Poll Routines

Overview

Poll options

Pollset Flags

// typedefs

typedef struct apr_pollfd_t apr_pollfd_t;
typedef struct apr_pollset_t apr_pollset_t;
typedef struct apr_pollcb_t apr_pollcb_t;

typedef apr_status_t (*apr_pollcb_cb_t)(
    void *baton,
    apr_pollfd_t *descriptor
    );

// enums

enum apr_datatype_e;
enum apr_pollset_method_e;

// structs

struct apr_pollfd_t;

// unions

union apr_descriptor;

// global functions

apr_status_t
apr_pollset_create(
    apr_pollset_t** pollset,
    apr_uint32_t size,
    apr_pool_t* p,
    apr_uint32_t flags
);

apr_status_t
apr_pollset_create_ex(
    apr_pollset_t** pollset,
    apr_uint32_t size,
    apr_pool_t* p,
    apr_uint32_t flags,
    apr_pollset_method_e method
);

apr_status_t
apr_pollset_destroy(apr_pollset_t* pollset);

apr_status_t
apr_pollset_add(
    apr_pollset_t* pollset,
    const apr_pollfd_t* descriptor
);

apr_status_t
apr_pollset_remove(
    apr_pollset_t* pollset,
    const apr_pollfd_t* descriptor
);

apr_status_t
apr_pollset_poll(
    apr_pollset_t* pollset,
    apr_interval_time_t timeout,
    apr_int32_t* num,
    const apr_pollfd_t** descriptors
);

apr_status_t
apr_pollset_wakeup(apr_pollset_t* pollset);

apr_status_t
apr_poll(
    apr_pollfd_t* aprset,
    apr_int32_t numsock,
    apr_int32_t* nsds,
    apr_interval_time_t timeout
);

const char*
apr_pollset_method_name(apr_pollset_t* pollset);

const char*
apr_poll_method_defname(void);

apr_status_t
apr_pollcb_create(
    apr_pollcb_t** pollcb,
    apr_uint32_t size,
    apr_pool_t* p,
    apr_uint32_t flags
);

apr_status_t
apr_pollcb_create_ex(
    apr_pollcb_t** pollcb,
    apr_uint32_t size,
    apr_pool_t* p,
    apr_uint32_t flags,
    apr_pollset_method_e method
);

apr_status_t
apr_pollcb_add(
    apr_pollcb_t* pollcb,
    apr_pollfd_t* descriptor
);

apr_status_t
apr_pollcb_remove(
    apr_pollcb_t* pollcb,
    apr_pollfd_t* descriptor
);

apr_status_t
apr_pollcb_poll(
    apr_pollcb_t* pollcb,
    apr_interval_time_t timeout,
    apr_pollcb_cb_t func,
    void* baton
);

Detailed Documentation

Typedefs

typedef struct apr_pollfd_t apr_pollfd_t

See also:

apr_pollfd_t

typedef struct apr_pollset_t apr_pollset_t

Opaque structure used for pollset API

typedef struct apr_pollcb_t apr_pollcb_t

Opaque structure used for pollcb API

typedef apr_status_t (*apr_pollcb_cb_t)(
    void *baton,
    apr_pollfd_t *descriptor
    )

Function prototype for pollcb handlers

Parameters:

baton	Opaque baton passed into apr_pollcb_poll()
descriptor	Contains the notification for an active descriptor, the rtnevents member contains what events were triggered for this descriptor.

Global Functions

apr_status_t
apr_pollset_create(
    apr_pollset_t** pollset,
    apr_uint32_t size,
    apr_pool_t* p,
    apr_uint32_t flags
)

Set up a pollset object If flags contains APR_POLLSET_THREADSAFE, then a pollset is created on which it is safe to make concurrent calls to apr_pollset_add(), apr_pollset_remove() and apr_pollset_poll() from separate threads. This feature is only supported on some platforms; the apr_pollset_create() call will fail with APR_ENOTIMPL on platforms where it is not supported.

If flags contains APR_POLLSET_WAKEABLE, then a pollset is created with an additional internal pipe object used for the apr_pollset_wakeup() call. The actual size of pollset is in that case size + 1. This feature is only supported on some platforms; the apr_pollset_create() call will fail with APR_ENOTIMPL on platforms where it is not supported.

If flags contains APR_POLLSET_NOCOPY, then the apr_pollfd_t structures passed to apr_pollset_add() are not copied and must have a lifetime at least as long as the pollset.

Some poll methods (including APR_POLLSET_KQUEUE, APR_POLLSET_PORT, and APR_POLLSET_EPOLL) do not have a fixed limit on the size of the pollset. For these methods, the size parameter controls the maximum number of descriptors that will be returned by a single call to apr_pollset_poll().

Parameters:

pollset	The pointer in which to return the newly created object
size	The maximum number of descriptors that this pollset can hold
p	The pool from which to allocate the pollset
flags	Optional flags to modify the operation of the pollset.

apr_status_t
apr_pollset_create_ex(
    apr_pollset_t** pollset,
    apr_uint32_t size,
    apr_pool_t* p,
    apr_uint32_t flags,
    apr_pollset_method_e method
)

Set up a pollset object If flags contains APR_POLLSET_THREADSAFE, then a pollset is created on which it is safe to make concurrent calls to apr_pollset_add(), apr_pollset_remove() and apr_pollset_poll() from separate threads. This feature is only supported on some platforms; the apr_pollset_create_ex() call will fail with APR_ENOTIMPL on platforms where it is not supported.

If flags contains APR_POLLSET_WAKEABLE, then a pollset is created with additional internal pipe object used for the apr_pollset_wakeup() call. The actual size of pollset is in that case size + 1. This feature is only supported on some platforms; the apr_pollset_create_ex() call will fail with APR_ENOTIMPL on platforms where it is not supported.

If flags contains APR_POLLSET_NOCOPY, then the apr_pollfd_t structures passed to apr_pollset_add() are not copied and must have a lifetime at least as long as the pollset.

Some poll methods (including APR_POLLSET_KQUEUE, APR_POLLSET_PORT, and APR_POLLSET_EPOLL) do not have a fixed limit on the size of the pollset. For these methods, the size parameter controls the maximum number of descriptors that will be returned by a single call to apr_pollset_poll().

Parameters:

pollset	The pointer in which to return the newly created object
size	The maximum number of descriptors that this pollset can hold
p	The pool from which to allocate the pollset
flags	Optional flags to modify the operation of the pollset.
method	Poll method to use. See apr_pollset_method_e. If this method cannot be used, the default method will be used unless the APR_POLLSET_NODEFAULT flag has been specified.

apr_status_t
apr_pollset_destroy(apr_pollset_t* pollset)

Destroy a pollset object

Parameters:

pollset

The pollset to destroy

apr_status_t
apr_pollset_add(
    apr_pollset_t* pollset,
    const apr_pollfd_t* descriptor
)

Add a socket or file descriptor to a pollset If you set client_data in the descriptor, that value will be returned in the client_data field whenever this descriptor is signalled in apr_pollset_poll().

If the pollset has been created with APR_POLLSET_THREADSAFE and thread T1 is blocked in a call to apr_pollset_poll() for this same pollset that is being modified via apr_pollset_add() in thread T2, the currently executing apr_pollset_poll() call in T1 will either: (1) automatically include the newly added descriptor in the set of descriptors it is watching or (2) return immediately with APR_EINTR. Option (1) is recommended, but option (2) is allowed for implementations where option (1) is impossible or impractical.

If the pollset has been created with APR_POLLSET_NOCOPY, the apr_pollfd_t structure referenced by descriptor will not be copied and must have a lifetime at least as long as the pollset.

Do not add the same socket or file descriptor to the same pollset multiple times, even if the requested events differ for the different calls to apr_pollset_add(). If the events of interest for a descriptor change, you must first remove the descriptor from the pollset with apr_pollset_remove(), then add it again specifying all requested events.

Parameters:

pollset	The pollset to which to add the descriptor
descriptor	The descriptor to add

apr_status_t
apr_pollset_remove(
    apr_pollset_t* pollset,
    const apr_pollfd_t* descriptor
)

Remove a descriptor from a pollset If the descriptor is not found, APR_NOTFOUND is returned.

If the pollset has been created with APR_POLLSET_THREADSAFE and thread T1 is blocked in a call to apr_pollset_poll() for this same pollset that is being modified via apr_pollset_remove() in thread T2, the currently executing apr_pollset_poll() call in T1 will either: (1) automatically exclude the newly added descriptor in the set of descriptors it is watching or (2) return immediately with APR_EINTR. Option (1) is recommended, but option (2) is allowed for implementations where option (1) is impossible or impractical.

apr_pollset_remove() cannot be used to remove a subset of requested events for a descriptor. The reqevents field in the apr_pollfd_t parameter must contain the same value when removing as when adding.

Parameters:

pollset	The pollset from which to remove the descriptor
descriptor	The descriptor to remove

apr_status_t
apr_pollset_poll(
    apr_pollset_t* pollset,
    apr_interval_time_t timeout,
    apr_int32_t* num,
    const apr_pollfd_t** descriptors
)

Block for activity on the descriptor(s) in a pollset APR_EINTR will be returned if the pollset has been created with APR_POLLSET_WAKEABLE, apr_pollset_wakeup() has been called while waiting for activity, and there were no signalled descriptors at the time of the wakeup call.

Multiple signalled conditions for the same descriptor may be reported in one or more returned apr_pollfd_t structures, depending on the implementation.

Parameters:

pollset	The pollset to use
timeout	The amount of time in microseconds to wait. This is a maximum, not a minimum. If a descriptor is signalled, the function will return before this time. If timeout is negative, the function will block until a descriptor is signalled or until apr_pollset_wakeup() has been called.
num	Number of signalled descriptors (output parameter)
descriptors	Array of signalled descriptors (output parameter)

apr_status_t
apr_pollset_wakeup(apr_pollset_t* pollset)

Interrupt the blocked apr_pollset_poll() call. If the pollset was not created with APR_POLLSET_WAKEABLE the return value is APR_EINIT.

Parameters:

pollset

The pollset to use

apr_status_t
apr_poll(
    apr_pollfd_t* aprset,
    apr_int32_t numsock,
    apr_int32_t* nsds,
    apr_interval_time_t timeout
)

Poll the descriptors in the poll structure The number of descriptors signalled is returned in the third argument. This is a blocking call, and it will not return until either a descriptor has been signalled or the timeout has expired.

The rtnevents field in the apr_pollfd_t array will only be filled- in if the return value is APR_SUCCESS.

Parameters:

aprset	The poll structure we will be using.
numsock	The number of descriptors we are polling
nsds	The number of descriptors signalled (output parameter)
timeout	The amount of time in microseconds to wait. This is a maximum, not a minimum. If a descriptor is signalled, the function will return before this time. If timeout is negative, the function will block until a descriptor is signalled or until apr_pollset_wakeup() has been called.

const char*
apr_pollset_method_name(apr_pollset_t* pollset)

Return a printable representation of the pollset method.

Parameters:

pollset

The pollset to use

const char*
apr_poll_method_defname(void)

Return a printable representation of the default pollset method (APR_POLLSET_DEFAULT).

apr_status_t
apr_pollcb_create(
    apr_pollcb_t** pollcb,
    apr_uint32_t size,
    apr_pool_t* p,
    apr_uint32_t flags
)

Set up a pollcb object Pollcb is only supported on some platforms; the apr_pollcb_create() call will fail with APR_ENOTIMPL on platforms where it is not supported.

Parameters:

pollcb	The pointer in which to return the newly created object
size	The maximum number of descriptors that a single _poll can return.
p	The pool from which to allocate the pollcb
flags	Optional flags to modify the operation of the pollcb.

apr_status_t
apr_pollcb_create_ex(
    apr_pollcb_t** pollcb,
    apr_uint32_t size,
    apr_pool_t* p,
    apr_uint32_t flags,
    apr_pollset_method_e method
)

Set up a pollcb object Pollcb is only supported on some platforms; the apr_pollcb_create_ex() call will fail with APR_ENOTIMPL on platforms where it is not supported.

Parameters:

pollcb	The pointer in which to return the newly created object
size	The maximum number of descriptors that a single _poll can return.
p	The pool from which to allocate the pollcb
flags	Optional flags to modify the operation of the pollcb.
method	Poll method to use. See apr_pollset_method_e. If this method cannot be used, the default method will be used unless the APR_POLLSET_NODEFAULT flag has been specified.

apr_status_t
apr_pollcb_add(
    apr_pollcb_t* pollcb,
    apr_pollfd_t* descriptor
)

Add a socket or file descriptor to a pollcb If you set client_data in the descriptor, that value will be returned in the client_data field whenever this descriptor is signalled in apr_pollcb_poll().

Unlike the apr_pollset API, the descriptor is not copied, and users must retain the memory used by descriptor, as the same pointer will be returned to them from apr_pollcb_poll.

Do not add the same socket or file descriptor to the same pollcb multiple times, even if the requested events differ for the different calls to apr_pollcb_add(). If the events of interest for a descriptor change, you must first remove the descriptor from the pollcb with apr_pollcb_remove(), then add it again specifying all requested events.

Parameters:

pollcb	The pollcb to which to add the descriptor
descriptor	The descriptor to add

apr_status_t
apr_pollcb_remove(
    apr_pollcb_t* pollcb,
    apr_pollfd_t* descriptor
)

Remove a descriptor from a pollcb apr_pollcb_remove() cannot be used to remove a subset of requested events for a descriptor. The reqevents field in the apr_pollfd_t parameter must contain the same value when removing as when adding.

Parameters:

pollcb	The pollcb from which to remove the descriptor
descriptor	The descriptor to remove

apr_status_t
apr_pollcb_poll(
    apr_pollcb_t* pollcb,
    apr_interval_time_t timeout,
    apr_pollcb_cb_t func,
    void* baton
)

Block for activity on the descriptor(s) in a pollcb Multiple signalled conditions for the same descriptor may be reported in one or more calls to the callback function, depending on the implementation.

Parameters:

pollcb	The pollcb to use
timeout	The amount of time in microseconds to wait. This is a maximum, not a minimum. If a descriptor is signalled, the function will return before this time. If timeout is negative, the function will block until a descriptor is signalled.
func	Callback function to call for each active descriptor.
baton	Opaque baton passed to the callback function.