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Retired Document

Important: This sample code may not represent best practices for current development. The project may use deprecated symbols and illustrate technologies and techniques that are no longer recommended.

Relevant replacement documents include:

http://developer.apple.com/library/mac/samplecode/sc2195/Introduction/Intro.html#//apple_ref/doc/uid/DTS40013969

PublicUtility/CAMutex.cpp

/*

 <codex>

 <abstract>CAMutex.h</abstract>

 <\codex>

*/

//==================================================================================================

//  Includes

//==================================================================================================

//  Self Include

#include "CAMutex.h"

#if TARGET_OS_MAC

    #include <errno.h>

#endif

//  PublicUtility Includes

#include "CADebugMacros.h"

#include "CAException.h"

#include "CAHostTimeBase.h"

//==================================================================================================

//  Logging

//==================================================================================================

#if CoreAudio_Debug

//  #define Log_Ownership       1

//  #define Log_Errors          1

//  #define Log_LongLatencies   1

//  #define LongLatencyThreshholdNS 1000000ULL  // nanoseconds

#endif

//==================================================================================================

//  CAMutex

//==================================================================================================

CAMutex::CAMutex(const char* inName)

    mName(inName),

    mOwner(0)

#if TARGET_OS_MAC

    OSStatus theError = pthread_mutex_init(&mMutex, NULL);

    ThrowIf(theError != 0, CAException(theError), "CAMutex::CAMutex: Could not init the mutex");

    #if Log_Ownership

        DebugPrintfRtn(DebugPrintfFileComma "%p %.4f: CAMutex::CAMutex: creating %s, owner: %p\n", pthread_self(), ((Float64)(CAHostTimeBase::GetCurrentTimeInNanos()) / 1000000.0), mName, mOwner);

    #endif

#elif TARGET_OS_WIN32

    mMutex = CreateMutex(NULL, false, NULL);

    ThrowIfNULL(mMutex, CAException(GetLastError()), "CAMutex::CAMutex: could not create the mutex.");

    #if Log_Ownership

        DebugPrintfRtn(DebugPrintfFileComma "%lu %.4f: CAMutex::CAMutex: creating %s, owner: %lu\n", GetCurrentThreadId(), ((Float64)(CAHostTimeBase::GetCurrentTimeInNanos()) / 1000000.0), mName, mOwner);

    #endif

#endif

CAMutex::~CAMutex()

#if TARGET_OS_MAC

    #if Log_Ownership

        DebugPrintfRtn(DebugPrintfFileComma "%p %.4f: CAMutex::~CAMutex: destroying %s, owner: %p\n", pthread_self(), ((Float64)(CAHostTimeBase::GetCurrentTimeInNanos()) / 1000000.0), mName, mOwner);

    #endif

    pthread_mutex_destroy(&mMutex);

#elif TARGET_OS_WIN32

    #if Log_Ownership

        DebugPrintfRtn(DebugPrintfFileComma "%lu %.4f: CAMutex::~CAMutex: destroying %s, owner: %lu\n", GetCurrentThreadId(), ((Float64)(CAHostTimeBase::GetCurrentTimeInNanos()) / 1000000.0), mName, mOwner);

    #endif

    if(mMutex != NULL)

        CloseHandle(mMutex);

#endif

bool    CAMutex::Lock()

    bool theAnswer = false;

#if TARGET_OS_MAC

    pthread_t theCurrentThread = pthread_self();

    if(!pthread_equal(theCurrentThread, mOwner))

        #if Log_Ownership

            DebugPrintfRtn(DebugPrintfFileComma "%p %.4f: CAMutex::Lock: thread %p is locking %s, owner: %p\n", theCurrentThread, ((Float64)(CAHostTimeBase::GetCurrentTimeInNanos()) / 1000000.0), theCurrentThread, mName, mOwner);

        #endif

        #if Log_LongLatencies

            UInt64 lockTryTime = CAHostTimeBase::GetCurrentTimeInNanos();

        #endif

        OSStatus theError = pthread_mutex_lock(&mMutex);

        ThrowIf(theError != 0, CAException(theError), "CAMutex::Lock: Could not lock the mutex");

        mOwner = theCurrentThread;

        theAnswer = true;

        #if Log_LongLatencies

            UInt64 lockAcquireTime = CAHostTimeBase::GetCurrentTimeInNanos();

            if (lockAcquireTime - lockTryTime >= LongLatencyThresholdNS)

                DebugPrintfRtn(DebugPrintfFileComma "Thread %p took %.6fs to acquire the lock %s\n", theCurrentThread, (lockAcquireTime - lockTryTime) * 1.0e-9 /* nanos to seconds */, mName);

        #endif

        #if Log_Ownership

            DebugPrintfRtn(DebugPrintfFileComma "%p %.4f: CAMutex::Lock: thread %p has locked %s, owner: %p\n", pthread_self(), ((Float64)(CAHostTimeBase::GetCurrentTimeInNanos()) / 1000000.0), pthread_self(), mName, mOwner);

        #endif

#elif TARGET_OS_WIN32

    if(mOwner != GetCurrentThreadId())

        #if Log_Ownership

            DebugPrintfRtn(DebugPrintfFileComma "%lu %.4f: CAMutex::Lock: thread %lu is locking %s, owner: %lu\n", GetCurrentThreadId(), ((Float64)(CAHostTimeBase::GetCurrentTimeInNanos()) / 1000000.0), GetCurrentThreadId(), mName, mOwner);

        #endif

        OSStatus theError = WaitForSingleObject(mMutex, INFINITE);

        ThrowIfError(theError, CAException(theError), "CAMutex::Lock: could not lock the mutex");

        mOwner = GetCurrentThreadId();

        theAnswer = true;

        #if Log_Ownership

            DebugPrintfRtn(DebugPrintfFileComma "%lu %.4f: CAMutex::Lock: thread %lu has locked %s, owner: %lu\n", GetCurrentThreadId(), ((Float64)(CAHostTimeBase::GetCurrentTimeInNanos()) / 1000000.0), GetCurrentThreadId(), mName, mOwner);

        #endif

#endif

    return theAnswer;

void    CAMutex::Unlock()

#if TARGET_OS_MAC

    if(pthread_equal(pthread_self(), mOwner))

        #if Log_Ownership

            DebugPrintfRtn(DebugPrintfFileComma "%p %.4f: CAMutex::Unlock: thread %p is unlocking %s, owner: %p\n", pthread_self(), ((Float64)(CAHostTimeBase::GetCurrentTimeInNanos()) / 1000000.0), pthread_self(), mName, mOwner);

        #endif

        mOwner = 0;

        OSStatus theError = pthread_mutex_unlock(&mMutex);

        ThrowIf(theError != 0, CAException(theError), "CAMutex::Unlock: Could not unlock the mutex");

        #if Log_Ownership

            DebugPrintfRtn(DebugPrintfFileComma "%p %.4f: CAMutex::Unlock: thread %p has unlocked %s, owner: %p\n", pthread_self(), ((Float64)(CAHostTimeBase::GetCurrentTimeInNanos()) / 1000000.0), pthread_self(), mName, mOwner);

        #endif

    else

        DebugMessage("CAMutex::Unlock: A thread is attempting to unlock a Mutex it doesn't own");

#elif TARGET_OS_WIN32

    if(mOwner == GetCurrentThreadId())

        #if Log_Ownership

            DebugPrintfRtn(DebugPrintfFileComma "%lu %.4f: CAMutex::Unlock: thread %lu is unlocking %s, owner: %lu\n", GetCurrentThreadId(), ((Float64)(CAHostTimeBase::GetCurrentTimeInNanos()) / 1000000.0), GetCurrentThreadId(), mName, mOwner);

        #endif

        mOwner = 0;

        bool wasReleased = ReleaseMutex(mMutex);

        ThrowIf(!wasReleased, CAException(GetLastError()), "CAMutex::Unlock: Could not unlock the mutex");

        #if Log_Ownership

            DebugPrintfRtn(DebugPrintfFileComma "%lu %.4f: CAMutex::Unlock: thread %lu has unlocked %s, owner: %lu\n", GetCurrentThreadId(), ((Float64)(CAHostTimeBase::GetCurrentTimeInNanos()) / 1000000.0), GetCurrentThreadId(), mName, mOwner);

        #endif

    else

        DebugMessage("CAMutex::Unlock: A thread is attempting to unlock a Mutex it doesn't own");

#endif

bool    CAMutex::Try(bool& outWasLocked)

    bool theAnswer = false;

    outWasLocked = false;

#if TARGET_OS_MAC

    pthread_t theCurrentThread = pthread_self();

    if(!pthread_equal(theCurrentThread, mOwner))

        //  this means the current thread doesn't already own the lock

        #if Log_Ownership

            DebugPrintfRtn(DebugPrintfFileComma "%p %.4f: CAMutex::Try: thread %p is try-locking %s, owner: %p\n", theCurrentThread, ((Float64)(CAHostTimeBase::GetCurrentTimeInNanos()) / 1000000.0), theCurrentThread, mName, mOwner);

        #endif

        //  go ahead and call trylock to see if we can lock it.

        int theError = pthread_mutex_trylock(&mMutex);

        if(theError == 0)

            //  return value of 0 means we successfully locked the lock

            mOwner = theCurrentThread;

            theAnswer = true;

            outWasLocked = true;

            #if Log_Ownership

                DebugPrintfRtn(DebugPrintfFileComma "%p %.4f: CAMutex::Try: thread %p has locked %s, owner: %p\n", theCurrentThread, ((Float64)(CAHostTimeBase::GetCurrentTimeInNanos()) / 1000000.0), theCurrentThread, mName, mOwner);

            #endif

        else if(theError == EBUSY)

            //  return value of EBUSY means that the lock was already locked by another thread

            theAnswer = false;

            outWasLocked = false;

            #if Log_Ownership

                DebugPrintfRtn(DebugPrintfFileComma "%p %.4f: CAMutex::Try: thread %p failed to lock %s, owner: %p\n", theCurrentThread, ((Float64)(CAHostTimeBase::GetCurrentTimeInNanos()) / 1000000.0), theCurrentThread, mName, mOwner);

            #endif

        else

            //  any other return value means something really bad happenned

            ThrowIfError(theError, CAException(theError), "CAMutex::Try: call to pthread_mutex_trylock failed");

    else

        //  this means the current thread already owns the lock

        theAnswer = true;

        outWasLocked = false;

#elif TARGET_OS_WIN32

    if(mOwner != GetCurrentThreadId())

        //  this means the current thread doesn't own the lock

        #if Log_Ownership

            DebugPrintfRtn(DebugPrintfFileComma "%lu %.4f: CAMutex::Try: thread %lu is try-locking %s, owner: %lu\n", GetCurrentThreadId(), ((Float64)(CAHostTimeBase::GetCurrentTimeInNanos()) / 1000000.0), GetCurrentThreadId(), mName, mOwner);

        #endif

        //  try to acquire the mutex

        OSStatus theError = WaitForSingleObject(mMutex, 0);

        if(theError == WAIT_OBJECT_0)

            //  this means we successfully locked the lock

            mOwner = GetCurrentThreadId();

            theAnswer = true;

            outWasLocked = true;

            #if Log_Ownership

                DebugPrintfRtn(DebugPrintfFileComma "%lu %.4f: CAMutex::Try: thread %lu has locked %s, owner: %lu\n", GetCurrentThreadId(), ((Float64)(CAHostTimeBase::GetCurrentTimeInNanos()) / 1000000.0), GetCurrentThreadId(), mName, mOwner);

            #endif

        else if(theError == WAIT_TIMEOUT)

            //  this means that the lock was already locked by another thread

            theAnswer = false;

            outWasLocked = false;

            #if Log_Ownership

                DebugPrintfRtn(DebugPrintfFileComma "%lu %.4f: CAMutex::Try: thread %lu failed to lock %s, owner: %lu\n", GetCurrentThreadId(), ((Float64)(CAHostTimeBase::GetCurrentTimeInNanos()) / 1000000.0), GetCurrentThreadId(), mName, mOwner);

            #endif

        else

            //  any other return value means something really bad happenned

            ThrowIfError(theError, CAException(GetLastError()), "CAMutex::Try: call to lock the mutex failed");

    else

        //  this means the current thread already owns the lock

        theAnswer = true;

        outWasLocked = false;

#endif

    return theAnswer;

bool    CAMutex::IsFree() const

    return mOwner == 0;

bool    CAMutex::IsOwnedByCurrentThread() const

    bool theAnswer = true;

#if TARGET_OS_MAC

    theAnswer = pthread_equal(pthread_self(), mOwner);

#elif TARGET_OS_WIN32

    theAnswer = (mOwner == GetCurrentThreadId());

#endif

    return theAnswer;

CAMutex::Unlocker::Unlocker(CAMutex& inMutex)

:   mMutex(inMutex),

    mNeedsLock(false)

    Assert(mMutex.IsOwnedByCurrentThread(), "Major problem: Unlocker attempted to unlock a mutex not owned by the current thread!");

    mMutex.Unlock();

    mNeedsLock = true;

CAMutex::Unlocker::~Unlocker()

    if(mNeedsLock)

        mMutex.Lock();

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