IID>#pragma once

IID>//
IID>// Наивная версия захвата/освобождения.
IID>// Максимально прозрачная.
IID>//
IID>class Semaphore
IID>{
IID>protected:
IID>    HANDLE m_hEvent;
IID>    volatile LONG m_lLockCount;
IID>    LONG m_lMaxCount;    

IID>public:
IID>    Semaphore();
IID>    ~Semaphore();

IID>    bool Init(
IID>        LONG lMaxCount
IID>        );
IID>    void Close();

IID>    bool Acquire(
IID>        DWORD dwTimeout = INFINITE
IID>        );
IID>    void Release();
IID>};

IID>Semaphore::Semaphore()
IID>    : m_hEvent(NULL)
IID>    , m_lLockCount(0)
IID>    , m_lMaxCount(0)
IID>{
IID>}

IID>Semaphore::~Semaphore()
IID>{
IID>    Close();
IID>}

IID>bool Semaphore::Init(
IID>    LONG lMaxCount
IID>    )
IID>{
IID>    ASSERT(!m_hEvent);
IID>    ASSERT(lMaxCount > 0);

IID>    if (lMaxCount <= 0)
IID>        return false;

IID>    m_lMaxCount = lMaxCount;

IID>    m_hEvent = CreateEvent(NULL, FALSE, FALSE, NULL);
IID>    return !!m_hEvent;
IID>}

IID>void Semaphore::Close()
IID>{
IID>    if (m_hEvent)
IID>    {
IID>        ASSERT(!m_lLockCount);
IID>        CloseHandle(m_hEvent);
IID>        m_hEvent = NULL;
IID>    }
IID>}

IID>bool Semaphore::Acquire(
IID>    DWORD dwTimeout /*= INFINITE */
IID>    )
IID>{
IID>    ASSERT( m_hEvent );
IID>    if (InterlockedIncrement(&m_lLockCount) <= m_lMaxCount)
IID>        return true;

IID>    if (WAIT_OBJECT_0 == WaitForSingleObject(m_hEvent, dwTimeout))
IID>        return true;

IID>    Release();
IID>    return false;
IID>}

IID>void Semaphore::Release()
IID>{
IID>    if (InterlockedDecrement(&m_lLockCount) >= m_lMaxCount)
IID>        return;

IID>    SetEvent(m_hEvent);
IID>}

IID>//
IID>// Версия захвата/освобождения, минимизирующая переключение в KM.
IID>//
IID>class SemaphoreSMP : public Semaphore
IID>{
IID>    LONG m_lWaitersCount;

IID>public:
IID>    SemaphoreSMP() : m_lWaitersCount(0) {}

IID>    bool Acquire(
IID>        DWORD dwTimeout = INFINITE
IID>        );
IID>    void Release();
IID>};

IID>bool SemaphoreSMP::Acquire(
IID>    DWORD dwTimeout /*= INFINITE */
IID>    )
IID>{
IID>    ASSERT( m_hEvent );
IID>    if (InterlockedIncrement(&m_lLockCount) <= m_lMaxCount)
IID>        return true;

IID>    int iSemSpinCount = 300;
IID>    for(int i = 0; i < iSemSpinCount; i++)
IID>    {
IID>        if (InterlockedCompareExchange(&m_lLockCount, m_lMaxCount, m_lMaxCount) == m_lMaxCount)
IID>            return true;
IID>    }

IID>    InterlockedIncrement(&m_lWaitersCount);
IID>    DWORD dwWaitResult = WaitForSingleObject(m_hEvent, dwTimeout);
IID>    if (WAIT_OBJECT_0 == dwWaitResult)
IID>        return true;

IID>    InterlockedDecrement(&m_lWaitersCount);
IID>    InterlockedDecrement(&m_lLockCount);
IID>    return false;
IID>}

IID>void SemaphoreSMP::Release()
IID>{
IID>    if (InterlockedDecrement(&m_lLockCount) >= m_lMaxCount)
IID>        return;

IID>    if (InterlockedDecrement(&m_lWaitersCount) >= 0)
IID>    {
IID>        SetEvent(m_hEvent);
IID>    } else {
IID>        InterlockedIncrement(&m_lWaitersCount);
IID>    }
IID>}

IID>