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Add base32 encoder/decoder.

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akwizgran
2019-04-17 16:23:01 +01:00
parent 6f0ab8b688
commit fc8ca872a8
1 changed files with 75 additions and 0 deletions
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75
bramble-api/src/main/java/org/briarproject/bramble/util/Base32.java Normal file
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package org.briarproject.bramble.util;
import java.io.ByteArrayOutputStream;
public class Base32 {
private static final char[] DIGITS = {
'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L',
'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
'Y', 'Z', '2', '3', '4', '5', '6', '7'
};
public static String encode(byte[] b) {
StringBuilder s = new StringBuilder();
int byteIndex = 0, currentCode = 0x00;
int byteMask = 0x80, codeMask = 0x10;
while (byteIndex < b.length) {
if ((b[byteIndex] & byteMask) != 0) currentCode |= codeMask;
// After every 8 bits, move on to the next byte
if (byteMask == 0x01) {
byteMask = 0x80;
byteIndex++;
} else {
byteMask >>>= 1;
}
// After every 5 bits, move on to the next digit
if (codeMask == 0x01) {
s.append(DIGITS[currentCode]);
codeMask = 0x10;
currentCode = 0x00;
} else {
codeMask >>>= 1;
}
}
// If we're part-way through a digit, output it
if (codeMask != 0x10) s.append(DIGITS[currentCode]);
return s.toString();
}
public static byte[] decode(String s) {
ByteArrayOutputStream b = new ByteArrayOutputStream();
int digitIndex = 0, digitCount = s.length(), currentByte = 0x00;
int byteMask = 0x80, codeMask = 0x10;
while (digitIndex < digitCount) {
int code = decodeDigit(s.charAt(digitIndex));
if ((code & codeMask) != 0) currentByte |= byteMask;
// After every 8 bits, move on to the next byte
if (byteMask == 0x01) {
b.write(currentByte);
byteMask = 0x80;
currentByte = 0x00;
} else {
byteMask >>>= 1;
}
// After every 5 bits, move on to the next digit
if (codeMask == 0x01) {
codeMask = 0x10;
digitIndex++;
} else {
codeMask >>>= 1;
}
}
// If any extra bits were used for encoding, they should all be zero
if (byteMask != 0x80 && currentByte != 0x00)
throw new IllegalArgumentException();
return b.toByteArray();
}
private static int decodeDigit(char c) {
if (c >= 'A' && c <= 'Z') return c - 'A';
if (c >= 'a' && c <= 'z') return c - 'a';
if (c >= '2' && c <= '7') return c - '2' + 26;
throw new IllegalArgumentException("Not a base32 digit: " + c);
}
}