Change base64 API

src/base64.h

@@ -1,5 +1,6 @@
 #pragma once
-int mg_base64_update(unsigned char p, char *to, int len);
-int mg_base64_final(char *to, int len);
-int mg_base64_encode(const unsigned char *p, int n, char *to);
-int mg_base64_decode(const char *src, int n, char *dst);
+#include "arch.h"
+size_t mg_base64_update(unsigned char input_byte, char *buf, size_t len);
+size_t mg_base64_final(char *buf, size_t len);
+size_t mg_base64_encode(const unsigned char *p, size_t n, char *buf, size_t);
+size_t mg_base64_decode(const char *src, size_t n, char *dst, size_t);