Function avio_alloc_context
pub unsafe extern "C" fn avio_alloc_context(
buffer: *mut u8,
buffer_size: i32,
write_flag: i32,
opaque: *mut c_void,
read_packet: Option<unsafe extern "C" fn(*mut c_void, *mut u8, i32) -> i32>,
write_packet: Option<unsafe extern "C" fn(*mut c_void, *const u8, i32) -> i32>,
seek: Option<unsafe extern "C" fn(*mut c_void, i64, i32) -> i64>,
) -> *mut AVIOContext