % 58
+    //
+    private static 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 static 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 static byte[] copyOfRange(byte[] source, int from, int to) {
+        byte[] range = new byte[to - from];
+        System.arraycopy(source, from, range, 0, range.length);
 
-	private static final String Alphabet = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";
-	private static final BigInteger Base58 = new BigInteger("58", 10);
-
-	public static String encode(byte[] indata) {
-		byte[] data = new byte[indata.length];
-		System.arraycopy(indata, 0, data, 0, data.length);
-		// convert big endian data to little endian
-		int len = data.length;
-		int mid = len / 2;
-		int i;
-		for (i = 0; i < mid; i++) {
-			byte tmp = data[i];
-			data[i] = data[len - 1 - i];
-			data[len - 1 - i] = tmp;
-		}
-		BigInteger value = new BigInteger(1, data);
-		StringBuilder result = new StringBuilder();
-
-		// divide until zero
-		while (value.compareTo(BigInteger.ZERO) > 0) {
-			BigInteger[] qr = value.divideAndRemainder(Base58);
-			value = qr[0];
-			BigInteger rem = qr[1];
-			result.append(Alphabet.charAt(rem.intValue()));
-		}
-		// append leading zeros
-		for (i = 0; i < len; i++) {
-			if (data[i] == 0) {
-				result.append(Alphabet.charAt(0));
-			}
-			else {
-				break;
-			}
-		}
-		// reverse to big endian
-		len = result.length();
-		mid = len / 2;
-		for (i = 0; i < mid; i++) {
-			char ch1 = result.charAt(i);
-			char ch2 = result.charAt(len - 1 - i);
-			result.setCharAt(len - 1 - i, ch1);
-			result.setCharAt(i, ch2);
-		}
-		return result.toString();
-	}
-
-	public static byte[] decode(String data) {
-		BigInteger value = BigInteger.ZERO;
-		BigInteger character;
-		// eat spaces
-		data = data.trim();
-		// encode to big number
-		int i;
-		int len = data.length();
-		for (i = 0; i < len; i++) {
-			int pos = Alphabet.indexOf(data.charAt(i));
-			if (pos < 0) { // not a valid char
-				return null;
-			}
-			character = new BigInteger(String.valueOf(pos), 10);
-			value = value.multiply(Base58);
-			value = value.add(character);
-		}
-
-		byte[] dec = value.toByteArray();
-		int declen = dec.length;
-		int decoff = 0;
-		// strip sign byte
-		if (dec.length > 2 && dec[0] == 0 && (dec[1] & 0x80) == 0x80) {
-			declen--;
-			decoff++;
-		}
-		// count leading zeros
-		int n = 0;
-		for (i = 0; i < len; i++) {
-			if (data.charAt(i) == Alphabet.charAt(0)) {
-				n++;
-			}
-			else {
-				break;
-			}
-		}
-		// reverse result at the right place
-		byte[] result = new byte[declen + n];
-		for (i = 0; i < declen; i++) {
-			result[i] = dec[(declen - 1 - i) + decoff];
-		}
-		return result;
-	}
+        return range;
+    }
 }