source.h

Includes:

"headerdoc.h"
<dispatch/base.h>
<mach/port.h>
<mach/message.h>
<signal.h>

Introduction

The dispatch framework provides a suite of interfaces for monitoring low- level system objects (file descriptors, Mach ports, signals, VFS nodes, etc.) for activity and automatically submitting event handler blocks to dispatch queues when such activity occurs.

This suite of interfaces is known as the Dispatch Source API.

Functions

dispatch_source_cancel: Asynchronously cancel the dispatch source, preventing any further invocation of its event handler block.
dispatch_source_create: Creates a new dispatch source to monitor low-level system objects and auto- matically submit a handler block to a dispatch queue in response to events.
dispatch_source_get_data: Returns pending data for the dispatch source.
dispatch_source_get_handle: Returns the underlying system handle associated with this dispatch source.
dispatch_source_get_mask: Returns the mask of events monitored by the dispatch source.
dispatch_source_merge_data: Merges data into a dispatch source of type DISPATCH_SOURCE_TYPE_DATA_ADD, DISPATCH_SOURCE_TYPE_DATA_OR or DISPATCH_SOURCE_TYPE_DATA_REPLACE, and submits its event handler block to its target queue.
dispatch_source_set_cancel_handler: Sets the cancellation handler block for the given dispatch source.
dispatch_source_set_cancel_handler_f: Sets the cancellation handler function for the given dispatch source.
dispatch_source_set_event_handler: Sets the event handler block for the given dispatch source.
dispatch_source_set_event_handler_f: Sets the event handler function for the given dispatch source.
dispatch_source_set_registration_handler: Sets the registration handler block for the given dispatch source.
dispatch_source_set_registration_handler_f: Sets the registration handler function for the given dispatch source.
dispatch_source_set_timer: Sets a start time, interval, and leeway value for a timer source.
dispatch_source_testcancel: Tests whether the given dispatch source has been canceled.

dispatch_source_cancel

Asynchronously cancel the dispatch source, preventing any further invocation of its event handler block.

(
    macos(
        10.6),
    ios(
        4.0))  void dispatch_source_cancel(
    dispatch_source_t source);

Parameters

source: The dispatch source to be canceled. The result of passing NULL in this parameter is undefined.

Discussion

Cancellation prevents any further invocation of the event handler block for the specified dispatch source, but does not interrupt an event handler block that is already in progress.

The cancellation handler is submitted to the source's target queue once the the source's event handler has finished, indicating it is now safe to close the source's handle (i.e. file descriptor or mach port).

See dispatch_source_set_cancel_handler() for more information.

dispatch_source_create

Creates a new dispatch source to monitor low-level system objects and auto- matically submit a handler block to a dispatch queue in response to events.

(
    macos(
        10.6),
    ios(
        4.0)) DISPATCH_MALLOC DISPATCH_RETURNS_RETAINED   dispatch_source_t dispatch_source_create(
    dispatch_source_type_t type, 
    uintptr_t handle, 
    uintptr_t mask, 
    dispatch_queue_t _Nullable queue);

Parameters

type: Declares the type of the dispatch source. Must be one of the defined dispatch_source_type_t constants.
handle: The underlying system handle to monitor. The interpretation of this argument is determined by the constant provided in the type parameter.
mask: A mask of flags specifying which events are desired. The interpretation of this argument is determined by the constant provided in the type parameter.
queue: The dispatch queue to which the event handler block will be submitted. If queue is DISPATCH_TARGET_QUEUE_DEFAULT, the source will submit the event handler block to the default priority global queue.

Return Value

The newly created dispatch source. Or NULL if invalid arguments are passed.

Discussion

Dispatch sources are not reentrant. Any events received while the dispatch source is suspended or while the event handler block is currently executing will be coalesced and delivered after the dispatch source is resumed or the event handler block has returned.

Dispatch sources are created in an inactive state. After creating the source and setting any desired attributes (i.e. the handler, context, etc.), a call must be made to dispatch_activate() in order to begin event delivery.

Calling dispatch_set_target_queue() on a source once it has been activated is not allowed (see dispatch_activate() and dispatch_set_target_queue()).

For backward compatibility reasons, dispatch_resume() on an inactive, and not otherwise suspended source has the same effect as calling dispatch_activate(). For new code, using dispatch_activate() is preferred.

dispatch_source_get_data

Returns pending data for the dispatch source.

(
    macos(
        10.6),
    ios(
        4.0))   uintptr_t dispatch_source_get_data(
    dispatch_source_t source);

Parameters

source: The result of passing NULL in this parameter is undefined.

Return Value

The return value should be interpreted according to the type of the dispatch source, and may be one of the following:

DISPATCH_SOURCE_TYPE_DATA_ADD: application defined data DISPATCH_SOURCE_TYPE_DATA_OR: application defined data DISPATCH_SOURCE_TYPE_DATA_REPLACE: application defined data DISPATCH_SOURCE_TYPE_MACH_SEND: dispatch_source_mach_send_flags_t DISPATCH_SOURCE_TYPE_MACH_RECV: n/a DISPATCH_SOURCE_TYPE_MEMORYPRESSURE dispatch_source_memorypressure_flags_t DISPATCH_SOURCE_TYPE_PROC: dispatch_source_proc_flags_t DISPATCH_SOURCE_TYPE_READ: estimated bytes available to read DISPATCH_SOURCE_TYPE_SIGNAL: number of signals delivered since the last handler invocation DISPATCH_SOURCE_TYPE_TIMER: number of times the timer has fired since the last handler invocation DISPATCH_SOURCE_TYPE_VNODE: dispatch_source_vnode_flags_t DISPATCH_SOURCE_TYPE_WRITE: estimated buffer space available

Discussion

This function is intended to be called from within the event handler block. The result of calling this function outside of the event handler callback is undefined.

dispatch_source_get_handle

Returns the underlying system handle associated with this dispatch source.

(
    macos(
        10.6),
    ios(
        4.0))   uintptr_t dispatch_source_get_handle(
    dispatch_source_t source);

Parameters

source: The result of passing NULL in this parameter is undefined.

Return Value

The return value should be interpreted according to the type of the dispatch source, and may be one of the following handles:

DISPATCH_SOURCE_TYPE_DATA_ADD: n/a DISPATCH_SOURCE_TYPE_DATA_OR: n/a DISPATCH_SOURCE_TYPE_DATA_REPLACE: n/a DISPATCH_SOURCE_TYPE_MACH_SEND: mach port (mach_port_t) DISPATCH_SOURCE_TYPE_MACH_RECV: mach port (mach_port_t) DISPATCH_SOURCE_TYPE_MEMORYPRESSURE n/a DISPATCH_SOURCE_TYPE_PROC: process identifier (pid_t) DISPATCH_SOURCE_TYPE_READ: file descriptor (int) DISPATCH_SOURCE_TYPE_SIGNAL: signal number (int) DISPATCH_SOURCE_TYPE_TIMER: n/a DISPATCH_SOURCE_TYPE_VNODE: file descriptor (int) DISPATCH_SOURCE_TYPE_WRITE: file descriptor (int)

dispatch_source_get_mask

Returns the mask of events monitored by the dispatch source.

(
    macos(
        10.6),
    ios(
        4.0))   uintptr_t dispatch_source_get_mask(
    dispatch_source_t source);

Parameters

source: The result of passing NULL in this parameter is undefined.

Return Value

The return value should be interpreted according to the type of the dispatch source, and may be one of the following flag sets:

DISPATCH_SOURCE_TYPE_DATA_ADD: n/a DISPATCH_SOURCE_TYPE_DATA_OR: n/a DISPATCH_SOURCE_TYPE_DATA_REPLACE: n/a DISPATCH_SOURCE_TYPE_MACH_SEND: dispatch_source_mach_send_flags_t DISPATCH_SOURCE_TYPE_MACH_RECV: n/a DISPATCH_SOURCE_TYPE_MEMORYPRESSURE dispatch_source_memorypressure_flags_t DISPATCH_SOURCE_TYPE_PROC: dispatch_source_proc_flags_t DISPATCH_SOURCE_TYPE_READ: n/a DISPATCH_SOURCE_TYPE_SIGNAL: n/a DISPATCH_SOURCE_TYPE_TIMER: dispatch_source_timer_flags_t DISPATCH_SOURCE_TYPE_VNODE: dispatch_source_vnode_flags_t DISPATCH_SOURCE_TYPE_WRITE: n/a

dispatch_source_merge_data

Merges data into a dispatch source of type DISPATCH_SOURCE_TYPE_DATA_ADD, DISPATCH_SOURCE_TYPE_DATA_OR or DISPATCH_SOURCE_TYPE_DATA_REPLACE, and submits its event handler block to its target queue.

(
    macos(
        10.6),
    ios(
        4.0))  void dispatch_source_merge_data(
    dispatch_source_t source,
    uintptr_t value);

Parameters

source: The result of passing NULL in this parameter is undefined.
value: The value to coalesce with the pending data using a logical OR or an ADD as specified by the dispatch source type. A value of zero has no effect and will not result in the submission of the event handler block.

dispatch_source_set_cancel_handler

Sets the cancellation handler block for the given dispatch source.

#if (defined( 1)) 
 (
    macos(
        10.6),
    ios(
        4.0)) DISPATCH_NONNULL1  void dispatch_source_set_cancel_handler(
    dispatch_source_t source, 
    dispatch_block_t _Nullable handler);  
#endif 
/* __BLOCKS__ */

Parameters

source: The dispatch source to modify. The result of passing NULL in this parameter is undefined.
handler: The cancellation handler block to submit to the source's target queue.

Discussion

The cancellation handler (if specified) will be submitted to the source's target queue in response to a call to dispatch_source_cancel() once the system has released all references to the source's underlying handle and the source's event handler block has returned.

IMPORTANT: Source cancellation and a cancellation handler are required for file descriptor and mach port based sources in order to safely close the descriptor or destroy the port. Closing the descriptor or port before the cancellation handler is invoked may result in a race condition. If a new descriptor is allocated with the same value as the recently closed descriptor while the source's event handler is still running, the event handler may read/write data to the wrong descriptor.

dispatch_source_set_cancel_handler_f

Sets the cancellation handler function for the given dispatch source.

(
    macos(
        10.6),
    ios(
        4.0)) DISPATCH_NONNULL1  void dispatch_source_set_cancel_handler_f(
    dispatch_source_t source, 
    dispatch_function_t _Nullable handler);

Parameters

source: The dispatch source to modify. The result of passing NULL in this parameter is undefined.
handler: The cancellation handler function to submit to the source's target queue. The context parameter passed to the event handler function is the current context of the dispatch source at the time the handler call is made.

Discussion

See dispatch_source_set_cancel_handler() for more details.

dispatch_source_set_event_handler

Sets the event handler block for the given dispatch source.

#if (defined( 1)) 
 (
    macos(
        10.6),
    ios(
        4.0)) DISPATCH_NONNULL1  void dispatch_source_set_event_handler(
    dispatch_source_t source, 
    dispatch_block_t _Nullable handler);  
#endif 
/* __BLOCKS__ */

Parameters

source: The dispatch source to modify. The result of passing NULL in this parameter is undefined.
handler: The event handler block to submit to the source's target queue.

dispatch_source_set_event_handler_f

Sets the event handler function for the given dispatch source.

(
    macos(
        10.6),
    ios(
        4.0)) DISPATCH_NONNULL1  void dispatch_source_set_event_handler_f(
    dispatch_source_t source, 
    dispatch_function_t _Nullable handler);

Parameters

source: The dispatch source to modify. The result of passing NULL in this parameter is undefined.
handler: The event handler function to submit to the source's target queue. The context parameter passed to the event handler function is the context of the dispatch source current at the time the event handler was set.

dispatch_source_set_registration_handler

Sets the registration handler block for the given dispatch source.

#if (defined( 1)) 
 (
    macos(
        10.7),
    ios(
        4.3)) DISPATCH_NONNULL1  void dispatch_source_set_registration_handler(
    dispatch_source_t source, 
    dispatch_block_t _Nullable handler);  
#endif 
/* __BLOCKS__ */

Parameters

source: The dispatch source to modify. The result of passing NULL in this parameter is undefined.
handler: The registration handler block to submit to the source's target queue.

Discussion

The registration handler (if specified) will be submitted to the source's target queue once the corresponding kevent() has been registered with the system, following the initial dispatch_resume() of the source.

If a source is already registered when the registration handler is set, the registration handler will be invoked immediately.

dispatch_source_set_registration_handler_f

Sets the registration handler function for the given dispatch source.

(
    macos(
        10.7),
    ios(
        4.3)) DISPATCH_NONNULL1  void dispatch_source_set_registration_handler_f(
    dispatch_source_t source, 
    dispatch_function_t _Nullable handler);

Parameters

source: The dispatch source to modify. The result of passing NULL in this parameter is undefined.
handler: The registration handler function to submit to the source's target queue. The context parameter passed to the registration handler function is the current context of the dispatch source at the time the handler call is made.

Discussion

See dispatch_source_set_registration_handler() for more details.

dispatch_source_set_timer

Sets a start time, interval, and leeway value for a timer source.

(
    macos(
        10.6),
    ios(
        4.0))  void dispatch_source_set_timer(
    dispatch_source_t source, 
    dispatch_time_t start, 
    uint64_t interval, 
    uint64_t leeway);

Parameters

start: The start time of the timer. See dispatch_time() and dispatch_walltime() for more information.
interval: The nanosecond interval for the timer. Use DISPATCH_TIME_FOREVER for a one-shot timer.
leeway: The nanosecond leeway for the timer.

Discussion

Once this function returns, any pending source data accumulated for the previous timer values has been cleared; the next fire of the timer will occur at 'start', and every 'interval' nanoseconds thereafter until the timer source is canceled.

Any fire of the timer may be delayed by the system in order to improve power consumption and system performance. The upper limit to the allowable delay may be configured with the 'leeway' argument, the lower limit is under the control of the system.

For the initial timer fire at 'start', the upper limit to the allowable delay is set to 'leeway' nanoseconds. For the subsequent timer fires at 'start' + N * 'interval', the upper limit is MIN('leeway','interval'/2).

The lower limit to the allowable delay may vary with process state such as visibility of application UI. If the specified timer source was created with a mask of DISPATCH_TIMER_STRICT, the system will make a best effort to strictly observe the provided 'leeway' value even if it is smaller than the current lower limit. Note that a minimal amount of delay is to be expected even if this flag is specified.

The 'start' argument also determines which clock will be used for the timer: If 'start' is DISPATCH_TIME_NOW or was created with dispatch_time(3), the timer is based on up time (which is obtained from mach_absolute_time() on Apple platforms). If 'start' was created with dispatch_walltime(3), the timer is based on gettimeofday(3).

Calling this function has no effect if the timer source has already been canceled.

dispatch_source_testcancel

Tests whether the given dispatch source has been canceled.

(
    macos(
        10.6),
    ios(
        4.0))   intptr_t dispatch_source_testcancel(
    dispatch_source_t source);

Parameters

source: The dispatch source to be tested. The result of passing NULL in this parameter is undefined.

Return Value

Non-zero if canceled and zero if not canceled.

Typedefs

DISPATCH_SOURCE_DECL: Constants of this type represent the class of low-level system object that is being monitored by the dispatch source. Constants of this type are passed as a parameter to dispatch_source_create() and determine how the handle argument is interpreted (i.e. as a file descriptor, mach port, signal number, process identifier, etc.), and how the mask argument is interpreted.
dispatch_source_mach_send_flags_t
dispatch_source_memorypressure_flags_t
dispatch_source_proc_flags_t
dispatch_source_timer_flags_t
dispatch_source_type_t: Constants of this type represent the class of low-level system object that is being monitored by the dispatch source. Constants of this type are passed as a parameter to dispatch_source_create() and determine how the handle argument is interpreted (i.e. as a file descriptor, mach port, signal number, process identifier, etc.), and how the mask argument is interpreted.
dispatch_source_vnode_flags_t

DISPATCH_SOURCE_DECL

Constants of this type represent the class of low-level system object that is being monitored by the dispatch source. Constants of this type are passed as a parameter to dispatch_source_create() and determine how the handle argument is interpreted (i.e. as a file descriptor, mach port, signal number, process identifier, etc.), and how the mask argument is interpreted.

DISPATCH_SOURCE_DECL(
    dispatch_source)     typedef const struct dispatch_source_type_s *dispatch_source_type_t;

See Also

dispatch_source_type_t

Availability

dispatch_source_mach_send_flags_t

typedef unsigned long dispatch_source_mach_send_flags_t;

Constants

DISPATCH_MACH_SEND_DEAD: The receive right corresponding to the given send right was destroyed.

Discussion

Type of dispatch_source_mach_send flags

See Also

DISPATCH_MACH_SEND_DEAD

dispatch_source_memorypressure_flags_t

typedef unsigned long dispatch_source_memorypressure_flags_t;

Constants

DISPATCH_MEMORYPRESSURE_NORMAL: The system memory pressure condition has returned to normal.
DISPATCH_MEMORYPRESSURE_WARN: The system memory pressure condition has changed to warning.
DISPATCH_MEMORYPRESSURE_CRITICAL: The system memory pressure condition has changed to critical.

Discussion

Elevated memory pressure is a system-wide condition that applications registered for this source should react to by changing their future memory use behavior, e.g. by reducing cache sizes of newly initiated operations until memory pressure returns back to normal. NOTE: applications should NOT traverse and discard existing caches for past operations when the system memory pressure enters an elevated state, as that is likely to trigger VM operations that will further aggravate system memory pressure.

See Also

DISPATCH_MEMORYPRESSURE_NORMAL
DISPATCH_MEMORYPRESSURE_WARN
DISPATCH_MEMORYPRESSURE_CRITICAL

dispatch_source_proc_flags_t

typedef unsigned long dispatch_source_proc_flags_t;

Constants

DISPATCH_PROC_EXIT: The process has exited (perhaps cleanly, perhaps not).
DISPATCH_PROC_FORK: The process has created one or more child processes.
DISPATCH_PROC_EXEC: The process has become another executable image via exec*() or posix_spawn*().
DISPATCH_PROC_SIGNAL: A Unix signal was delivered to the process.

Discussion

Type of dispatch_source_proc flags

See Also

DISPATCH_PROC_EXIT
DISPATCH_PROC_FORK
DISPATCH_PROC_EXEC
DISPATCH_PROC_SIGNAL

dispatch_source_timer_flags_t

typedef unsigned long dispatch_source_timer_flags_t;

Constants

DISPATCH_TIMER_STRICT

Specifies that the system should make a best effort to strictly observe the leeway value specified for the timer via dispatch_source_set_timer(), even if that value is smaller than the default leeway value that would be applied to the timer otherwise. A minimal amount of leeway will be applied to the timer even if this flag is specified.

CAUTION: Use of this flag may override power-saving techniques employed by the system and cause higher power consumption, so it must be used with care and only when absolutely necessary.

Discussion

Type of dispatch_source_timer flags

See Also

DISPATCH_TIMER_STRICT

dispatch_source_type_t

DISPATCH_SOURCE_DECL(
    dispatch_source)     typedef const struct dispatch_source_type_s *dispatch_source_type_t;

See Also

DISPATCH_SOURCE_DECL

Availability

dispatch_source_vnode_flags_t

typedef unsigned long dispatch_source_vnode_flags_t;

Constants

DISPATCH_VNODE_DELETE: The filesystem object was deleted from the namespace.
DISPATCH_VNODE_WRITE: The filesystem object data changed.
DISPATCH_VNODE_EXTEND: The filesystem object changed in size.
DISPATCH_VNODE_ATTRIB: The filesystem object metadata changed.
DISPATCH_VNODE_LINK: The filesystem object link count changed.
DISPATCH_VNODE_RENAME: The filesystem object was renamed in the namespace.
DISPATCH_VNODE_REVOKE: The filesystem object was revoked.
DISPATCH_VNODE_FUNLOCK: The filesystem object was unlocked.

Discussion

Type of dispatch_source_vnode flags

See Also

DISPATCH_VNODE_DELETE
DISPATCH_VNODE_WRITE
DISPATCH_VNODE_EXTEND
DISPATCH_VNODE_ATTRIB
DISPATCH_VNODE_LINK
DISPATCH_VNODE_RENAME
DISPATCH_VNODE_REVOKE
DISPATCH_VNODE_FUNLOCK

Macro Definitions

DISPATCH_MACH_SEND_DEAD
DISPATCH_MEMORYPRESSURE_CRITICAL
DISPATCH_MEMORYPRESSURE_NORMAL
DISPATCH_MEMORYPRESSURE_WARN
DISPATCH_PROC_EXEC
DISPATCH_PROC_EXIT
DISPATCH_PROC_FORK
DISPATCH_PROC_SIGNAL
DISPATCH_SOURCE_TYPE_DATA_ADD
DISPATCH_SOURCE_TYPE_DATA_OR
DISPATCH_SOURCE_TYPE_DATA_REPLACE
DISPATCH_SOURCE_TYPE_MACH_RECV
DISPATCH_SOURCE_TYPE_MACH_SEND
DISPATCH_SOURCE_TYPE_MEMORYPRESSURE
DISPATCH_SOURCE_TYPE_PROC
DISPATCH_SOURCE_TYPE_READ
DISPATCH_SOURCE_TYPE_SIGNAL
DISPATCH_SOURCE_TYPE_TIMER
DISPATCH_SOURCE_TYPE_VNODE
DISPATCH_SOURCE_TYPE_WRITE
DISPATCH_TIMER_STRICT
DISPATCH_VNODE_ATTRIB
DISPATCH_VNODE_DELETE
DISPATCH_VNODE_EXTEND
DISPATCH_VNODE_FUNLOCK
DISPATCH_VNODE_LINK
DISPATCH_VNODE_RENAME
DISPATCH_VNODE_REVOKE
DISPATCH_VNODE_WRITE

DISPATCH_MACH_SEND_DEAD

#define DISPATCH_MACH_SEND_DEAD 0x1

Discussion

Type of dispatch_source_mach_send flags

See Also

dispatch_source_mach_send_flags_t

DISPATCH_MEMORYPRESSURE_CRITICAL

#define DISPATCH_MEMORYPRESSURE_CRITICAL 0x04

Discussion

See Also

DISPATCH_MEMORYPRESSURE_NORMAL
DISPATCH_MEMORYPRESSURE_WARN
dispatch_source_memorypressure_flags_t

DISPATCH_MEMORYPRESSURE_NORMAL

#define DISPATCH_MEMORYPRESSURE_NORMAL 0x01

Discussion

See Also

DISPATCH_MEMORYPRESSURE_WARN
DISPATCH_MEMORYPRESSURE_CRITICAL
dispatch_source_memorypressure_flags_t

DISPATCH_MEMORYPRESSURE_WARN

#define DISPATCH_MEMORYPRESSURE_WARN 0x02

Discussion

See Also

DISPATCH_MEMORYPRESSURE_NORMAL
DISPATCH_MEMORYPRESSURE_CRITICAL
dispatch_source_memorypressure_flags_t

DISPATCH_PROC_EXEC

#define DISPATCH_PROC_EXEC 0x20000000

Discussion

Type of dispatch_source_proc flags

See Also

DISPATCH_PROC_EXIT
DISPATCH_PROC_FORK
DISPATCH_PROC_SIGNAL
dispatch_source_proc_flags_t

DISPATCH_PROC_EXIT

#define DISPATCH_PROC_EXIT 0x80000000

Discussion

Type of dispatch_source_proc flags

See Also

DISPATCH_PROC_FORK
DISPATCH_PROC_EXEC
DISPATCH_PROC_SIGNAL
dispatch_source_proc_flags_t

DISPATCH_PROC_FORK

#define DISPATCH_PROC_FORK 0x40000000

Discussion

Type of dispatch_source_proc flags

See Also

DISPATCH_PROC_EXIT
DISPATCH_PROC_EXEC
DISPATCH_PROC_SIGNAL
dispatch_source_proc_flags_t

DISPATCH_PROC_SIGNAL

#define DISPATCH_PROC_SIGNAL 0x08000000

Discussion

Type of dispatch_source_proc flags

See Also

DISPATCH_PROC_EXIT
DISPATCH_PROC_FORK
DISPATCH_PROC_EXEC
dispatch_source_proc_flags_t

DISPATCH_SOURCE_TYPE_DATA_ADD

#define DISPATCH_SOURCE_TYPE_DATA_ADD

Discussion

A dispatch source that coalesces data obtained via calls to dispatch_source_merge_data(). An ADD is used to coalesce the data. The handle is unused (pass zero for now). The mask is unused (pass zero for now).

DISPATCH_SOURCE_TYPE_DATA_OR

#define DISPATCH_SOURCE_TYPE_DATA_OR

Discussion

A dispatch source that coalesces data obtained via calls to dispatch_source_merge_data(). A bitwise OR is used to coalesce the data. The handle is unused (pass zero for now). The mask is unused (pass zero for now).

DISPATCH_SOURCE_TYPE_DATA_REPLACE

#define DISPATCH_SOURCE_TYPE_DATA_REPLACE

Discussion

A dispatch source that tracks data obtained via calls to dispatch_source_merge_data(). Newly obtained data values replace existing data values not yet delivered to the source handler

A data value of zero will cause the source handler to not be invoked.

The handle is unused (pass zero for now). The mask is unused (pass zero for now).

DISPATCH_SOURCE_TYPE_MACH_RECV

#define DISPATCH_SOURCE_TYPE_MACH_RECV

Discussion

A dispatch source that monitors a Mach port for pending messages. The handle is a Mach port with a receive right (mach_port_t). The mask is unused (pass zero for now).

DISPATCH_SOURCE_TYPE_MACH_SEND

#define DISPATCH_SOURCE_TYPE_MACH_SEND

Discussion

A dispatch source that monitors a Mach port for dead name notifications (send right no longer has any corresponding receive right). The handle is a Mach port with a send or send-once right (mach_port_t). The mask is a mask of desired events from dispatch_source_mach_send_flags_t.

DISPATCH_SOURCE_TYPE_MEMORYPRESSURE

#define DISPATCH_SOURCE_TYPE_MEMORYPRESSURE \ 
    (&_dispatch_source_type_memorypressure)

Discussion

A dispatch source that monitors the system for changes in memory pressure condition. The handle is unused (pass zero for now). The mask is a mask of desired events from dispatch_source_memorypressure_flags_t.

DISPATCH_SOURCE_TYPE_PROC

#define DISPATCH_SOURCE_TYPE_PROC

Discussion

A dispatch source that monitors an external process for events defined by dispatch_source_proc_flags_t. The handle is a process identifier (pid_t). The mask is a mask of desired events from dispatch_source_proc_flags_t.

DISPATCH_SOURCE_TYPE_READ

#define DISPATCH_SOURCE_TYPE_READ

Discussion

A dispatch source that monitors a file descriptor for pending bytes available to be read. The handle is a file descriptor (int). The mask is unused (pass zero for now).

DISPATCH_SOURCE_TYPE_SIGNAL

#define DISPATCH_SOURCE_TYPE_SIGNAL

Discussion

A dispatch source that monitors the current process for signals. The handle is a signal number (int). The mask is unused (pass zero for now).

DISPATCH_SOURCE_TYPE_TIMER

#define DISPATCH_SOURCE_TYPE_TIMER

Discussion

A dispatch source that submits the event handler block based on a timer. The handle is unused (pass zero for now). The mask specifies which flags from dispatch_source_timer_flags_t to apply.

DISPATCH_SOURCE_TYPE_VNODE

#define DISPATCH_SOURCE_TYPE_VNODE

Discussion

A dispatch source that monitors a file descriptor for events defined by dispatch_source_vnode_flags_t. The handle is a file descriptor (int). The mask is a mask of desired events from dispatch_source_vnode_flags_t.

DISPATCH_SOURCE_TYPE_WRITE

#define DISPATCH_SOURCE_TYPE_WRITE

Discussion

A dispatch source that monitors a file descriptor for available buffer space to write bytes. The handle is a file descriptor (int). The mask is unused (pass zero for now).