Add mg_url_encode_opt()

CL: Add `mg_url_encode_opt()` - a parametrized version of `mg_url_encode()`

PUBLISHED_FROM=17fa57a7a5325b51b6e3aef3855eac4e82c35782

mongoose.h

@@ -2314,6 +2314,14 @@ void cs_base64_finish(struct cs_base64_ctx *ctx);
 
 void cs_base64_encode(const unsigned char *src, int src_len, char *dst);
 void cs_fprint_base64(FILE *f, const unsigned char *src, int src_len);
+
+/*
+ * Decodes a base64 string `s` length `len` into `dst`.
+ * `dst` must have enough space to hold the result.
+ * `*dec_len` will contain the resulting length of the string in `dst`
+ * while return value will return number of processed bytes in `src`.
+ * Return value == len indicates successful processing of all the data.
+ */
 int cs_base64_decode(const unsigned char *s, int len, char *dst, int *dec_len);
 
 #ifdef __cplusplus
@@ -4501,10 +4509,17 @@ void mg_basic_auth_header(const struct mg_str user, const struct mg_str pass,
 
 /*
  * URL-escape the specified string.
- * All non-printable characters are escaped, plus `._-$,;~()/`.
+ * All characters acept letters, numbers and characters listed in
+ * `safe` are escaped. If `hex_upper`is true, `A-F` are used for hex digits.
  * Input need not be NUL-terminated, but the returned string is.
  * Returned string is heap-allocated and must be free()'d.
  */
+#define MG_URL_ENCODE_F_SPACE_AS_PLUS (1 << 0)
+#define MG_URL_ENCODE_F_UPPERCASE_HEX (1 << 1)
+struct mg_str mg_url_encode_opt(const struct mg_str src,
+                                const struct mg_str safe, unsigned int flags);
+
+/* Same as `mg_url_encode_opt(src, "._-$,;~()/", 0)`. */
 struct mg_str mg_url_encode(const struct mg_str src);
 
 #ifdef __cplusplus