微薄短地址的实现-python

几乎全部的微薄都提供了缩短网址的服务，其原理就是将一个url地址按照必定的算法生成一段字符串，而后加在一个短域名后面边成了一个新的url地址，数 据库中会存放这个短地址和原始的地址，当用户点击这个新的短地址后，短地址服务会根据短域名后面的几个字符串从数据库中读出原来的地址而后页面进行跳转 。

好比新浪微薄中的url 是 http://t.cn/xxxxxxx  t.cn是其域名 ，其后面跟着的是7位算出来的字符串

http://www.guokr.com/question/297490/ 这个url 通过短地址算法后就成了 http://t.cn/zWCRWpM 

现将本身的算法提供出来 使用python语言实现

#!/usr/bin/env python
#coding=utf-8
import hashlib


chars = (
"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","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",)

def shorten(origin):
key = "fuck-gfw.ooxx.shorten"
#对传入网址进行MD5加密
hex = hashlib.md5(key + origin).hexdigest()
res = [0 for i in range(4)]
for i in range(4):
#把加密字符按照8位一组16进制与0x3FFFFFFF进行位与运算
hexint = 0x3FFFFFFF & int("0x" + hex[i * 8: i*8+8], 16)
outChars = ""
for j in range(7):
#把获得的值与0x0000003D进行位与运算，取得字符数组chars索引
index = 0x0000003D & hexint
#把取得的字符相加
outChars += chars[index]
#每次循环按位右移5位
hexint = hexint >> 5
#把字符串存入对应索引的输出数组
res[i] = outChars
return res

print shorten('http://www.google.com')

shorten(url) 这个方法会返回一个包含4个字符串的地址

上面代码返回的将是

 ['3IJJ7va', '6ZZfUfa', 'YNJniia', 'UFVRzea'] 

那麽这个短地址的形式将是 http://oo.xx/ 3IJJ7va