Add mg_url_encode_opt()

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

PUBLISHED_FROM=17fa57a7a5325b51b6e3aef3855eac4e82c35782

src/mg_util.c

@@ -313,17 +313,21 @@ void mg_basic_auth_header(const struct mg_str user, const struct mg_str pass,
   mbuf_append(buf, header_suffix, strlen(header_suffix));
 }
 
-struct mg_str mg_url_encode(const struct mg_str src) {
-  static const char *dont_escape = "._-$,;~()/";
-  static const char *hex = "0123456789abcdef";
+struct mg_str mg_url_encode_opt(const struct mg_str src,
+                                const struct mg_str safe, unsigned int flags) {
+  const char *hex =
+      (flags & MG_URL_ENCODE_F_UPPERCASE_HEX ? "0123456789ABCDEF"
+                                             : "0123456789abcdef");
   size_t i = 0;
   struct mbuf mb;
   mbuf_init(&mb, src.len);
 
   for (i = 0; i < src.len; i++) {
     const unsigned char c = *((const unsigned char *) src.p + i);
-    if (isalnum(c) || strchr(dont_escape, c) != NULL) {
+    if (isalnum(c) || mg_strchr(safe, c) != NULL) {
       mbuf_append(&mb, &c, 1);
+    } else if (c == ' ' && (flags & MG_URL_ENCODE_F_SPACE_AS_PLUS)) {
+      mbuf_append(&mb, "+", 1);
     } else {
       mbuf_append(&mb, "%", 1);
       mbuf_append(&mb, &hex[c >> 4], 1);
@@ -334,3 +338,7 @@ struct mg_str mg_url_encode(const struct mg_str src) {
   mbuf_trim(&mb);
   return mg_mk_str_n(mb.buf, mb.len - 1);
 }
+
+struct mg_str mg_url_encode(const struct mg_str src) {
+  return mg_url_encode_opt(src, mg_mk_str("._-$,;~()/"), 0);
+}

src/mg_util.h

@@ -196,10 +196,17 @@ 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