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cn.hutool.core.codec.Base62Codec Maven / Gradle / Ivy
package cn.hutool.core.codec;
import cn.hutool.core.util.ArrayUtil;
import java.io.ByteArrayOutputStream;
import java.io.Serializable;
/**
* Base62编码解码实现，常用于短URL[email protected]
* @since 4.5.9
*/
public class Base62Codec implements Encoder, Decoder, Serializable {
private static final long serialVersionUID = 1L;
private static final int STANDARD_BASE = 256;
private static final int TARGET_BASE = 62;
public static Base62Codec INSTANCE = new Base62Codec();
/**
* 编码指定消息bytes为Base62格式的bytes
*
* @param data 被编码的消息
* @return Base62内容
*/
@Override
public byte[] encode(byte[] data) {
return encode(data, false);
}
/**
* 编码指定消息bytes为Base62格式的bytes
*
* @param data 被编码的消息
* @param useInverted 是否使用反转风格，即将GMP风格中的大小写做转换
* @return Base62内容
*/
public byte[] encode(byte[] data, boolean useInverted) {
final Base62Encoder encoder = useInverted ? Base62Encoder.INVERTED_ENCODER : Base62Encoder.GMP_ENCODER;
return encoder.encode(data);
}
/**
* 解码Base62消息
*
* @param encoded Base62内容
* @return 消息
*/
@Override
public byte[] decode(byte[] encoded) {
return decode(encoded, false);
}
/**
* 解码Base62消息
*
* @param encoded Base62内容
* @param useInverted 是否使用反转风格，即将GMP风格中的大小写做转换
* @return 消息
*/
public byte[] decode(byte[] encoded, boolean useInverted) {
final Base62Decoder decoder = useInverted ? Base62Decoder.INVERTED_DECODER : Base62Decoder.GMP_DECODER;
return decoder.decode(encoded);
}
/**
* Base62编码器
*
* @since 5.8.0
*/
public static class Base62Encoder implements Encoder {
/**
* GMP风格
*/
private static final byte[] GMP = { //
'0', '1', '2', '3', '4', '5', '6', '7', //
'8', '9', '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', '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' //
};
/**
* 反转风格，即将GMP风格中的大小写做转换
*/
private static final byte[] INVERTED = { //
'0', '1', '2', '3', '4', '5', '6', '7', //
'8', '9', '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', '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' //
};
public static Base62Encoder GMP_ENCODER = new Base62Encoder(GMP);
public static Base62Encoder INVERTED_ENCODER = new Base62Encoder(INVERTED);
private final byte[] alphabet;
/**
* 构造
*
* @param alphabet 字符表
*/
public Base62Encoder(byte[] alphabet) {
this.alphabet = alphabet;
}
@Override
public byte[] encode(byte[] data) {
final byte[] indices = convert(data, STANDARD_BASE, TARGET_BASE);
return translate(indices, alphabet);
}
}
/**
* Base62解码器
*
* @since 5.8.0
*/
public static class Base62Decoder implements Decoder {
public static Base62Decoder GMP_DECODER = new Base62Decoder(Base62Encoder.GMP);
public static Base62Decoder INVERTED_DECODER = new Base62Decoder(Base62Encoder.INVERTED);
private final byte[] lookupTable;
/**
* 构造
*
* @param alphabet 字母表
*/
public Base62Decoder(byte[] alphabet) {
lookupTable = new byte['z' + 1];
for (int i = 0; i < alphabet.length; i++) {
lookupTable[alphabet[i]] = (byte) i;
}
}
@Override
public byte[] decode(byte[] encoded) {
final byte[] prepared = translate(encoded, lookupTable);
return convert(prepared, TARGET_BASE, STANDARD_BASE);
}
}
// region Private Methods
/**
* 按照字典转换bytes
*
* @param indices 内容
* @param dictionary 字典
* @return 转换值
*/
private static byte[] translate(byte[] indices, byte[] dictionary) {
final byte[] translation = new byte[indices.length];
for (int i = 0; i < indices.length; i++) {
translation[i] = dictionary[indices[i]];
}
return translation;
}
/**
* 使用定义的字母表从源基准到目标基准
*
* @param message 消息bytes
* @param sourceBase 源基准长度
* @param targetBase 目标基准长度
* @return 计算结果
*/
private static byte[] convert(byte[] message, int sourceBase, int targetBase) {
// 计算结果长度，算法来自：http://codegolf.stackexchange.com/a/21672
final int estimatedLength = estimateOutputLength(message.length, sourceBase, targetBase);
final ByteArrayOutputStream out = new ByteArrayOutputStream(estimatedLength);
byte[] source = message;
while (source.length > 0) {
final ByteArrayOutputStream quotient = new ByteArrayOutputStream(source.length);
int remainder = 0;
for (byte b : source) {
final int accumulator = (b & 0xFF) + remainder * sourceBase;
final int digit = (accumulator - (accumulator % targetBase)) / targetBase;
remainder = accumulator % targetBase;
if (quotient.size() > 0 || digit > 0) {
quotient.write(digit);
}
}
out.write(remainder);
source = quotient.toByteArray();
}
// pad output with zeroes corresponding to the number of leading zeroes in the message
for (int i = 0; i < message.length - 1 && message[i] == 0; i++) {
out.write(0);
}
return ArrayUtil.reverse(out.toByteArray());
}
/**
* 估算结果长度
*
* @param inputLength 输入长度
* @param sourceBase 源基准长度
* @param targetBase 目标基准长度
* @return 估算长度
*/
private static int estimateOutputLength(int inputLength, int sourceBase, int targetBase) {
return (int) Math.ceil((Math.log(sourceBase) / Math.log(targetBase)) * inputLength);
}
// endregion
}
