Here's how to use WM_WA_IPC messages from an external app

[herbie123]

Here's a technique to use the WM_WA_IPC messages that return pointers to strings from an external app.
More details in an article by Jeffrey Richter may be found here: http://msdn.microsoft.com/library/pe.../win320997.htm

It involves these steps:
- Get the winamp process id from the hwnd
- Create a buffer in winamp's process space
- Use ReadProcessMemory and WriteProcessMemory to read/write to this buffer
- Use this buffer in SendMessage

Example:

HWND hwndWinamp = FindWindow("Winamp v1.x", NULL);
if (!hwndWinamp) return;
DWORD dwProcessId;
GetWindowThreadProcessId(hwndWinamp, &dwProcessId);

// Check if our process can read/write in winamp's process space
HANDLE hProcess = OpenProcess(PROCESS_VM_OPERATION | PROCESS_VM_READ | PROCESS_VM_WRITE, FALSE, dwProcessId);
if (!hProcess) return;

// Create the buffer in winamp's process space
LPTSTR pWinampBuf = (LPTSTR) VirtualAllocEx(hProcess, NULL, BUFSIZE, MEM_RESERVE | MEM_COMMIT, PAGE_READWRITE);

// Example: Get all playlist entries
TCHAR szBuf[BUFSIZE];
int nPLCount = SendMessage(hwndWinamp, WM_WA_IPC, 0, IPC_GETLISTLENGTH);
for (int i=0; i<nPLCount; i++)
{
LPVOID pBase = (LPVOID)::SendMessage(hwndWinamp, WM_USER, i, IPC_GETPLAYLISTFILE);
ReadProcessMemory(hProcess, pBase, szBuf, sizeof(szBuf), NULL);
// szBuf now contains the filename for entry i
}

// Example: Set a skin
_tcscpy(szBuf, _T("Our_Friend_Joe_Final.zip"));
WriteProcessMemory(hProcess, pWinampBuf, szBuf, _tcslen(szBuf),NULL);
::SendMessage(hwndWinamp, WM_WA_IPC, (WPARAM)pWinampBuf, IPC_SETSKIN);

// Clean up
VirtualFreeEx(hProcess, pWinampBuf, 0, MEM_RELEASE);

[blomme]

We already knew that

------------------
Thomas S. P.
__programmer at Blox Technologies__

[herbie123]

We already knew that


I wish I had seen this before , could've saved me a lot of time. May be worth mentioning in NSDN.