<转>CProcessData : A template class to ease up SendMessage calls across processes

Overview

CProcessData is a template class that makes it easy to use data allocated in a different process, and is useful when making inter-process SendMessage/PostMessage calls.

Example Scenario - 1

Imagine that you are sending a DTM_SETSYSTEMTIME message to a Date/Time picker control in a different process.

Without CProcessData

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SYSTEMTIME systim;

//Populate systim



HANDLE hProc = OpenProcess(PROCESS_ALL_ACCESS, FALSE, pid);

LPVOID lpData = VirtualAllocEx(hProc, NULL, 

    sizeof SYSTEMTIME, MEM_COMMIT, PAGE_READWRITE);

WriteProcessMemory(hProc, lpData, (LPCVOID)&systim, 

    sizeof SYSTEMTIME, NULL);            



DWORD dwResult = (DWORD)::SendMessage(hwnd, 

    DTM_SETSYSTEMTIME, GDT_VALID, (LPARAM)&lpData);



if(dwResult == 0)

{

    DWORD err = GetLastError();

    //...

}



VirtualFreeEx(hProc, lpData, NULL, MEM_RELEASE);

CloseHandle(hProc);

Using CProcessData

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SYSTEMTIME systim;

//Populate systim



CProcessData<SYSTEMTIME> data(pid);

data.WriteData(systim);



DWORD dwResult = (DWORD)::SendMessage(hwnd, 

    DTM_SETSYSTEMTIME, GDT_VALID, (LPARAM)data.GetData());

    

if(dwResult == 0)

{

    DWORD err = GetLastError();

    //...

}

Note only have you saved on lines of code, but you don't run the risk of forgetting to free the allocated memory or closing the process handle.

Example Scenario - 2

Imagine that you are retrieving toolbar info from a toolbar control in a different process.

Without CProcessData

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HANDLE hProc = OpenProcess(PROCESS_ALL_ACCESS, FALSE, pid);

LPVOID lpData = VirtualAllocEx(hProc, NULL, 

    sizeof TBBUTTON, MEM_COMMIT, PAGE_READWRITE);      



::SendMessage(hwnd, TB_GETBUTTON, index, (LPARAM)lpData);



TBBUTTON tb;

ReadProcessMemory(hProc, lpData,(LPVOID)&tb, 

    sizeof TBBUTTON, NULL)



CUSTOMDATA cus;

ReadProcessMemory(hProc, (LPCVOID)tb.dwData, (LPVOID)&cus, 

    sizeof CUSTOMDATA, NULL)



VirtualFreeEx(hProc,lpData,NULL,MEM_RELEASE);

CloseHandle(hProc);

Using CProcessData

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CProcessData<TBBUTTON> data(pid);



::SendMessage(hwnd, TB_GETBUTTON, index, 

    (LPARAM)data.GetData());



TBBUTTON tb;

data.ReadData(&tb);    



CUSTOMDATA cus;

data.ReadData<CUSTOMDATA>(&cus,(LPCVOID)tb.dwData);

Pretty neat, huh?

Class Reference

Constructor

CProcessData(DWORD dwProcessId = 0, DWORD dwDesiredAccess = PROCESS_ALL_ACCESS, DWORD flAllocationType = MEM_COMMIT, DWORD flProtect = PAGE_READWRITE)

If you pass in a dwProcessId of 0, the current process Id is used. For the other arguments, see MSDN documentation for OpenProcess and VirtualAllocEx.

WriteData

BOOL WriteData(const T& data)

WriteData copies data to memory in the foreign process

ReadData

BOOL ReadData(T* data)

ReadData reads back from the memory in the foreign process into data.

ReadData (template version)

template<typename TSUBTYPE> BOOL ReadData(TSUBTYPE* data, LPCVOID lpData)

Templated ReadData that's used to read a specific data type from a memory address located in the foreign process.

Full source listing

[Listing has been formatted to fit within 600 pixels. Actual source code (included as a download) is formatted for wider screens]

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/*

    Author  :    Nishant Sivakumar

    Date    :    June 9, 2005

    Info    :    Template class that makes it easy to use data allocated

                 in a different process. Useful when making inter-process

                 SendMessage/PostMessage calls.            

    Contact :    nish#voidnish.com

*/



//ProcessData.h



#pragma once



template<typename T> class CProcessData

{

public:    

    /*

        If you pass in a dwProcessId of 0, the current process Id is used.

        For the other arguments, see MSDN documentation for OpenProcess and

        VirtualAllocEx.

    */

    CProcessData(DWORD dwProcessId = 0, 

        DWORD dwDesiredAccess = PROCESS_ALL_ACCESS,

        DWORD flAllocationType = MEM_COMMIT, DWORD flProtect = PAGE_READWRITE)

    {

        m_hProcess = OpenProcess(dwDesiredAccess, FALSE, 

            dwProcessId ? dwProcessId : GetCurrentProcessId());

        ASSERT(m_hProcess);

        if(m_hProcess)

        {

            m_lpData = VirtualAllocEx(m_hProcess, NULL, sizeof T, 

                flAllocationType, flProtect);

            ASSERT(m_lpData);

        }

    }



    ~CProcessData()

    {

        if(m_hProcess)

        {            

            if(m_lpData)

            {

                VirtualFreeEx(m_hProcess, m_lpData, NULL, MEM_RELEASE);

            }

            CloseHandle(m_hProcess);

        }

    }



    //WriteData is used to copy data to memory in the foreign process

    BOOL WriteData(const T& data)

    {

        return (m_hProcess && m_lpData) ? WriteProcessMemory(

            m_hProcess, m_lpData, 

            (LPCVOID)&data, sizeof T, NULL) : FALSE;

    }



    //ReadData reads back data from memory in the foreign process

    BOOL ReadData(T* data)

    {

        return (m_hProcess && m_lpData) ? ReadProcessMemory(

            m_hProcess, m_lpData, 

            (LPVOID)data, sizeof T, NULL) : FALSE;

    }



    //Templated ReadData that's used to read a specific data type from

    //a memory address located in the foreign process

    template<typename TSUBTYPE> BOOL ReadData(

        TSUBTYPE* data, LPCVOID lpData)

    {

        return m_hProcess ? ReadProcessMemory(m_hProcess, lpData, 

            (LPVOID)data, sizeof TSUBTYPE, NULL) : FALSE;

    }



    //Gets the address of the allocated memory in the foreign process

    const T* GetData()

    {

        return (m_hProcess && m_lpData) ? (T*)m_lpData : NULL;

    }

private:

    T m_Data;

    HANDLE m_hProcess;

    LPVOID m_lpData;

};

History

• June 16, 2005 : Small bug fix in destructor. (VirtualFreeEx and CloseHandle were in the wrong order)
• June 10, 2005 : Article first published.
• June 9, 2005 : Class written.

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