Shadow after using CFiledialog in the dialog - C / C++ / MFC Discussion Boards

__DanC__28-Jul-08 4:08

28-Jul-08 4:08

I have a structure in C# which is read using a BinaryReader like so:

binaryReader.ReadInt32();
binaryReader.ReadInt32();
binaryReader.ReadString();
binaryReader.ReadString();

I need to be able to send this structure from a C++ app, I have managed to send across the two ints and I realise that the strings have a length marker in front of them but I cannot get it to send the string.

I am currently using a struct like this:

struct MyData
{
  int val1;
  int val2;
  int strLength1;
  LPCTSTR string1;
  int strLength2;
  LPCTSTR string2;
};

This send the ints fine but I get 2 0 length strings.

What am I doing wrong?

Re: Translating C# structure to C++

Luc Pattyn28-Jul-08 4:21

Luc Pattyn

28-Jul-08 4:21

One way that works AFAIK is using fixed-length strings, put them in length+chararray on the C/C++ side
and in length+array on the managed side, using some Marshal attribute to indicate that the
array data has to be there, not just a reference.

It is something like [MarshalAs(UnmanagedType.ByValArray, SizeConst=16)]

BTW: as always, be wary of different character types.

Smile | :)

Luc Pattyn [Forum Guidelines] [My Articles]

Voting for dummies? No thanks. Dead | X|

Re: Translating C# structure to C++

Matthew Faithfull28-Jul-08 4:21

Matthew Faithfull

28-Jul-08 4:21

At a guess I'd day you need two shorts for your string lengths or possibly even two BYTEs. If C# strings are a development of BSTRs then I doubt the string lengths will be as much as the 4 bytes you get with an int. 4GB long strings are really not what MS want to be supporting I guess. The other thing is you need the character data itself effectively in the structure rather than pointers to the characters (LPCTSTR).
You want something like this.

<br />
struct MyData<br />
{<br />
  int val1;<br />
  int val2;<br />
  unsigned short strLength1;<br />
  TCHAR string1[strLength1];<br />
  unsigned short strLength2;<br />
  TCHAR string2[strLength2];<br />
};<br />

but of course you can't do that directly as strLength1 and strLength2 are not known at compile time. This means you're likely going to have to use some form of serialization/deserilaization rather then just passing a structure unless you can use fixed length strings.

"The secret of happiness is freedom, and the secret of freedom, courage."
Thucydides (B.C. 460-400)

Re: Translating C# structure to C++

__DanC__28-Jul-08 4:34

__DanC__

28-Jul-08 4:34

Thanks, I thought I would end up doing some serialization. I have checked the BinaryWriter documentation and it states

This method first writes the length of the string as a four-byte unsigned integer, and then writes that many characters to the stream. This method writes a length-prefixed string to this stream using the BinaryWriter instance's current Encoding.

So it seems it does need a 4-bytes uint to prefix the length. So my next question is how would I create a byte array containing the strings and the lengths? (C++ is not my strong point!), I know how to create the array using malloc and copy the strings in but not the ints.

Re: Translating C# structure to C++

Matthew Faithfull28-Jul-08 4:49

Matthew Faithfull

28-Jul-08 4:49

Yep, I'd say a malloc, or more properly, BYTE* pBuffer = new BYTE[uBufferSize]; is the way to go.
Once you've got your buffer you write the strings in by casting a copy of pBuffer + n to a TCHAR* and
copy your ints in by casting pBuffer + n to an int* and setting its value.

<br />
int* pFirstInt = reinterpret_cast<int*>(pBuffer + 0);<br />
*pFirstInt = nValue;<br />
int* pSecondInt = reinterpret_cast<int*>(pBuffer + 4);<br />
*SecondInt = nValue2;<br />

It's not pretty but then this sort of stuff seldom is. You could create some struct types and cast to
those. Up to you really. There are almost certainly fancier ways to do this with operator << overloading
and stl string stream modifiers but I wouldn't go there unless you've got a lot of complex data to
transfer and you know your stl.

"The secret of happiness is freedom, and the secret of freedom, courage."
Thucydides (B.C. 460-400)

Re: Translating C# structure to C++

__DanC__28-Jul-08 6:33

__DanC__

28-Jul-08 6:33

Thanks for the tip, that worked for the ints perfectly but still not getting the strings.

My code now is:

int* pFirstValue = reinterpret_cast<int*>(pBuffer + 0);  // First integer
int* pSecondValue = reinterpret_cast<int*>(pBuffer + 4); // Second integer
unsigned int* pStringLength1 = reinterpret_cast<unsigned>(pBuffer + 8); // First string length marker
unsigned int* pStringLength2 = reinterpret_cast<unsigned>(pBuffer + 12 + (sizeof(WCHAR) * firststring)); // Second string length marker

*pFirstValue = 1;
*pSecondValue = 2;
*pStringLength1 = strlen(firststring);
*pStringLength2 = strlen(secondstring);

strcpy((char*)(pBuffer + 12), firststring);
strcpy((char*)(pBuffer + 16 + (sizeof(WCHAR) * firststring)), secondstring);
</unsigned></unsigned>

That appears to me to be correct but as I've said before, C++ is not my strong point. Does that look correct?

Re: Translating C# structure to C++

Mark Salsbery28-Jul-08 7:19

Mark Salsbery

28-Jul-08 7:19

This won't solve your marshaling problem, but:

You can't use strcpy, or TCHAR. All your strings are wchar_t
in C# so you should be using only wide character functions and types.

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Shadow after using CFiledialog in the dialog

bhanu_850928-Jul-08 3:44

bhanu_8509

28-Jul-08 3:44

Hello my dear friends,

I have developed a code to analyze a file (huge size). My application is MFC Dialog based. I use CFiledialog to open the files, after selecting the files I click OK and after that a shadow is appearing on my dialog for the size of the CFiledialog. This is very distraction to the GUI I have developed. Is there any way to remove the shadow after selecting the file.

Code is :

CString Test::OpenFile()
{
        CString fname=LPCTSTR("");
	CFileDialog fileDlg(TRUE, _T (".dat"),NULL,OFN_FILEMUSTEXIST | OFN_PATHMUSTEXIST, _T ("Data File (*.dat)|*.dat|Data File (*.dat)|*.dat|"),this);
        if(fileDlg.DoModal()==IDOK)
	{
	    fname = fileDlg.GetPathName();
	}	
	else
	{
	    MessageBox(TEXT("Select the File"));
	}
	return fname;
}

Please advice. Many thanks in advance.

Re: Shadow after using CFiledialog in the dialog

bhanu_850928-Jul-08 4:55

bhanu_8509

28-Jul-08 4:55

Please help me...

Re: Shadow after using CFiledialog in the dialog

Rajesh R Subramanian28-Jul-08 5:31

Rajesh R Subramanian

28-Jul-08 5:31

I don't see any problem in the code you've provided. Probably you must try to do that "huge processing" in a worker thread and see if that helps. Smile | :)

Nobody can give you wiser advice than yourself. - Cicero
.·´¯`·->Rajesh<-·´¯`·.

Microsoft MVP - Visual C++[^]

Re: Shadow after using CFiledialog in the dialog

Mark Salsbery28-Jul-08 7:27

Mark Salsbery

28-Jul-08 7:27

You could try using Invalidate(); UpdateWindow(); on your dialog
after the call to fileDlg.DoModal() but before you do any lengthy
processing on the UI thread (which you shouldn't be doing anyway).

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Re: Shadow after using CFiledialog in the dialog

shivareaj7-Oct-12 23:17

shivareaj

7-Oct-12 23:17

Hi, Did you resolve this issue if yes please let me know how it worked.

Thanks

converting char* into BYTE*

subramanyeswari28-Jul-08 3:17

subramanyeswari

28-Jul-08 3:17

Hi,

how to conver char* into BYTE* in C++

Regards

Re: converting char* into BYTE*

CPallini28-Jul-08 3:22

CPallini

28-Jul-08 3:22

Short (and dangerous) answer: with a cast, for instance

char  * myCharPointer ="hello";
BYTE * myBytePointer = (BYTE *) myCharPointer;

A better answer may follow a more detailed request.
Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke

[My articles]

Re: converting char* into BYTE*

toxcct28-Jul-08 3:33

toxcct

28-Jul-08 3:33

of course, you're looking for devil every where :p

a char* is not always a string Wink | ;)

char c = 'c';
char* pc = &c;
 
BYTE* pb1 = (BYTE*)pc;
BYTE* pb2 = reinterpret_cast<BYTE*>(pc);

BTW, looking at the level of the question, i think it's worth saying that a char IS a BYTE:

char c = 'c';
 
BYTE b = c;

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Re: converting char* into BYTE*

VaDa Um Uie28-Jul-08 3:45

VaDa Um Uie

28-Jul-08 3:45

toxcct wrote:
a char* is not always a string

char* is never a string. Laugh | :laugh:

Re: converting char* into BYTE*

toxcct28-Jul-08 3:50

toxcct

28-Jul-08 3:50

what do you know about C++, you Mr univoter ?

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Re: converting char* into BYTE*

VaDa Um Uie28-Jul-08 3:52

VaDa Um Uie

28-Jul-08 3:52

nice arguments Laugh | :laugh:

Re: converting char* into BYTE*

CPallini28-Jul-08 7:20

CPallini

28-Jul-08 7:20

toxcct wrote:
of course, you're looking for devil every where [Poke tongue]

of course. Smile | :)

toxcct wrote:
BTW, looking at the level of the question, i think it's worth saying that a char IS a BYTE:

Nope. As you know (I know that you know Wink | ;)

), char is a signed integer ranging from -128 to 127, while a BYTE is an unsigned integer ranging from 0 to 255.
Poke tongue | ;-P

Re: converting char* into BYTE*

toxcct28-Jul-08 9:04

toxcct

28-Jul-08 9:04

but you're already going to far by interpreting the bits pattern.

a BYTE is 8 bits, which is exactly what a char is supposed to be too. Wink | ;)

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Re: converting char* into BYTE*

CPallini28-Jul-08 11:34

CPallini

28-Jul-08 11:34

toxcct wrote:
but you're already going to far by interpreting the bits pattern.

Duty sir, duty. Roll eyes | :rolleyes:

toxcct wrote:
a BYTE is 8 bits, which is exactly what a char is supposed to be too.

float and int (even pointers!) have the same size on 32 bit systems but we usually don't consider them being the same.

Big Grin | :-D

Re: converting char* into BYTE*

Matthew Faithfull28-Jul-08 3:22

Matthew Faithfull

28-Jul-08 3:22

Something like:

<br />
BYTE* pByte = reinterpretcast< BYTE* >( pChar );<br />

"The secret of happiness is freedom, and the secret of freedom, courage."
Thucydides (B.C. 460-400)

Re: converting char* into BYTE*

toxcct28-Jul-08 3:30

toxcct

28-Jul-08 3:30

Matthew Faithfull wrote:
BYTE* pByte = reinterpretcast< BYTE* >( pChar );

quite... reinterpret_cast is the correct word ^^

BTW, i didn't try, but wouldn't static_cast just work here ?

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Re: converting char* into BYTE*

Matthew Faithfull28-Jul-08 4:11

Matthew Faithfull

28-Jul-08 4:11

Right you are, I knew that looked wrong somehow. I don't think static_cast works on pointers even when there are in fact a type match as these probably would be. Would have to try it to be sure.

"The secret of happiness is freedom, and the secret of freedom, courage."
Thucydides (B.C. 460-400)

Re: converting char* into BYTE*

Rajesh R Subramanian28-Jul-08 4:30

Rajesh R Subramanian

28-Jul-08 4:30

toxcct wrote:
BTW, i didn't try, but wouldn't static_cast just work here ?

A static_cast won't work.

Nobody can give you wiser advice than yourself. - Cicero
.·´¯`·->Rajesh<-·´¯`·.

Microsoft MVP - Visual C++[^]

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