1 整数转为短字符串的应用
网站生成的动态 URL 往往以内容序列号id为标识与参数，比如：
http://www.jerry.com/tom.aspx?id=1
使用 Web Rewrite，可以实现网页静态化，称为：
http://www.jerry.com/content/1.html
对于爬虫软件而言，这最好不过了。
即使中学生也可以从 id=1 爬到 id=10000 ，分分钟爬你个底掉。
对策之一，就是把 id 隐藏起来，转为“短字符串”就是技术之一。
http://www.jerry.com/content/9Rus3d.html
2 源程序
using System;
using System.Text;
using System.Collections;
using System.Collections.Generic;
/// <summary>
/// 整数转为“短字符串”
/// </summary>
public static class ShortHelper
{
// 修改这个字符串，就可以生成与别人不同的结果！！！
private static string cs = "m65pKkCes8VzxhGby9XNcfqPaWuE2jFYnUDT104LOdA3HIZoSvBigMwlrQ7JRt";
private static Hashtable hash = new Hashtable();
private static uint offset = (uint)cs.Length / 2;
public static uint begin = 1020304050;
public static string Encode(int v)
{
StringBuilder sb = new StringBuilder();
uint va = (uint)v;
va += begin;
uint lastv = 0;
while (va > 0)
{
uint vb = va % offset;
va = (va - vb) / offset;
if (sb.Length == 0) lastv = vb;
sb.Append((sb.Length == 0) ? cs.Substring((int)vb, 1) : cs.Substring((int)(vb + lastv), 1));
}
return sb.ToString();
}
private static void Init()
{
for (int i = 0; i < cs.Length; i++)
{
hash.Add(cs.Substring(i, 1), i);
}
}
public static int Decode(string s)
{
if (hash.Count == 0) Init();
if (s.Length < 2) return 0;
uint v = 0;
uint lastv = 0;
for (int i = 0; i < s.Length; i++)
{
if (i == 0) { v = (uint)((int)hash[s.Substring(i, 1)]); lastv = v; continue; }
else { v += ((uint)((int)hash[s.Substring(i, 1)] - lastv)) * (uint)Math.Pow(offset, i); }
}
v -= begin;
return (int)v;
}
}
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3 代码格式
using System;
using System.Text;
using System.Collections;
using System.Collections.Generic;/// <summary>
/// 整数转为“短字符串”
/// </summary>
public static class ShortHelper
{// 修改这个字符串，就可以生成与别人不同的结果！！！private static string cs = "m65pKkCes8VzxhGby9XNcfqPaWuE2jFYnUDT104LOdA3HIZoSvBigMwlrQ7JRt";private static Hashtable hash = new Hashtable();private static uint offset = (uint)cs.Length / 2;public static uint begin = 1020304050;public static string Encode(int v){StringBuilder sb = new StringBuilder();uint va = (uint)v;va += begin;uint lastv = 0;while (va > 0){uint vb = va % offset;va = (va - vb) / offset;if (sb.Length == 0) lastv = vb;sb.Append((sb.Length == 0) ? cs.Substring((int)vb, 1) : cs.Substring((int)(vb + lastv), 1));}return sb.ToString();}private static void Init(){for (int i = 0; i < cs.Length; i++){hash.Add(cs.Substring(i, 1), i);}}public static int Decode(string s){if (hash.Count == 0) Init();if (s.Length < 2) return 0;uint v = 0;uint lastv = 0;for (int i = 0; i < s.Length; i++){if (i == 0) { v = (uint)((int)hash[s.Substring(i, 1)]); lastv = v; continue; }else { v += ((uint)((int)hash[s.Substring(i, 1)] - lastv)) * (uint)Math.Pow(offset, i); }}v -= begin;return (int)v;}
}
