How to assign value to LPVOID buffer of ReadFile - c++

Question

I am developing a win32 API hook program.
Accordingly to my understanding, when a program calls ReadFile for a particular file, the content of that file is copied to lpBuffer(see the definition below),
ReadFile definition:
BOOL ReadFile(
HANDLE hFile,
LPVOID lpBuffer,
DWORD nNumberOfBytesToRead,
LPDWORD lpNumberOfBytesRead,
LPOVERLAPPED lpOverlapped
);
Now, my target is to alter this lpBuffer and fill it with provided content by me!
I am using EasyHook to hook ReadFile. I am not familiar with LPVOID type. I was able to alter the content for GetCurrentDirectory using the following code.
string b = "C:\\my\\altered\\directory";
DWORD returnLength = b.length();
int i;
for (i = 0; i<b.length(); i++)
{
lpBuffer[i] = b[i];
}
lpBuffer[i++] = '\0';
GetCurrentDirectory definition:
DWORD GetCurrentDirectory(
DWORD nBufferLength,
LPTSTR lpBuffer
);
How to do similar value assignment for ReadFile (LPVOID lpBuffer)?

Answer 1

Here's the LPVOID typedef:
#define far
typedef void far *LPVOID;
The far macro is defined as nothing, I guess it's because of some historical reasons (baggage).
So you can almost directly treat the LPVOID as void*.
And now, suppose you have a std::vector<uint8_t> named FakeData, just:
if (nNumberOfBytesToRead < FakeData.size()) {
SetLastError(ERROR_INSUFFICIENT_BUFFER);
return FALSE;
}
memcpy(lpBuffer, FakeData.data(), FakeData.size());
*lpNumberOfBytesRead = FakeData.size();
SetLastError(ERROR_SUCCESS);
return TRUE;