Method
GioSocketreceive_messages
since: 2.48
Declaration
gint
g_socket_receive_messages (
GSocket* socket,
GInputMessage* messages,
guint num_messages,
gint flags,
GCancellable* cancellable,
GError** error
)
Description
Receive multiple data messages from socket in one go. This is the most
complicated and fully-featured version of this call. For easier use, see
g_socket_receive(), g_socket_receive_from(), and g_socket_receive_message().
messages must point to an array of GInputMessage structs and
num_messages must be the length of this array. Each GInputMessage
contains a pointer to an array of GInputVector structs describing the
buffers that the data received in each message will be written to. Using
multiple GInputVectors is more memory-efficient than manually copying data
out of a single buffer to multiple sources, and more system-call-efficient
than making multiple calls to g_socket_receive(), such as in scenarios where
a lot of data packets need to be received (e.g. high-bandwidth video
streaming over RTP/UDP).
flags modify how all messages are received. The commonly available
arguments for this are available in the GSocketMsgFlags enum, but the
values there are the same as the system values, and the flags
are passed in as-is, so you can pass in system-specific flags too. These
flags affect the overall receive operation. Flags affecting individual
messages are returned in GInputMessage.flags.
The other members of GInputMessage are treated as described in its documentation.
If GSocket:blocking is TRUE the call will block until num_messages have
been received, or the end of the stream is reached.
If GSocket:blocking is FALSE the call will return up to num_messages
without blocking, or G_IO_ERROR_WOULD_BLOCK if no messages are queued in the
operating system to be received.
In blocking mode, if GSocket:timeout is positive and is reached before any
messages are received, G_IO_ERROR_TIMED_OUT is returned, otherwise up to
num_messages are returned. (Note: This is effectively the
behaviour of MSG_WAITFORONE with recvmmsg().)
To be notified when messages are available, wait for the
G_IO_IN condition. Note though that you may still receive
G_IO_ERROR_WOULD_BLOCK from g_socket_receive_messages() even if you were
previously notified of a G_IO_IN condition.
If the remote peer closes the connection, any messages queued in the
operating system will be returned, and subsequent calls to
g_socket_receive_messages() will return 0 (with no error set).
On error -1 is returned and error is set accordingly. An error will only
be returned if zero messages could be received; otherwise the number of
messages successfully received before the error will be returned.
Available since: 2.48
Parameters
messages-
Type: An array of
GInputMessageAn array of
GInputMessagestructs.The length of the array is specified in the num_messagesargument.The data is owned by the caller of the method. num_messages-
Type:
guintThe number of elements in
messages. flags-
Type:
gintAn int containing
GSocketMsgFlagsflags for the overall operation, which may additionally contain other platform specific flags. cancellable-
Type:
GCancellableA %GCancellable or
NULL.The argument can be NULL.The data is owned by the caller of the method. error-
Type:
GError **The return location for a recoverable error.
The argument can be NULL.If the return location is not NULL, then you must initialize it to aNULLGError*.The argument will be left initialized to NULLby the method if there are no errors.In case of error, the argument will be set to a newly allocated GError; the caller will take ownership of the data, and be responsible for freeing it.
Return value
Type: gint
Number of messages received, or -1 on error. Note that the number
of messages received may be smaller than num_messages if in non-blocking
mode, if the peer closed the connection, or if num_messages
was larger than UIO_MAXIOV (1024), in which case the caller may re-try
to receive the remaining messages.