330 lines
11 KiB
C++
330 lines
11 KiB
C++
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//+-------------------------------------------------------------------
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//
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// File: RWLock.hxx
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//
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// Contents: Reader writer lock implementation that supports the
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// following features
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// 1. Cheap enough to be used in large numbers
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// such as per object synchronization.
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// 2. Supports timeout. This is a valuable feature
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// to detect deadlocks
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// 3. Supports caching of events. The allows
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// the events to be moved from least contentious
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// regions to the most contentious regions.
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// In other words, the number of events needed by
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// Reader-Writer lockls is bounded by the number
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// of threads in the process.
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// 4. Supports nested locks by readers and writers
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// 5. Supports spin counts for avoiding context switches
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// on multi processor machines.
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// 6. Supports functionality for upgrading to a writer
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// lock with a return argument that indicates
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// intermediate writes. Downgrading from a writer
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// lock restores the state of the lock.
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// 7. Supports functionality to Release Lock for calling
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// app code. RestoreLock restores the lock state and
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// indicates intermediate writes.
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// 8. Recovers from most common failures such as creation of
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// events. In other words, the lock mainitains consistent
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// internal state and remains usable
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//
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// Classes: CRWLock,
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// CStaticRWLock
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//
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// History: 19-Aug-98 Gopalk Created
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//
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//--------------------------------------------------------------------
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#ifndef _RWLOCK_HXX_
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#define _RWLOCK_HXX_
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#if LOCK_PERF==1
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#define RWLOCK_STATISTICS 1
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#endif
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extern DWORD gdwDefaultTimeout;
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extern DWORD gdwDefaultSpinCount;
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extern DWORD gdwNumberOfProcessors;
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typedef struct {
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DWORD dwFlags;
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DWORD dwWriterSeqNum;
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WORD *pwReaderLevel;
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WORD wReaderLevel;
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WORD wWriterLevel;
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} LockCookie;
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typedef DWORD WriterCookie;
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//+-------------------------------------------------------------------
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//
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// Class: CRWLock
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//
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// Synopsis: Abstract base class the implements the locking
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// functionality. It supports nested read locks and
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// guarantees progress when the derived class is capable
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// of creating ReaderSlot
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//
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// History: 21-Aug-98 Gopalk Created
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//
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//+-------------------------------------------------------------------
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#define RWLOCKFLAG_INITIALIZED 1
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#ifdef RWLOCK_FULL_FUNCTIONALITY
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#define RWLOCKFLAG_CACHEEVENTS 2
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#define RWLOCKFLAG_RETURNERRORS 4
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#endif
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class CRWLock
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{
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public:
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// Constuctor
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CRWLock() :
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_hWriterEvent(NULL),
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_hReaderEvent(NULL),
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_dwState(0),
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_dwWriterID(0),
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_dwWriterSeqNum(1),
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_wFlags(0),
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_wWriterLevel(0)
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#ifdef RWLOCK_STATISTICS
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,
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_dwReaderEntryCount(0),
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_dwReaderContentionCount(0),
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_dwWriterEntryCount(0),
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_dwWriterContentionCount(0)
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#endif
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#if DBG==1
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,
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_dwDeadLockCounter(0)
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#endif
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{
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}
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// Initialize
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virtual void Initialize() { _wFlags |= RWLOCKFLAG_INITIALIZED; }
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BOOL IsInitialized() { return(_wFlags & RWLOCKFLAG_INITIALIZED); }
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// Cleanup
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virtual void Cleanup();
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// Lock functions
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HRESULT AcquireReaderLock(
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#ifdef RWLOCK_FULL_FUNCTIONALITY
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BOOL fReturnErrors = FALSE,
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DWORD dwDesiredTimeout = gdwDefaultTimeout
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#if LOCK_PERF==1
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,
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#endif
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#endif
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#if LOCK_PERF==1
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const char *pszFile = "Unknown File",
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DWORD dwLine = 0,
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const char *pszLockName = "Unknown RWLock"
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#endif
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);
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HRESULT AcquireWriterLock(
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#ifdef RWLOCK_FULL_FUNCTIONALITY
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BOOL fReturnErrors = FALSE,
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DWORD dwDesiredTimeout = gdwDefaultTimeout
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#if LOCK_PERF==1
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,
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#endif
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#endif
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#if LOCK_PERF==1
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const char *pszFile = "Unknown File",
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DWORD dwLine = 0,
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const char *pszLockName = "Unknown RWLock"
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#endif
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);
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HRESULT ReleaseReaderLock();
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HRESULT ReleaseWriterLock();
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HRESULT UpgradeToWriterLock(LockCookie *pLockCookie,
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BOOL *pfInterveningWrites = NULL
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#ifdef RWLOCK_FULL_FUNCTIONALITY
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,
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BOOL fReturnErrors = FALSE,
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DWORD dwDesiredTimeout = gdwDefaultTimeout
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#endif
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#if LOCK_PERF==1
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,
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const char *pszFile = "Unknown File",
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DWORD dwLine = 0,
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const char *pszLockName = "Unknown RWLock"
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#endif
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);
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HRESULT DowngradeFromWriterLock(LockCookie *pLockCookie
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#if LOCK_PERF==1
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,
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const char *pszFile = "Unknown File",
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DWORD dwLine = 0,
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const char *pszLockName = "Unknown RWLock"
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#endif
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);
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HRESULT ReleaseLock(LockCookie *pLockCookie);
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HRESULT RestoreLock(LockCookie *pLockCookie,
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BOOL *pfInterveningWrites = NULL
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#if LOCK_PERF==1
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,
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const char *pszFile = "Unknown File",
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DWORD dwLine = 0,
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const char *pszLockName = "Unknown RWLock"
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#endif
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);
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// Assert functions
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#if DBG==1
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BOOL AssertWriterLockHeld();
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BOOL AssertWriterLockNotHeld();
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BOOL AssertReaderLockHeld();
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BOOL AssertReaderLockNotHeld();
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BOOL AssertReaderOrWriterLockHeld();
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void AssertHeld() { AssertWriterLockHeld(); }
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void AssertNotHeld() { AssertWriterLockNotHeld();
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AssertReaderLockNotHeld(); }
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#else
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void AssertWriterLockHeld() { }
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void AssertWriterLockNotHeld() { }
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void AssertReaderLockHeld() { }
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void AssertReaderLockNotHeld() { }
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void AssertReaderOrWriterLockHeld() { }
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void AssertHeld() { }
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void AssertNotHeld() { }
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#endif
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// Helper functions
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WriterCookie GetWriterCookie() { return(_dwWriterSeqNum); }
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BOOL IntermediateWrites(WriterCookie cookie) { return((cookie+1) != _dwWriterSeqNum); }
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BOOL HeldExclusive() { return _dwWriterID == GetCurrentThreadId(); }
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#ifdef RWLOCK_FULL_FUNCTIONALITY
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void ReturnErrors() { _wFlags |= RWLOCKFLAG_RETURNERRORS; }
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void CacheEvents() { _wFlags |= RWLOCKFLAG_CACHEEVENTS; }
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#endif
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#ifdef RWLOCK_STATISTICS
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DWORD GetReaderEntryCount() { return(_dwReaderEntryCount); }
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DWORD GetReaderContentionCount() { return(_dwReaderContentionCount); }
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DWORD GetWriterEntryCount() { return(_dwWriterEntryCount); }
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DWORD GetWriterContentionCount() { return(_dwWriterContentionCount); }
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#endif
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// Static functions
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static void InitDefaults();
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static void SetTimeout(DWORD dwTimeout) { gdwDefaultTimeout = dwTimeout; }
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static DWORD GetTimeout() { return(gdwDefaultTimeout); }
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static void SetSpinCount(DWORD dwSpinCount) { gdwDefaultSpinCount = gdwNumberOfProcessors > 1
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? dwSpinCount
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: 0; }
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static DWORD GetSpinCount() { return(gdwDefaultSpinCount); }
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private:
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virtual HRESULT GetTLSLockData(WORD **ppwReaderLevel) = 0;
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HANDLE GetReaderEvent();
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HANDLE GetWriterEvent();
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ULONG ModifyState(ULONG dwModifyState);
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#ifdef RWLOCK_FULL_FUNCTIONALITY
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void ReleaseEvents();
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#endif
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static void RWSetEvent(HANDLE event);
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static void RWResetEvent(HANDLE event);
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static void RWSleep(DWORD dwTime);
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HANDLE _hWriterEvent;
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HANDLE _hReaderEvent;
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DWORD _dwState;
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DWORD _dwWriterID;
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DWORD _dwWriterSeqNum;
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WORD _wFlags;
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WORD _wWriterLevel;
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#ifdef RWLOCK_STATISTICS
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DWORD _dwReaderEntryCount;
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DWORD _dwReaderContentionCount;
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DWORD _dwWriterEntryCount;
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DWORD _dwWriterContentionCount;
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#endif
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#if DBG==1
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DWORD _dwDeadLockCounter;
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#endif
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};
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//+-------------------------------------------------------------------
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//
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// Class: CStaticRWLock
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//
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// Synopsis: Instances of this class are statically created. It
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// manages creation and allocation of ReaderSlots
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//
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// History: 21-Aug-98 Gopalk Created
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//
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//+-------------------------------------------------------------------
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class CStaticRWLock : public CRWLock
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{
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public:
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// Constructor
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CStaticRWLock() :
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_dwLockNum(-1)
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{
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}
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// Initialize
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void Initialize();
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// Compatibility functions
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void Request(
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const char *pszFile = "Unknown File",
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DWORD dwLine = 0,
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const char* pszLockName = "Unknown RWLock"
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)
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{
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AcquireWriterLock(
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#if LOCK_PERF==1
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#ifdef RWLOCK_FULL_FUNCTIONALITY
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FALSE, gdwDefaultTimeout,
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#endif
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pszFile, dwLine, pszLockName
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#endif
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);
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}
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void Release()
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{
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ReleaseWriterLock();
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}
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private:
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HRESULT GetTLSLockData(WORD **ppwReaderLevel);
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DWORD _dwLockNum;
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};
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//+-------------------------------------------------------------------
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//
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// Class: CStaticWriteLock
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//
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// Synopsis: Helper class that simulates acquiring/releasing
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// write lock as constructing/destroying an object
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// on the stack
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//
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// History: 21-Aug-98 Gopalk Created
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//
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//+-------------------------------------------------------------------
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class CStaticWriteLock
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{
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public:
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CStaticWriteLock(
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CStaticRWLock &rwLock,
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const char *pszFile = "Unknown File",
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DWORD dwLine = 0,
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const char* pszLockName = "Unknown RWLock") :
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_rwLock(rwLock)
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{
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_rwLock.Request(pszFile, dwLine, pszLockName);
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}
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~CStaticWriteLock()
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{
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_rwLock.Release();
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}
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private:
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CStaticRWLock &_rwLock;
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};
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#endif // _RWLOCK_HXX_
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