CCoContext.cpp

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#include "stdafx.h"

namespace AxPipe {
    CCoContext::CCoContext(CError *pErr, void (*pfStart)(void *), void *pvParam) {
        m_pFiber = NULL;
        Init(pErr, pfStart, pvParam);
    }

    void
    CCoContext::Init(CError *pErr, void (*pfStart)(void *), void *pvParam) {
        m_pErr = pErr;
        m_pfStart = pfStart;
        m_pvParam = pvParam;
    }
    
    CCoContext::~CCoContext() {
        Stop();
    }

    VOID CALLBACK
    CCoContext::Start(PVOID lpParam) {
        ((CCoContext *)lpParam)->m_pfStart(((CCoContext *)lpParam)->m_pvParam);
        // Should never get here.
    }
    
    bool
    CCoContext::Go() {
        // First assure we really do have a TLS index. If we don't - this is
        // an error condition.
        if (dwTlsIndex == TLS_OUT_OF_INDEXES) {
            m_pErr->SetError(ERROR_CODE_INTERNAL, ERROR_MSG_INTERNAL, _T("CoContext::Go() [No TLS available]"));
            return false;
        }
        // If this is the first call to Go() - i.e. initialize
        if (!m_pFiber) {
            m_dwThreadId = GetCurrentThreadId();
            // If we're to initialize in the current context
            if (!m_pfStart) {
                //OutputDebugString(_T("CCoContext::Go() !m_pfStart Init in current context\n"));
                // If we're not a fiber, we need to convert to one.
                if (TlsGetValue(dwTlsIndex) == NULL) {
                    //OutputDebugString(_T("CCoContext::Go() ConvertThreadToFiber(0)\n"));
                    m_pFiber = ConvertThreadToFiber(0);
                    // And now we've converted to one, we need to remember that this thread
                    // is now a fiber. If we have TLS, we set the value to true to inidcate this.
                    TlsSetValue(dwTlsIndex, (LPVOID)true);
                } else {
                    //OutputDebugString(_T("CCoContext::Go() GetCurrentFiber()\n"));
                    m_pFiber = GetCurrentFiber();
                }
                // Now m_pFiber is the current fiber.

                // We must guard against effectively doing SwitchToFiber(GetCurrentFiber())
                // Since we're just initializing this context, and want to remain here,
                // we just do a return.
                return true;
            }
            // We're to create a new fiber with a specific starting point, so
            // let's do that.
            //OutputDebugString(_T("CCoContext::Go() CreateFiber(0, Start, this)\n"));
            m_pFiber = CreateFiber(0, Start, this);
            // ...we fall through below to actually start the fiber too.
        }
        // Here the thread must have been converted to a fiber, to allow the switch.
        ASSCHK(TlsGetValue(dwTlsIndex) != NULL, _T("CoContext::Go() [Attempt to switch to fiber from non-fiber]"));
//        ASSCHK(m_dwThreadId == GetCurrentThreadId(), _T("CoContext::Go() [Attempt to schedule fiber in different thread]"));
        //OutputDebugString(_T("CCoContext::Go() SwitchToFiber()\n"));
        SwitchToFiber(m_pFiber);
        // Now we're back, because someone switched to us
        return true;
    }

    void
    CCoContext::Stop() {
        // If we have a StartProc and we have a fiber...
        if (m_pFiber && m_pfStart) {
            // ...and this fiber is not the current fiber...
            if (m_pFiber != GetCurrentFiber()) {
                // ... then we delete it, and forget it.
                DeleteFiber(m_pFiber);
                m_pFiber = NULL;
            } else {
                // ... otherwise we're trying to stop ourselves, which we can't do.
                ASSCHK(false, _T("Attempting to stop self"));
            }
        }
    }
};

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