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// Copyright (c) 1999-2004 Brian Wellington (bwelling@xbill.org)
package org.xbill.DNS.utils;
import java.io.*;
/**
* Routines for converting between Strings of base32-encoded data and arrays
* of binary data. This currently supports the base32 and base32hex alphabets
* specified in RFC 4648, sections 6 and 7.
*
* @author Brian Wellington
*/
public class base32 {
public static class Alphabet {
private Alphabet() {}
public static final String BASE32 =
"ABCDEFGHIJKLMNOPQRSTUVWXYZ234567=";
public static final String BASE32HEX =
"0123456789ABCDEFGHIJKLMNOPQRSTUV=";
};
private String alphabet;
private boolean padding, lowercase;
/**
* Creates an object that can be used to do base32 conversions.
* @param alphabet Which alphabet should be used
* @param padding Whether padding should be used
* @param lowercase Whether lowercase characters should be used.
* default parameters (The standard base32 alphabet, no padding, uppercase)
*/
public
base32(String alphabet, boolean padding, boolean lowercase) {
this.alphabet = alphabet;
this.padding = padding;
this.lowercase = lowercase;
}
static private int
blockLenToPadding(int blocklen) {
switch (blocklen) {
case 1:
return 6;
case 2:
return 4;
case 3:
return 3;
case 4:
return 1;
case 5:
return 0;
default:
return -1;
}
}
static private int
paddingToBlockLen(int padlen) {
switch (padlen) {
case 6:
return 1;
case 4:
return 2;
case 3:
return 3;
case 1:
return 4;
case 0:
return 5;
default :
return -1;
}
}
/**
* Convert binary data to a base32-encoded String
*
* @param b An array containing binary data
* @return A String containing the encoded data
*/
public String
toString(byte [] b) {
ByteArrayOutputStream os = new ByteArrayOutputStream();
for (int i = 0; i < (b.length + 4) / 5; i++) {
short s[] = new short[5];
int t[] = new int[8];
int blocklen = 5;
for (int j = 0; j < 5; j++) {
if ((i * 5 + j) < b.length)
s[j] = (short) (b[i * 5 + j] & 0xFF);
else {
s[j] = 0;
blocklen--;
}
}
int padlen = blockLenToPadding(blocklen);
// convert the 5 byte block into 8 characters (values 0-31).
// upper 5 bits from first byte
t[0] = (byte) ((s[0] >> 3) & 0x1F);
// lower 3 bits from 1st byte, upper 2 bits from 2nd.
t[1] = (byte) (((s[0] & 0x07) << 2) | ((s[1] >> 6) & 0x03));
// bits 5-1 from 2nd.
t[2] = (byte) ((s[1] >> 1) & 0x1F);
// lower 1 bit from 2nd, upper 4 from 3rd
t[3] = (byte) (((s[1] & 0x01) << 4) | ((s[2] >> 4) & 0x0F));
// lower 4 from 3rd, upper 1 from 4th.
t[4] = (byte) (((s[2] & 0x0F) << 1) | ((s[3] >> 7) & 0x01));
// bits 6-2 from 4th
t[5] = (byte) ((s[3] >> 2) & 0x1F);
// lower 2 from 4th, upper 3 from 5th;
t[6] = (byte) (((s[3] & 0x03) << 3) | ((s[4] >> 5) & 0x07));
// lower 5 from 5th;
t[7] = (byte) (s[4] & 0x1F);
// write out the actual characters.
for (int j = 0; j < t.length - padlen; j++) {
char c = alphabet.charAt(t[j]);
if (lowercase)
c = Character.toLowerCase(c);
os.write(c);
}
// write out the padding (if any)
if (padding) {
for (int j = t.length - padlen; j < t.length; j++)
os.write('=');
}
}
return new String(os.toByteArray());
}
/**
* Convert a base32-encoded String to binary data
*
* @param str A String containing the encoded data
* @return An array containing the binary data, or null if the string is invalid
*/
public byte[]
fromString(String str) {
ByteArrayOutputStream bs = new ByteArrayOutputStream();
byte [] raw = str.getBytes();
for (int i = 0; i < raw.length; i++)
{
char c = (char) raw[i];
if (!Character.isWhitespace(c)) {
c = Character.toUpperCase(c);
bs.write((byte) c);
}
}
if (padding) {
if (bs.size() % 8 != 0)
return null;
} else {
while (bs.size() % 8 != 0)
bs.write('=');
}
byte [] in = bs.toByteArray();
bs.reset();
DataOutputStream ds = new DataOutputStream(bs);
for (int i = 0; i < in.length / 8; i++) {
short[] s = new short[8];
int[] t = new int[5];
int padlen = 8;
for (int j = 0; j < 8; j++) {
char c = (char) in[i * 8 + j];
if (c == '=')
break;
s[j] = (short) alphabet.indexOf(in[i * 8 + j]);
if (s[j] < 0)
return null;
padlen--;
}
int blocklen = paddingToBlockLen(padlen);
if (blocklen < 0)
return null;
// all 5 bits of 1st, high 3 (of 5) of 2nd
t[0] = (s[0] << 3) | s[1] >> 2;
// lower 2 of 2nd, all 5 of 3rd, high 1 of 4th
t[1] = ((s[1] & 0x03) << 6) | (s[2] << 1) | (s[3] >> 4);
// lower 4 of 4th, high 4 of 5th
t[2] = ((s[3] & 0x0F) << 4) | ((s[4] >> 1) & 0x0F);
// lower 1 of 5th, all 5 of 6th, high 2 of 7th
t[3] = (s[4] << 7) | (s[5] << 2) | (s[6] >> 3);
// lower 3 of 7th, all of 8th
t[4] = ((s[6] & 0x07) << 5) | s[7];
try {
for (int j = 0; j < blocklen; j++)
ds.writeByte((byte) (t[j] & 0xFF));
}
catch (IOException e) {
}
}
return bs.toByteArray();
}
}
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