Added AFB Helper Guide in Developer Guides

Revised and added AFB Helper Guide as a part of Developer Guides.

Bug-AGL: [SPEC-3633]

Signed-off-by: Shankho Boron Ghosh <shankhoghosh123@gmail.com>
Change-Id: I3df9265ae0570e987d80bc4bd2d3d14e7743b26a

1 files changed, 50 insertions, 0 deletions

diff --git a/docs/3_Developer_Guides/4_AFB_Helper_Guide/2_AFB_Timer.md b/docs/3_Developer_Guides/4_AFB_Helper_Guide/2_AFB_Timer.md
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+---
+title: AFB Timer functions
+---
+
+## TimerHandleT
+
+Members are:
+
+* `count`: integer representing the number of times the timers should run.
+* `delay`: millisecond integer representing the delay to wait before and between
+ the callback run.
+* `uid`: a string identifying the timer.
+* `context`: an opaq pointer that could be used in the callback function.
+* `evtSource`: a systemd event source struct. Should be NULL.
+* `api`: the AFB api pointer.
+* `callback`: a function pointer for the callback to call at timer expiration
+* `freeCB`: a function pointer called after expiration of the timer. Mainly meant
+ to release the context pointer by example.
+
+## void TimerEvtStart(afb_api_t api, TimerHandleT *timerHandle, timerCallbackT callback, void *context)
+
+Start a timer which invokes the callback when the delay expires for `count`
+times.
+
+* `api`: AFB api pointer.
+* `timerHandle`: pointer to struct representing a timer.
+* `callback`: a function pointer for the callback to call at timer expiration
+* `context`: an opaq pointer that could be used in the callback function.
+
+## void TimerEvtStop(TimerHandleT *timerHandle)
+
+Manually stop the timer's run. If the `count` isn't finished then it will end
+the timer and no other runs will occur.
+
+* `timerHandle`: pointer to struct representing a timer.
+
+## uint64_t LockWait(afb_api_t api, uint64_t utimeout)
+
+It is function acting like a non-blocking sleep for an API. It lets the main API
+event loop runs while you are waiting and will unlock at the first received
+event and returns the remaining time to wait if an event occurs or 0 if no events
+occured and timeout hits. Then you have to manually ensure that once an event
+has been received that it was the one you are waiting for and if not launch again
+the wait with the remaining time returned.
+
+* `api`: AFB api pointer.
+* `timeout`: timeout in microsecond.
+
+Returns the remaining time in microsecond to wait if an event occurs or 0 if no
+events occured and timeout hits.
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