stream can be read.
Note that some stream types may not be able to implement this 100%
reliably, and it is possible that a call to
after this returns
TRUE would still block. To guarantee
non-blocking behavior, you should always use
g_pollable_input_stream_read_nonblocking(), which will return a
G_IO_ERROR_WOULD_BLOCK error rather than blocking.
Available since: 2.28