+// © 2016 and later: Unicode, Inc. and others.
+// License & terms of use: http://www.unicode.org/copyright.html
/*
**********************************************************************
-* Copyright (C) 1997-2001, International Business Machines
+* Copyright (C) 1997-2015, International Business Machines
* Corporation and others. All Rights Reserved.
**********************************************************************
*
#ifndef UMUTEX_H
#define UMUTEX_H
+#include <atomic>
+#include <condition_variable>
+#include <mutex>
+
#include "unicode/utypes.h"
+#include "unicode/uclean.h"
+#include "unicode/uobject.h"
-/**
- * Mutex data type.
- * @internal
- */
-typedef void *UMTX;
+#include "putilimp.h"
-/* APP_NO_THREADS is an old symbol. We'll honour it if present. */
-#ifdef APP_NO_THREADS
-# define ICU_USE_THREADS 0
+#if defined(U_USER_ATOMICS_H) || defined(U_USER_MUTEX_H)
+// Support for including an alternate implementation of atomic & mutex operations has been withdrawn.
+// See issue ICU-20185.
+#error U_USER_ATOMICS and U_USER_MUTEX_H are not supported
#endif
-/* Default: use threads. */
-#ifndef ICU_USE_THREADS
-# define ICU_USE_THREADS 1
+
+// Export an explicit template instantiation of std::atomic<int32_t>.
+// When building DLLs for Windows this is required as it is used as a data member of the exported SharedObject class.
+// See digitlst.h, pluralaffix.h, datefmt.h, and others for similar examples.
+#if U_PF_WINDOWS <= U_PLATFORM && U_PLATFORM <= U_PF_CYGWIN && !defined(U_IN_DOXYGEN)
+#if defined(__clang__) || defined(_MSC_VER)
+ #if defined(__clang__)
+ // Suppress the warning that the explicit instantiation after explicit specialization has no effect.
+ #pragma clang diagnostic push
+ #pragma clang diagnostic ignored "-Winstantiation-after-specialization"
+ #endif
+template struct U_COMMON_API std::atomic<int32_t>;
+ #if defined(__clang__)
+ #pragma clang diagnostic pop
+ #endif
+#elif defined(__GNUC__)
+// For GCC this class is already exported/visible, so no need for U_COMMON_API.
+template struct std::atomic<int32_t>;
+#endif
#endif
-/*
- * Code within this library which accesses protected data should
- * instantiate a Mutex object while doing so. Notice that there is
- * only one coarse-grained lock which applies to this entire library,
- * so keep locking short and sweet.
- *
- * For example:
+
+U_NAMESPACE_BEGIN
+
+/****************************************************************************
*
- * void Function(int arg1, int arg2)
- * {
- * static Object* foo; // Shared read-write object
- * Mutex mutex;
- * foo->Method();
- * // When 'mutex' goes out of scope and gets destroyed here
- * // the lock is released
- * }
+ * Low Level Atomic Operations, ICU wrappers for.
*
- * Note: Do NOT use the form 'Mutex mutex();' as that merely
- * forward-declares a function returning a Mutex. This is a common
- * mistake which silently slips through the compiler!! */
+ ****************************************************************************/
+typedef std::atomic<int32_t> u_atomic_int32_t;
+#define ATOMIC_INT32_T_INITIALIZER(val) ATOMIC_VAR_INIT(val)
-/* Lock a mutex. Pass in NULL if you want the (ick) Single Global
- Mutex.
- * @param mutex The given mutex to be locked
- */
-U_CAPI void U_EXPORT2 umtx_lock ( UMTX* mutex );
+inline int32_t umtx_loadAcquire(u_atomic_int32_t &var) {
+ return var.load(std::memory_order_acquire);
+}
-/* Unlock a mutex. Pass in NULL if you want the single global
- mutex.
- * @param mutex The given mutex to be unlocked
- */
-U_CAPI void U_EXPORT2 umtx_unlock ( UMTX* mutex );
+inline void umtx_storeRelease(u_atomic_int32_t &var, int32_t val) {
+ var.store(val, std::memory_order_release);
+}
-/* Initialize a mutex. Use it this way:
- umtx_init( &aMutex );
- * ICU Mutexes, aside from the global mutex, must be explicitly initialized
- * before use.
- * @param mutex The given mutex to be initialized
- */
-U_CAPI void U_EXPORT2 umtx_init ( UMTX* mutex );
+inline int32_t umtx_atomic_inc(u_atomic_int32_t *var) {
+ return var->fetch_add(1) + 1;
+}
-/* Destroy a mutex. This will free the resources of a mutex.
- Use it this way:
- umtx_destroy( &aMutex );
- * @param mutex The given mutex to be destroyed
- */
-U_CAPI void U_EXPORT2 umtx_destroy( UMTX *mutex );
-
-/* Is a mutex initialized?
- Use it this way:
- umtx_isInitialized( &aMutex );
- This function is not normally needed. It is more efficient to
- unconditionally call umtx_init(&aMutex) than it is to check first.
- * @param mutex The given mutex to be tested
-*/
-U_CAPI UBool U_EXPORT2 umtx_isInitialized( UMTX *mutex );
+inline int32_t umtx_atomic_dec(u_atomic_int32_t *var) {
+ return var->fetch_sub(1) - 1;
+}
-/*
- * Atomic Increment and Decrement of an int32_t value.
+
+/*************************************************************************************************
+ *
+ * UInitOnce Definitions.
+ *
+ *************************************************************************************************/
+
+struct UInitOnce {
+ u_atomic_int32_t fState;
+ UErrorCode fErrCode;
+ void reset() {fState = 0;}
+ UBool isReset() {return umtx_loadAcquire(fState) == 0;}
+// Note: isReset() is used by service registration code.
+// Thread safety of this usage needs review.
+};
+
+#define U_INITONCE_INITIALIZER {ATOMIC_INT32_T_INITIALIZER(0), U_ZERO_ERROR}
+
+
+U_COMMON_API UBool U_EXPORT2 umtx_initImplPreInit(UInitOnce &);
+U_COMMON_API void U_EXPORT2 umtx_initImplPostInit(UInitOnce &);
+
+template<class T> void umtx_initOnce(UInitOnce &uio, T *obj, void (U_CALLCONV T::*fp)()) {
+ if (umtx_loadAcquire(uio.fState) == 2) {
+ return;
+ }
+ if (umtx_initImplPreInit(uio)) {
+ (obj->*fp)();
+ umtx_initImplPostInit(uio);
+ }
+}
+
+
+// umtx_initOnce variant for plain functions, or static class functions.
+// No context parameter.
+inline void umtx_initOnce(UInitOnce &uio, void (U_CALLCONV *fp)()) {
+ if (umtx_loadAcquire(uio.fState) == 2) {
+ return;
+ }
+ if (umtx_initImplPreInit(uio)) {
+ (*fp)();
+ umtx_initImplPostInit(uio);
+ }
+}
+
+// umtx_initOnce variant for plain functions, or static class functions.
+// With ErrorCode, No context parameter.
+inline void umtx_initOnce(UInitOnce &uio, void (U_CALLCONV *fp)(UErrorCode &), UErrorCode &errCode) {
+ if (U_FAILURE(errCode)) {
+ return;
+ }
+ if (umtx_loadAcquire(uio.fState) != 2 && umtx_initImplPreInit(uio)) {
+ // We run the initialization.
+ (*fp)(errCode);
+ uio.fErrCode = errCode;
+ umtx_initImplPostInit(uio);
+ } else {
+ // Someone else already ran the initialization.
+ if (U_FAILURE(uio.fErrCode)) {
+ errCode = uio.fErrCode;
+ }
+ }
+}
+
+// umtx_initOnce variant for plain functions, or static class functions,
+// with a context parameter.
+template<class T> void umtx_initOnce(UInitOnce &uio, void (U_CALLCONV *fp)(T), T context) {
+ if (umtx_loadAcquire(uio.fState) == 2) {
+ return;
+ }
+ if (umtx_initImplPreInit(uio)) {
+ (*fp)(context);
+ umtx_initImplPostInit(uio);
+ }
+}
+
+// umtx_initOnce variant for plain functions, or static class functions,
+// with a context parameter and an error code.
+template<class T> void umtx_initOnce(UInitOnce &uio, void (U_CALLCONV *fp)(T, UErrorCode &), T context, UErrorCode &errCode) {
+ if (U_FAILURE(errCode)) {
+ return;
+ }
+ if (umtx_loadAcquire(uio.fState) != 2 && umtx_initImplPreInit(uio)) {
+ // We run the initialization.
+ (*fp)(context, errCode);
+ uio.fErrCode = errCode;
+ umtx_initImplPostInit(uio);
+ } else {
+ // Someone else already ran the initialization.
+ if (U_FAILURE(uio.fErrCode)) {
+ errCode = uio.fErrCode;
+ }
+ }
+}
+
+
+/**
+ * ICU Mutex wrappers. Originally wrapped operating system mutexes, giving the rest of ICU a
+ * platform independent set of mutex operations. Now vestigial, wrapping std::mutex only.
+ * For internal ICU use only.
+ *
+ * Caution: do not directly declare static or global instances of UMutex. Doing so can introduce
+ * static initializers, which are disallowed in ICU library code. Instead, use the following
+ * idiom, which avoids static init and also avoids ordering issues on destruction
+ * (use after delete) by avoiding destruction altogether.
*
- * Return Values:
- * If the result of the operation is zero, the return zero.
- * If the result of the operation is not zero, the sign of returned value
- * is the same as the sign of the result, but the returned value itself may
- * be different from the result of the operation.
+ * UMutex *myMutex() {
+ * static UMutex *m = STATIC_NEW(UMutex);
+ * return m;
+ * }
+ * ...
+ *
+ * Mutex lock(myMutex()); // hold myMutex until the variable "lock" goes out of scope.
*/
-U_CAPI int32_t U_EXPORT2 umtx_atomic_inc(int32_t *);
-U_CAPI int32_t U_EXPORT2 umtx_atomic_dec(int32_t *);
+struct UMutex : public icu::UMemory {
+ UMutex() = default;
+ ~UMutex() = default;
+ UMutex(const UMutex &other) = delete;
+ UMutex &operator =(const UMutex &other) = delete;
-#endif /*_CMUTEX*/
-/*eof*/
+ std::mutex fMutex = {}; // Note: struct - pubic members - because most access is from
+ // // plain C style functions (umtx_lock(), etc.)
+};
+/* Lock a mutex.
+ * @param mutex The given mutex to be locked. Pass NULL to specify
+ * the global ICU mutex. Recursive locks are an error
+ * and may cause a deadlock on some platforms.
+ */
+U_INTERNAL void U_EXPORT2 umtx_lock(UMutex* mutex);
+/* Unlock a mutex.
+ * @param mutex The given mutex to be unlocked. Pass NULL to specify
+ * the global ICU mutex.
+ */
+U_INTERNAL void U_EXPORT2 umtx_unlock (UMutex* mutex);
+
+U_NAMESPACE_END
+
+#endif /* UMUTEX_H */
+/*eof*/
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