mongoose/docs/c-api/util.h/mg_base64_decode.md

title	decl_name	symbol_kind	signature
mg_base64_decode()	mg_base64_decode	func	int mg_base64_decode(const unsigned char *s, int len, char *dst);

Decodes base64-encoded string s, len into the destination dst. The destination has to have enough space to hold the decoded buffer. Decoding stops either when all strings have been decoded or invalid an character appeared. Destination is '\0'-terminated. Returns the number of decoded characters. On success, that should be equal to len. On error (invalid character) the return value is smaller then len.