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143 lines
4.2 KiB
C
143 lines
4.2 KiB
C
/*
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**********************************************************************
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* Copyright (C) 1997-2006, 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 "unicode/utypes.h"
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#include "unicode/uclean.h"
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/* APP_NO_THREADS is an old symbol. We'll honour it if present. */
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#ifdef APP_NO_THREADS
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# define ICU_USE_THREADS 0
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#endif
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/* ICU_USE_THREADS
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*
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* Allows thread support (use of mutexes) to be compiled out of ICU.
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* Default: use threads.
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* Even with thread support compiled out, applications may override the
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* (empty) mutex implementation with the u_setMutexFunctions() functions.
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*/
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#ifndef ICU_USE_THREADS
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# define ICU_USE_THREADS 1
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#endif
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/**
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* By default assume that we are on a machine with a weak memory model,
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* and the double check lock won't work reliably.
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*/
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#if !defined(UMTX_STRONG_MEMORY_MODEL)
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#define UMTX_STRONG_MEMORY_MODEL 0
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#endif
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/**
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* \def UMTX_CHECK
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* Encapsulates a safe check for an expression (usually a condition)
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* for lazy variable inititialization.
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* On CPUs with weak memory models, this must use memory fence instructions
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* or mutexes.
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* @internal
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*/
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#if UMTX_STRONG_MEMORY_MODEL
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#define UMTX_CHECK(pMutex, expression, result) \
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(result)=(expression)
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#else
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#define UMTX_CHECK(pMutex, expression, result) \
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umtx_lock(pMutex); \
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(result)=(expression); \
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umtx_unlock(pMutex)
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#endif
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/*
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* Code within ICU that accesses shared static or global data should
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* instantiate a Mutex object while doing so. The unnamed global mutex
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* is used throughout ICU, so keep locking short and sweet.
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*
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* For example:
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*
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* void Function(int arg1, int arg2)
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* {
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* static Object* foo; // Shared read-write object
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* umtx_lock(NULL); // Lock the ICU global mutex
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* foo->Method();
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* umtx_unlock(NULL);
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* }
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*
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* an alternative C++ mutex API is defined in the file common/mutex.h
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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 ( UMTX* mutex );
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/* Unlock a mutex. Pass in NULL if you want the single global
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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 ( UMTX* mutex );
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/* Initialize a mutex. Use it this way:
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umtx_init( &aMutex );
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* ICU Mutexes do not need explicit initialization before use. Use of this
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* function is not necessary.
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* Initialization of an already initialized mutex has no effect, and is safe to do.
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* Initialization of mutexes is thread safe. Two threads can concurrently
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* initialize the same mutex without causing problems.
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* @param mutex The given mutex to be initialized
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*/
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U_CAPI void U_EXPORT2 umtx_init ( UMTX* mutex );
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/* Destroy a mutex. This will free the resources of a mutex.
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* Use it this way:
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* umtx_destroy( &aMutex );
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* Destroying an already destroyed mutex has no effect, and causes no problems.
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* This function is not thread safe. Two threads must not attempt to concurrently
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* destroy the same mutex.
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* @param mutex The given mutex to be destroyed.
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*/
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U_CAPI void U_EXPORT2 umtx_destroy( UMTX *mutex );
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/*
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* Atomic Increment and Decrement of an int32_t value.
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*
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* Return Values:
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* If the result of the operation is zero, the return zero.
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* If the result of the operation is not zero, the sign of returned value
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* is the same as the sign of the result, but the returned value itself may
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* be different from the result of the operation.
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*/
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U_CAPI int32_t U_EXPORT2 umtx_atomic_inc(int32_t *);
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U_CAPI int32_t U_EXPORT2 umtx_atomic_dec(int32_t *);
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#endif /*_CMUTEX*/
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/*eof*/
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