Check in the pristine copy of ICU 4.6...

icu46/source/common/umutex.h

+/*
+**********************************************************************
+*   Copyright (C) 1997-2008, International Business Machines
+*   Corporation and others.  All Rights Reserved.
+**********************************************************************
+*
+* File UMUTEX.H
+*
+* Modification History:
+*
+*   Date        Name        Description
+*   04/02/97  aliu        Creation.
+*   04/07/99  srl         rewrite - C interface, multiple mutices
+*   05/13/99  stephen     Changed to umutex (from cmutex)
+******************************************************************************
+*/
+
+#ifndef UMUTEX_H
+#define UMUTEX_H
+
+#include "unicode/utypes.h"
+#include "unicode/uclean.h"  
+
+
+/* APP_NO_THREADS is an old symbol. We'll honour it if present. */
+#ifdef APP_NO_THREADS
+# define ICU_USE_THREADS 0
+#endif
+
+/* ICU_USE_THREADS
+ *
+ *   Allows thread support (use of mutexes) to be compiled out of ICU.
+ *   Default: use threads.
+ *   Even with thread support compiled out, applications may override the
+ *   (empty) mutex implementation with the u_setMutexFunctions() functions.
+ */ 
+#ifndef ICU_USE_THREADS
+# define ICU_USE_THREADS 1
+#endif
+
+/**
+ * By default assume that we are on a machine with a weak memory model,
+ * and the double check lock won't work reliably.
+ */
+#if !defined(UMTX_STRONG_MEMORY_MODEL)
+#define UMTX_STRONG_MEMORY_MODEL 0
+#endif
+
+/**
+ * \def UMTX_CHECK
+ * Encapsulates a safe check of an expression 
+ * for use with double-checked lazy inititialization.
+ * On CPUs with weak memory models, this must use memory fence instructions
+ * or mutexes.
+ * The expression must involve only a  _single_ variable, typically
+ *    a possibly null pointer or a boolean that indicates whether some service
+ *    is initialized or not.
+ * The setting of the variable involved in the test must be the last step of
+ *    the initialization process.
+ *
+ * 
+ * @internal
+ */
+#if UMTX_STRONG_MEMORY_MODEL
+
+#define UMTX_CHECK(pMutex, expression, result) \
+    (result)=(expression)
+
+#else
+
+#define UMTX_CHECK(pMutex, expression, result) \
+    umtx_lock(pMutex); \
+    (result)=(expression); \
+    umtx_unlock(pMutex)
+
+#endif
+
+/*
+ * Code within ICU that accesses shared static or global data should
+ * instantiate a Mutex object while doing so.  The unnamed global mutex
+ * is used throughout ICU, so keep locking short and sweet.
+ *
+ * For example:
+ *
+ * void Function(int arg1, int arg2)
+ * {
+ *   static Object* foo;     // Shared read-write object
+ *   umtx_lock(NULL);        // Lock the ICU global mutex
+ *   foo->Method();
+ *   umtx_unlock(NULL);
+ * }
+ *
+ * an alternative C++ mutex API is defined in the file common/mutex.h
+ */
+
+/* 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_CAPI void U_EXPORT2 umtx_lock   ( UMTX* mutex ); 
+
+/* Unlock a mutex. Pass in NULL if you want the single global
+   mutex. 
+ * @param mutex The given mutex to be unlocked.  Pass NULL to specify
+ *              the global ICU mutex.
+ */
+U_CAPI void U_EXPORT2 umtx_unlock ( UMTX* mutex );
+
+/* Initialize a mutex. Use it this way:
+   umtx_init( &aMutex ); 
+ * ICU Mutexes do not need explicit initialization before use.  Use of this
+ *   function is not necessary.
+ * Initialization of an already initialized mutex has no effect, and is safe to do.
+ * Initialization of mutexes is thread safe.  Two threads can concurrently 
+ *   initialize the same mutex without causing problems.
+ * @param mutex The given mutex to be initialized
+ */
+U_CAPI void U_EXPORT2 umtx_init   ( UMTX* mutex );
+
+/* Destroy a mutex. This will free the resources of a mutex.
+ * Use it this way:
+ *   umtx_destroy( &aMutex ); 
+ * Destroying an already destroyed mutex has no effect, and causes no problems.
+ * This function is not thread safe.  Two threads must not attempt to concurrently
+ *   destroy the same mutex.
+ * @param mutex The given mutex to be destroyed.
+ */
+U_CAPI void U_EXPORT2 umtx_destroy( UMTX *mutex );
+
+
+
+/*
+ * Atomic Increment and Decrement of an int32_t value.
+ *
+ * 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.
+ */
+U_CAPI int32_t U_EXPORT2 umtx_atomic_inc(int32_t *);
+U_CAPI int32_t U_EXPORT2 umtx_atomic_dec(int32_t *);
+
+
+#endif /*_CMUTEX*/
+/*eof*/
+
+
+