CODEWITHSUNDEEP
c++winapi
dsp_099
dsp_099

Reputation: 6121

WriteFile writes incorrectly

I'm trying to copy a file from resources to %localappdata%. I've something like this:

HINSTANCE hInstance = GetModuleHandle(NULL);
HANDLE hFile = INVALID_HANDLE_VALUE;

HRSRC hrsrc = FindResource(hInstance, MAKEINTRESOURCE(MSIE), RT_RCDATA);
HGLOBAL exeRes = LoadResource(hInstance, hrsrc);

DWORD size = SizeofResource(hInstance, hrsrc);

TCHAR szPath[MAX_PATH];
HANDLE hfile;
if(SUCCEEDED(SHGetFolderPath(NULL, CSIDL_LOCAL_APPDATA|CSIDL_FLAG_CREATE, NULL, 0, szPath))) { 
    PathAppend(szPath, TEXT("test.exe")); 
    hFile = CreateFile(szPath, GENERIC_WRITE, 0, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
}

LPVOID exePtr = LockResource(hrsrc);
DWORD exeWritten = 0;

BOOL writeResult = WriteFile(hFile, exePtr, size, &exeWritten, NULL);

cout << GetLastError() << endl;

BOOL closed = CloseHandle(hFile);

system("PAUSE");
return 0;

I'm able to locate the HRSRC and confirm the size using SizeofResource() just fine. CreateFile is in fact creating the file and returning the handle. GetLastError() reports that there are no errors. The amount of bytes written to disk is exactly right.

The output exe however is corrupted (the version of this file is incompatible with the version of Windows... blah blah) - it's lost its icon and everything. Looking at the original and the output file side-by-side in a hex editor it appears there's random data at the start of file.

What am I missing here?

Upvotes: 0

Views: 669

Answers (1)

WhozCraig
WhozCraig

Reputation: 66254

Your LockResource is not correct. It should be passed the HGLOBAL exeRes you loaded previously.

LockResource(hrsrc);

should be

LockResource(exeRes);

From the MS documentation on LockResource() :

Do not try to lock a resource by using the handle returned by the FindResource or FindResourceEx function. Such a handle points to random data.

And as a side note, you may want to try cleaning up that loaded-and-locked resource when you're through with it.

Upvotes: 7

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