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21 
22 
23 
24 #ifndef INCLUDED_UNOTOOLS_READWRITEMUTEXGUARD_HXX
25 #define INCLUDED_UNOTOOLS_READWRITEMUTEXGUARD_HXX
26 
27 #include <osl/mutex.hxx>
28 
29 namespace utl {
30 
31 class ReadWriteGuard;
32 class ReadWriteMutex
33 {
34     friend class ReadWriteGuard;
35 
36             sal_uInt32          nReadCount;
37             sal_uInt32          nBlockCriticalCount;
38             ::osl::Mutex*       pMutex;
39             ::osl::Mutex*       pWriteMutex;
40 
41 public:
ReadWriteMutex()42                                 ReadWriteMutex()
43                                     : nReadCount(0)
44                                     , nBlockCriticalCount(0)
45                                     , pMutex( new ::osl::Mutex )
46                                     , pWriteMutex( new ::osl::Mutex )
47                                     {}
~ReadWriteMutex()48                                 ~ReadWriteMutex()
49                                     {
50                                         delete pMutex;
51                                         delete pWriteMutex;
52                                     }
53 };
54 
55 
56 namespace ReadWriteGuardMode {
57 const sal_Int32 nWrite          = 0x01;
58 const sal_Int32 nCriticalChange = 0x02 | nWrite;
59 const sal_Int32 nBlockCritical  = 0x04;     // only a block, not a read, exclusive flag!
60 }
61 
62 /** Enable multiple threads to read simultaneously, but a write blocks all
63     other reads and writes, and a read blocks any write.
64     Used in I18N wrappers to be able to maintain a single instance of a wrapper
65     for the standard Office locale.
66     NEVER construct a writing guard if there is already a reading guard in the
67     same context, the following will dead lock EVEN IN THE SAME THREAD!
68     void foo()
69     {
70         ReadWriteGuard aGuard1( aMutex );
71         bar();
72     }
73     void bar()
74     {
75         // waits forever for aGuard1
76         ReadWriteGuard aGuard2( aMutex, ReadWriteGuardMode::nWrite );
77     }
78  */
79 class ReadWriteGuard
80 {
81             ReadWriteMutex&     rMutex;
82             sal_Int32           nMode;
83 public:
84                                 ReadWriteGuard(
85                                     ReadWriteMutex& rMutex,
86                                     sal_Int32 nRequestMode = 0  // read only
87                                     );
88                                 ~ReadWriteGuard();
89 
90     /** Be careful with this, it does wait for ANY read to complete.
91         The following will dead lock EVEN IN THE SAME THREAD!
92         void foo()
93         {
94             ReadWriteGuard aGuard1( aMutex );
95             bar();
96         }
97         void bar()
98         {
99             ReadWriteGuard aGuard2( aMutex );
100             aGuard2.changeReadToWrite();    // waits forever for aGuard1
101         }
102      */
103             void                changeReadToWrite();
104 };
105 
106 }   // namespace utl
107 
108 #endif // INCLUDED_UNOTOOLS_READWRITEMUTEXGUARD_HXX
109 
110