icuSources/common/mutex.h

   1 // © 2016 and later: Unicode, Inc. and others.
   2 // License & terms of use: http://www.unicode.org/copyright.html
   3 /*
   4 ******************************************************************************
   5 *
   6 *   Copyright (C) 1997-2013, International Business Machines
   7 *   Corporation and others.  All Rights Reserved.
   8 *
   9 ******************************************************************************
  10 */
  11 //----------------------------------------------------------------------------
  12 // File:     mutex.h
  13 //
  14 // Lightweight C++ wrapper for umtx_ C mutex functions
  15 //
  16 // Author:   Alan Liu  1/31/97
  17 // History:
  18 // 06/04/97   helena         Updated setImplementation as per feedback from 5/21 drop.
  19 // 04/07/1999  srl               refocused as a thin wrapper
  20 //
  21 //----------------------------------------------------------------------------
  22 #ifndef MUTEX_H
  23 #define MUTEX_H
  24
  25 #include "unicode/utypes.h"
  26 #include "unicode/uobject.h"
  27 #include "umutex.h"
  28
  29 U_NAMESPACE_BEGIN
  30
  31 /**
  32   * Mutex is a helper class for convenient locking and unlocking of a UMutex.
  33   *
  34   * Creating a local scope Mutex will lock a UMutex, holding the lock until the Mutex
  35   * goes out of scope.
  36   *
  37   *  If no UMutex is specified, the ICU global mutex is implied.
  38   *
  39   *  For example:
  40   *
  41   *  UMutex *myMutex() {
  42   *    static UMutex *m = STATIC_NEW(UMutex);
  43   *    return m;
  44   *  }
  45   *
  46   *  void Function(int arg1, int arg2)
  47   *  {
  48   *     static Object* foo;      // Shared read-write object
  49   *     Mutex mutex(myMutex());  // or no args for the global lock
  50   *     foo->Method();
  51   *     // When 'mutex' goes out of scope and gets destroyed here, the lock is released
  52   *  }
  53   *
  54   *  Note:  Do NOT use the form 'Mutex mutex();' as that merely forward-declares a function
  55   *         returning a Mutex. This is a common mistake which silently slips through the
  56   *         compiler!!
  57   */
  58
  59 class U_COMMON_API Mutex : public UMemory {
  60 public:
  61     Mutex(UMutex *mutex = nullptr) : fMutex(mutex) {
  62         umtx_lock(fMutex);
  63     };
  64     ~Mutex() {
  65         umtx_unlock(fMutex);
  66     };
  67
  68     Mutex(const Mutex &other) = delete; // forbid assigning of this class
  69     Mutex &operator=(const Mutex &other) = delete; // forbid copying of this class
  70     void *operator new(size_t s) = delete;  // forbid heap allocation. Locals only.
  71
  72 private:
  73     UMutex   *fMutex;
  74 };
  75
  76
  77 U_NAMESPACE_END
  78
  79 #endif //_MUTEX_
  80 //eof