偶看新闻青藏引水到沙漠:Base32.java
来源：百度文库 编辑：偶看新闻 时间：2024/04/30 06:30:37
package com.raymon.bizos.pjt.util;
public class Base32 {
private static final char[] ALPHABET = {
‘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‘
};
private static final byte[] DECODE_TABLE;
static {
DECODE_TABLE = new byte[128];
for (int i = 0; i < DECODE_TABLE.length; i++) {
DECODE_TABLE[i] = (byte) 0xFF;
}
for (int i = 0; i < ALPHABET.length; i++) {
DECODE_TABLE[(int) ALPHABET[i]] = (byte) i;
if (i < 24) {
DECODE_TABLE[(int) Character.toLowerCase(ALPHABET[i])] = (byte) i;
}
}
}
public static String encode(byte[] data) {
char[] chars = new char[((data.length * 8) / 5)
+ ((data.length % 5) != 0 ? 1 : 0)];
for (int i = 0, j = 0, index = 0; i < chars.length; i++) {
if (index > 3) {
int b = data[j] & (0xFF >> index);
index = (index + 5) % 8;
b <<= index;
if (j < data.length - 1) {
b |= (data[j + 1] & 0xFF) >> (8 - index);
}
chars[i] = ALPHABET[b];
j++;
}
else {
chars[i] = ALPHABET[((data[j] >> (8 - (index + 5))) & 0x1F)];
index = (index + 5) % 8;
if (index == 0) {
j++;
}
}
}
return new String(chars);
}
public static byte[] decode(String s) throws Exception
{
char[] stringData = s.toCharArray();
byte[] data = new byte[(stringData.length * 5) / 8];
for (int i = 0, j = 0, index = 0; i < stringData.length; i++) {
int val;
try {
val = DECODE_TABLE[stringData[i]];
} catch(ArrayIndexOutOfBoundsException e) {
throw new Exception("Illegal character");
}
if (val == 0xFF) {
throw new Exception("Illegal character");
}
if (index <= 3) {
index = (index + 5) % 8;
if (index == 0) {
data[j++] |= val;
}
else {
data[j] |= val << (8 - index);
}
}
else {
index = (index + 5) % 8;
data[j++] |= (val >> index);
if (j < data.length) {
data[j] |= val << (8 - index);
}
}
}
return data;
}
}