为短炼增加签名校验

src/Library/ShortURL.php

@@ -3,7 +3,7 @@
  * class ShortURL
  * usage:
  * 
- * ShortURL::build($url);
+ * \Qii\Library\ShortURL::build($url);
  */
 namespace Qii\Library;
 
@@ -15,17 +15,20 @@ class ShortURL {
         "I" , "J" , "K" , "L" , "M" , "N" , "O" , "P" , "Q" , "R" , "S" , "T" ,  
         "U" , "V" , "W" , "X" , "Y" , "Z"  
     ];
+
+    static $secKey = 'sU0dl';
   
     public static function build($url){  
         if($url == null){  
             return null ;  
-        }  
+        }
+        $group = [];
         //先得到url的32个字符的md5码  
         $md5 = md5($url);
         //将32个字符的md5码分成4段处理，每段8个字符  
         for ($i = 0; $i < 4 ; $i++) {   
             $offset = i * 8 ;  
-            $sub = substr($md5, $offset, $offset + 8) ;   
+            $sub = substr($md5, $offset, $offset + 8);
             $sub16 = base_convert($sub, 16, 10); //将sub当作一个16进制的数，转成long    
             // & 0X3FFFFFFF，去掉最前面的2位，只留下30位  
             $sub16 &= 0X3FFFFFFF ;  
@@ -38,9 +41,29 @@ class ShortURL {
                   
                 $sub16 >>= 5 ;  //将sub16右移5位  
             }
-            return $shortURL;
+            return self::sign($shortURL);
         }
         return null ;  
     } 
-  
+    /**
+     * 对生成的短链 key 进行签名
+     */
+    public static function sign($str)
+    {
+        $sign = md5(self::$secKey . $str);
+        return $str . substr($sign, 8, 2);
+    }
+    /**
+     * 验证生成的URL是否正确
+     * @param string $str URL 串
+     * @return bool
+     */
+    public static function verify($str)
+    {
+        $urlSign = substr($str, -2);
+        $str = substr($str, 0, -2);
+        $sign = md5(self::$secKey . $str);
+        if(substr($sign, 8, 2) !== $urlSign) return false;
+        return true;
+    }
 }