[out,ref,size_is(buf_size)] uint8 *buffer,
[in] [range(0,8192)] uint32 buf_size,
[out,ref] [range(0,8192)] uint32 *bytes_needed
[out,ref,size_is(buf_size)] uint8 *buffer,
[in] [range(0,8192)] uint32 buf_size,
[out,ref] [range(0,8192)] uint32 *bytes_needed