Дональд Бокс - Сущность технологии СОМ. Библиотека программиста

• Название: Сущность технологии СОМ. Библиотека программиста
• Автор: Дональд Бокс
• Издательство: Питер
• Жанр: Программирование
• Год: 2001
• ISBN: 5-318-00058-4

В этой книге СОМ исследуется с точки зрения разработчика C++. Написанная ведущим специалистом по модели компонентных объектов СОМ, она раскрывает сущность СОМ, помогая разработчикам правильно понять не только методы модели программирования СОМ, но и ее основу. Понимание мотивов создания СОМ и ее аспектов, касающихся распределенных систем, чрезвычайно важно для тех разработчиков, которые желают пойти дальше простейших приложений СОМ и стать по-настоящему эффективными СОМ-программистами. Показывая, почему СОМ для распределенных систем (Distributed СОМ) работает именно так, а не иначе, Дон Бокс дает вам возможность применять эту модель творчески и эффективно для ежедневных задач программирования.

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STDMETHODIMP

ChatSession::get_SessionName(OLECHAR **ppwsz)

{

if (!ppwsz)

return E_INVALIDARG;

else if ((*ppwsz = OLESTRDUP(m_wszSessionName)) == 0)

return E_OUTOFMEMORY;

return S_OK;

}

STDMETHODIMP

ChatSession::Say(const OLECHAR *pwszStatement)

{

HRESULT hr = S_OK;

// protect access to method

OLECHAR *pwszUser = GetCaller();

if (pwszUser && CheckAccess(pwszUser))

{

SLock();

try

{

wstring s = pwszUser;

s += L":";

s += pwszStatement;

m_statements.push_back(s);

}

catch(...)

{

hr = E_OUTOFMEMORY;

}

SUnlock();

if (SUCCEEDED(hr))

Fire_OnNewStatement(pwszUser, pwszStatement);

}

else

hr = E_ACCESSDENIED;

CoTaskMemFree(pwszUser);

return hr;

}

STDMETHODIMP

ChatSession::GetStatements(IEnumString **ppes)

{

if (ppes == 0)

return E_INVALIDARG;

*ppes = new StatementEnumerator(this);

if (*ppes == 0)

return E_OUTOFMEMORY;

(*ppes)->AddRef();

return S_OK;

}

STDMETHODIMP

ChatSession::Advise(IChatSessionEvents *pEventSink,

DWORD *pdwReg)

{

HRESULT hr = S_OK;

if (pEventSink == 0 || pdwReg == 0)

return E_INVALIDARG;

LISTENER *pNew = new LISTENER;

if (pNew == 0)

return E_OUTOFMEMORY;

OLECHAR *pwszUser = GetCaller();

if (pwszUser)

{

Fire_OnNewUser(pwszUser);

ALock();

pNew->pwszUser = pwszUser;

if (pNew->pItf = pEventSink)

pEventSink->AddRef();

pNew->pNext = m_pHeadListeners;

if (m_pHeadListeners)

m_pHeadListeners->pPrev = pNew;

pNew->pPrev = 0;

m_pHeadListeners = pNew;

AUnlock();

}

else

{

delete pNew;

return E_OUTOFMEMORY;

}

*pdwReg = reinterpret_cast<DWORD>(pNew);

return hr;

}

STDMETHODIMP

ChatSession::Unadvise(DWORD dwReg)

{

if (dwReg == 0)

return E_INVALIDARG;

HRESULT hr = S_OK;

LISTENER *pThisNode = reinterpret_cast<LISTENER *>(dwReg);

ALock();

if (pThisNode->pPrev)

pThisNode->pPrev->pNext = pThisNode->pNext;

else

m_pHeadListeners = pThisNode->pNext;

if (pThisNode->pNext)

pThisNode->pNext->pPrev = pThisNode->pPrev;

if (pThisNode->pItf)

pThisNode->pItf->Release();

OLECHAR *pwszUser = pThisNode->pwszUser;

delete pThisNode;

AUnlock();

Fire_OnUserLeft(pwszUser);

CoTaskMemFree(pwszUser);

return hr;

}

// class StatementEnumerator ///////////////////

StatementEnumerator::StatementEnumerator(ChatSession *pThis)

: m_cRef(0),

m_pThis(pThis),

m_cursor(pThis->m_statements.begin())

{

m_pThis->AddRef();

InitializeCriticalSection(&m_csLock);

}

StatementEnumerator::~StatementEnumerator(void)

{

m_pThis->Release();

DeleteCriticalSection(&m_csLock);

}

// lock helpers (note that ChatSession is locked

// simultaneously)

void

StatementEnumerator::Lock(void)

{

EnterCriticalSection(&m_csLock);

m_pThis->SLock();

}

void

StatementEnumerator::Unlock(void)

{

LeaveCriticalSection(&m_csLock);

m_pThis->SUnlock();

}

// IUnknown methods

STDMETHODIMP

StatementEnumerator::QueryInterface(REFIID riid, void **ppv)

{

if (riid == IID_IUnknown)

*ppv = static_cast<IEnumString*>(this);

else if (riid == IID_IEnumString)

*ppv = static_cast<IEnumString*>(this);

else

return (*ppv = 0), E_NOINTERFACE;

reinterpret_cast<IUnknown*>(*ppv)->AddRef();

return S_OK;

}

STDMETHODIMP_(ULONG)

StatementEnumerator::AddRef(void)

{

return InterlockedIncrement(&m_cRef);

}

STDMETHODIMP_(ULONG)

StatementEnumerator::Release(void)

{

LONG res = InterlockedDecrement(&m_cRef);

if (res == 0)

delete this;

return res;

}

// IEnumString methods

STDMETHODIMP

StatementEnumerator::Next(ULONG cElems, OLECHAR **rgElems,

ULONG *pcFetched)

{

if (pcFetched == 0 && cElems > 1)

return E_INVALIDARG;

ZeroMemory(rgElems, sizeof(OLECHAR*) * cElems);

Lock();

ULONG cActual = 0;

while (cActual < cElems

&& m_cursor != m_pThis->m_statements.end())

{

if (rgElems[cActual] = OLESTRDUP((*m_cursor).c_str()))

{

m_cursor++;

cActual++;

}

else // allocation error, unwind

{

while (cActual > 0)

{

cActual–;

CoTaskMemFree(rgElems[cActual]);

rgElems[cActual] = 0;

}

break;

}

}

Unlock();

if (pcFetched)

*pcFetched = cActual;

return cElems == cActual ? S_OK : S_FALSE;

}

STDMETHODIMP

StatementEnumerator::Skip(ULONG cElems)

{

Lock();

ULONG cActual = 0;

while (cActual < cElems

&& m_cursor != m_pThis->m_statements.end())

{

m_cursor++;

cActual++;

}

Unlock();

return cElems == cActual ? S_OK : S_FALSE;

}

STDMETHODIMP

StatementEnumerator::Reset(void)

{

Lock();

m_cursor = m_pThis->m_statements.begin();

Unlock();

return S_OK;

}

STDMETHODIMP

StatementEnumerator::Clone(IEnumString **ppes)

{

if (ppes == 0)

return E_INVALIDARG;

if (*ppes = new StatementEnumerator(m_pThis))

return S_OK;

return E_OUTOFMEMORY;

}

// class ChatSessionClass /////////////////////

ChatSessionClass::ChatSessionClass(void)

: m_cStrongLocks(0)

{

InitializeCriticalSection(&m_csSessionLock);

}

ChatSessionClass::~ChatSessionClass(void)

{

DeleteCriticalSection(&m_csSessionLock);

}

void

ChatSessionClass::Lock(void)

{

EnterCriticalSection(&m_csSessionLock);

}

void

ChatSessionClass::Unlock(void)

{

LeaveCriticalSection(&m_csSessionLock);

}

// helper method to protect access to DeleteSession

// to only allow COMChat Admins to delete groups

bool

ChatSessionClass::CheckAccess(const OLECHAR *pwszUser)

{

if (wcscmp(pwszUser, L"anonymous") == 0)

return false;

TRUSTEEW trustee = {

0, NO_MULTIPLE_TRUSTEE, TRUSTEE_IS_NAME,

TRUSTEE_IS_USER, const_cast<OLECHAR*>(pwszUser)

};

BOOL bIsAllowed;

HRESULT hr = g_pacAdmins->IsAccessAllowed(&trustee,0,

COM_RIGHTS_EXECUTE,

&bIsAllowed);

if (FAILED(hr))

bIsAllowed = false;

return SUCCEEDED(hr) && bIsAllowed != FALSE;

}

// IUnknown methods

STDMETHODIMP

ChatSessionClass::QueryInterface(REFIID riid, void **ppv)

{

if (riid == IID_IUnknown)

*ppv = static_cast<IChatSessionManager*>(this);

else if (riid == IID_IChatSessionManager)

*ppv = static_cast<IChatSessionManager*>(this);

else if (riid == IID_IExternalConnection)

*ppv = static_cast<IExternalConnection*>(this);

else

return (*ppv = 0), E_NOINTERFACE;

reinterpret_cast<IUnknown*>(*ppv)->AddRef();

return S_OK;

}

STDMETHODIMP_(ULONG)

ChatSessionClass::AddRef(void)

{

return 2;

}

STDMETHODIMP_(ULONG)

ChatSessionClass::Release(void)

{

return 1;

}

// IExternalConnection methods

STDMETHODIMP_(DWORD)

ChatSessionClass::AddConnection(DWORD extconn, DWORD)

{

if (extconn & EXTCONN_STRONG)

{

ModuleLock();

return InterlockedIncrement(&m_cStrongLocks);

}

return 0;

}

STDMETHODIMP_(DWORD)

ChatSessionClass::ReleaseConnection(DWORD extconn, DWORD,

BOOL bLastReleaseKillsStub)

{

if (extconn & EXTCONN_STRONG)

{

LONG res = InterlockedDecrement(&m_cStrongLocks);

if (res == 0 && bLastReleaseKillsStub)

CoDisconnectObject(

static_cast<IExternalConnection*>(this), 0);

ModuleUnlock();

return res;

}

return 0;

}

// IChatSessionManager methods

STDMETHODIMP

ChatSessionClass::GetSessionNames(IEnumString **ppes)

{

if (ppes == 0)

return E_INVALIDARG;

if (*ppes = new SessionNamesEnumerator(this))

{

(*ppes)->AddRef();

return S_OK;

}

else

return E_OUTOFMEMORY;

}

STDMETHODIMP

ChatSessionClass::FindSession(const OLECHAR *pwszSessionName,

BOOL bDontCreate,

BOOL bAllowAnonymousAccess,

IChatSession **ppcs)

{

if (ppcs == 0)

return E_INVALIDARG;

HRESULT hr = E_FAIL;

*ppcs = 0;

OLECHAR *pwszUser = GetCaller();

Lock();

SESSIONMAP::iterator it = m_sessions.find(pwszSessionName);

if (it == m_sessions.end())

{

if (bDontCreate)

hr = E_FAIL;

else if (!bAllowAnonymousAccess

&& wcscmp(pwszUser, L"anonymous") == 0)

hr = E_ACCESSDENIED;

else

{

ChatSession *pNew =

new ChatSession(pwszSessionName,

bAllowAnonymousAccess != FALSE);

if (pNew)

{

pNew->AddRef();

m_sessions.insert(

pair<wstring,

ChatSession*>(pwszSessionName,

pNew));

(*ppcs = pNew)->AddRef();

hr = S_OK;

}

else

hr = E_OUTOFMEMORY;

}

}

else

{

(*ppcs = (*it).second)->AddRef();

hr = S_OK;

}

Unlock();

CoTaskMemFree(pwszUser);

return hr;

}

STDMETHODIMP

ChatSessionClass::DeleteSession(const OLECHAR *pwszSessionName)

{

if (pwszSessionName == 0)

return E_INVALIDARG;

HRESULT hr = E_FAIL;

OLECHAR *pwszUser = GetCaller();

if (CheckAccess(pwszUser))

{

Lock();

SESSIONMAP::iterator it

= m_sessions.find(pwszSessionName);

if (it == m_sessions.end())

{

hr = E_FAIL;

}

else

{

(*it).second->Disconnect();

(*it).second->Release();

m_sessions.erase(it);

hr = S_OK;

}

Unlock();

}

else

hr = E_ACCESSDENIED;

CoTaskMemFree(pwszUser);

return hr;

}

// class SessionNamesEnumerator

vector<wstring>&

SessionNamesEnumerator::Strings(void)

{

if (m_pStrings)

return *m_pStrings;

else

return *(m_pCloneSource->m_pStrings);

}

void

SessionNamesEnumerator::Lock(void)

{

EnterCriticalSection(&m_csLock);

}

void

SessionNamesEnumerator::Unlock(void)

{

LeaveCriticalSection(&m_csLock);

}

SessionNamesEnumerator::SessionNamesEnumerator(

ChatSessionClass *pSessionClass)

: m_cRef(0),

m_pStrings(0),

m_pCloneSource(0)

{

typedef ChatSessionClass::SESSIONMAP::iterator iterator;

ChatSessionClass::SESSIONMAP &sessions

= pSessionClass->m_sessions;

m_pStrings = new vector<wstring>;

pSessionClass->Lock();

for (iterator it = sessions.begin();

it != sessions.end();

it++)

{

m_pStrings->push_back((*it).first);

}

pSessionClass->Unlock();

m_cursor = Strings().begin();

InitializeCriticalSection(&m_csLock);

}

SessionNamesEnumerator::SessionNamesEnumerator(

SessionNamesEnumerator *pCloneSource)

: m_cRef(0),

m_pStrings(0),

m_pCloneSource(pCloneSource)

{

m_pCloneSource->AddRef();

m_cursor = Strings().begin();

InitializeCriticalSection(&m_csLock);

}

SessionNamesEnumerator::~SessionNamesEnumerator(void)

{

if (m_pCloneSource)

m_pCloneSource->Release();

else if (m_pStrings)

delete m_pStrings;

DeleteCriticalSection(&m_csLock);

}

// IUnknown methods

STDMETHODIMP

SessionNamesEnumerator::QueryInterface(REFIID riid, void **ppv)

{

if (riid == IID_IUnknown)

*ppv = static_cast<IEnumString*>(this);

else if (riid == IID_IEnumString)

*ppv = static_cast<IEnumString*>(this);

else

return (*ppv = 0), E_NOINTERFACE;

reinterpret_cast<IUnknown*>(*ppv)->AddRef();

return S_OK;

}

STDMETHODIMP_(ULONG)

SessionNamesEnumerator::AddRef(void)

{

ModuleLock();

return InterlockedIncrement(&m_cRef);

}

STDMETHODIMP_(ULONG)

SessionNamesEnumerator::Release(void)

{

LONG res = InterlockedDecrement(&m_cRef);

if (res == 0)

delete this;

ModuleUnlock();

return res;

}

// IEnumString methods

STDMETHODIMP

SessionNamesEnumerator::Next(ULONG cElems, OLECHAR **rgElems,

ULONG *pcFetched)

{

if (cElems > 1 && pcFetched == 0)

return E_INVALIDARG;

ULONG cActual = 0;

vector<wstring> &rstrings = Strings();

Lock();

while (cActual < cElems

&& m_cursor != rstrings.end())

{

if (rgElems[cActual] = OLESTRDUP((*m_cursor).c_str()))

{

m_cursor++;

cActual++;

}

else // allocation error, unwind

{

while (cActual > 0)

{

cActual–;

CoTaskMemFree(rgElems[cActual]);

rgElems[cActual] = 0;

}

break;

}

}

Unlock();

if (cActual)

*pcFetched = cActual;

return cActual == cElems ? S_OK : S_FALSE;

}

STDMETHODIMP

SessionNamesEnumerator::Skip(ULONG cElems)

{

ULONG cActual = 0;

vector<wstring> &rstrings = Strings();

Lock();

while (cActual < cElems

&& m_cursor != rstrings.end())

{

m_cursor++;

cActual++;

}

Unlock();

return cActual == cElems ? S_OK : S_FALSE;

}

STDMETHODIMP

SessionNamesEnumerator::Reset(void)

{

Lock();

m_cursor = Strings().begin();

Unlock();

return S_OK;

}

STDMETHODIMP

SessionNamesEnumerator::Clone(IEnumString **ppes)

{

if (ppes == 0)

return E_INVALIDARG;

SessionNamesEnumerator *pCloneSource = m_pCloneSource;

if (pCloneSource == 0) // we are the source

m_pCloneSource = this;

*ppes = new SessionNamesEnumerator(pCloneSource);