com.jchanghong.core.codec.Rot Maven / Gradle / Ivy
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package com.jchanghong.core.codec;
/**
* RotN（rotate by N places），回转N位密码，是一种简易的替换式密码，也是过去在古罗马开发的凯撒加密的一种变体。
* 代码来自：https://github.com/orclight/jencrypt
*
* @author looly,shuzhilong
* @since 4.4.1
*/
public class Rot {
private static final char aCHAR = 'a';
private static final char zCHAR = 'z';
private static final char ACHAR = 'A';
private static final char ZCHAR = 'Z';
private static final char CHAR0 = '0';
private static final char CHAR9 = '9';
/**
* Rot-13编码，同时编码数字
*
* @param message 被编码的消息
* @return 编码后的字符串
*/
public static String encode13(String message) {
return encode13(message, true);
}
/**
* Rot-13编码
*
* @param message 被编码的消息
* @param isEnocdeNumber 是否编码数字
* @return 编码后的字符串
*/
public static String encode13(String message, boolean isEnocdeNumber) {
return encode(message, 13, isEnocdeNumber);
}
/**
* RotN编码
*
* @param message 被编码的消息
* @param offset 位移，常用位移13
* @param isEnocdeNumber 是否编码数字
* @return 编码后的字符串
*/
public static String encode(String message, int offset, boolean isEnocdeNumber) {
final int len = message.length();
final char[] chars = new char[len];
for (int i = 0; i < len; i++) {
chars[i] = encodeChar(message.charAt(i), offset, isEnocdeNumber);
}
return new String(chars);
}
/**
* Rot-13解码，同时解码数字
*
* @param rot 被解码的消息密文
* @return 解码后的字符串
*/
public static String decode13(String rot) {
return decode13(rot, true);
}
/**
* Rot-13解码
*
* @param rot 被解码的消息密文
* @param isDecodeNumber 是否解码数字
* @return 解码后的字符串
*/
public static String decode13(String rot, boolean isDecodeNumber) {
return decode(rot, 13, isDecodeNumber);
}
/**
* RotN解码
*
* @param rot 被解码的消息密文
* @param offset 位移，常用位移13
* @param isDecodeNumber 是否解码数字
* @return 解码后的字符串
*/
public static String decode(String rot, int offset, boolean isDecodeNumber) {
final int len = rot.length();
final char[] chars = new char[len];
for (int i = 0; i < len; i++) {
chars[i] = decodeChar(rot.charAt(i), offset, isDecodeNumber);
}
return new String(chars);
}
// ------------------------------------------------------------------------------------------ Private method start
/**
* 解码字符
*
* @param c 字符
* @param offset 位移
* @param isDecodeNumber 是否解码数字
* @return 解码后的字符串
*/
private static char encodeChar(char c, int offset, boolean isDecodeNumber) {
if (isDecodeNumber) {
if (c >= CHAR0 && c <= CHAR9) {
c -= CHAR0;
c = (char) ((c + offset) % 10);
c += CHAR0;
}
}
// A == 65, Z == 90
if (c >= ACHAR && c <= ZCHAR) {
c -= ACHAR;
c = (char) ((c + offset) % 26);
c += ACHAR;
}
// a == 97, z == 122.
else if (c >= aCHAR && c <= zCHAR) {
c -= aCHAR;
c = (char) ((c + offset) % 26);
c += aCHAR;
}
return c;
}
/**
* 编码字符
*
* @param c 字符
* @param offset 位移
* @param isDecodeNumber 是否编码数字
* @return 编码后的字符串
*/
private static char decodeChar(char c, int offset, boolean isDecodeNumber) {
int temp = c;
// if converting numbers is enabled
if (isDecodeNumber) {
if (temp >= CHAR0 && temp <= CHAR9) {
temp -= CHAR0;
temp = temp - offset;
while (temp < 0) {
temp += 10;
}
temp += CHAR0;
}
}
// A == 65, Z == 90
if (temp >= ACHAR && temp <= ZCHAR) {
temp -= ACHAR;
temp = temp - offset;
while (temp < 0) {
temp = 26 + temp;
}
temp += ACHAR;
} else if (temp >= aCHAR && temp <= zCHAR) {
temp -= aCHAR;
temp = temp - offset;
if (temp < 0)
temp = 26 + temp;
temp += aCHAR;
}
return (char) temp;
}
// ------------------------------------------------------------------------------------------ Private method end
}