<p>This function is used to provide a properly-sized buffer for writing.
<p>Buffer space which has already been returned is cleared, and the buffer is extended as necessary by the size plus some additional bytes. Within the current implementation, an extra 4096 bytes are allocated, but applications should not rely on this additional buffer space.
<p>The buffer exposed by this function is empty internal storage from the <ahref="ogg_sync_state.html">ogg_sync_state</a> struct, beginning at the fill mark within the struct.
<p>A pointer to this buffer is returned to be used by the calling application.