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274 lines
8.9 KiB
C++
274 lines
8.9 KiB
C++
// © 2016 and later: Unicode, Inc. and others.
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// License & terms of use: http://www.unicode.org/copyright.html
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/*
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**********************************************************************
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* Copyright (C) 1997-2015, International Business Machines
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* Corporation and others. All Rights Reserved.
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**********************************************************************
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*
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* File UMUTEX.H
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*
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* Modification History:
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*
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* Date Name Description
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* 04/02/97 aliu Creation.
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* 04/07/99 srl rewrite - C interface, multiple mutices
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* 05/13/99 stephen Changed to umutex (from cmutex)
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******************************************************************************
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*/
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#ifndef UMUTEX_H
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#define UMUTEX_H
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#include <atomic>
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#include <condition_variable>
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#include <mutex>
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#include <type_traits>
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#include "unicode/utypes.h"
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#include "unicode/uclean.h"
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#include "unicode/uobject.h"
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#include "putilimp.h"
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#if defined(U_USER_ATOMICS_H) || defined(U_USER_MUTEX_H)
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// Support for including an alternate implementation of atomic & mutex operations has been withdrawn.
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// See issue ICU-20185.
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#error U_USER_ATOMICS and U_USER_MUTEX_H are not supported
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#endif
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// Export an explicit template instantiation of std::atomic<int32_t>.
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// When building DLLs for Windows this is required as it is used as a data member of the exported SharedObject class.
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// See digitlst.h, pluralaffix.h, datefmt.h, and others for similar examples.
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//
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// Similar story for std::atomic<std::mutex *>, and the exported UMutex class.
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#if U_PF_WINDOWS <= U_PLATFORM && U_PLATFORM <= U_PF_CYGWIN && !defined(U_IN_DOXYGEN)
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#if defined(__clang__) || defined(_MSC_VER)
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#if defined(__clang__)
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// Suppress the warning that the explicit instantiation after explicit specialization has no effect.
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#pragma clang diagnostic push
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#pragma clang diagnostic ignored "-Winstantiation-after-specialization"
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#endif
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template struct U_COMMON_API std::atomic<int32_t>;
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template struct U_COMMON_API std::atomic<std::mutex *>;
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#if defined(__clang__)
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#pragma clang diagnostic pop
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#endif
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#elif defined(__GNUC__)
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// For GCC this class is already exported/visible, so no need for U_COMMON_API.
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template struct std::atomic<int32_t>;
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template struct std::atomic<std::mutex *>;
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#endif
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#endif
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U_NAMESPACE_BEGIN
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/****************************************************************************
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*
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* Low Level Atomic Operations, ICU wrappers for.
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*
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****************************************************************************/
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typedef std::atomic<int32_t> u_atomic_int32_t;
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inline int32_t umtx_loadAcquire(u_atomic_int32_t &var) {
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return var.load(std::memory_order_acquire);
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}
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inline void umtx_storeRelease(u_atomic_int32_t &var, int32_t val) {
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var.store(val, std::memory_order_release);
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}
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inline int32_t umtx_atomic_inc(u_atomic_int32_t *var) {
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return var->fetch_add(1) + 1;
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}
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inline int32_t umtx_atomic_dec(u_atomic_int32_t *var) {
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return var->fetch_sub(1) - 1;
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}
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/*************************************************************************************************
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*
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* UInitOnce Definitions.
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*
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*************************************************************************************************/
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struct U_COMMON_API UInitOnce {
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u_atomic_int32_t fState {0};
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UErrorCode fErrCode {U_ZERO_ERROR};
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void reset() {fState = 0;}
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UBool isReset() {return umtx_loadAcquire(fState) == 0;}
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// Note: isReset() is used by service registration code.
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// Thread safety of this usage needs review.
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};
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U_COMMON_API UBool U_EXPORT2 umtx_initImplPreInit(UInitOnce &);
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U_COMMON_API void U_EXPORT2 umtx_initImplPostInit(UInitOnce &);
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template<class T> void umtx_initOnce(UInitOnce &uio, T *obj, void (U_CALLCONV T::*fp)()) {
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if (umtx_loadAcquire(uio.fState) == 2) {
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return;
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}
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if (umtx_initImplPreInit(uio)) {
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(obj->*fp)();
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umtx_initImplPostInit(uio);
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}
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}
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// umtx_initOnce variant for plain functions, or static class functions.
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// No context parameter.
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inline void umtx_initOnce(UInitOnce &uio, void (U_CALLCONV *fp)()) {
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if (umtx_loadAcquire(uio.fState) == 2) {
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return;
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}
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if (umtx_initImplPreInit(uio)) {
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(*fp)();
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umtx_initImplPostInit(uio);
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}
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}
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// umtx_initOnce variant for plain functions, or static class functions.
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// With ErrorCode, No context parameter.
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inline void umtx_initOnce(UInitOnce &uio, void (U_CALLCONV *fp)(UErrorCode &), UErrorCode &errCode) {
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if (U_FAILURE(errCode)) {
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return;
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}
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if (umtx_loadAcquire(uio.fState) != 2 && umtx_initImplPreInit(uio)) {
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// We run the initialization.
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(*fp)(errCode);
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uio.fErrCode = errCode;
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umtx_initImplPostInit(uio);
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} else {
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// Someone else already ran the initialization.
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if (U_FAILURE(uio.fErrCode)) {
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errCode = uio.fErrCode;
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}
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}
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}
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// umtx_initOnce variant for plain functions, or static class functions,
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// with a context parameter.
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template<class T> void umtx_initOnce(UInitOnce &uio, void (U_CALLCONV *fp)(T), T context) {
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if (umtx_loadAcquire(uio.fState) == 2) {
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return;
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}
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if (umtx_initImplPreInit(uio)) {
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(*fp)(context);
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umtx_initImplPostInit(uio);
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}
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}
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// umtx_initOnce variant for plain functions, or static class functions,
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// with a context parameter and an error code.
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template<class T> void umtx_initOnce(UInitOnce &uio, void (U_CALLCONV *fp)(T, UErrorCode &), T context, UErrorCode &errCode) {
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if (U_FAILURE(errCode)) {
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return;
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}
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if (umtx_loadAcquire(uio.fState) != 2 && umtx_initImplPreInit(uio)) {
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// We run the initialization.
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(*fp)(context, errCode);
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uio.fErrCode = errCode;
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umtx_initImplPostInit(uio);
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} else {
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// Someone else already ran the initialization.
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if (U_FAILURE(uio.fErrCode)) {
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errCode = uio.fErrCode;
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}
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}
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}
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// UMutex should be constexpr-constructible, so that no initialization code
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// is run during startup.
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// This works on all C++ libraries except MS VS before VS2019.
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#if (defined(_CPPLIB_VER) && !defined(_MSVC_STL_VERSION)) || \
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(defined(_MSVC_STL_VERSION) && _MSVC_STL_VERSION < 142)
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// (VS std lib older than VS2017) || (VS std lib version < VS2019)
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# define UMUTEX_CONSTEXPR
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#else
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# define UMUTEX_CONSTEXPR constexpr
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#endif
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/**
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* UMutex - ICU Mutex class.
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*
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* This is the preferred Mutex class for use within ICU implementation code.
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* It is a thin wrapper over C++ std::mutex, with these additions:
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* - Static instances are safe, not triggering static construction or destruction,
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* and the associated order of construction or destruction issues.
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* - Plumbed into u_cleanup() for destructing the underlying std::mutex,
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* which frees any OS level resources they may be holding.
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*
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* Limitations:
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* - Static or global instances only. Cannot be heap allocated. Cannot appear as a
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* member of another class.
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* - No condition variables or other advanced features. If needed, you will need to use
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* std::mutex and std::condition_variable directly. For an example, see unifiedcache.cpp
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*
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* Typical Usage:
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* static UMutex myMutex;
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*
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* {
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* Mutex lock(myMutex);
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* ... // Do stuff that is protected by myMutex;
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* } // myMutex is released when lock goes out of scope.
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*/
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class U_COMMON_API UMutex {
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public:
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UMUTEX_CONSTEXPR UMutex() {}
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~UMutex() = default;
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UMutex(const UMutex &other) = delete;
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UMutex &operator =(const UMutex &other) = delete;
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void *operator new(size_t) = delete;
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// requirements for C++ BasicLockable, allows UMutex to work with std::lock_guard
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void lock() {
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std::mutex *m = fMutex.load(std::memory_order_acquire);
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if (m == nullptr) { m = getMutex(); }
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m->lock();
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}
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void unlock() { fMutex.load(std::memory_order_relaxed)->unlock(); }
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static void cleanup();
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private:
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alignas(std::mutex) char fStorage[sizeof(std::mutex)] {};
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std::atomic<std::mutex *> fMutex { nullptr };
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/** All initialized UMutexes are kept in a linked list, so that they can be found,
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* and the underlying std::mutex destructed, by u_cleanup().
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*/
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UMutex *fListLink { nullptr };
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static UMutex *gListHead;
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/** Out-of-line function to lazily initialize a UMutex on first use.
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* Initial fast check is inline, in lock(). The returned value may never
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* be nullptr.
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*/
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std::mutex *getMutex();
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};
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/* Lock a mutex.
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* @param mutex The given mutex to be locked. Pass NULL to specify
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* the global ICU mutex. Recursive locks are an error
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* and may cause a deadlock on some platforms.
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*/
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U_CAPI void U_EXPORT2 umtx_lock(UMutex* mutex);
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/* Unlock a mutex.
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* @param mutex The given mutex to be unlocked. Pass NULL to specify
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* the global ICU mutex.
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*/
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U_CAPI void U_EXPORT2 umtx_unlock (UMutex* mutex);
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U_NAMESPACE_END
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#endif /* UMUTEX_H */
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/*eof*/
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