/*

    File:       WorkerThread.c

    Description: Sample code showing how to send messages between the main thread and a worker pthread.

                 You could have an instance of this worker pthread interface for each window, for example.

    Author:     QuickTime Engineering, dts

    Copyright:  © Copyright 2003-2004 Apple Computer, Inc. All rights reserved.

    Disclaimer: IMPORTANT:  This Apple software is supplied to you by Apple Computer, Inc.

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                Software may be incorporated.

                The Apple Software is provided by Apple on an "AS IS" basis.  APPLE MAKES NO

                WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION THE IMPLIED

                WARRANTIES OF NON-INFRINGEMENT, MERCHANTABILITY AND FITNESS FOR A PARTICULAR

                PURPOSE, REGARDING THE APPLE SOFTWARE OR ITS USE AND OPERATION ALONE OR IN

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    Change History (most recent first):  <1> qte 04/05/04 minor fixes for initial release

*/

//////////

//

// header files

//

//////////

#include <pthread.h>

#include <semaphore.h>

#include <stddef.h> // for offsetof() macro

// Enqueue etc. are in OSUtils.h

// TestAndSet etc. and IncrementAtomic etc. are in DriverSynchronization.h

// EventLoopTimer APIs are in CarbonEventsCore.h

#include <Carbon/Carbon.h>

#include <QuickTime/QuickTime.h>

#include "WorkerThread.h"

//////////

//

// data structures

//

//////////

typedef struct WorkerThread {

    SInt32                              referenceCount;

    WorkerActionRoutine                 actionRoutine;

    WorkerCancelRoutine                 cancelRoutine;

    WorkerResponseMainThreadCallback    responseCallback;

    void *              refcon;

    SInt32              numberOfActiveRequests;     // number of requests that have been created but not yet released

    pthread_t           workerThread;

    //POSIX sem_t               shutdownSemaphore;

    //POSIX sem_t               requestSemaphore;

    MPSemaphoreID       shutdownSemaphore;

    MPSemaphoreID       requestSemaphore;

    QHdr                requestQueue;               // messages going from main thread to worker thread

    EventLoopTimerUPP   responseEventLoopTimerUPP;

    EventLoopTimerRef   responseEventLoopTimer;

    QHdr                responseQueue;              // messages going from worker thread to main thread

    UInt8               responseQueueArmed;

    Boolean             shutdown;                   // set to ask worker thread to shut down when all request queue is empty

    unsigned long       osVersion;                  // the OS version we are running on

} WorkerThread;

typedef struct WorkerRequest {

    SInt32              referenceCount;

    WorkerThreadRef     worker;                     // note: each active request maintains a reference to its worker

    QElemPtr            nextRequest;                // used when linked into worker->requestQueue

    QElemPtr            nextResponse;               // used when linked into worker->responseQueue

    Boolean             wasSent;

    Boolean             wasCancelled;

    Boolean             wasStartedOrCancelled;

    Boolean             actionFinished;

    // add client-use fields here

    FSRef               fileRef;

    UInt32              doc;

    void *              threadData;

} WorkerRequest;

//////////

//

// function prototypes

//

//////////

static void *runWorkerThread ( void *argWorkerThreadRef );

static void runWorkerResponseEventLoopTimer ( EventLoopTimerRef timer, void *refcon );

#pragma mark-

//////////

//

// worker thread routines

//

//////////

OSErr createWorkerThread (

    WorkerActionRoutine actionRoutine,

    WorkerCancelRoutine cancelRoutine,

    WorkerResponseMainThreadCallback responseCallback,

    void *refcon,

    WorkerThreadRef *outWorker )

{

    WorkerThreadRef worker;

    if ( !actionRoutine || !responseCallback || !outWorker ) return paramErr;

    worker = calloc( 1, sizeof( WorkerThread ) );

    if ( ! worker ) return memFullErr;

    worker->referenceCount = 1;

    worker->actionRoutine = actionRoutine;

    worker->cancelRoutine = cancelRoutine;

    worker->responseCallback = responseCallback;

    worker->refcon = refcon;

    // get the OS version

    Gestalt(gestaltSystemVersion, &worker->osVersion);

    // create a one-shot event loop timer

    worker->responseEventLoopTimerUPP = NewEventLoopTimerUPP( runWorkerResponseEventLoopTimer );

    InstallEventLoopTimer( GetMainEventLoop(), kEventDurationForever, kEventDurationForever, 

        worker->responseEventLoopTimerUPP, worker, &worker->responseEventLoopTimer );

    // sem_init() not yet implemented as of MacOS X 10.3 - so we're going to use the MP APIs instead

    // the POSIX calls we could use when sem_init() is supported are clearly marked with the POSIX prefix

    // Named semaphors are available but not really ideal for our needs in this sample

    // Reference: http://developer.apple.com/documentation/Carbon/Reference/Multiprocessing_Services/multiproc_ref/function_group_3.html

    //POSIX sem_init( &worker->requestSemaphore, 0 /* not shared */, 0 /* initial value */ );

    //POSIX sem_init( &worker->shutdownSemaphore, 0 /* not shared */, 0 /* initial value */ );

    MPCreateSemaphore(1, 0, &worker->requestSemaphore);

    MPCreateSemaphore(1, 0, &worker->shutdownSemaphore);

    pthread_create( &worker->workerThread, NULL, runWorkerThread, worker );

    *outWorker = worker;

    return noErr;

}

void retainWorkerThread ( WorkerThreadRef worker )

{

    if ( !worker ) return;

    IncrementAtomic( &worker->referenceCount );

}

void releaseWorkerThread ( WorkerThreadRef worker )

{

    if ( !worker ) return;

    if ( 1 == DecrementAtomic( &worker->referenceCount ) ) {

        if ( 0 != worker->numberOfActiveRequests ) {

            DebugStr("\preleaseWorkerThread: reference count went to zero, but there are still active requests" );

        }

        ExitMoviesOnThread();

        pthread_detach( worker->workerThread );

        // ask worker thread to clean up and exit

        worker->shutdown = true;

        //POSIX sem_post( &worker->requestSemaphore );

        //POSIX sem_post( &worker->shutdownSemaphore ); // avoid race condition where busy thread disposes requestSemaphore before we post to it

        MPSignalSemaphore(worker->requestSemaphore);

        MPSignalSemaphore(worker->shutdownSemaphore); // avoid race condition where busy thread disposes requestSemaphore before we post to it

    }

}

#pragma mark-

//////////

//

// worker request routines

//

//////////

OSErr createWorkerRequest ( 

    WorkerThreadRef worker, 

    WorkerRequestRef *outRequest )

{

    if ( !outRequest ) return paramErr;

    WorkerRequestRef request = calloc( 1, sizeof( WorkerRequest ) );

    if ( !request ) return memFullErr;

    request->referenceCount = 1;

    request->worker = worker;

    IncrementAtomic( &worker->numberOfActiveRequests );

    retainWorkerThread( worker );

    *outRequest = request;

    return noErr;

}

static void *runWorkerThread ( void *argWorkerThreadRef )

{

    WorkerThreadRef worker = argWorkerThreadRef;

    // protect this thread from calling non-thread-safe components

    EnterMoviesOnThread(0);

    while ( true ) {

        // handle all queued requests, then wait on the semaphore

        QElemPtr requestElem = worker->requestQueue.qHead; // NULL, or the address of a nextRequest field in a WorkerRequest

        if ( requestElem ) {

            WorkerRequestRef request = (WorkerRequestRef)((long)requestElem - offsetof(WorkerRequest, nextRequest));

            Dequeue( requestElem, &worker->requestQueue );

            if ( request->worker != worker ) {

                DebugStr("\prunWorkerThread: bad request in requestQueue" );

                continue;

            }

            if ( TestAndSet( 0, &request->wasStartedOrCancelled ) ) {

                // this request was cancelled.

                request->wasCancelled = true;

            }

            else {

                // this request was not cancelled.  run it.

                (*worker->actionRoutine)( worker->refcon, request );

                request->actionFinished = true;

            }

            // queue the request on the response queue.

            Enqueue( (QElemPtr)&request->nextResponse, &worker->responseQueue );

            if ( 0 == TestAndSet( 0, &worker->responseQueueArmed ) ) {

                SetEventLoopTimerNextFireTime( worker->responseEventLoopTimer, kEventDurationNoWait );

            }

        }

        else if( worker->shutdown ) {

            // go peacefully

            break;

        }

        else {

            //POSIX sem_wait( &worker->requestSemaphore );

            MPWaitOnSemaphore(worker->requestSemaphore, kDurationForever);

        }

    }

    // wait so that we can be sure that the main thread is done signalling requestSemaphore.

    //POSIX sem_wait( &worker->shutdownSemaphore );

    MPWaitOnSemaphore(worker->shutdownSemaphore, kDurationForever);

    // clean up.

    //POSIX sem_destroy( &worker->requestSemaphore );

    //POSIX sem_destroy( &worker->shutdownSemaphore );

    MPDeleteSemaphore(worker->requestSemaphore);

    MPDeleteSemaphore(worker->shutdownSemaphore);

    RemoveEventLoopTimer( worker->responseEventLoopTimer );

    DisposeEventLoopTimerUPP( worker->responseEventLoopTimerUPP );

    free( worker );

    return NULL;

}

static void runWorkerResponseEventLoopTimer ( EventLoopTimerRef timer, void *refcon )

{

    WorkerThreadRef worker = refcon;

    while ( TestAndClear( 0, &worker->responseQueueArmed ) ) {

        QElemPtr responseElem = worker->responseQueue.qHead; // NULL, or the address of a nextResponse field in a WorkerRequest

        while ( responseElem ) {

            WorkerRequestRef request = (WorkerRequestRef)((long)responseElem - offsetof(WorkerRequest, nextResponse));

            Dequeue( responseElem, &worker->responseQueue );

            // run the response callback.

            (*worker->responseCallback)( worker->refcon, request );

            // (note that the response callback may release the request)

            responseElem = worker->responseQueue.qHead;

        }

    }

}

#pragma mark-

// accessors

OSErr setWorkerRequestFile ( 

    WorkerRequestRef request, 

    FSRef fileRef )

{

    if ( !request ) return paramErr;

    request->fileRef = fileRef;

    return noErr;

}

OSErr getWorkerRequestFile ( 

    WorkerRequestRef request, 

    FSRef *fileRef )

{

    if (( !request ) || ( !fileRef ) ) return paramErr;

    *fileRef = request->fileRef;

    return noErr;

}

OSErr setWorkerRequestDoc ( 

    WorkerRequestRef request, 

    UInt32 doc )

{

    if ( !request ) return paramErr;

    request->doc = doc;

    return noErr;

}

OSErr getWorkerRequestDoc ( 

    WorkerRequestRef request, 

    UInt32 *doc )

{

    if (( !request ) || ( !doc ) ) return paramErr;

    *doc = request->doc;

    return noErr;

}

OSErr setWorkerRequestThreadData ( 

    WorkerRequestRef request, 

    void *threadData )

{

    if ( !request ) return paramErr;

    request->threadData = threadData;

    return noErr;

}

OSErr getWorkerRequestThreadData ( 

        WorkerRequestRef request, 

        void **threadDataPtr )

{

    if (( !request ) || ( !threadDataPtr ) ) return paramErr;

    *threadDataPtr = request->threadData;

    return noErr;

}

// add more accessors as you like

#pragma mark-

OSErr sendWorkerRequest ( WorkerRequestRef request )

{

    if ( !request ) return paramErr;

    if ( request->wasSent ) {

        DebugStr("\psendWorkerRequest: request was already sent");

        return paramErr;

    }

    request->wasSent = true;

    Enqueue( (QElemPtr)&request->nextRequest, &request->worker->requestQueue );

    //POSIX sem_post( &request->worker->requestSemaphore );

    MPSignalSemaphore(request->worker->requestSemaphore);

    return noErr;

}

void cancelWorkerRequest ( WorkerRequestRef request )

{

    if ( !request ) return;

    if ( !request->wasSent ) {

        DebugStr("\pcancelWorkerRequest: request was not sent");

        return;

    }

    if ( request->wasCancelled ) {

        DebugStr("\pcancelWorkerRequest: request was already cancelled");

        return;

    }

    if ( TestAndSet( 0, &request->wasStartedOrCancelled ) ) {

        // request has already started

        if ( request->actionFinished ) {

            // request has already finished: nothing we can do

        }

        else {

            // request action routine is currently running: call the cancel function, if set

            request->wasCancelled = true;

            if ( request->worker->cancelRoutine )

                (*request->worker->cancelRoutine)( request->worker->refcon, request );

        }

    }

    else {

        // request had not yet started, and by setting wasStartedOrCancelled we've cancelled it

        request->wasCancelled = true;

    }

}

Boolean wasWorkerRequestCancelled ( WorkerRequestRef request )

{

    if ( !request ) return false;

    return request->wasCancelled;

}

void releaseWorkerRequest ( WorkerRequestRef request )

{

    if ( 1 == DecrementAtomic( &request->referenceCount ) ) {

        DecrementAtomic( &request->worker->numberOfActiveRequests );

        releaseWorkerThread( request->worker );

        free( request );

    }

}

void retainWorkerRequest ( WorkerRequestRef request )

{

    IncrementAtomic( &request->referenceCount );

}