Like InputStream.read, this tries to read count bytes from the stream in a blocking fashion. However, rather than reading into a user-supplied buffer, this will create a new glib.Bytes containing the data that was read. This may be easier to use from language bindings.
If count is zero, returns a zero-length glib.Bytes and does nothing. A value of count larger than G_MAXSSIZE will cause a G_IO_ERROR_INVALID_ARGUMENT error.
On success, a new glib.Bytes is returned. It is not an error if the size of this object is not the same as the requested size, as it can happen e.g. near the end of a file. A zero-length glib.Bytes is returned on end of file (or if count is zero), but never otherwise.
If cancellable is not NULL, then the operation can be cancelled by triggering the cancellable object from another thread. If the operation was cancelled, the error G_IO_ERROR_CANCELLED will be returned. If an operation was partially finished when the operation was cancelled the partial result will be returned, without an error.
On error NULL is returned and error is set accordingly.