GI.Gio.Interfaces.DatagramBased

A 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 Socket, which wraps the UNIX socket API on UNIX and winsock2 on Windows.

DatagramBased is entirely platform independent, and is intended to be used alongside higher-level networking APIs such as 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, 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 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 IOErrorEnumWouldBlock 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 IOErrorEnumTimedOut if no progress was made. To know when a call would successfully run you can call datagramBasedConditionCheck or datagramBasedConditionWait. You can also use datagramBasedCreateSource and attach it to a MainContext to get callbacks when I/O is possible.

When running a non-blocking operation applications should always be able to handle getting a IOErrorEnumWouldBlock 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 IOErrorEnumWouldBlock.

As with Socket, GDatagramBaseds can be either connection oriented (for example, SCTP) or connectionless (for example, UDP). GDatagramBaseds 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 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, DatagramBased is not inherently thread safe. To use a DatagramBased concurrently from multiple threads, you must implement your own locking.

Since: 2.48

Exported types

newtype DatagramBased

Memory-managed wrapper type.

Constructors

DatagramBased (ManagedPtr DatagramBased)

Instances

Eq DatagramBased

Defined in GI.Gio.Interfaces.DatagramBased

Methods

(==) :: DatagramBased -> DatagramBased -> Bool

(/=) :: DatagramBased -> DatagramBased -> Bool

IsGValue DatagramBased

Convert DatagramBased to and from GValue with toGValue and fromGValue.

Defined in GI.Gio.Interfaces.DatagramBased

Methods

toGValue :: DatagramBased -> IO GValue

fromGValue :: GValue -> IO DatagramBased

ManagedPtrNewtype DatagramBased

Defined in GI.Gio.Interfaces.DatagramBased

Methods

toManagedPtr :: DatagramBased -> ManagedPtr DatagramBased

TypedObject DatagramBased

Defined in GI.Gio.Interfaces.DatagramBased

Methods

glibType :: IO GType

GObject DatagramBased

Defined in GI.Gio.Interfaces.DatagramBased

HasParentTypes DatagramBased

Defined in GI.Gio.Interfaces.DatagramBased

type ParentTypes DatagramBased

Defined in GI.Gio.Interfaces.DatagramBased

type ParentTypes DatagramBased = '[Object]

class (GObject o, IsDescendantOf DatagramBased o) => IsDatagramBased o

Type class for types which can be safely cast to DatagramBased, for instance with toDatagramBased.

Instances

(GObject o, IsDescendantOf DatagramBased o) => IsDatagramBased o

Defined in GI.Gio.Interfaces.DatagramBased

toDatagramBased :: (MonadIO m, IsDatagramBased o) => o -> m DatagramBased

Cast to DatagramBased, for types for which this is known to be safe. For general casts, use castTo.

Methods

Overloaded methods

conditionCheck

datagramBasedConditionCheck

Arguments

:: (HasCallStack, MonadIO m, IsDatagramBased a)

=> a

datagramBased: a DatagramBased

-> [IOCondition]

condition: a IOCondition mask to check

-> m [IOCondition]

Returns: the IOCondition mask of the current state

Checks on the readiness of datagramBased to perform operations. The operations specified in condition are checked for and masked against the currently-satisfied conditions on datagramBased. The result is returned.

IOConditionIn will be set in the return value if data is available to read with datagramBasedReceiveMessages, 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 socketClose or socketShutdown with shutdownRead set, if it’s a Socket).

If the connection is shut down or closed (by calling socketClose or socketShutdown with shutdownRead set, if it’s a Socket, for example), all calls to this function will return IOErrorEnumClosed.

IOConditionOut will be set if it is expected that at least one byte can be sent using datagramBasedSendMessages without blocking. It will not be set if the datagram_based has been closed locally.

IOConditionHup will be set if the connection has been closed locally.

IOConditionErr will be set if there was an asynchronous error in transmitting data previously enqueued using datagramBasedSendMessages.

Note that on Windows, it is possible for an operation to return IOErrorEnumWouldBlock even immediately after datagramBasedConditionCheck has claimed that the DatagramBased is ready for writing. Rather than calling datagramBasedConditionCheck and then writing to the DatagramBased if it succeeds, it is generally better to simply try writing right away, and try again later if the initial attempt returns IOErrorEnumWouldBlock.

It is meaningless to specify IOConditionErr or IOConditionHup 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.

Since: 2.48

conditionWait

datagramBasedConditionWait

Arguments

:: (HasCallStack, MonadIO m, IsDatagramBased a, IsCancellable b)

=> a

datagramBased: a DatagramBased

-> [IOCondition]

condition: a IOCondition mask to wait for

-> Int64

timeout: the maximum time (in microseconds) to wait, 0 to not block, or -1 to block indefinitely

-> Maybe b

cancellable: a Cancellable

-> m ()

(Can throw GError)

Waits for up to timeout microseconds for condition to become true on datagramBased. 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 (IOErrorEnumCancelled or IOErrorEnumTimedOut).

Since: 2.48

createSource

datagramBasedCreateSource

Arguments

:: (HasCallStack, MonadIO m, IsDatagramBased a, IsCancellable b)

=> a

datagramBased: a DatagramBased

-> [IOCondition]

condition: a IOCondition mask to monitor

-> Maybe b

cancellable: a Cancellable

-> m Source

Returns: a newly allocated Source

Creates a Source that can be attached to a MainContext to monitor for the availability of the specified condition on the DatagramBased. The Source keeps a reference to the datagramBased.

The callback on the source is of the DatagramBasedSourceFunc type.

It is meaningless to specify IOConditionErr or IOConditionHup in condition; these conditions will always be reported in the callback if they are true.

If non-Nothing, 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 cancellableIsCancelled.

Since: 2.48

receiveMessages

datagramBasedReceiveMessages

Arguments

:: (HasCallStack, MonadIO m, IsDatagramBased a, IsCancellable b)

=> a

datagramBased: a DatagramBased

-> [InputMessage]

messages: an array of InputMessage structs

-> Int32

flags: an int containing SocketMsgFlags flags for the overall operation

-> Int64

timeout: the maximum time (in microseconds) to wait, 0 to not block, or -1 to block indefinitely

-> Maybe b

cancellable: a GCancellable

-> m Int32

Returns: number of messages received, or -1 on error. Note that the number of messages received may be smaller than numMessages if timeout is zero or positive, if the peer closed the connection, or if numMessages was larger than UIO_MAXIOV (1024), in which case the caller may re-try to receive the remaining messages. (Can throw GError)

Receive one or more data messages from datagramBased in one go.

messages must point to an array of InputMessage structs and numMessages must be the length of this array. Each InputMessage contains a pointer to an array of InputVector structs describing the buffers that the data received in each message will be written to.

flags modify how all messages are received. The commonly available arguments for this are available in the SocketMsgFlags 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 InputMessage.flags.

The other members of InputMessage are treated as described in its documentation.

If timeout is negative the call will block until numMessages have been received, the connection is closed remotely (EOS), cancellable is cancelled, or an error occurs.

If timeout is 0 the call will return up to numMessages without blocking, or IOErrorEnumWouldBlock if no messages are queued in the operating system to be received.

If timeout is positive the call will block on the same conditions as if timeout were negative. If the timeout is reached before any messages are received, IOErrorEnumTimedOut is returned, otherwise it will return the number of messages received before timing out. (Note: This is effectively the behaviour of MSG_WAITFORONE with recvmmsg().)

To be notified when messages are available, wait for the IOConditionIn condition. Note though that you may still receive IOErrorEnumWouldBlock from datagramBasedReceiveMessages even if you were previously notified of a IOConditionIn condition.

If the remote peer closes the connection, any messages queued in the underlying receive buffer will be returned, and subsequent calls to datagramBasedReceiveMessages will return 0 (with no error set).

If the connection is shut down or closed (by calling socketClose or socketShutdown with shutdownRead set, if it’s a Socket, for example), all calls to this function will return IOErrorEnumClosed.

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. If cancellable is cancelled, IOErrorEnumCancelled is returned as with any other error.

Since: 2.48

sendMessages

datagramBasedSendMessages

Arguments

:: (HasCallStack, MonadIO m, IsDatagramBased a, IsCancellable b)

=> a

datagramBased: a DatagramBased

-> [OutputMessage]

messages: an array of OutputMessage structs

-> Int32

flags: an int containing SocketMsgFlags flags

-> Int64

timeout: the maximum time (in microseconds) to wait, 0 to not block, or -1 to block indefinitely

-> Maybe b

cancellable: a GCancellable

-> m Int32

Returns: number of messages sent, or -1 on error. Note that the number of messages sent may be smaller than numMessages if timeout is zero or positive, or if numMessages was larger than UIO_MAXIOV (1024), in which case the caller may re-try to send the remaining messages. (Can throw GError)

Send one or more data messages from datagramBased in one go.

messages must point to an array of OutputMessage structs and numMessages must be the length of this array. Each OutputMessage contains an address to send the data to, and a pointer to an array of OutputVector structs to describe the buffers that the data to be sent for each message will be gathered from.

flags modify how the message is sent. The commonly available arguments for this are available in the SocketMsgFlags 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.

The other members of OutputMessage are treated as described in its documentation.

If timeout is negative the call will block until numMessages have been sent, cancellable is cancelled, or an error occurs.

If timeout is 0 the call will send up to numMessages without blocking, or will return IOErrorEnumWouldBlock if there is no space to send messages.

If timeout is positive the call will block on the same conditions as if timeout were negative. If the timeout is reached before any messages are sent, IOErrorEnumTimedOut is returned, otherwise it will return the number of messages sent before timing out.

To be notified when messages can be sent, wait for the IOConditionOut condition. Note though that you may still receive IOErrorEnumWouldBlock from datagramBasedSendMessages even if you were previously notified of a IOConditionOut condition. (On Windows in particular, this is very common due to the way the underlying APIs work.)

If the connection is shut down or closed (by calling socketClose or socketShutdown with shutdownWrite set, if it’s a Socket, for example), all calls to this function will return IOErrorEnumClosed.

On error -1 is returned and error is set accordingly. An error will only be returned if zero messages could be sent; otherwise the number of messages successfully sent before the error will be returned. If cancellable is cancelled, IOErrorEnumCancelled is returned as with any other error.

Since: 2.48