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

, 10 Jun 2005
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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.

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

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

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

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

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]

/*
    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.

License

This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here

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About the Author

Nish Nishant

United States United States
Nish Nishant is a Software Architect/Consultant based out of Columbus, Ohio. He has over 15 years of software industry experience in various roles including Lead Software Architect, Principal Software Engineer, and Product Manager. Nish is a recipient of the annual Microsoft Visual C++ MVP Award since 2002 (13 consecutive awards as of 2014).

Nish is an industry acknowledged expert in the Microsoft technology stack. He authored
C++/CLI in Action for Manning Publications in 2005, and had previously co-authored
Extending MFC Applications with the .NET Framework for Addison Wesley in 2003. In addition, he has over 140 published technology articles on CodeProject.com and another 250+ blog articles on his
WordPress blog. Nish is vastly experienced in team management, mentoring teams, and directing all stages of software development.

Contact Nish : You can reach Nish on his google email id voidnish.

Website and Blog

Comments and Discussions

 
Generalerror Pinmemberswarup4-Jan-07 20:52 
QuestionScenario Example 1 problems PinmemberGraemeS15-Aug-06 12:15 
GeneralAPI Hook OpenProcess PinmemberVitoto3-Jan-06 5:30 
GeneralNicely done! PinmemberJörgen Sigvardsson28-Jul-05 12:57 
GeneralRe: Nicely done! PinstaffNishant Sivakumar14-Dec-05 12:08 
Generalcool article Pinmembermeir_rivkin4-Jul-05 6:42 
GeneralNice article! Pinmemberdmetzler3-Jul-05 18:17 
GeneralRe: Nice article! PinstaffNishant Sivakumar3-Jul-05 19:30 
Hello Don,

You could try this code :-

int nSel = (int)::SendMessage(hWndLB,LB_GETCURSEL,0,0);
if(nSel != LB_ERR)
{	
	typedef TCHAR BUFFER[128];
	CProcessData<BUFFER> data(pid);
	::SendMessage(hWndLB,LB_GETTEXT,nSel,(LPARAM)data.GetData());
	TCHAR buff[129];
	data.ReadData((BUFFER*)buff);
	//buff now contains the selected item's text
}

GeneralRe: Nice article! Pinmemberdmetzler3-Jul-05 19:31 
GeneralVery Nice... PinmemberPeregrine Falcon16-Jun-05 5:26 
Generaldtor order PinsussAnonymous15-Jun-05 5:06 
GeneralRe: dtor order and more PinsussAnonymous15-Jun-05 5:20 
GeneralRe: dtor order and more PinstaffNishant Sivakumar15-Jun-05 19:55 
GeneralRe: dtor order PinstaffNishant Sivakumar15-Jun-05 19:40 
GeneralNice work &amp;&amp; AnswerToQAboutExample PinmemberTom Archer12-Jun-05 2:05 
GeneralRe: Nice work &amp;&amp; AnswerToQAboutExample PinstaffNishant Sivakumar15-Jun-05 20:00 
GeneralOh my... PinmemberYoSilver11-Jun-05 14:49 
GeneralRe: Oh my... PinstaffNishant Sivakumar15-Jun-05 20:00 
GeneralGood Work PinmemberMichael A. Barnhart11-Jun-05 12:54 
GeneralRe: Good Work PinstaffNishant Sivakumar15-Jun-05 20:00 
GeneralLooks interesting, but... Pinmemberthe-unforgiven10-Jun-05 1:29 
GeneralRe: Looks interesting, but... PinstaffNishant Sivakumar10-Jun-05 1:37 
GeneralRe: Looks interesting, but... Pinmemberthe-unforgiven10-Jun-05 1:46 
GeneralRe: Looks interesting, but... PinmemberBugByter11-Jun-05 2:43 
GeneralRe: Looks interesting, but... PinmemberGary R. Wheeler11-Jun-05 2:44 

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