Copyright	Will Thompson Iñaki García Etxebarria and Jonas Platte
License	LGPL-2.1
Maintainer	Iñaki García Etxebarria
Safe Haskell	None
Language	Haskell2010

GI.Gst.Structs.Poll

Contents

Exported types
Methods

Description

A Poll keeps track of file descriptors much like fd_set (used with select()) or a struct pollfd array (used with poll()). Once created with gst_poll_new(), the set can be used to wait for file descriptors to be readable and/or writable. It is possible to make this wait be controlled by specifying True for the controllable flag when creating the set (or later calling pollSetControllable).

New file descriptors are added to the set using pollAddFd, and removed using pollRemoveFd. Controlling which file descriptors should be waited for to become readable and/or writable are done using pollFdCtlRead, pollFdCtlWrite and pollFdCtlPri.

Use pollWait to wait for the file descriptors to actually become readable and/or writable, or to timeout if no file descriptor is available in time. The wait can be controlled by calling pollRestart and pollSetFlushing.

Once the file descriptor set has been waited for, one can use pollFdHasClosed to see if the file descriptor has been closed, pollFdHasError to see if it has generated an error, pollFdCanRead to see if it is possible to read from the file descriptor, and pollFdCanWrite to see if it is possible to write to it.

Synopsis

newtype Poll = Poll (ManagedPtr Poll)
pollAddFd :: (HasCallStack, MonadIO m) => Poll -> PollFD -> m Bool
pollFdCanRead :: (HasCallStack, MonadIO m) => Poll -> PollFD -> m Bool
pollFdCanWrite :: (HasCallStack, MonadIO m) => Poll -> PollFD -> m Bool
pollFdCtlPri :: (HasCallStack, MonadIO m) => Poll -> PollFD -> Bool -> m Bool
pollFdCtlRead :: (HasCallStack, MonadIO m) => Poll -> PollFD -> Bool -> m Bool
pollFdCtlWrite :: (HasCallStack, MonadIO m) => Poll -> PollFD -> Bool -> m Bool
pollFdHasClosed :: (HasCallStack, MonadIO m) => Poll -> PollFD -> m Bool
pollFdHasError :: (HasCallStack, MonadIO m) => Poll -> PollFD -> m Bool
pollFdHasPri :: (HasCallStack, MonadIO m) => Poll -> PollFD -> m Bool
pollFdIgnored :: (HasCallStack, MonadIO m) => Poll -> PollFD -> m ()
pollGetReadGpollfd :: (HasCallStack, MonadIO m) => Poll -> PollFD -> m ()
pollReadControl :: (HasCallStack, MonadIO m) => Poll -> m Bool
pollRemoveFd :: (HasCallStack, MonadIO m) => Poll -> PollFD -> m Bool
pollRestart :: (HasCallStack, MonadIO m) => Poll -> m ()
pollSetControllable :: (HasCallStack, MonadIO m) => Poll -> Bool -> m Bool
pollSetFlushing :: (HasCallStack, MonadIO m) => Poll -> Bool -> m ()
pollWait :: (HasCallStack, MonadIO m) => Poll -> Word64 -> m Int32
pollWriteControl :: (HasCallStack, MonadIO m) => Poll -> m Bool

Exported types

newtype Poll Source #

Memory-managed wrapper type.

Constructors

Poll (ManagedPtr Poll)

Instances

Instances details

Eq Poll Source #
Instance details Defined in GI.Gst.Structs.Poll Methods (==) :: Poll -> Poll -> Bool (/=) :: Poll -> Poll -> Bool
BoxedPtr Poll Source #
Instance details Defined in GI.Gst.Structs.Poll Methods boxedPtrCopy :: Poll -> IO Poll boxedPtrFree :: Poll -> IO ()
ManagedPtrNewtype Poll Source #
Instance details Defined in GI.Gst.Structs.Poll Methods toManagedPtr :: Poll -> ManagedPtr Poll

Methods

Overloaded methods

addFd

pollAddFd Source #

Arguments

:: (HasCallStack, MonadIO m)
=> Poll	`set`: a file descriptor set.
-> PollFD	`fd`: a file descriptor.
-> m Bool	Returns: `True` if the file descriptor was successfully added to the set.

Add a file descriptor to the file descriptor set.

fdCanRead

pollFdCanRead Source #

Arguments

:: (HasCallStack, MonadIO m)
=> Poll	`set`: a file descriptor set.
-> PollFD	`fd`: a file descriptor.
-> m Bool	Returns: `True` if the descriptor has data to be read.

Check if fd in set has data to be read.

fdCanWrite

pollFdCanWrite Source #

Arguments

:: (HasCallStack, MonadIO m)
=> Poll	`set`: a file descriptor set.
-> PollFD	`fd`: a file descriptor.
-> m Bool	Returns: `True` if the descriptor can be used for writing.

Check if fd in set can be used for writing.

fdCtlPri

pollFdCtlPri Source #

Arguments

:: (HasCallStack, MonadIO m)
=> Poll	`set`: a file descriptor set.
-> PollFD	`fd`: a file descriptor.
-> Bool	`active`: a new status.
-> m Bool	Returns: `True` if the descriptor was successfully updated.

Control whether the descriptor fd in set will be monitored for exceptional conditions (POLLPRI).

Not implemented on Windows (will just return False there).

Since: 1.16

fdCtlRead

pollFdCtlRead Source #

Arguments

:: (HasCallStack, MonadIO m)
=> Poll	`set`: a file descriptor set.
-> PollFD	`fd`: a file descriptor.
-> Bool	`active`: a new status.
-> m Bool	Returns: `True` if the descriptor was successfully updated.

Control whether the descriptor fd in set will be monitored for readability.

fdCtlWrite

pollFdCtlWrite Source #

Arguments

:: (HasCallStack, MonadIO m)
=> Poll	`set`: a file descriptor set.
-> PollFD	`fd`: a file descriptor.
-> Bool	`active`: a new status.
-> m Bool	Returns: `True` if the descriptor was successfully updated.

Control whether the descriptor fd in set will be monitored for writability.

fdHasClosed

pollFdHasClosed Source #

Arguments

:: (HasCallStack, MonadIO m)
=> Poll	`set`: a file descriptor set.
-> PollFD	`fd`: a file descriptor.
-> m Bool	Returns: `True` if the connection was closed.

Check if fd in set has closed the connection.

fdHasError

pollFdHasError Source #

Arguments

:: (HasCallStack, MonadIO m)
=> Poll	`set`: a file descriptor set.
-> PollFD	`fd`: a file descriptor.
-> m Bool	Returns: `True` if the descriptor has an error.

Check if fd in set has an error.

fdHasPri

pollFdHasPri Source #

Arguments

:: (HasCallStack, MonadIO m)
=> Poll	`set`: a file descriptor set.
-> PollFD	`fd`: a file descriptor.
-> m Bool	Returns: `True` if the descriptor has an exceptional condition.

Check if fd in set has an exceptional condition (POLLPRI).

Not implemented on Windows (will just return False there).

Since: 1.16

fdIgnored

pollFdIgnored Source #

Arguments

:: (HasCallStack, MonadIO m)
=> Poll	`set`: a file descriptor set.
-> PollFD	`fd`: a file descriptor.
-> m ()

Mark fd as ignored so that the next call to pollWait will yield the same result for fd as last time. This function must be called if no operation (read/write/recv/send/etc.) will be performed on fd before the next call to pollWait.

The reason why this is needed is because the underlying implementation might not allow querying the fd more than once between calls to one of the re-enabling operations.

getReadGpollfd

pollGetReadGpollfd Source #

Arguments

:: (HasCallStack, MonadIO m)
=> Poll	`set`: a `Poll`
-> PollFD	`fd`: a `PollFD`
-> m ()

Get a GPollFD for the reading part of the control socket. This is useful when integrating with a GSource and GMainLoop.

readControl

pollReadControl Source #

Arguments

:: (HasCallStack, MonadIO m)
=> Poll	`set`: a `Poll`.
-> m Bool	Returns: `True` on success. `False` when when there was no byte to read or reading the byte failed. If there was no byte to read, and only then, errno will contain EWOULDBLOCK or EAGAIN. For all other values of errno this always signals a critical error.

Read a byte from the control socket of the controllable set.

This function only works for timer Poll objects created with gst_poll_new_timer().

removeFd

pollRemoveFd Source #

Arguments

:: (HasCallStack, MonadIO m)
=> Poll	`set`: a file descriptor set.
-> PollFD	`fd`: a file descriptor.
-> m Bool	Returns: `True` if the file descriptor was successfully removed from the set.

Remove a file descriptor from the file descriptor set.

restart

pollRestart Source #

Arguments

:: (HasCallStack, MonadIO m)
=> Poll	`set`: a `Poll`.
-> m ()

Restart any pollWait that is in progress. This function is typically used after adding or removing descriptors to set.

If set is not controllable, then this call will have no effect.

This function only works for non-timer Poll objects created with gst_poll_new().

setControllable

pollSetControllable Source #

Arguments

:: (HasCallStack, MonadIO m)
=> Poll	`set`: a `Poll`.
-> Bool	`controllable`: new controllable state.
-> m Bool	Returns: `True` if the controllability of `set` could be updated.

When controllable is True, this function ensures that future calls to pollWait will be affected by pollRestart and pollSetFlushing.

This function only works for non-timer Poll objects created with gst_poll_new().

setFlushing

pollSetFlushing Source #

Arguments

:: (HasCallStack, MonadIO m)
=> Poll	`set`: a `Poll`.
-> Bool	`flushing`: new flushing state.
-> m ()

When flushing is True, this function ensures that current and future calls to pollWait will return -1, with errno set to EBUSY.

Unsetting the flushing state will restore normal operation of set.

This function only works for non-timer Poll objects created with gst_poll_new().

wait

pollWait Source #

Arguments

:: (HasCallStack, MonadIO m)
=> Poll	`set`: a `Poll`.
-> Word64	`timeout`: a timeout in nanoseconds.
-> m Int32	Returns: The number of `PollFD` in `set` that have activity or 0 when no activity was detected after `timeout`. If an error occurs, -1 is returned and errno is set.

Wait for activity on the file descriptors in set. This function waits up to the specified timeout. A timeout of CLOCK_TIME_NONE waits forever.

For Poll objects created with gst_poll_new(), this function can only be called from a single thread at a time. If called from multiple threads, -1 will be returned with errno set to EPERM.

This is not true for timer Poll objects created with gst_poll_new_timer(), where it is allowed to have multiple threads waiting simultaneously.

writeControl

pollWriteControl Source #

Arguments

:: (HasCallStack, MonadIO m)
=> Poll	`set`: a `Poll`.
-> m Bool	Returns: `True` on success. `False` when when the byte could not be written. errno contains the detailed error code but will never be EAGAIN, EINTR or EWOULDBLOCK. `False` always signals a critical error.

Write a byte to the control socket of the controllable set. This function is mostly useful for timer Poll objects created with gst_poll_new_timer().

It will make any current and future pollWait function return with 1, meaning the control socket is set. After an equal amount of calls to pollReadControl have been performed, calls to pollWait will block again until their timeout expired.

This function only works for timer Poll objects created with gst_poll_new_timer().