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// © 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"
U_NAMESPACE_BEGIN
#if defined(U_USER_MUTEX_CPP)
// Support for including an alternate implementation of mutexes has been withdrawn.
// See issue ICU-20185.
#error U_USER_MUTEX_CPP not supported
#endif
/*************************************************************************************************
*
* ICU Mutex wrappers.
*
*************************************************************************************************/
// The ICU global mutex. Used when ICU implementation code passes NULL for the mutex pointer.
static UMutex *globalMutex() {
static UMutex m = U_MUTEX_INITIALIZER;
return &m;
}
U_CAPI void U_EXPORT2
umtx_lock(UMutex *mutex) {
if (mutex == nullptr) {
mutex = globalMutex();
}
mutex->fMutex.lock();
}
U_CAPI void U_EXPORT2
umtx_unlock(UMutex* mutex)
{
if (mutex == nullptr) {
mutex = globalMutex();
}
mutex->fMutex.unlock();
}
UConditionVar::UConditionVar() : fCV() {
}
UConditionVar::~UConditionVar() {
}
U_CAPI void U_EXPORT2
umtx_condWait(UConditionVar *cond, UMutex *mutex) {
if (mutex == nullptr) {
mutex = globalMutex();
}
cond->fCV.wait(mutex->fMutex);
}
U_CAPI void U_EXPORT2
umtx_condBroadcast(UConditionVar *cond) {
cond->fCV.notify_all();
}
U_CAPI void U_EXPORT2
umtx_condSignal(UConditionVar *cond) {
cond->fCV.notify_one();
}
/*************************************************************************************************
*
* UInitOnce Implementation
*
*************************************************************************************************/
static std::mutex &initMutex() {
static std::mutex m;
return m;
}
static std::condition_variable &initCondition() {
static std::condition_variable cv;
return cv;
}
// This function is called when a test of a UInitOnce::fState reveals that
// initialization has not completed, that we either need to call the init
// 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) {
std::unique_lock<std::mutex> lock(initMutex());
if (umtx_loadAcquire(uio.fState) == 0) {
umtx_storeRelease(uio.fState, 1);
return true; // Caller will next call the init function.
} else {
while (umtx_loadAcquire(uio.fState) == 1) {
// Another thread is currently running the initialization.
// Wait until it completes.
initCondition().wait(lock);
}
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) {
{
std::unique_lock<std::mutex> lock(initMutex());
umtx_storeRelease(uio.fState, 2);
}
initCondition().notify_all();
}
U_NAMESPACE_END
/*************************************************************************************************
*
* 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;
}