Network Enumeration(2)

This class introduces minor modifications to a Network
enumeration
article by Joerg
Koenig
.

Great! However, I wanted to use it locally within a function. The problem
is that if you create a CNetSearch object within a function, you don’t
have access to it within a callback function called when a network resource
is hit (the object itself is used to get properties of a network resource).
Also, it is not possible to use one callback function in several situations
(for example, search for network resources on application startup or updating
network resources while application is running). Of course, these problems
can always be solved using the original implementations.

To solve these problems, I introduced minor modifications (marked in
bold):

Step 1:

This step contains all the modifications (done in netsearch.h include
file).

template <class T>
class CNetSearch : public CNetwork {
    typedef BOOL (T::*NsFnc)(CNetSearch*, NETRESOURCE &, DWORD);
    T *m_pTheObject;
    NsFnc m_NsFnc;

    DWORD Data;

    public:
        CNetSearch() : m_pTheObject(0), m_NsFnc(0) {}
        void Create(T * pObj, NsFnc fnc, DWORD data) {
            ASSERT(pObj != 0);
            ASSERT(fnc != 0);
            m_pTheObject = pObj;
            m_NsFnc = fnc;

            Data = data;

        }
    protected: // overridables
        virtual BOOL OnHitResource(NETRESOURCE & rNetRC) {
            return (m_pTheObject->*m_NsFnc)(this,rNetRC,Data);
        }
    virtual BOOL NetError(DWORD dwErrorCode, LPCTSTR lpszFunction) {
        switch(dwErrorCode) {
            case ERROR_BAD_NETPATH:
            case ERROR_NO_NETWORK:
                // minor errors: continue enumeration
                return TRUE;
        }
        // serious error: break enumeration
        return CNetwork::NetError(dwErrorCode, lpszFunction);
    }
};

That’s all.

Step 2:

To use this class now, all you have to do (let’s assume that you are
doing it locally from a function) is following:

 

// Update argument is FALSE on initial serch and TRUE when updating
void CMyDocument::scanNetworkMachines(BOOL update)
{
    CNetSearch<CMyDocument> netWalker;
    netWalker.Create(this,onNetResourceHit,(DWORD)update);
    netWalker.Enumerate();
}
BOOL CMyDocument::onNetResourceHit(CNetSearch<CMyDocument> *net, NETRESOURCE& res, DWORD data)
{
    int ndx;
    if (net->IsServer(res)) {
        CString str = net->GetRemoteName(res);
        for (int ndx = 0; str[ndx] == '\' ; ++ndx) ;
        if (ndx)
            str = str.Mid(ndx);
        str.MakeUpper();
        if (data == 0) {
            // This is an initial scan !!!
            // For example, create TComputer object and add it to the list
        } else if (data == 1) {
            // This is an update !!!
            // For example, search for a TComputer object in a list and if not found,
            // create a new one and add it to the list.
        }
    }
    return TRUE;    // continue enumeration 
}

 

Last updated: 17 May 1998.

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