中文转换PunyCode

梦里梦外; 2022-06-16 07:27 122阅读 0赞

Punycode是一个根据RFC 3492标准而制定的编码系统，主要用于把域名从地方语言所采用的Unicode编码转换成为可用于DNS系统的编码

“中文域名”不被标准的解析服务器支持，需转化为Punycode码进行解析，例如“清华大学”的转码为：  xn--xkry9kk1bz66a

目前，因为操作系统的核心都是英文组成，DNS服务器的解析也是由英文代码交换，所以DNS服务器上并不支持直接的中文域名解析，所有中文域名的解析都需要转成Punycode码，然后由DNS解析Punycode码

其实目前所说的各种浏览器完美支持中文域名，只是浏览器中主动加入了中文域名自动转码，不需要再次安装中文域名转码控件来完成整个流程

package com.xinnet.smart.common.vo.instance;
    
    public class PunyTest {
    	static int TMIN = 1;
    	static int TMAX = 26;
    	static int BASE = 36;
    	static int INITIAL_N = 128;
    	static int INITIAL_BIAS = 72;
    	static int DAMP = 700;
    	static int SKEW = 38;
    	static char DELIMITER = '-';
    
    	public static void main(String[] args) throws Exception {
    		String punyCode = "xn--" + encode("清华大学");
    		System.out.println(punyCode);
    		String chinese = decode("xkry9kk1bz66a");
    		System.out.println(chinese);
    	}
    
    	/**
    	 * Punycodes a unicode string.
    	 * 
    	 * @param input
    	 *            Unicode string.
    	 * 
    	 * @return Punycoded string.
    	 */
    	public static String encode(String input) throws Exception {
    		int n = INITIAL_N;
    		int delta = 0;
    		int bias = INITIAL_BIAS;
    		StringBuilder output = new StringBuilder();
    		// Copy all basic code points to the output
    		int b = 0;
    		for (int i = 0; i < input.length(); i++) {
    			char c = input.charAt(i);
    			if (isBasic(c)) {
    				output.append(c);
    				b++;
    			}
    		}
    		// Append delimiter
    		if (b > 0) {
    			output.append(DELIMITER);
    		}
    		int h = b;
    		while (h < input.length()) {
    			int m = Integer.MAX_VALUE;
    			// Find the minimum code point >= n
    			for (int i = 0; i < input.length(); i++) {
    				int c = input.charAt(i);
    				if (c >= n && c < m) {
    					m = c;
    				}
    			}
    			if (m - n > (Integer.MAX_VALUE - delta) / (h + 1)) {
    				throw new Exception("OVERFLOW");
    			}
    			delta = delta + (m - n) * (h + 1);
    			n = m;
    			for (int j = 0; j < input.length(); j++) {
    				int c = input.charAt(j);
    				if (c < n) {
    					delta++;
    					if (0 == delta) {
    						throw new Exception("OVERFLOW");
    					}
    				}
    				if (c == n) {
    					int q = delta;
    					for (int k = BASE;; k += BASE) {
    						int t;
    						if (k <= bias) {
    							t = TMIN;
    						} else if (k >= bias + TMAX) {
    							t = TMAX;
    						} else {
    							t = k - bias;
    						}
    						if (q < t) {
    							break;
    						}
    						output.append((char) digit2codepoint(t + (q - t) % (BASE - t)));
    						q = (q - t) / (BASE - t);
    					}
    					output.append((char) digit2codepoint(q));
    					bias = adapt(delta, h + 1, h == b);
    					delta = 0;
    					h++;
    				}
    			}
    			delta++;
    			n++;
    		}
    		return output.toString();
    	}
    
    	/**
    	 * Decode a punycoded string.
    	 * 
    	 * @param input
    	 *            Punycode string
    	 * 
    	 * @return Unicode string.
    	 */
    	public static String decode(String input) throws Exception {
    		int n = INITIAL_N;
    		int i = 0;
    		int bias = INITIAL_BIAS;
    		StringBuilder output = new StringBuilder();
    		int d = input.lastIndexOf(DELIMITER);
    		if (d > 0) {
    			for (int j = 0; j < d; j++) {
    				char c = input.charAt(j);
    				if (!isBasic(c)) {
    					throw new Exception("BAD_INPUT");
    				}
    				output.append(c);
    			}
    			d++;
    		} else {
    			d = 0;
    		}
    		while (d < input.length()) {
    			int oldi = i;
    			int w = 1;
    			for (int k = BASE;; k += BASE) {
    				if (d == input.length()) {
    					throw new Exception("BAD_INPUT");
    				}
    				int c = input.charAt(d++);
    				int digit = codepoint2digit(c);
    				if (digit > (Integer.MAX_VALUE - i) / w) {
    					throw new Exception("OVERFLOW");
    				}
    				i = i + digit * w;
    				int t;
    				if (k <= bias) {
    					t = TMIN;
    				} else if (k >= bias + TMAX) {
    					t = TMAX;
    				} else {
    					t = k - bias;
    				}
    				if (digit < t) {
    					break;
    				}
    				w = w * (BASE - t);
    			}
    			bias = adapt(i - oldi, output.length() + 1, oldi == 0);
    			if (i / (output.length() + 1) > Integer.MAX_VALUE - n) {
    				throw new Exception("OVERFLOW");
    			}
    			n = n + i / (output.length() + 1);
    			i = i % (output.length() + 1);
    			output.insert(i, (char) n);
    			i++;
    		}
    		return output.toString();
    	}
    
    	public static int adapt(int delta, int numpoints, boolean first) {
    		if (first) {
    			delta = delta / DAMP;
    		} else {
    			delta = delta / 2;
    		}
    		delta = delta + (delta / numpoints);
    		int k = 0;
    		while (delta > ((BASE - TMIN) * TMAX) / 2) {
    			delta = delta / (BASE - TMIN);
    			k = k + BASE;
    		}
    		return k + ((BASE - TMIN + 1) * delta) / (delta + SKEW);
    	}
    
    	public static boolean isBasic(char c) {
    		return c < 0x80;
    	}
    
    
    	public static int digit2codepoint(int d) throws Exception {
    		if (d < 26) {
    			// 0..25 : 'a'..'z'
    			return d + 'a';
    		} else if (d < 36) {
    			// 26..35 : '0'..'9';
    			return d - 26 + '0';
    		} else {
    			throw new Exception("BAD_INPUT");
    		}
    	}
    
    	public static int codepoint2digit(int c) throws Exception {
    		if (c - '0' < 10) {
    			// '0'..'9' : 26..35
    			return c - '0' + 26;
    		} else if (c - 'a' < 26) {
    			// 'a'..'z' : 0..25
    			return c - 'a';
    		} else {
    			throw new Exception("BAD_INPUT");
    		}
    	}
    }

运行结果为：

xn--xkry9kk1bz66a
    清华大学