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* This file is subject to the terms of the GFX License. If a copy of
* the license was not distributed with this file, you can obtain one at:
* @file src/gevent/gevent.h
* @addtogroup GEVENT
* @brief Module to build a complete many-to-many event system
* @details GEVENT provides a simple to use but yet powerful event
* system.
* @pre GFX_USE_GEVENT must be set to GFXON in your gfxconf.h
* @{
#ifndef _GEVENT_H
#define _GEVENT_H
#include "../../gfx.h"
#if GFX_USE_GEVENT || defined(__DOXYGEN__)
/* Type definitions */
typedef gU16 GEventType;
#define GEVENT_NULL 0x0000 // Null Event - Do nothing
#define GEVENT_EXIT 0x0001 // The listener is being forced to exit (someone is destroying the listener)
/* Other event types are allocated in ranges in their respective include files */
#define GEVENT_GINPUT_FIRST 0x0100 // GINPUT events range from 0x0100 to 0x01FF
#define GEVENT_GWIN_FIRST 0x0200 // GWIN events range from 0x0200 to 0x02FF
#define GEVENT_GADC_FIRST 0x0300 // GADC events range from 0x0300 to 0x033F
#define GEVENT_GAUDIO_FIRST 0x0340 // GAUDIO events range from 0x0340 to 0x037F
#define GEVENT_USER_FIRST 0x8000 // Any application defined events start at 0x8000
// This object can be typecast to any GEventXxxxx type to allow any sub-system (or the application) to create events.
// The prerequisite is that the new status structure type starts with a field named 'type' of type 'GEventType'.
// The total status structure also must not exceed GEVENT_MAXIMUM_SIZE bytes.
// For example, this is used by GWIN button events, GINPUT data streams etc.
typedef union GEvent_u {
GEventType type; // The type of this event
char pad[GEVENT_MAXIMUM_SIZE]; // This is here to allow static initialisation of GEventObject's in the application.
} GEvent;
// A special callback function
typedef void (*GEventCallbackFn)(void *param, GEvent *pe);
// The Listener Object
typedef struct GListener {
gSem waitqueue; // Private: Semaphore for the listener to wait on.
gU16 flags; // Private: Flags for operation
GEventCallbackFn callback; // Private: Call back Function
void *param; // Private: Parameter for the callback function.
GEvent event; // Public: The event object into which the event information is stored.
} GListener;
// The Source Object
typedef struct GSource_t GSource, *GSourceHandle;
// This structure is passed to a source to describe a contender listener for sending the current event.
typedef struct GSourceListener_t {
GListener *pListener; // The listener
GSource *pSource; // The source
gU32 listenflags; // The flags the listener passed when the source was assigned to it.
gU32 srcflags; // For the source's exclusive use. Initialised as 0 for a new listener source assignment.
} GSourceListener;
/* External declarations. */
/* How to listen for events (act as a Listener)...
1. Get handles for all the event sources you are interested in.
2. Initialise a listener
3. Attach sources to your listener.
- Sources can be attached or detached from a listener at any time.
- A source can be attached to more than one listener.
4. Loop on getting listener events
5. When finished detach all sources from the listener
How to create events (act as a Source)...
1. Provide a funtion to the application that returns a GSourceHandle (which can be a pointer to whatever the source wants)
2. Whenever a possible event occurs call geventGetSourceListener() to get a pointer to a GSourceListener.
This will return NULL when there are no more listeners.
For each listener - check the flags to see if an event should be sent.
- use geventGetEventBuffer() to get the event buffer supplied by the listener
and then call geventSendEvent() to send the event.
- Note: geventGetEventBuffer() may return gFalse to indicate the listener is currently not listening and
therefore no event should be sent. This situation enables the source to (optionally) flag
to the listener on its next wait that there have been missed events.
- Note: The GSourceListener pointer (and the GEvent buffer) are only valid between
the geventGetSourceListener() call and either the geventSendEvent call or the next
geventGetSourceListener() call.
- Note: All listeners must be processed for this event before anything else is processed.
/*---------- Listener Functions --------------------------------------------*/
* @brief Create a Listener
* @details If insufficient resources are available it will either assert or return NULL
* depending on the value of GEVENT_ASSERT_NO_RESOURCE.
* @param[in] pl A listener
void geventListenerInit(GListener *pl);
* @brief Attach a source to a listener
* @details Flags are interpreted by the source when generating events for each listener.
* If this source is already assigned to the listener it will update the flags.
* If insufficient resources are available it will either assert or return gFalse
* depending on the value of GEVENT_ASSERT_NO_RESOURCE.
* @param[in] pl The listener
* @param[in] gsh The source which has to be attached to the listener
* @param[in] flags The flags
* @return gTrue if succeeded, gFalse otherwise
gBool geventAttachSource(GListener *pl, GSourceHandle gsh, gU32 flags);
* @brief Detach a source from a listener
* @details If gsh is NULL detach all sources from this listener and if there is still
* a thread waiting for events on this listener, it is sent the exit event.
* @param[in] pl The listener
* @param[in] gsh The source
void geventDetachSource(GListener *pl, GSourceHandle gsh);
* @brief Wait for an event on a listener from an assigned source.
* @details The type of the event should be checked (pevent->type) and then pevent should
* be typecast to the actual event type if it needs to be processed.
* gDelayForever means no timeout - wait forever for an event.
* gDelayNone means return immediately
* @note The returned GEvent is released when this routine is called again
* or when optionally @p geventEventComplete() is called. Calling @p geventEventComplete()
* allows the GEvent object to be reused earlier which can reduce missed events. The GEvent
* object MUST NOT be used after this function is called (and is blocked waiting for the next
* event) or after geventEventComplete() is called.
* The one listener object should not be waited on using more than one thread simultanously
* because of the implicit geventEventComplete() that occurs when this function is called.
* @param[in] pl The listener
* @param[in] timeout The timeout in milliseconds
* @return NULL on timeout
GEvent *geventEventWait(GListener *pl, gDelay timeout);
* @brief Release the GEvent buffer associated with a listener.
* @details The GEvent returned by @p geventEventWait() is released.
* @note The GEvent pointer returned by @p geventEventWait() is released when @p geventEventWait()
* is called again or when this function is called. The GEvent
* object MUST NOT be used after this function is called.
* @param[in] pl The listener
void geventEventComplete(GListener *pl);
/* @brief Register a callback for an event on a listener from an assigned source.
* @details The type of the event should be checked (pevent->type) and then pevent should be typecast to the
* actual event type if it needs to be processed.
* @params[in] pl The Listener
* @params[in] fn The function to call back
* @params[in] param A parameter to pass the callback function
* @note The GEvent buffer is valid only during the time of the callback. The callback MUST NOT save
* a pointer to the buffer for use outside the callback.
* @note An existing callback function is de-registered by passing a NULL for 'fn'. Any existing
* callback function is replaced. Any thread currently waiting using geventEventWait will be sent the exit event.
* @note Callbacks occur in a thread context but stack space must be kept to a minumum and
* the callback must process quickly as all other events are performed on a single thread.
* @note In the callback function you should never call ANY event functions using your own GListener handle
* as it WILL create a deadlock and lock the system up.
* @note Applications should not use this call - geventEventWait() is the preferred mechanism for an
* application. This call is provided for GUI objects that may not have their own thread.
void geventRegisterCallback(GListener *pl, GEventCallbackFn fn, void *param);
/*---------- Source Functions --------------------------------------------*/
* @brief Called by a source with a possible event to get a listener record.
* @details @p lastlr should be NULL on the first call and thereafter the result of the previous call.
* @param[in] gsh The source handler
* @param[in] lastlr The source listener
* @return NULL when there are no more listeners for this source
GSourceListener *geventGetSourceListener(GSourceHandle gsh, GSourceListener *lastlr);
* @brief Get the event buffer from the GSourceListener.
* @details A NULL return allows the source to record (perhaps in glr->scrflags) that the listener
* has missed events. This can then be notified as part of the next event for the listener.
* The buffer can only be accessed untill the next call to @p geventGetSourceListener()
* or @p geventSendEvent()
* @param[in] psl The source listener
* @return NULL if the event buffer for this listener is currently in use.
GEvent *geventGetEventBuffer(GSourceListener *psl);
* @brief Called by a source to indicate the listener's event buffer has been filled.
* @details After calling this function the source must not reference in fields in the @p GSourceListener or the event buffer.
* @param[in] psl The source listener
void geventSendEvent(GSourceListener *psl);
* @brief Detach any listener that has this source attached
* @param[in] gsh The source handle
void geventDetachSourceListeners(GSourceHandle gsh);
#endif /* GFX_USE_GEVENT */
#endif /* _GEVENT_H */
/** @} */