I am writing an application that used to backup some specified file, therefore using the backup API calls i.e CreateFile BackupRead and WriteFile API's.

getting errors Access violation reading location.

I have attached code below.

#include <windows.h>

int main()
{
    HANDLE hInput, hOutput;

//m_filename is a variable holding the file path to read from
hInput = CreateFile(L"C:\\Key.txt", GENERIC_READ, 0, NULL, OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, NULL);

//strLocation contains the path of the file I want to create.
hOutput= CreateFile(L"C:\\tmp\\", GENERIC_WRITE, NULL, NULL, CREATE_ALWAYS, NULL, NULL); 


DWORD dwBytesToRead = 1024 * 1024 * 10;
BYTE *buffer;
buffer = new BYTE[dwBytesToRead];
BOOL bReadSuccess = false,bWriteSuccess = false;
DWORD dwBytesRead,dwBytesWritten;
LPVOID lpContext;
//Now comes the important bit:

do
{
    bReadSuccess = BackupRead(hInput, buffer, sizeof(BYTE) *dwBytesToRead, &dwBytesRead, false, true, &lpContext);

    bWriteSuccess= WriteFile(hOutput, buffer, sizeof(BYTE) *dwBytesRead, &dwBytesWritten, NULL); 

}while(dwBytesRead == dwBytesToRead);

return 0;

}

Any one suggest me how to use these API's?

Thanks.