cn.hutool.core.codec.Base32Codec Maven / Gradle / Ivy
package cn.hutool.core.codec;
import java.util.Arrays;
/**
* Base32 - encodes and decodes RFC4648 Base32 (see https://datatracker.ietf.org/doc/html/rfc4648#section-6 )
* base32就是用32（2的5次方）个特定ASCII码来表示256个ASCII码。
* 所以，5个ASCII字符经过base32编码后会变为8个字符（公约数为40），长度增加3/5.不足8n用“=”补足。
* 根据RFC4648 Base32规范，支持两种模式：
*
* - Base 32 Alphabet (ABCDEFGHIJKLMNOPQRSTUVWXYZ234567)
* - "Extended Hex" Base 32 Alphabet (0123456789ABCDEFGHIJKLMNOPQRSTUV)
*
*
* @author Looly
* @since 5.8.0
*/
public class Base32Codec implements Encoder, Decoder {
public static Base32Codec INSTANCE = new Base32Codec();
@Override
public String encode(byte[] data) {
return encode(data, false);
}
/**
* 编码数据
*
* @param data 数据
* @param useHex 是否使用Hex Alphabet
* @return 编码后的Base32字符串
*/
public String encode(byte[] data, boolean useHex) {
final Base32Encoder encoder = useHex ? Base32Encoder.HEX_ENCODER : Base32Encoder.ENCODER;
return encoder.encode(data);
}
@Override
public byte[] decode(CharSequence encoded) {
return decode(encoded, false);
}
/**
* 解码数据
*
* @param encoded base32字符串
* @param useHex 是否使用Hex Alphabet
* @return 解码后的内容
*/
public byte[] decode(CharSequence encoded, boolean useHex) {
final Base32Decoder decoder = useHex ? Base32Decoder.HEX_DECODER : Base32Decoder.DECODER;
return decoder.decode(encoded);
}
/**
* Bas32编码器
*/
public static class Base32Encoder implements Encoder {
private static final String DEFAULT_ALPHABET = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
private static final String HEX_ALPHABET = "0123456789ABCDEFGHIJKLMNOPQRSTUV";
private static final Character DEFAULT_PAD = '=';
private static final int[] BASE32_FILL = {-1, 4, 1, 6, 3};
public static final Base32Encoder ENCODER = new Base32Encoder(DEFAULT_ALPHABET, DEFAULT_PAD);
public static final Base32Encoder HEX_ENCODER = new Base32Encoder(HEX_ALPHABET, DEFAULT_PAD);
private final char[] alphabet;
private final Character pad;
/**
* 构造
*
* @param alphabet 自定义编码字母表，见 {@link #DEFAULT_ALPHABET}和 {@link #HEX_ALPHABET}
* @param pad 补位字符
*/
public Base32Encoder(String alphabet, Character pad) {
this.alphabet = alphabet.toCharArray();
this.pad = pad;
}
@Override
public String encode(byte[] data) {
int i = 0;
int index = 0;
int digit;
int currByte;
int nextByte;
int encodeLen = data.length * 8 / 5;
if (encodeLen != 0) {
encodeLen = encodeLen + 1 + BASE32_FILL[(data.length * 8) % 5];
}
StringBuilder base32 = new StringBuilder(encodeLen);
while (i < data.length) {
// unsign
currByte = (data[i] >= 0) ? data[i] : (data[i] + 256);
/* Is the current digit going to span a byte boundary? */
if (index > 3) {
if ((i + 1) < data.length) {
nextByte = (data[i + 1] >= 0) ? data[i + 1] : (data[i + 1] + 256);
} else {
nextByte = 0;
}
digit = currByte & (0xFF >> index);
index = (index + 5) % 8;
digit <<= index;
digit |= nextByte >> (8 - index);
i++;
} else {
digit = (currByte >> (8 - (index + 5))) & 0x1F;
index = (index + 5) % 8;
if (index == 0) {
i++;
}
}
base32.append(alphabet[digit]);
}
if (null != pad) {
// 末尾补充不足长度的
while (base32.length() < encodeLen) {
base32.append(pad.charValue());
}
}
return base32.toString();
}
}
/**
* Base32解码器
*/
public static class Base32Decoder implements Decoder {
private static final char BASE_CHAR = '0';
public static final Base32Decoder DECODER = new Base32Decoder(Base32Encoder.DEFAULT_ALPHABET);
public static final Base32Decoder HEX_DECODER = new Base32Decoder(Base32Encoder.HEX_ALPHABET);
private final byte[] lookupTable;
/**
* 构造
*
* @param alphabet 编码字母表
*/
public Base32Decoder(String alphabet) {
lookupTable = new byte[128];
Arrays.fill(lookupTable, (byte) -1);
final int length = alphabet.length();
char c;
for (int i = 0; i < length; i++) {
c = alphabet.charAt(i);
lookupTable[c - BASE_CHAR] = (byte) i;
// 支持小写字母解码
if(c >= 'A' && c <= 'Z'){
lookupTable[Character.toLowerCase(c) - BASE_CHAR] = (byte) i;
}
}
}
@Override
public byte[] decode(CharSequence encoded) {
int i, index, lookup, offset, digit;
final String base32 = encoded.toString();
int len = base32.endsWith("=") ? base32.indexOf("=") * 5 / 8 : base32.length() * 5 / 8;
byte[] bytes = new byte[len];
for (i = 0, index = 0, offset = 0; i < base32.length(); i++) {
lookup = base32.charAt(i) - BASE_CHAR;
/* Skip chars outside the lookup table */
if (lookup < 0 || lookup >= lookupTable.length) {
continue;
}
digit = lookupTable[lookup];
/* If this digit is not in the table, ignore it */
if (digit < 0) {
continue;
}
if (index <= 3) {
index = (index + 5) % 8;
if (index == 0) {
bytes[offset] |= digit;
offset++;
if (offset >= bytes.length) {
break;
}
} else {
bytes[offset] |= digit << (8 - index);
}
} else {
index = (index + 5) % 8;
bytes[offset] |= (digit >>> index);
offset++;
if (offset >= bytes.length) {
break;
}
bytes[offset] |= digit << (8 - index);
}
}
return bytes;
}
}
}