// © 2016 and later: Unicode, Inc. and others.

// License & terms of use: http://www.unicode.org/copyright.html

/*

******************************************************************************

*

*   Copyright (C) 1997-2016, International Business Machines

*   Corporation and others.  All Rights Reserved.

*

******************************************************************************

*

* File umutex.cpp

*

* Modification History:

*

*   Date        Name        Description

*   04/02/97    aliu        Creation.

*   04/07/99    srl         updated

*   05/13/99    stephen     Changed to umutex (from cmutex).

*   11/22/99    aliu        Make non-global mutex autoinitialize [j151]

******************************************************************************

*/

#include "umutex.h"

#include "unicode/utypes.h"

#include "uassert.h"

#include "cmemory.h"

// The ICU global mutex. Used when ICU implementation code passes NULL for the mutex pointer.

static UMutex   globalMutex = U_MUTEX_INITIALIZER;

/*

 * ICU Mutex wrappers.  Wrap operating system mutexes, giving the rest of ICU a

 * platform independent set of mutex operations.  For internal ICU use only.

 */

#if defined(U_USER_MUTEX_CPP)

// Build time user mutex hook: #include "U_USER_MUTEX_CPP"

#include U_MUTEX_XSTR(U_USER_MUTEX_CPP)

#elif U_PLATFORM_USES_ONLY_WIN32_API

#if defined U_NO_PLATFORM_ATOMICS

#error ICU on Win32 requires support for low level atomic operations.

// Visual Studio, gcc, clang are OK. Shouldn't get here.

#endif

// This function is called when a test of a UInitOnce::fState reveals that

//   initialization has not completed, that we either need to call the

//   function on this thread, or wait for some other thread to complete.

//

// The actual call to the init function is made inline by template code

//   that knows the C++ types involved. This function returns TRUE if

//   the caller needs to call the Init function.

//

U_NAMESPACE_BEGIN

U_COMMON_API UBool U_EXPORT2 umtx_initImplPreInit(UInitOnce &uio) {

    for (;;) {

        int32_t previousState = InterlockedCompareExchange(

            (LONG volatile *) // this is the type given in the API doc for this function.

                &uio.fState,  //  Destination

            1,            //  Exchange Value

            0);           //  Compare value

        if (previousState == 0) {

            return true;   // Caller will next call the init function.

                           // Current state == 1.

        } else if (previousState == 2) {

            // Another thread already completed the initialization.

            //   We can simply return FALSE, indicating no

            //   further action is needed by the caller.

            return FALSE;

        } else {

            // Another thread is currently running the initialization.

            // Wait until it completes.

            do {

                Sleep(1);

                previousState = umtx_loadAcquire(uio.fState);

            } while (previousState == 1);

        }

    }

}

// This function is called by the thread that ran an initialization function,

// just after completing the function.

U_COMMON_API void U_EXPORT2 umtx_initImplPostInit(UInitOnce &uio) {

    umtx_storeRelease(uio.fState, 2);

}

U_NAMESPACE_END

static void winMutexInit(CRITICAL_SECTION *cs) {

    InitializeCriticalSection(cs);

    return;

}

U_CAPI void  U_EXPORT2

umtx_lock(UMutex *mutex) {

    if (mutex == NULL) {

        mutex = &globalMutex;

    }

    CRITICAL_SECTION *cs = &mutex->fCS;

    umtx_initOnce(mutex->fInitOnce, winMutexInit, cs);

    EnterCriticalSection(cs);

}

U_CAPI void  U_EXPORT2

umtx_unlock(UMutex* mutex)

{

    if (mutex == NULL) {

        mutex = &globalMutex;

    }

    LeaveCriticalSection(&mutex->fCS);

}

U_CAPI void U_EXPORT2

umtx_condBroadcast(UConditionVar *condition) {

    // We require that the associated mutex be held by the caller,

    //  so access to fWaitCount is protected and safe. No other thread can

    //  call condWait() while we are here.

    if (condition->fWaitCount == 0) {

        return;

    }

    ResetEvent(condition->fExitGate);

    SetEvent(condition->fEntryGate);

}

U_CAPI void U_EXPORT2

umtx_condSignal(UConditionVar *condition) {

    // Function not implemented. There is no immediate requirement from ICU to have it.

    // Once ICU drops support for Windows XP and Server 2003, ICU Condition Variables will be

    // changed to be thin wrappers on native Windows CONDITION_VARIABLEs, and this function

    // becomes trivial to provide.

    U_ASSERT(FALSE);

}

U_CAPI void U_EXPORT2

umtx_condWait(UConditionVar *condition, UMutex *mutex) {

    if (condition->fEntryGate == NULL) {

        // Note: because the associated mutex must be locked when calling

        //       wait, we know that there can not be multiple threads

        //       running here with the same condition variable.

        //       Meaning that lazy initialization is safe.

        U_ASSERT(condition->fExitGate == NULL);

        condition->fEntryGate = CreateEvent(NULL,   // Security Attributes

                                            TRUE,   // Manual Reset

                                            FALSE,  // Initially reset

                                            NULL);  // Name.

        U_ASSERT(condition->fEntryGate != NULL);

        condition->fExitGate = CreateEvent(NULL, TRUE, TRUE, NULL);

        U_ASSERT(condition->fExitGate != NULL);

    }

    condition->fWaitCount++;

    umtx_unlock(mutex);

    WaitForSingleObject(condition->fEntryGate, INFINITE); 

    umtx_lock(mutex);

    condition->fWaitCount--;

    if (condition->fWaitCount == 0) {

        // All threads that were waiting at the entry gate have woken up

        // and moved through. Shut the entry gate and open the exit gate.

        ResetEvent(condition->fEntryGate);

        SetEvent(condition->fExitGate);

    } else {

        umtx_unlock(mutex);

        WaitForSingleObject(condition->fExitGate, INFINITE);

        umtx_lock(mutex);

    }

}

#elif U_PLATFORM_IMPLEMENTS_POSIX

//-------------------------------------------------------------------------------------------

//

//  POSIX specific definitions

//

//-------------------------------------------------------------------------------------------

# include <pthread.h>

// Each UMutex consists of a pthread_mutex_t.

// All are statically initialized and ready for use.

// There is no runtime mutex initialization code needed.

U_CAPI void  U_EXPORT2

umtx_lock(UMutex *mutex) {

    if (mutex == NULL) {

        mutex = &globalMutex;

    }

    int sysErr = pthread_mutex_lock(&mutex->fMutex);

    (void)sysErr;   // Suppress unused variable warnings.

    U_ASSERT(sysErr == 0);

}

U_CAPI void  U_EXPORT2

umtx_unlock(UMutex* mutex)

{

    if (mutex == NULL) {

        mutex = &globalMutex;

    }

    int sysErr = pthread_mutex_unlock(&mutex->fMutex);

    (void)sysErr;   // Suppress unused variable warnings.

    U_ASSERT(sysErr == 0);

}

U_CAPI void U_EXPORT2

umtx_condWait(UConditionVar *cond, UMutex *mutex) {

    if (mutex == NULL) {

        mutex = &globalMutex;

    }

    int sysErr = pthread_cond_wait(&cond->fCondition, &mutex->fMutex);

    (void)sysErr;

    U_ASSERT(sysErr == 0);

}

U_CAPI void U_EXPORT2

umtx_condBroadcast(UConditionVar *cond) {

    int sysErr = pthread_cond_broadcast(&cond->fCondition);

    (void)sysErr;

    U_ASSERT(sysErr == 0);

}

U_CAPI void U_EXPORT2

umtx_condSignal(UConditionVar *cond) {

    int sysErr = pthread_cond_signal(&cond->fCondition);

    (void)sysErr;

    U_ASSERT(sysErr == 0);

}

U_NAMESPACE_BEGIN

static pthread_mutex_t initMutex = PTHREAD_MUTEX_INITIALIZER;

static pthread_cond_t initCondition = PTHREAD_COND_INITIALIZER;

// This function is called when a test of a UInitOnce::fState reveals that

//   initialization has not completed, that we either need to call the

//   function on this thread, or wait for some other thread to complete.

//

// The actual call to the init function is made inline by template code

//   that knows the C++ types involved. This function returns TRUE if

//   the caller needs to call the Init function.

//

U_COMMON_API UBool U_EXPORT2

umtx_initImplPreInit(UInitOnce &uio) {

    pthread_mutex_lock(&initMutex);

    int32_t state = uio.fState;

    if (state == 0) {

        umtx_storeRelease(uio.fState, 1);

        pthread_mutex_unlock(&initMutex);

        return TRUE;   // Caller will next call the init function.

    } else {

        while (uio.fState == 1) {

            // Another thread is currently running the initialization.

            // Wait until it completes.

            pthread_cond_wait(&initCondition, &initMutex);

        }

        pthread_mutex_unlock(&initMutex);

        U_ASSERT(uio.fState == 2);

        return FALSE;

    }

}

// This function is called by the thread that ran an initialization function,

// just after completing the function.

//   Some threads may be waiting on the condition, requiring the broadcast wakeup.

//   Some threads may be racing to test the fState variable outside of the mutex,

//   requiring the use of store/release when changing its value.

U_COMMON_API void U_EXPORT2

umtx_initImplPostInit(UInitOnce &uio) {

    pthread_mutex_lock(&initMutex);

    umtx_storeRelease(uio.fState, 2);

    pthread_cond_broadcast(&initCondition);

    pthread_mutex_unlock(&initMutex);

}

U_NAMESPACE_END

// End of POSIX specific umutex implementation.

#else  // Platform #define chain.

#error Unknown Platform

#endif  // Platform #define chain.

//-------------------------------------------------------------------------------

//

//   Atomic Operations, out-of-line versions.

//                      These are conditional, only defined if better versions

//                      were not available for the platform.

//

//                      These versions are platform neutral.

//

//--------------------------------------------------------------------------------

#if defined U_NO_PLATFORM_ATOMICS

static UMutex   gIncDecMutex = U_MUTEX_INITIALIZER;

U_NAMESPACE_BEGIN

U_COMMON_API int32_t U_EXPORT2

umtx_atomic_inc(u_atomic_int32_t *p)  {

    int32_t retVal;

    umtx_lock(&gIncDecMutex);

    retVal = ++(*p);

    umtx_unlock(&gIncDecMutex);

    return retVal;

}

U_COMMON_API int32_t U_EXPORT2

umtx_atomic_dec(u_atomic_int32_t *p) {

    int32_t retVal;

    umtx_lock(&gIncDecMutex);

    retVal = --(*p);

    umtx_unlock(&gIncDecMutex);

    return retVal;

}

U_COMMON_API int32_t U_EXPORT2

umtx_loadAcquire(u_atomic_int32_t &var) {

    umtx_lock(&gIncDecMutex);

    int32_t val = var;

    umtx_unlock(&gIncDecMutex);

    return val;

}

U_COMMON_API void U_EXPORT2

umtx_storeRelease(u_atomic_int32_t &var, int32_t val) {

    umtx_lock(&gIncDecMutex);

    var = val;

    umtx_unlock(&gIncDecMutex);

}

U_NAMESPACE_END

#endif

//--------------------------------------------------------------------------

//

//  Deprecated functions for setting user mutexes.

//

//--------------------------------------------------------------------------

U_DEPRECATED void U_EXPORT2

u_setMutexFunctions(const void * /*context */, UMtxInitFn *, UMtxFn *,

                    UMtxFn *,  UMtxFn *, UErrorCode *status) {

    if (U_SUCCESS(*status)) {

        *status = U_UNSUPPORTED_ERROR;

    }

    return;

}

U_DEPRECATED void U_EXPORT2

u_setAtomicIncDecFunctions(const void * /*context */, UMtxAtomicFn *, UMtxAtomicFn *,

                           UErrorCode *status) {

    if (U_SUCCESS(*status)) {

        *status = U_UNSUPPORTED_ERROR;

    }

    return;

}