Update FilesSignature.cs (#1087)

做了以下几点改动：
1.使用 Path.Combine() 确保路径的正确性，使其在各系统下均能兼容
2.修复了代码中的一些变量命名和拼写错误
3.对文件处理部分做了优化

Author: xiezheng-XD

General/Src/FilesSignature.cs

@@ -6,51 +6,54 @@ namespace XLua
 {
     public class FilesSignature
     {
-        static void useage()
+        static void usage()
         {
             Console.WriteLine("FilesSignature from_path to_path");
         }
 
         static void doSignature(string from, string to, SHA1 sha, RSACryptoServiceProvider rsa)
         {
-            if(!Directory.Exists(to))
+            if (!Directory.Exists(to))
             {
                 Directory.CreateDirectory(to);
             }
-            foreach(var filename in Directory.GetFiles(from, "*.lua"))
+            foreach (var filename in Directory.GetFiles(from, "*.lua"))
             {
                 byte[] filecontent = File.ReadAllBytes(filename);
                 byte[] sig = rsa.SignData(filecontent, sha);
-                FileStream fs = new FileStream(to + "/" + Path.GetFileName(filename), FileMode.Create);
-                fs.Write(sig, 0, sig.Length);
-                fs.Write(filecontent, 0, filecontent.Length);
-                fs.Close();
+                string sigFilePath = Path.Combine(to, Path.GetFileName(filename));
+                using (FileStream fs = new FileStream(sigFilePath, FileMode.Create))
+                {
+                    fs.Write(sig, 0, sig.Length);
+                    fs.Write(filecontent, 0, filecontent.Length);
+                    fs.Flush();
+                }
             }
-            foreach(var dir in Directory.GetDirectories(from))
+            foreach (var dir in Directory.GetDirectories(from))
             {
-
-                doSignature(dir, to + "/" + new DirectoryInfo(dir).Name, sha, rsa);
+                string newDir = Path.Combine(to, new DirectoryInfo(dir).Name);
+                doSignature(dir, newDir, sha, rsa);
             }
         }
 
         public static void Main(string[] args)
         {
-            if (!File.Exists("key_ras"))
+            if (!File.Exists("key_rsa"))
             {
-                Console.WriteLine("no key_ras!");
+                Console.WriteLine("No key_rsa file found!");
                 return;
             }
 
             if (args.Length != 2)
             {
-                useage();
+                usage();
                 return;
             }
 
             SHA1 sha = new SHA1CryptoServiceProvider();
             RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
-            rsa.FromXmlString(File.ReadAllText("key_ras"));
+            rsa.FromXmlString(File.ReadAllText("key_rsa"));
             doSignature(args[0], args[1], sha, rsa);
         }
     }
-}
+}