le_eventLoop.h

    1 /**
    2  * @page c_eventLoop Event Loop API
    3  *
    4  * @subpage le_eventLoop.h "API Reference"
    5  *
    6  * <HR>
    7  *
    8  * The Event Loop API supports the event-driven programming model, which is favoured in Legato
    9  * (but not forced).  Each thread that uses this system has a central <b>event loop</b>
   10  * which calls <b>event handler</b> functions in response to <b>event reports</b>.
   11  *
   12  * Software components register their event handler functions with the event system (either
   13  * directly through the Event Loop API or indirectly through other APIs that use the Event Loop API)
   14  * so the central event loop knows the functions to call in response to defined events.
   15  *
   16  * Every event loop has an <b>event queue</b>, which is a queue of events waiting to be handled by
   17  * that event loop.
   18  *
   19  * @note When the process dies, all events, event loops, queues, reports, and handlers will be
   20  * automatically cleared.
   21  *
   22  * The following different usage patterns are supported by the Event Loop API:
   23  *
   24  * @ref c_event_deferredFunctionCalls <br>
   25  * @ref c_event_dispatchingToOtherThreads <br>
   26  * @ref c_event_publishSubscribe <br>
   27  * @ref c_event_layeredPublishSubscribe <br>
   28  *
   29  * Other Legato C Runtime Library APIs using the event loop include:
   30  *
   31  * @ref c_fdMonitor <br>
   32  * @ref c_timer <br>
   33  * @ref c_args <br>
   34  * @ref c_signals <br>
   35  * @ref c_messaging <br>
   36  *
   37  *
   38  * @section c_event_deferredFunctionCalls Deferred Function Calls
   39  *
   40  * A basic Event Queue usage is to queue a function for the Event Loop to call
   41  * later (when that function gets to the head of the Event Queue) by calling l@c e_event_QueueFunction().
   42  *
   43  * This code sample has a component initialization function queueing another function
   44  * to be call later, by the process's main thread when the Event Loop is running.  Two
   45  * parameters are needed by the deferred function.  The third is just filled with NULL and ignored
   46  * by the deferred function.
   47  *
   48  * @code
   49  * static void MyDeferredFunction
   50  * (
   51  *     void* param1Ptr,
   52  *     void* param2Ptr
   53  * )
   54  * {
   55  *     // Type cast the parameters to what they really are and do whatever it is that
   56  *     // I need to do with them.
   57  * }
   58  *
   59  * ...
   60  *
   61  * COMPONENT_INIT
   62  * {
   63  *     le_event_QueueFunction(MyDeferredFunction, firstParamPtr, secondParamPtr);
   64  * }
   65  * @endcode
   66  *
   67  * Deferred function calls are useful when implementing APIs with asynchronous
   68  * result call-backs. If an error is detected before the API function returns, it can't just
   69  * call the call-back directly, because it could cause re-entrancy problems in the client code
   70  * or cause recursive loops.  Instead of forcing the API function to return an error code
   71  * in special cases (which will increase the client's code complexity and may leak API
   72  * implementation details to the client), the API function can defers executing the
   73  * call-back until later by queuing an error handling function onto the Event Queue.
   74  *
   75  * @section c_event_dispatchingToOtherThreads Dispatching Function Execution to Other Threads
   76  *
   77  * In multi-threaded programs, sometimes the implementor needs
   78  * to ask another thread to run a function because:
   79  * - The function to be executed takes a long time, but doesn't have to be done at a high priority.
   80  * - A call needs to be made into a non-thread-safe API function.
   81  * - A blocking function needs to be called, but the current thread can't afford to block.
   82  *
   83  * To assist with this, the Event Loop API provides @c le_event_QueueFunctionToThread(). It
   84  * works the same as le_event_QueueFunction(), except that it queues the function onto a
   85  * specific thread's Event Queue.
   86  *
   87  * If the other thread isn't running the Event Loop, then the queued function will
   88  * never be executed.
   89  *
   90  * This code sample shows two arguments started by the process's main
   91  * thread, and executed in the background by a low-priority thread. The result is reported back
   92  * to the client through a completion callback running in the same thread that requested that the
   93  * computation be performed.
   94  *
   95  * @code
   96  * static le_mem_PoolRef_t ComputeRequestPool;
   97  * static le_thread_Ref_t LowPriorityThreadRef;
   98  *
   99  * typedef struct
  100  * {
  101  *     size_t           arg1;                                   // First argument
  102  *     size_t           arg2;                                   // Second argument
  103  *     ssize_t          result;                                 // The result
  104  *     void           (*completionCallback)(ssize_t result);    // The client's completion callback
  105  *     le_thread_Ref_t  requestingThreadRef;                    // The client's thread.
  106  * }
  107  * ComputeRequest_t;
  108  *
  109  * // Main function of low-priority background thread.
  110  * static void* LowPriorityThreadMain
  111  * (
  112  *     void* contextPtr // not used.
  113  * )
  114  * {
  115  *     le_event_RunLoop();
  116  * }
  117  *
  118  * COMPONENT_INIT
  119  * {
  120  *     ComputeRequestPool = le_mem_CreatePool("Compute Request", sizeof(ComputeRequest_t));
  121  *
  122  *     LowPriorityThreadRef = le_thread_Create("Background Computation Thread",
  123  *                                             LowPriorityThreadMain,
  124  *                                             NULL);
  125  *     le_thread_SetPriority(LowPriorityThreadRef, LE_THREAD_PRIORITY_IDLE);
  126  *     le_thread_Start(LowPriorityThreadRef);
  127  * }
  128  *
  129  * // This function gets run by a low-priority, background thread.
  130  * static void ComputeResult
  131  * (
  132  *     void* param1Ptr, // request object pointer
  133  *     void* param2Ptr  // not used
  134  * )
  135  * {
  136  *     ComputeRequest_t* requestPtr = param1Ptr;
  137  *
  138  *     requestPtr->result = DoSomeReallySlowComputation(requestPtr->arg1, requestPtr->arg2);
  139  *
  140  *     le_event_QueueFunctionToThread(requestPtr->requestingThreadRef,
  141  *                                    ProcessResult,
  142  *                                    requestPtr,
  143  *                                    NULL);
  144  * }
  145  *
  146  * // This function gets called by a component running in the main thread.
  147  * static void ComputeResultInBackground
  148  * (
  149  *      size_t arg1,
  150  *      size_t arg2,
  151  *      void (*completionCallback)(ssize_t result)
  152  * )
  153  * {
  154  *     ComputeRequest_t* requestPtr = le_mem_ForceAlloc(ComputeRequestPool);
  155  *     requestPtr->arg1 = arg1;
  156  *     requestPtr->arg2 = arg2;
  157  *     requestPtr->requestingThreadRef = le_thread_GetCurrent();
  158  *     requestPtr->completionCallback = completionCallback;
  159  *     le_event_QueueFunctionToThread(LowPriorityThreadRef,
  160  *                                    ComputeResult,
  161  *                                    requestPtr,
  162  *                                    NULL);
  163  * }
  164  *
  165  * // This function gets run by the main thread.
  166  * static void ProcessResult
  167  * (
  168  *     void* param1Ptr, // request object pointer
  169  *     void* param2Ptr  // not used
  170  * )
  171  * {
  172  *     ComputeRequest_t* requestPtr = param1Ptr;
  173  *     completionCallback(requestPtr->result);
  174  *     le_mem_Release(requestPtr);
  175  * }
  176  * @endcode
  177  *
  178  * @section c_event_publishSubscribe Publish-Subscribe Events
  179  *
  180  * In the publish-subscribe pattern, someone publishes information and if anyone cares about
  181  * that information, they subscribe to receive it. The publisher doesn't have to know whether
  182  * anything is listening, or how many subscribers might be listening.
  183  * Likewise, the subscribers don't have to know whether anything is publishing or how many
  184  * publishers there might be.  This decouples publishers and subscribers.
  185  *
  186  * Subscribers @b add handlers for events and wait for those handlers to be executed.
  187  *
  188  * Publishers @b report events.
  189  *
  190  * When an event report reaches the front of an Event Queue, the Event Loop will pop it from the
  191  * queue and call any handlers that have been registered for that event.
  192  *
  193  * Events are identified using an <b> Event ID </b> created by calling
  194  * @c le_event_CreateId() before registering an handler for that event or report.
  195  * Any thread within the process with an Event ID can register a handler or report
  196  * events.
  197  *
  198  * @note These Event IDs are only valid within the process where they were created. The
  199  *       Event Loop API can't be used for inter-process communication (IPC).
  200  *
  201  * @code
  202  * le_event_Id_t eventId = le_event_CreateId("MyEvent", sizeof(MyEventReport_t));
  203  * @endcode
  204  *
  205  * Event reports can carry a payload. The size and format of the payload depends on the type of
  206  * event.  For example, reports of temperature changes may need to carry the new temperature.
  207  * To support this, @c le_event_CreateId() takes the payload size as a parameter.
  208  *
  209  * To report an event, the publisher builds their report payload in their own buffer and passes
  210  * a pointer to that buffer (and its size) to @c le_event_Report():
  211  *
  212  * @code
  213  * MyEventReport_t report;
  214  * ...     // Fill in the event report.
  215  * le_event_Report(EventId, &report, sizeof(report));
  216  * @endcode
  217  *
  218  * This  results in the report getting queued to the Event Queues of all threads with
  219  * handlers registered for that event ID.
  220  *
  221  * To register a handler, the subscriber calls @c le_event_AddHandler().
  222  *
  223  * @note    It's okay to have a payload size of zero, in which case NULL can be passed into
  224  *          le_event_Report().
  225  *
  226  * @code
  227  * le_event_HandlerRef_t handlerRef = le_event_AddHandler("MyHandler", eventId, MyHandlerFunc);
  228  * @endcode
  229  *
  230  * When an event report reaches the front of a thread's Event Queue, that thread's Event Loop
  231  * reads the report and then:
  232  * - Calls the handler functions registered by that thread.
  233  * - Points to the report payload passed to the handler as a parameter.
  234  * - Reports the payload was deleted on return, so the handler
  235  * function must copy any contents to keep.
  236  *
  237  * @code
  238  * static void MyHandlerFunc
  239  * (
  240  *     void* reportPayloadPtr
  241  * )
  242  * {
  243  *     MyEventReport_t* reportPtr = reportPayloadPtr;
  244  *     // Process the report.
  245  *     ...
  246  * }
  247  * @endcode
  248  *
  249  * Another opaque pointer, called the <b> context pointer </b> can be set for
  250  * the handler using @c le_event_SetContextPtr().  When the handler function is called, it can call
  251  * le_event_GetContextPtr() to fetch the context pointer.
  252  *
  253  * @code
  254  * static void MyHandlerFunc
  255  * (
  256  *     void* reportPayloadPtr
  257  * )
  258  * {
  259  *     MyEventReport_t* reportPtr = reportPayloadPtr;
  260  *     MyContext_t* contextPtr = le_event_GetContextPtr();
  261  *
  262  *     // Process the report.
  263  *     ...
  264  * }
  265  *
  266  * COMPONENT_INIT
  267  * {
  268  *     MyEventId = le_event_CreateId("MyEvent", sizeof(MyEventReport_t));
  269  *
  270  *     MyHandlerRef = le_event_AddHandler("MyHandler", MyEventId, MyHandlerFunc);
  271  *     le_event_SetContextPtr(MyHandlerRef, sizeof(float));
  272  * }
  273  * @endcode
  274  *
  275  * Finally, le_event_RemoveHandler() can be used to remove an event handler registration,
  276  * if necessary.
  277  *
  278  * @code
  279  * le_event_RemoveHandler(MyHandlerRef);
  280  * @endcode
  281  *
  282  * If a handler is removed after the report for that event has been added to the event queue, but
  283  * before the report reaches the head of the queue, then the handler will not be called.
  284  *
  285  * @note To prevent race conditions, it's not permitted for one thread to remove another thread's
  286  * handlers.
  287  *
  288  * @section c_event_layeredPublishSubscribe Layered Publish-Subscribe Handlers
  289  *
  290  * If you need to implement an API that allows clients to register "handler"
  291  * functions to be called-back after a specific event occurs, the Event Loop API
  292  * provides some special help.
  293  *
  294  * You can have the Event Loop call your handler function (the first-layer handler),
  295  * to unpack specified items from the Event Report and call the client's handler function (the
  296  * second-layer handler).
  297  *
  298  * For example, you could create a "Temperature Sensor API" that allows its clients to register
  299  * handler functions to be called to handle changes in the temperature, like this:
  300  *
  301  * @code
  302  * // Temperature change handler functions must look like this.
  303  * typedef void (*tempSensor_ChangeHandlerFunc_t)(int32_t newTemperature, void* contextPtr);
  304  *
  305  * // Opaque type used to refer to a registered temperature change handler.
  306  * typedef struct tempSensor_ChangeHandler* tempSensor_ChangeHandlerRef_t;
  307  *
  308  * // Register a handler function to be called when the temperature changes.
  309  * tempSensor_ChangeHandlerRef_t tempSensor_AddChangeHandler
  310  * (
  311  *     tempSensor_ChangeHandlerFunc_t  handlerFunc,  // The handler function.
  312  *     void*                           contextPtr    // Opaque pointer to pass to handler function.
  313  * );
  314  *
  315  * // De-register a handler function that was previously registered using
  316  * // tempSensor_AddChangeHandler().
  317  * void tempSensor_RemoveChangeHandler
  318  * (
  319  *     tempSensor_ChangeHandlerRef_t  handlerRef
  320  * );
  321  * @endcode
  322  *
  323  * The implementation could look like this:
  324  *
  325  * @code
  326  * COMPONENT_INIT
  327  * {
  328  *     TempChangeEventId = le_event_CreateId("TempChange", sizeof(int32_t));
  329  * }
  330  *
  331  * static void TempChangeHandler
  332  * (
  333  *     void* reportPtr,
  334  *     void* secondLayerHandlerFunc
  335  * )
  336  * {
  337  *     int32_t* temperaturePtr = reportPtr;
  338  *     tempSensor_ChangeHandlerRef_t clientHandlerFunc = secondLayerHandlerFunc;
  339  *
  340  *     clientHandlerFunc(*temperaturePtr, le_event_GetContextPtr());
  341  * }
  342  *
  343  * tempSensor_ChangeHandlerRef_t tempSensor_AddChangeHandler
  344  * (
  345  *     tempSensor_ChangeHandlerFunc_t  handlerFunc,
  346  *     void*                           contextPtr
  347  * )
  348  * {
  349  *     le_event_HandlerRef_t handlerRef;
  350  *
  351  *     handlerRef = le_event_AddLayeredHandler("TempChange",
  352  *                                             TempChangeEventId,
  353  *                                             TempChangeHandler,
  354  *                                             handlerFunc);
  355  *     le_event_SetContextPtr(handlerRef, contextPtr);
  356  *
  357  *     return (tempSensor_ChangeHandlerRef_t)handlerRef;
  358  * }
  359  *
  360  * void tempSensor_RemoveChangeHandler
  361  * (
  362  *     tempSensor_ChangeHandlerRef_t    handlerRef
  363  * )
  364  * {
  365  *     le_event_RemoveHandler((le_event_HandlerRef_t)handlerRef);
  366  * }
  367  * @endcode
  368  *
  369  *This approach gives strong type checking of both handler references and handler
  370  * function pointers in code that uses this Temperature Sensor API.
  371  *
  372  *
  373  * @section c_event_reportingRefCountedObjects Event Reports Containing Reference-Counted Objects
  374  *
  375  *Sometimes you need to report an event where the report payload is pointing to a
  376  * reference-counted object allocated from a memory pool (see @ref c_memory).
  377  * Memory leaks and/or crashes can result if its is sent through the Event Loop API
  378  * without telling the Event Loop API it's pointing to a reference counted object.
  379  * If there are no subscribers, the Event Loop API iscards the reference without releasing it,
  380  * and the object is never be deleted. If multiple handlers are registered,
  381  * the reference could be released by the handlers too many times. Also, there are
  382  * other, subtle issues that are nearly impossible to solve if threads terminate while
  383  * reports containing pointers to reference-counted objects are on their Event Queues.
  384  *
  385  * To help with this, the functions @c le_event_CreateIdWithRefCounting() and
  386  * @c le_event_ReportWithRefCounting() have been provided. These allow a pointer to a
  387  * reference-counted memory pool object to be sent as the payload of an Event Report.
  388  *
  389  * @c le_event_ReportWithRefCounting() passes ownership of one reference to the Event Loop API, and
  390  * when the handler is called, it receives ownership for one reference.  It then becomes
  391  * the handler's responsibility to release its reference (using le_mem_Release()) when it's done.
  392  *
  393  *
  394  * @c le_event_CreateIdWithRefCounting() is used the same way as le_event_CreateId(), except that
  395  * it doesn't require a payload size as the payload is always
  396  * known from the pointer to a reference-counted memory pool object.  Only Event IDs
  397  * created using le_event_CreateIdWithRefCounting() can be used with
  398  * le_event_ReportWithRefCounting().
  399  *
  400  * @code
  401  * static le_event_Id_t EventId;
  402  * le_mem_PoolRef_t MyObjectPoolRef;
  403  *
  404  * static void MyHandler
  405  * (
  406  *     void* reportPtr  // Pointer to my reference-counted object.
  407  * )
  408  * {
  409  *     MyObj_t* objPtr = reportPtr;
  410  *
  411  *     // Do something with the object.
  412  *     ...
  413  *
  414  *     // Okay, I'm done with the object now.
  415  *     le_mem_Release(objPtr);
  416  * }
  417  *
  418  * COMPONENT_INIT
  419  * {
  420  *     EventId = le_event_CreateIdWithRefCounting("SomethingHappened");
  421  *     le_event_AddHandler("SomethingHandler", EventId, MyHandler);
  422  *     MyObjectPoolRef = le_mem_CreatePool("MyObjects", sizeof(MyObj_t));
  423  * }
  424  *
  425  * static void ReportSomethingDetected
  426  * (
  427  *     ...
  428  * )
  429  * {
  430  *     MyObj_t* objPtr = le_mem_ForceAlloc(MyObjectPool);
  431  *
  432  *     // Fill in the object.
  433  *     ...
  434  *
  435  *     le_event_ReportWithRefCounting(EventId, objPtr);
  436  * }
  437  *
  438  * @endcode
  439  *
  440  * @section c_event_miscThreadingTopics Miscellaneous Multithreading Topics
  441  *
  442  * All functions in this API are thread safe.
  443  *
  444  * Each thread can have only one Event Loop.
  445  * The main thread in every Legato process will always run an Event Loop after it's run
  446  * the component initialization functions.  As soon as all component initialization functions
  447  * have returned, the main thread will start processing its event queue.
  448  *
  449  * When a function is called to "Add" an event handler, that handler is associated with the
  450  * calling thread's Event Loop. If the calling thread doesn't run its Event Loop, the event
  451  * reports will pile up in the queue, never getting serviced and never releasing their memory.
  452  * This will appear in the logs as event queue growth warnings.
  453  *
  454  * If a client starts its own thread (e.g., by calling le_thread_Create() ), then
  455  * that thread will @b not automatically run an Event Loop.   To make it run an Event Loop, it must
  456  * call @c le_event_RunLoop() (which will never return).
  457  *
  458  * If a thread running an Event Loop terminates, the Legato framework automatically
  459  * deregisters any handlers and deletes the thread's Event Loop, its Event
  460  * Queue, and any event reports still in that Event Queue.
  461  *
  462  * @section c_event_integratingLegacyPosix Integrating with Legacy POSIX Code
  463  *
  464  * Many legacy programs written on top of POSIX APIs will have previously built their own event loop
  465  * using poll(), select(), or some other blocking functions. It may be difficult to refactor this type of
  466  * event loop to use the Legato event loop instead.
  467  *
  468  * Two functions are provided to assist integrating legacy code with the Legato
  469  * Event Loop:
  470  *  - @c le_event_GetFd() - Fetches a file descriptor that can be monitored using some variant of
  471  *                       poll() or select() (including epoll).  It will appear readable when the
  472  *                       Event Loop needs servicing.
  473  *  - @c le_event_ServiceLoop() - Services the event loop.  This should be called if the file
  474  *                       descriptor returned by le_event_GetFd() appears readable to poll() or
  475  *                       select().
  476  *
  477  * In an attempt to avoid starving the caller when there are a lot of things that need servicing
  478  * on the Event Loop, @c le_event_ServiceLoop() will only perform one servicing step (i.e., call one
  479  * event handler function) before returning, regardless of how much work there is to do.  It's
  480  * the caller's responsibility to check the return code from le_event_ServiceLoop() and keep
  481  * calling until it indicates that there is no more work to be done.
  482  *
  483  * @section c_event_troubleshooting Troubleshooting
  484  *
  485  * A logging keyword can be enabled to view a given thread's event handling activity.  The keyword name
  486  * depends on the thread and process name where the thread is located.
  487  * For example, the keyword "P/T/events" controls logging for a thread named "T" running inside
  488  * a process named "P".
  489  *
  490  * @todo Add a reference to the Process Inspector and its capabilities for inspecting Event Queues,
  491  * Event Loops, Handlers and Event Report statistics.
  492 
  493  * <HR>
  494  *
  495  * Copyright (C) Sierra Wireless Inc.
  496  */
  497 
  498 //--------------------------------------------------------------------------------------------------
  499 /** @file le_eventLoop.h
  500  *
  501  * Legato @ref c_eventLoop include file.
  502  *
  503  * Copyright (C) Sierra Wireless Inc.
  504  */
  505 
  506 #ifndef LEGATO_EVENTLOOP_INCLUDE_GUARD
  507 #define LEGATO_EVENTLOOP_INCLUDE_GUARD
  508 
  509 #include "le_thread.h"
  510 
  511 
  512 //--------------------------------------------------------------------------------------------------
  513 /**
  514  * Event ID.
  515  *
  516  * An Event ID ties event reports to event handlers.  See @ref c_event_publishSubscribe for
  517  * more details.
  518  */
  519 //--------------------------------------------------------------------------------------------------
  520 typedef struct le_event_Id* le_event_Id_t;
  521 
  522 
  523 //--------------------------------------------------------------------------------------------------
  524 /**
  525  * Initialization event handler function declaration macro.
  526  *
  527  * Use this macro instead of a normal function prototype to create an Initialization Event Handler
  528  * function.  E.g.,
  529  *
  530  * @code
  531  * COMPONENT_INIT
  532  * {
  533  *     // Do my initialization here...
  534  * }
  535  * @endcode
  536  *
  537  * @return Nothing.
  538  */
  539 //--------------------------------------------------------------------------------------------------
  540 
  541 #ifdef __cplusplus
  542     #define LE_CI_LINKAGE extern "C"
  543 #else
  544     #define LE_CI_LINKAGE
  545 #endif
  546 
  547 // This macro is set by the build system.  However, if it hasn't been set, use a sensible default.
  548 #ifndef LE_COMPONENT_NAME
  549 #   define LE_COMPONENT_NAME    le
  550 #endif
  551 
  552 /// Construct prototype of component init function
  553 #define COMPONENT_INIT_PROTOTYPE(name)  LE_CI_LINKAGE LE_SHARED void name               \
  554                                         (                                               \
  555                                             __attribute__((unused)) void *param1Ptr,    \
  556                                             __attribute__((unused)) void *param2Ptr     \
  557                                         )
  558 
  559 /// Compose component initialization function name
  560 #define COMPONENT_INIT_NAME             CAT(CAT(_, LE_COMPONENT_NAME), _COMPONENT_INIT)
  561 
  562 /// Compose component initialization function prototype
  563 #define COMPONENT_INIT                  COMPONENT_INIT_PROTOTYPE(COMPONENT_INIT_NAME)
  564 
  565 /// Compose one-time component initialization function name
  566 #define COMPONENT_INIT_ONCE_NAME        CAT(COMPONENT_INIT_NAME, _ONCE)
  567 
  568 /// Compose one-time component initialization function prototype
  569 #define COMPONENT_INIT_ONCE             COMPONENT_INIT_PROTOTYPE(COMPONENT_INIT_ONCE_NAME)
  570 
  571 /// Deprecated name for @ref COMPONENT_INIT.
  572 #define LE_EVENT_INIT_HANDLER COMPONENT_INIT
  573 
  574 
  575 //--------------------------------------------------------------------------------------------------
  576 /**
  577  * Prototype for publish-subscribe event handler functions look like this:
  578  *
  579  * @param reportPtr [in] Pointer to the event report payload.
  580  *
  581  * @warning The reportPtr is only valid until the handler function returns.
  582  */
  583 //--------------------------------------------------------------------------------------------------
  584 typedef void (*le_event_HandlerFunc_t)
  585 (
  586     void* reportPtr
  587 );
  588 
  589 
  590 //--------------------------------------------------------------------------------------------------
  591 /**
  592  * Prototype for the first layer of a layered publish-subscribe event handler function
  593  * look like this:
  594  *
  595  * @param reportPtr [in] Pointer to the event report payload.
  596  *
  597  * @param secondLayerFunc [in] Address of the second layer handler function.
  598  *
  599  * @warning The reportPtr is only valid until the handler function returns.
  600  */
  601 //--------------------------------------------------------------------------------------------------
  602 typedef void (*le_event_LayeredHandlerFunc_t)
  603 (
  604     void*   reportPtr,
  605     void*   secondLayerFunc
  606 );
  607 
  608 
  609 //--------------------------------------------------------------------------------------------------
  610 /**
  611  * Prototype for deferred functions look like this:
  612  * @param param1Ptr [in] Value passed in as param1Ptr to le_event_QueueFunction().
  613  * @param param2Ptr [in] Value passed in as param2Ptr to le_event_QueueFunction().
  614  *
  615  * See @ref c_event_deferredFunctionCalls for more information.
  616  */
  617 //--------------------------------------------------------------------------------------------------
  618 typedef void (*le_event_DeferredFunc_t)
  619 (
  620     void* param1Ptr,
  621     void* param2Ptr
  622 );
  623 
  624 
  625 //--------------------------------------------------------------------------------------------------
  626 /**
  627  * Handler reference.
  628  *
  629  *Used to refer to handlers that have been added for events. Only needed if
  630  * you want to set the handler's context pointer or need to remove the handler later.
  631  */
  632 //--------------------------------------------------------------------------------------------------
  633 typedef struct le_event_Handler* le_event_HandlerRef_t;
  634 
  635 
  636 #if LE_CONFIG_EVENT_NAMES_ENABLED
  637 //--------------------------------------------------------------------------------------------------
  638 /**
  639  * Create a new event ID.
  640  *
  641  *  @param[in]  name        Name of the event ID.  (Named for diagnostic purposes.)
  642  *  @param[in]  payloadSize Data payload size (in bytes) of the event reports (can be 0).
  643  *
  644  *  @return Event ID.
  645  *
  646  *  @note Doesn't return on failure, there's no need to check the return value for errors.
  647  */
  648 //--------------------------------------------------------------------------------------------------
  649 le_event_Id_t le_event_CreateId
  650 (
  651     const char *name,
  652     size_t      payloadSize
  653 );
  654 #else /* if not LE_CONFIG_EVENT_NAMES_ENABLED */
  655 /// @cond HIDDEN_IN_USER_DOCS
  656 //--------------------------------------------------------------------------------------------------
  657 /**
  658  * Internal function used to implement le_event_CreateId().
  659  */
  660 //--------------------------------------------------------------------------------------------------
  661 le_event_Id_t _le_event_CreateId(size_t payloadSize);
  662 /// @endcond
  663 //--------------------------------------------------------------------------------------------------
  664 /**
  665  * Create a new event ID.
  666  *
  667  *  @param[in]  name        Name of the event ID.  (Named for diagnostic purposes.)
  668  *  @param[in]  payloadSize Data payload size (in bytes) of the event reports (can be 0).
  669  *
  670  *  @return Event ID.
  671  *
  672  *  @note Doesn't return on failure, there's no need to check the return value for errors.
  673  */
  674 //--------------------------------------------------------------------------------------------------
  675 LE_DECLARE_INLINE le_event_Id_t le_event_CreateId
  676 (
  677     const char *name,
  678     size_t      payloadSize
  679 )
  680 {
  681     LE_UNUSED(name);
  682     return _le_event_CreateId(payloadSize);
  683 }
  684 #endif /* end LE_CONFIG_EVENT_NAMES_ENABLED */
  685 
  686 
  687 #if LE_CONFIG_EVENT_NAMES_ENABLED
  688 //--------------------------------------------------------------------------------------------------
  689 /**
  690  * Create a new event ID to report events where the payload is a pointer to
  691  * a reference-counted memory pool object allocated using the @ref c_memory.
  692  *
  693  *  @param[in]  name    Name of the event ID.  (Named for diagnostic purposes.)
  694  *
  695  *  @return Event ID.
  696  *
  697  *  @note Doesn't return on failure, there's no need to check the return value for errors.
  698  */
  699 //--------------------------------------------------------------------------------------------------
  700 le_event_Id_t le_event_CreateIdWithRefCounting
  701 (
  702     const char *name
  703 );
  704 #else /* if not LE_CONFIG_EVENT_NAMES_ENABLED */
  705 /// @cond HIDDEN_IN_USER_DOCS
  706 //--------------------------------------------------------------------------------------------------
  707 /**
  708  * Internal function used to implement le_event_CreateIdWithRefCounting().
  709  */
  710 //--------------------------------------------------------------------------------------------------
  711 le_event_Id_t _le_event_CreateIdWithRefCounting(void);
  712 /// @endcond
  713 //--------------------------------------------------------------------------------------------------
  714 /**
  715  * Create a new event ID to report events where the payload is a pointer to
  716  * a reference-counted memory pool object allocated using the @ref c_memory.
  717  *
  718  *  @param[in]  name    Name of the event ID.  (Named for diagnostic purposes.)
  719  *
  720  *  @return Event ID.
  721  *
  722  *  @note Doesn't return on failure, there's no need to check the return value for errors.
  723  */
  724 //--------------------------------------------------------------------------------------------------
  725 LE_DECLARE_INLINE le_event_Id_t le_event_CreateIdWithRefCounting
  726 (
  727     const char *name
  728 )
  729 {
  730     LE_UNUSED(name);
  731     return _le_event_CreateIdWithRefCounting();
  732 }
  733 #endif /* end LE_CONFIG_EVENT_NAMES_ENABLED */
  734 
  735 
  736 #if LE_CONFIG_EVENT_NAMES_ENABLED
  737 //--------------------------------------------------------------------------------------------------
  738 /**
  739  * Adds a handler function for a publish-subscribe event ID.
  740  *
  741  * Tells the calling thread event loop to call a specified handler function when a defined event
  742  * reaches the front of the event queue.
  743  *
  744  *  @param[in]  name        Handler name.
  745  *  @param[in]  eventId     Event ID.
  746  *  @param[in]  handlerFunc Handler function.
  747  *
  748  *  @return
  749  *      Handler reference, only needed to remove the handler (using
  750  *      le_event_RemoveHandler() ).  Can be ignored if the handler will never be removed.
  751  *
  752  *  @note Doesn't return on failure, there's no need to check the return value for errors.
  753  */
  754 //--------------------------------------------------------------------------------------------------
  755 le_event_HandlerRef_t le_event_AddHandler
  756 (
  757     const char              *name,
  758     le_event_Id_t            eventId,
  759     le_event_HandlerFunc_t   handlerFunc
  760 );
  761 #else /* if not LE_CONFIG_EVENT_NAMES_ENABLED */
  762 /// @cond HIDDEN_IN_USER_DOCS
  763 //--------------------------------------------------------------------------------------------------
  764 /**
  765  * Internal function used to implement le_event_AddHandler().
  766  */
  767 //--------------------------------------------------------------------------------------------------
  768 le_event_HandlerRef_t _le_event_AddHandler(le_event_Id_t eventId, le_event_HandlerFunc_t handlerFunc);
  769 /// @endcond
  770 //--------------------------------------------------------------------------------------------------
  771 /**
  772  * Adds a handler function for a publish-subscribe event ID.
  773  *
  774  * Tells the calling thread event loop to call a specified handler function when a defined event
  775  * reaches the front of the event queue.
  776  *
  777  *  @param[in]  name        Handler name.
  778  *  @param[in]  eventId     Event ID.
  779  *  @param[in]  handlerFunc Handler function.
  780  *
  781  *  @return
  782  *      Handler reference, only needed to remove the handler (using
  783  *      le_event_RemoveHandler() ).  Can be ignored if the handler will never be removed.
  784  *
  785  *  @note Doesn't return on failure, there's no need to check the return value for errors.
  786  */
  787 //--------------------------------------------------------------------------------------------------
  788 LE_DECLARE_INLINE le_event_HandlerRef_t le_event_AddHandler
  789 (
  790     const char              *name,
  791     le_event_Id_t            eventId,
  792     le_event_HandlerFunc_t   handlerFunc
  793 )
  794 {
  795     LE_UNUSED(name);
  796     return _le_event_AddHandler(eventId, handlerFunc);
  797 }
  798 #endif /* end LE_CONFIG_EVENT_NAMES_ENABLED */
  799 
  800 
  801 #if LE_CONFIG_EVENT_NAMES_ENABLED
  802 //--------------------------------------------------------------------------------------------------
  803 /**
  804  * Adds a layered handler function for a publish-subscribe event ID.
  805  *
  806  * Tells the calling thread event loop to call a specified handler function when a defined event
  807  * reaches the front of the event queue.  Passes the required handler functions when called.
  808  *
  809  * This is intended for use in implementing @ref c_event_layeredPublishSubscribe.
  810  *
  811  *  @param[in]  name    Handler name.
  812  *  @param[in]  name    Event ID.
  813  *  @param[in]  name    Pointer to first-layer handler func.
  814  *  @param[in]  name    Pointer to second-layer handler func.
  815  *
  816  *  @return
  817  *      Handler reference, only needed for later removal of the handler (using
  818  *      le_event_RemoveHandler() ).  Can be ignored if the handler will never be removed.
  819  *
  820  *  @note Doesn't return on failure, there's no need to check the return value for errors.
  821  */
  822 //--------------------------------------------------------------------------------------------------
  823 le_event_HandlerRef_t le_event_AddLayeredHandler
  824 (
  825     const char                      *name,
  826     le_event_Id_t                    eventId,
  827     le_event_LayeredHandlerFunc_t    firstLayerFunc,
  828     void*                            secondLayerFunc
  829 );
  830 #else /* if not LE_CONFIG_EVENT_NAMES_ENABLED */
  831 /// @cond HIDDEN_IN_USER_DOCS
  832 //--------------------------------------------------------------------------------------------------
  833 /**
  834  * Internal function used to implement le_event_AddLayeredHandler().
  835  */
  836 //--------------------------------------------------------------------------------------------------
  837 le_event_HandlerRef_t _le_event_AddLayeredHandler(le_event_Id_t eventId,
  838                                                  le_event_LayeredHandlerFunc_t firstLayerFunc,
  839                                                  void* secondLayerFunc);
  840 /// @endcond
  841 //--------------------------------------------------------------------------------------------------
  842 /**
  843  * Adds a layered handler function for a publish-subscribe event ID.
  844  *
  845  * Tells the calling thread event loop to call a specified handler function when a defined event
  846  * reaches the front of the event queue.  Passes the required handler functions when called.
  847  *
  848  * This is intended for use in implementing @ref c_event_layeredPublishSubscribe.
  849  *
  850  *  @param[in]  name    Handler name.
  851  *  @param[in]  name    Event ID.
  852  *  @param[in]  name    Pointer to first-layer handler func.
  853  *  @param[in]  name    Pointer to second-layer handler func.
  854  *
  855  *  @return
  856  *      Handler reference, only needed for later removal of the handler (using
  857  *      le_event_RemoveHandler() ).  Can be ignored if the handler will never be removed.
  858  *
  859  *  @note Doesn't return on failure, there's no need to check the return value for errors.
  860  */
  861 //--------------------------------------------------------------------------------------------------
  862 LE_DECLARE_INLINE le_event_HandlerRef_t le_event_AddLayeredHandler
  863 (
  864     const char                      *name,
  865     le_event_Id_t                    eventId,
  866     le_event_LayeredHandlerFunc_t    firstLayerFunc,
  867     void*                            secondLayerFunc
  868 )
  869 {
  870     LE_UNUSED(name);
  871     return _le_event_AddLayeredHandler(eventId, firstLayerFunc, secondLayerFunc);
  872 }
  873 #endif /* end LE_CONFIG_EVENT_NAMES_ENABLED */
  874 
  875 
  876 //--------------------------------------------------------------------------------------------------
  877 /**
  878  * Remove Handler
  879  *
  880  * Removes a previously added event handler function.
  881  */
  882 //--------------------------------------------------------------------------------------------------
  883 void le_event_RemoveHandler
  884 (
  885     le_event_HandlerRef_t   handlerRef  ///< [in] Handler reference.
  886 );
  887 
  888 
  889 //--------------------------------------------------------------------------------------------------
  890 /**
  891  * Report an Event
  892  *
  893  * Queues an Event Report to any and all event loops that have handlers for that event.
  894  *
  895  * @note Copies the event report payload, so it is safe to release or reuse the buffer that
  896  *       payloadPtr points to as soon as le_event_Report() returns.
  897  */
  898 //--------------------------------------------------------------------------------------------------
  899 void le_event_Report
  900 (
  901     le_event_Id_t   eventId,    ///< [in] Event ID created using le_event_CreateId().
  902     void*           payloadPtr, ///< [in] Pointer to the payload bytes to be copied into the report.
  903     size_t          payloadSize ///< [in] Number of bytes of payload to copy into the report.
  904 );
  905 
  906 
  907 //--------------------------------------------------------------------------------------------------
  908 /**
  909  * Sends an Event Report with a pointer to a reference-counted object as its payload.
  910  * The pointer must have been obtained from a memory pool using the @ref c_memory.
  911  *
  912  * Calling this function passes ownership of the reference to the Event Loop API.
  913  * The Event Loop API will ensure that the reference is properly counted while it passes
  914  * through the event report dispatching system.  Each handler will receive one counted reference
  915  * to the object, so the handler is responsible for releasing the object when it is finished with
  916  * it.
  917  */
  918 //--------------------------------------------------------------------------------------------------
  919 void le_event_ReportWithRefCounting
  920 (
  921     le_event_Id_t   eventId,    ///< [in] Event ID created using le_event_CreateIdWithRefCounting().
  922     void*           objectPtr   ///< [in] Pointer to an object allocated from a memory pool
  923                                 ///       (using the @ref c_memory).
  924 );
  925 
  926 
  927 //--------------------------------------------------------------------------------------------------
  928 /**
  929  * Sets the context pointer for a given event handler.
  930  *
  931  * This can later be retrieved using le_event_GetContextPtr() from within the handler function
  932  * when it is called.
  933  */
  934 //--------------------------------------------------------------------------------------------------
  935 void le_event_SetContextPtr
  936 (
  937     le_event_HandlerRef_t   handlerRef, ///< [in] Handler where context pointer is to be set.
  938     void*                   contextPtr  ///< [in] Context pointer value.
  939 );
  940 
  941 //--------------------------------------------------------------------------------------------------
  942 /**
  943  * Fetches the context pointer for a given event handler.
  944  *
  945  * @return
  946  *      The context pointer associated to the handlerRef.
  947  */
  948 //--------------------------------------------------------------------------------------------------
  949 void* le_event_GetContextPtrFromRef
  950 (
  951     le_event_HandlerRef_t   handlerRef  ///< [in] Handler whose context pointer is to be set.
  952 );
  953 
  954 //--------------------------------------------------------------------------------------------------
  955 /**
  956  * Fetches the context pointer for the currently running event handler.
  957  *
  958  * Can only be called from within an event handler function.
  959  *
  960  * @return
  961  *      Context pointer that was set using le_event_SetContextPtr(), or NULL if
  962  *      le_event_SetContextPtr() was not called.
  963  */
  964 //--------------------------------------------------------------------------------------------------
  965 void* le_event_GetContextPtr
  966 (
  967     void
  968 );
  969 
  970 
  971 //--------------------------------------------------------------------------------------------------
  972 /**
  973  * Queue a function onto the calling thread's Event Queue.  When it reaches the head of the
  974  * Event Queue, it will be called by the calling thread's Event Loop.
  975  */
  976 //--------------------------------------------------------------------------------------------------
  977 void le_event_QueueFunction
  978 (
  979     le_event_DeferredFunc_t func,       ///< [in] Function to be called later.
  980     void*                   param1Ptr,  ///< [in] Value to be passed to the function when called.
  981     void*                   param2Ptr   ///< [in] Value to be passed to the function when called.
  982 );
  983 
  984 
  985 //--------------------------------------------------------------------------------------------------
  986 /**
  987  * Queue a function onto a specific thread's Event Queue.  When it reaches the head of that
  988  * Event Queue, it will be called by that thread's Event Loop.
  989  */
  990 //--------------------------------------------------------------------------------------------------
  991 void le_event_QueueFunctionToThread
  992 (
  993     le_thread_Ref_t         thread,     ///< [in] Thread to queue the function to.
  994     le_event_DeferredFunc_t func,       ///< [in] The function.
  995     void*                   param1Ptr,  ///< [in] Value to be passed to the function when called.
  996     void*                   param2Ptr   ///< [in] Value to be passed to the function when called.
  997 );
  998 
  999 //--------------------------------------------------------------------------------------------------
 1000 /**
 1001  * Queue a function onto a specific thread's Event Queue if it isn't already on the Event
 1002  * Queue with the same parameters.  When it reaches the head of that Event Queue, it will be
 1003  * called by that thread's Event Loop.
 1004  *
 1005  * Using this function generally indicates poor design.
 1006  * It's generally better to ensure the event is only generated once, for example by disabling
 1007  * generating the event until the event handler is run.
 1008  *
 1009  * @return LE_OK if the function was queued to the Event Queue
 1010  * @return LE_DUPLICATE if the function was already in the Event Queue
 1011  */
 1012 //--------------------------------------------------------------------------------------------------
 1013 le_result_t le_event_QueueFunctionToThreadUnique
 1014 (
 1015     le_thread_Ref_t         thread,     ///< [in] Thread to queue the function to.
 1016     le_event_DeferredFunc_t func,       ///< [in] The function.
 1017     void*                   param1Ptr,  ///< [in] Value to be passed to the function when called.
 1018     void*                   param2Ptr   ///< [in] Value to be passed to the function when called.
 1019 );
 1020 
 1021 
 1022 //--------------------------------------------------------------------------------------------------
 1023 /**
 1024  * Runs the event loop for the calling thread.
 1025  *
 1026  * This starts processing events by the calling thread.
 1027  *
 1028  * Can only be called once for each thread, and must never be called in
 1029  * the process's main thread.
 1030  *
 1031  * @note
 1032  *      Function never returns.
 1033  */
 1034 //--------------------------------------------------------------------------------------------------
 1035 void le_event_RunLoop
 1036 (
 1037     void
 1038 )
 1039 __attribute__ ((noreturn));
 1040 
 1041 
 1042 //--------------------------------------------------------------------------------------------------
 1043 /**
 1044  * Fetches a file descriptor that will appear readable to poll(), select(), epoll_wait(), etc.
 1045  * when the calling thread's Event Loop needs servicing (via a call to le_event_ServiceLoop()).
 1046  *
 1047  * @warning Only intended for use when integrating with legacy POSIX-based software
 1048  * that cannot be easily refactored to use the Legato Event Loop.  The preferred approach is
 1049  * to call le_event_RunLoop().
 1050  *
 1051  * @return The file descriptor.
 1052  */
 1053 //--------------------------------------------------------------------------------------------------
 1054 LE_FULL_API int le_event_GetFd
 1055 (
 1056     void
 1057 );
 1058 
 1059 
 1060 //--------------------------------------------------------------------------------------------------
 1061 /**
 1062  * Services the calling thread's Event Loop.
 1063  *
 1064  * @warning Only intended for use when integrating with legacy POSIX-based software
 1065  * that can't be easily refactored to use the Legato Event Loop.  The preferred approach is
 1066  * to call le_event_RunLoop().
 1067  *
 1068  * See also: le_event_GetFd().
 1069  *
 1070  * @return
 1071  *  - LE_OK if there is more to be done.  DO NOT GO BACK TO SLEEP without calling
 1072  *          le_event_ServiceLoop() again.
 1073  *  - LE_WOULD_BLOCK if there is nothing left to do for now and it is safe to go back to sleep.
 1074  */
 1075 //--------------------------------------------------------------------------------------------------
 1076 LE_FULL_API le_result_t le_event_ServiceLoop
 1077 (
 1078     void
 1079 );
 1080 
 1081 
 1082 #endif // LEGATO_EVENTLOOP_INCLUDE_GUARD
le_thread_Ref_t
struct le_thread * le_thread_Ref_t
Definition: le_thread.h:180
le_event_GetContextPtrFromRef
void * le_event_GetContextPtrFromRef(le_event_HandlerRef_t handlerRef)
le_event_CreateIdWithRefCounting
le_event_Id_t le_event_CreateIdWithRefCounting(const char *name)
le_event_LayeredHandlerFunc_t
void(* le_event_LayeredHandlerFunc_t)(void *reportPtr, void *secondLayerFunc)
Definition: le_eventLoop.h:603
le_result_t
le_result_t
Definition: le_basics.h:46
LE_UNUSED
#define LE_UNUSED(v)
Definition: le_basics.h:369
le_event_GetFd
LE_FULL_API int le_event_GetFd(void)
le_event_HandlerRef_t
struct le_event_Handler * le_event_HandlerRef_t
Definition: le_eventLoop.h:633
le_event_Id_t
struct le_event_Id * le_event_Id_t
Definition: le_eventLoop.h:520
le_event_QueueFunctionToThread
void le_event_QueueFunctionToThread(le_thread_Ref_t thread, le_event_DeferredFunc_t func, void *param1Ptr, void *param2Ptr)
le_event_QueueFunctionToThreadUnique
le_result_t le_event_QueueFunctionToThreadUnique(le_thread_Ref_t thread, le_event_DeferredFunc_t func, void *param1Ptr, void *param2Ptr)
le_event_Report
void le_event_Report(le_event_Id_t eventId, void *payloadPtr, size_t payloadSize)
le_event_RunLoop
void le_event_RunLoop(void)
le_thread.h
le_event_GetContextPtr
void * le_event_GetContextPtr(void)
le_event_DeferredFunc_t
void(* le_event_DeferredFunc_t)(void *param1Ptr, void *param2Ptr)
Definition: le_eventLoop.h:619
le_event_CreateId
le_event_Id_t le_event_CreateId(const char *name, size_t payloadSize)
LE_FULL_API
#define LE_FULL_API
Definition: le_apiFeatures.h:40
le_event_SetContextPtr
void le_event_SetContextPtr(le_event_HandlerRef_t handlerRef, void *contextPtr)
le_event_ReportWithRefCounting
void le_event_ReportWithRefCounting(le_event_Id_t eventId, void *objectPtr)
le_event_HandlerFunc_t
void(* le_event_HandlerFunc_t)(void *reportPtr)
Definition: le_eventLoop.h:585
le_event_AddHandler
le_event_HandlerRef_t le_event_AddHandler(const char *name, le_event_Id_t eventId, le_event_HandlerFunc_t handlerFunc)
le_event_RemoveHandler
void le_event_RemoveHandler(le_event_HandlerRef_t handlerRef)
le_event_AddLayeredHandler
le_event_HandlerRef_t le_event_AddLayeredHandler(const char *name, le_event_Id_t eventId, le_event_LayeredHandlerFunc_t firstLayerFunc, void *secondLayerFunc)
le_event_ServiceLoop
LE_FULL_API le_result_t le_event_ServiceLoop(void)
LE_DECLARE_INLINE
#define LE_DECLARE_INLINE
Definition: le_basics.h:320
le_event_QueueFunction
void le_event_QueueFunction(le_event_DeferredFunc_t func, void *param1Ptr, void *param2Ptr)