|
Richard MacCutchan wrote: You should use the OnInitDialog method of CDialog Class | Microsoft Docs[^] to set the focus.
I stated that the focus edit is being set from the OnInitialUpdate override of the CFormView derived class, I should have clarified that this has been called from the CDialog OnInitDialog method via a call to
SendMessageToDescendants(WM_INITIALUPDATE, 0, 0, TRUE, TRUE);
Also, the OnInitDialog method returns FALSE to indicate that I have set the focus to a control.
.
|
|
|
|
|
Sorry, I cannot help further as I don't have MFC.
|
|
|
|
|
Is it possible to somehow check during compile time if an enum exists, i.e. something like this:
typedef enum {
MY_ENUM_VALUE = 0
} myEnum_e;
#define DOES_ENUM_EXIT(__ARG__) ??? What goes here???
if (DOES_ENUM_EXIT(myEnum)) {
}I know that I could achieve something similar easily be using
#define MY_ENUM_VALUE (0)
instead, but then my code wouldn't be type safe.
|
|
|
|
|
|
No, because the #define statement is handled by the preprocessor, and the enum value is not known until it is fed into the compiler, which comes later.
|
|
|
|
|
|
|
I have written a little piece of code to read few (first 512) bytes from USB drive. here is the code:
HANDLE hVolume = ::CreateFile(sVolume, GENERIC_READ,
FILE_SHARE_READ | FILE_SHARE_WRITE,
NULL, OPEN_EXISTING, FILE_FLAG_SEQUENTIAL_SCAN, NULL);
TRACE("Volume handle: %p\n", hVolume);
LONG lDistLow = 0;
PLONG plDistHigh = 0;
if (INVALID_SET_FILE_POINTER == SetFilePointer(hVolume, lDistLow, plDistHigh, FILE_BEGIN) &&
NO_ERROR != GetLastError())
{
TRACE("Error: %d\n", GetLastError());
return FALSE;
}
else
{
TRACE("%d\t%d\n", lDistLow, plDistHigh);
}
DWORD dwLen = 512;
DWORD dwNum = 0;
void* pBuffer = NULL;
ReadFile(hVolume, pBuffer, dwLen, &dwNum, NULL);
TRACE("%p\t%d\t%d\n", pBuffer, dwLen, dwNum);
but the result is:
Volume handle: 00000438
0 0
00000000 512 0
this pBuffer NULL tell me that I am not able to read that sectors ... why ? The program is running as admin and sVolume is feed by _T("\\\\.\\F:"), first TRACE macro printed is a prove that is OK that part. SetFilePointer is used to position the reading part, and I intend to setup offset to the beginning, right ?
|
|
|
|
|
What does ReadFile return? TRUE or FALSE?
|
|
|
|
|
The ReadFile function returned FALSE, which tell me that reading has failed.
|
|
|
|
|
In this case you have to call GetLastError to obtain the exact reason of the failure!
|
|
|
|
|
I didn't feed correctly the buffer. After I setup correctly that parameter, ReadFile return TRUE.
|
|
|
|
|
Your pBuffer value is NULL, so you are trying to read data into the memory address 0 - you have to allocate some space to read the data into and use that for your pBuffer value. For 512 bytes a stack-based array should do the trick.
|
|
|
|
|
_Flaviu wrote: pBuffer NULL tell me that I am not able to read that sectors
No, pBuffer = NULL; tells you that you have not allocated any space to pBuffer. And don't use void* unless you are trying to allocate nothing.
You can allocate space either of the following ways.
unsigned char* pBuffer = new unsigned char[dwLen]; unsigned char buffer[dwLen]; ReadFile(hVolume, buffer, dwLen, &dwNum, NULL);
|
|
|
|
|
Is not accepted:
unsigned char buffer[dwLen];
Of course, putting 512 is ok, but I need to allocate that length of buffer through a variable.
I prefer this option, on stack, as far as I know, is faster than heap.
|
|
|
|
|
You can fix that easily by doing it this way:
#define SECTOR_SIZE 512
DWORD dwLen = SECTOR_SIZE;
DWORD dwNum = 0;
char buffer[SECTOR_SIZE];
ReadFile(hVolume, buffer, dwLen, &dwNum, NULL);
If you are using C++ then instead of #define you can use this:
const int SECTOR_SIZE = 512
|
|
|
|
|
Good idea. I have tried in this way:
CByteArray arrByte;
arrByte.SetSize(512);
BOOL bRet = ReadFile(hVolume, arrByte.GetData(), dwLen, &dwNum, NULL);
and seem to go well.
|
|
|
|
|
If you are writing MFC code then you should be using CFile to handle all your I/O.
|
|
|
|
|
|
|
|
I should know that ... thank you.
|
|
|
|
|
Good idea. I have few troubles with accessing USB drive with CFile, but once I'll solve it, the code will be simple.
Here is my trial, none on them has worked:
file.Open(_T("\\\\.\\F:"), CFile::modeRead | CFile::osSequentialScan);
file.Open(_T("F:"), CFile::modeRead | CFile::osSequentialScan);
file.Open(_T("F:\\"), CFile::modeRead | CFile::osSequentialScan);
HANDLE hVolume = ::CreateFile(sVolume, GENERIC_READ,
FILE_SHARE_READ | FILE_SHARE_WRITE,
NULL, OPEN_EXISTING, FILE_FLAG_SEQUENTIAL_SCAN, NULL);
CFile file(hVolume);
CFileStatus status;
file.GetStatus(status);
|
|
|
|
|
When using CFile::Open you should pass the CFileException* parameter to get the failure cause if CFile::Open fails.
See the example in CFile::Open
|
|
|
|
|
It is just the same as OpenFile behind the scenes so nothing to do with CFile. Your call probably fails because you are not including the share flags in your call to CFile::Open(), which are required when trying to access a device.
|
|
|
|
General 
News 
Suggestion 
Question 
Bug 
Answer 
Joke 
Praise 
Rant 
Admin 
Submit an article or tip
