Add helper function for percent encoding

httplib.h

@@ -114,6 +114,14 @@ char * httplib_request_get_query_value(http_request * self, char * key);
  */
 int httplib_is_valid_header(const char * key, const char * value);
 
+/**
+ * Helper function to decode a percent encoded character.
+ * @param encoded a pointer to the first of the two characters in the string
+ * after the percent symbol, which make up the encoded character
+ * @return the decoded character
+ */
+char httplib_decode_hex(const char * encoded);
+
 #define SOCKET_ERROR -1
 #define BIND_ERROR -2
 #define LISTEN_ERROR -3

httputil.c

@@ -167,4 +167,12 @@ void httplib_tmp_increase(struct tmp * tmp) {
 void httplib_tmp_reset(struct tmp * tmp) {
     tmp->pos = 0;
     bzero(tmp->buf, tmp->size);
+}
+
+char httplib_decode_hex(const char * encoded) {
+    char input[3];
+    input[0] = encoded[0];
+    input[1] = encoded[1];
+    input[2] = '\0';
+    return (char) strtoul(input, 0, 16);
 }