New function: uh_unescape()

Signed-off-by: Jianhui Zhao <jianhuizhao329@gmail.com>

README.md

@@ -83,9 +83,20 @@ Run
 
 	~/libuhttp$ ./build/example/helloworld
 	
-Then use the command curl or browser to access https://127.0.0.1:8000/test
+Then use the command curl or browser to test
 
-	$ curl -k https://127.0.0.1:8000/test -v
+	$ curl -k 'https://127.0.0.1:8000/test?name=context%3d%7b"nid"%3a"test"%7d' -v
+
+If use browser to test, it will be show
+
+	Hello World
+	Libuhttp v0.1
+	Url: /test?name=context%3d%7b%22nid%22%3a%22test%22%7d
+	Path: /test
+	Name: context%3d%7b%22nid%22%3a%22test%22%7d
+	Unescaped Name: context={"nid":"test"}
+	Host: 192.168.0.100:8000
+	User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/61.0.3163.100 Safari/537.36
 	
 # [Example](https://github.com/zhaojh329/libuhttp/blob/master/example/helloworld.c)
 

example/helloworld.c

@@ -15,6 +15,9 @@ void route_test(struct uh_connection *con)
     struct uh_value name = uh_get_var(con, "name");
     struct uh_value *header_host = uh_get_header(con, "Host");
     struct uh_value *header_ua = uh_get_header(con, "User-Agent");
+    char unescaped_name[128];
+
+    uh_unescape(name.at, name.len, unescaped_name, sizeof(unescaped_name));
 
     uh_send_head(con, UH_STATUS_OK, -1, NULL);
     uh_printf_chunk(con, "<h1>Hello World</h1>");
@@ -22,6 +25,7 @@ void route_test(struct uh_connection *con)
     uh_printf_chunk(con, "<h1>Url: %.*s</h1>", (int)url->len, url->at);
     uh_printf_chunk(con, "<h1>Path: %.*s</h1>", (int)path->len, path->at);
     uh_printf_chunk(con, "<h1>Name: %.*s</h1>", (int)name.len, name.at);
+    uh_printf_chunk(con, "<h1>Unescaped Name: %s</h1>", unescaped_name);
 
     if (header_host)
         uh_printf_chunk(con, "<h1>Host: %.*s</h1>", (int)header_host->len, header_host->at);

src/uhttp.c

@@ -577,42 +577,42 @@ inline struct uh_value *uh_get_query(struct uh_connection *con)
     return &con->req.query;
 }
 
-#if 0
 static inline char c2hex(char c)
 {
     return c >= '0' && c <= '9' ? c - '0' : c >= 'A' && c <= 'F' ? c - 'A' + 10 : c - 'a' + 10; /* accept small letters just in case */
 }
 
-static char *uh_unescape(char *str)
+int uh_unescape(const char *str, int len, char *out, int olen)
 {
-    char *p = str;
-    char *q = str;
+    const char *p = str;
+    char *o = out;
 
-    if (!str)
-        return ("");
+    assert(str && out);
 
-    while (*p) {
+    olen -= 1;
+    
+    while ((p - str < len) && (o - out < olen)) {
         if (*p == '%') {
             p++;
-            if (*p)
-                *q = c2hex(*p++) * 16;
-            if (*p)
-                *q = (*q + c2hex(*p++));
-            q++;
-        } else {
-            if (*p == '+') {
-                *q++ = ' ';
-                p++;
-            } else {
-                *q++ = *p++;
+
+            if (p + 1 - str < len) {
+                *o = c2hex(*p++) << 4;
+                *o += c2hex(*p++);
+                o++;
             }
+            
+        } else if (*p == '+') {
+            *o++ = ' ';
+            p++;
+        } else {
+            *o++ = *p++;
         }
     }
 
-    *q++ = 0;
-    return str;
+    *o = 0;
+    
+    return 0;
 }
-#endif
 
 struct uh_value uh_get_var(struct uh_connection *con, const char *name)
 {

src/uhttp.h

@@ -157,6 +157,9 @@ struct uh_value *uh_get_query(struct uh_connection *con);
 struct uh_value uh_get_var(struct uh_connection *con, const char *name);
 struct uh_value *uh_get_header(struct uh_connection *con, const char *name);
 
+/* Unescapes strings like '%7B1,%202,%203%7D' would become '{1, 2, 3}' */
+int uh_unescape(const char *str, int len, char *out, int olen);
+
 #if (UHTTP_SSL_ENABLED)
 /* Init ssl for the server */
 int uh_ssl_init(struct uh_server *srv, const char *cert, const char *key);