a buffer to read data into (which should be at least count bytes long)
the [I/O priority][io-priority] of the request
optional #GCancellable object, %NULL to ignore
callback to call when the request is satisfied
the data to pass to callback function
2.44
Request an asynchronous read of @count bytes from the stream into the buffer starting at @buffer.
This is the asynchronous equivalent of g_input_stream_read_all().
Call g_input_stream_read_all_finish() to collect the result.
Any outstanding I/O request with higher priority (lower numerical value) will be executed before an outstanding request with lower priority. Default priority is %G_PRIORITY_DEFAULT.