Hello
While profiling my application, i found that there is uneficient implementation of some function related to use of g_base64_decode
In it's current interface i can't decode base64_decoded data which is part of string, and i have to create copy for that, when is really does not nessecary.

Just a little illustration, if i have some function with prototype
gboolean f(const gchar* big_data, gsize data_len);
and it is known that all content of big_data is base64_encoded data except last 6 bytes, i have to copy all this big data just to make base64_encoded data null terminated
Of course, i can hack it by overwriting one byte to '\0' and than restore it, or use g_base64_decode_step. But first is not thread-safe(or i should use mutexes), second is inconvenient and unevident.

So, if it is possible, please add to glib something like this:
guchar* g_base64_decode_len(const gchar *text, gsize text_len, gsize *out_len);