gio.datagram_based_mixin
Module for DatagramBased interface mixin
Templates 2
Interface for socket-like objects with datagram semantics.
A gio.datagram_based.DatagramBased is a networking interface for representing datagram-based communications. It is a more or less direct mapping of the core parts of the BSD socket API in a portable GObject interface. It is implemented by gio.socket.Socket, which wraps the UNIX socket API on UNIX and winsock2 on Windows.
gio.datagram_based.DatagramBased is entirely platform independent, and is intended to be used alongside higher-level networking APIs such as gio.iostream.IOStream.
It uses vectored scatter/gather I/O by default, allowing for many messages to be sent or received in a single call. Where possible, implementations of the interface should take advantage of vectored I/O to minimise processing or system calls. For example, gio.socket.Socket uses recvmmsg() and sendmmsg() where possible. Callers should take advantage of scatter/gather I/O (the use of multiple buffers per message) to avoid unnecessary copying of data to assemble or disassemble a message.
Each gio.datagram_based.DatagramBased operation has a timeout parameter which may be negative for blocking behaviour, zero for non-blocking behaviour, or positive for timeout behaviour. A blocking operation blocks until finished or there is an error. A non-blocking operation will return immediately with a gio.types.IOErrorEnum.WouldBlock error if it cannot make progress. A timeout operation will block until the operation is complete or the timeout expires; if the timeout expires it will return what progress it made, or gio.types.IOErrorEnum.TimedOut if no progress was made. To know when a call would successfully run you can call gio.datagram_based.DatagramBased.conditionCheck or gio.datagram_based.DatagramBased.conditionWait. You can also use gio.datagram_based.DatagramBased.createSource and attach it to a glib.main_context.MainContext to get callbacks when I/O is possible.
When running a non-blocking operation applications should always be able to handle getting a gio.types.IOErrorEnum.WouldBlock error even when some other function said that I/O was possible. This can easily happen in case of a race condition in the application, but it can also happen for other reasons. For instance, on Windows a socket is always seen as writable until a write returns gio.types.IOErrorEnum.WouldBlock.
As with gio.socket.Socket, gio.datagram_based.DatagramBaseds can be either connection oriented (for example, SCTP) or connectionless (for example, UDP). gio.datagram_based.DatagramBaseds must be datagram-based, not stream-based. The interface does not cover connection establishment — use methods on the underlying type to establish a connection before sending and receiving data through the gio.datagram_based.DatagramBased API. For connectionless socket types the target/source address is specified or received in each I/O operation.
Like most other APIs in GLib, gio.datagram_based.DatagramBased is not inherently thread safe. To use a gio.datagram_based.DatagramBased concurrently from multiple threads, you must implement your own locking.
Checks on the readiness of datagram_based to perform operations. The operations specified in condition are checked for and masked against the currently-satisfied conditions on datagram_based. The result is returned.
glib.types.IOCondition.In will be set in the return value if data is available to read with gio.datagram_based.DatagramBased.receiveMessages, or if the connection is closed remotely (EOS); and if the datagram_based has not been closed locally using some implementation-specific method (such as gio.socket.Socket.close or gio.socket.Socket.shutdown with shutdown_read set, if it’s a #GSocket).
If the connection is shut down or closed (by calling gio.socket.Socket.close or gio.socket.Socket.shutdown with shutdown_read set, if it’s a #GSocket, for example), all calls to this function will return gio.types.IOErrorEnum.Closed.
glib.types.IOCondition.Out will be set if it is expected that at least one byte can be sent using gio.datagram_based.DatagramBased.sendMessages without blocking. It will not be set if the datagram_based has been closed locally.
glib.types.IOCondition.Hup will be set if the connection has been closed locally.
glib.types.IOCondition.Err will be set if there was an asynchronous error in transmitting data previously enqueued using gio.datagram_based.DatagramBased.sendMessages.
Note that on Windows, it is possible for an operation to return gio.types.IOErrorEnum.WouldBlock even immediately after gio.datagram_based.DatagramBased.conditionCheck has claimed that the #GDatagramBased is ready for writing. Rather than calling gio.datagram_based.DatagramBased.conditionCheck and then writing to the #GDatagramBased if it succeeds, it is generally better to simply try writing right away, and try again later if the initial attempt returns gio.types.IOErrorEnum.WouldBlock.
It is meaningless to specify glib.types.IOCondition.Err or glib.types.IOCondition.Hup in condition; these conditions will always be set in the output if they are true. Apart from these flags, the output is guaranteed to be masked by condition.
This call never blocks.
Parameters
condition | a #GIOCondition mask to check |
Returns
Waits for up to timeout microseconds for condition to become true on datagram_based. If the condition is met, true is returned.
If cancellable is cancelled before the condition is met, or if timeout is reached before the condition is met, then false is returned and error is set appropriately (gio.types.IOErrorEnum.Cancelled or gio.types.IOErrorEnum.TimedOut).
Parameters
condition | a #GIOCondition mask to wait for |
timeout | the maximum time (in microseconds) to wait, 0 to not block, or -1 to block indefinitely |
cancellable | a #GCancellable |
Returns
Throws
Creates a #GSource that can be attached to a #GMainContext to monitor for the availability of the specified condition on the #GDatagramBased. The #GSource keeps a reference to the datagram_based.
The callback on the source is of the #GDatagramBasedSourceFunc type.
It is meaningless to specify glib.types.IOCondition.Err or glib.types.IOCondition.Hup in condition; these conditions will always be reported in the callback if they are true.
If non-null, cancellable can be used to cancel the source, which will cause the source to trigger, reporting the current condition (which is likely 0 unless cancellation happened at the same time as a condition change). You can check for this in the callback using gio.cancellable.Cancellable.isCancelled.
Parameters
condition | a #GIOCondition mask to monitor |
cancellable | a #GCancellable |
Returns
Fluent builder implementation template for gio.datagram_based.DatagramBased