C / C++ / MFC

HOW TO get length of BYTE variable in C++

4-Nov-07 16:16

Amjath Rahman wrote:
Plz any have the code for socket programming in vc++ for dialog based application...

There are several listed here.

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Ontanggabe Parulian4-Nov-07 14:56

Ontanggabe Parulian

4-Nov-07 14:56

Dear all,

I want to know the length of some BYTE variable (unsigned char). Here I included snippet of the code:

#include <iostream><br />
#include <string><br />
<br />
using namespace std;<br />
typedef unsigned char BYTE_T;<br />
<br />
void printLen(BYTE_T *ld_pbyteTemp);<br />
<br />
int main(int argc, char *argv[])<br />
{<br />
	BYTE_T *ld_pbyteChar = new BYTE_T[50];<br />
	memset(ld_pbyteChar, 'a', 50);<br />
<br />
	for(int i=0; i<50; i++) cout << "i = " << i << " -> " << ld_pbyteChar[i] << endl;<br />
<br />
	printLen(ld_pbyteChar);<br />
	<br />
	return 1;<br />
}<br />
<br />
void printLen(BYTE_T *ld_pbyteTemp)<br />
{<br />
	int ld_intLen = sizeof ld_pbyteTemp;<br />
	cout << "Length = " << ld_intLen << endl;<br />
}

Is there anyone know how to get the length of the "ld_pbyteTemp" in function printLen?

Thanks before...

Regards,

Ian

Llasus4-Nov-07 15:06

4-Nov-07 15:06

try:
int ld_intLen = sizeof(*ld_pbyteTemp);

Ontanggabe Parulian4-Nov-07 15:55

Ontanggabe Parulian

4-Nov-07 15:55

Llasus wrote:
int ld_intLen = sizeof(*ld_pbyteTemp);

It didn't work. It return 1 not 50 as expected.

Llasus4-Nov-07 16:59

4-Nov-07 16:59

Oops, sorry I didn't notice that. As the others explained you can't obtain it just by using sizeof. You can get the size that you want only thru some changes. instead of unsigned char you can use char. And instead of sizeof() use strlen(ld_pbyteTemp). I don't know if you'd want to change your variable though. Anyway its a simpler workaround if you really want to get the size.
Just another thing though. Since it is a char end the last element with NULL.

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C^hris L^osinger4-Nov-07 15:49

C^hris L^osinger

4-Nov-07 15:49

you can't. there's no safe way to get the size of a dynamic array in C/C++.

you must either pass the size of the allocated data along with the pointer, or use a container class (like std::vector) that keeps track of it for you.

Ontanggabe Parulian4-Nov-07 22:30

Ontanggabe Parulian

4-Nov-07 22:30

Ok, Chris, thanks for your suggestion. As I guess it can't be measure. And the best way is passing the size of the allocated data along with the pointer. Thanks for all too... Smile | :)

David Crow4-Nov-07 16:15

4-Nov-07 16:15

Ontanggabe Parulian wrote:
BYTE_T *ld_pbyteChar = new BYTE_T[50];

Did you look at the DWORD preceeding ld_pbyteChar in debug memory?

James R. Twine5-Nov-07 1:41

James R. Twine

5-Nov-07 1:41

Is the OP allocating BSTRs? Smile | :)

Peace!

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kcynic4-Nov-07 16:47

kcynic

4-Nov-07 16:47

In fact,at C/C++ RUNTIME,when you new or malloc a block memory,the system really allocate 4 bytes more than the count you want(you can find at the memory window of VC):0xFD,0xFD,0xFD,0xFD.
When you delete or free the pointer,the system will check the end of pointer you want to free,if they are not 0xFD,0xFD,0xFD,0xFD,system will indicate that block was ruined and an assert would occur!

So,you also can do your work by find the end 4 special bytes.
But you have to make sure that the block's real data does not include a four-byte sequence:0xFD,0xFD,0xFD,0xFD,if so,the result would not believable.
Make the code work well is your own job.
I am sorry,my english is poor.Have a good day!

James R. Twine5-Nov-07 1:41

James R. Twine

5-Nov-07 1:41

Do not do this - the sentries you are talking about are only reliable in debug builds, not release builds.

Peace!

kcynic5-Nov-07 14:06

kcynic

5-Nov-07 14:06

Yes,you are right.
If so,transfer a length param is required.
Thank you.

cmk4-Nov-07 18:28

cmk

4-Nov-07 18:28

See:
_msize : http://msdn2.microsoft.com/en-us/library/z2s077bc(VS.71).aspx[^]
HeapSize : http://msdn2.microsoft.com/en-us/library/aa366706.aspx[^]

Note: I believe they will tell you the size of the allocated block, this may be larger than what was requested.

...cmk

The idea that I can be presented with a problem, set out to logically solve it with the tools at hand, and wind up with a program that could not be legally used because someone else followed the same logical steps some years ago and filed for a patent on it is horrifying.
- John Carmack

Socket ptogramming

Amjath Rahman4-Nov-07 14:34

Amjath Rahman

4-Nov-07 14:34

Hi All,

Im implementing socket in my application.
its working fine, but my problem is i want to attach a thread for socket receive.
how can i implement this, plz help me out...

im using CAsyncSocket.
its a dialog based application.

With Regards
Amjath

Llasus4-Nov-07 14:41

4-Nov-07 14:41

Do you mean that you want to pass the socket to a thread for receiving? You can do that by using the thread's parameter and pass the socket variable to it.

Amjath Rahman4-Nov-07 15:38

Amjath Rahman

4-Nov-07 15:38

First of all thanks for ur reply......
if possible plz help me through some sample code..........
can u plz do this needful help...

With regards
Amjath

Llasus4-Nov-07 15:53

4-Nov-07 15:53

Here's a somewhat sample code to pass the SOCKET to a thread. Hope this helps.

<br />
CAsyncSocket ListenSocket; //global socket variable, declare this in the header file<br />
<br />
BOOL CClassSample::Initialize()<br />
{<br />
//initialize the pipe variable<br />
<br />
//create the thread<br />
HListenThread = CreateThread(NULL,<br />
			0,<br />
			&ListenThread,<br />
			(LPVOID)&ListenSocket,<br />
			0,<br />
			&ListenThreadID<br />
			);<br />
//Error handling for CreateThread<br />
if (HListenThread == NULL || HListenThread == INVALID_HANDLE_VALUE)<br />
{<br />
	return FALSE;<br />
}<br />
}<br />
<br />
DWORD WINAPI CClassSample::ListenThread(LPVOID lpParameter)<br />
{<br />
//assign the parameter to the SOCKET variable<br />
CAsyncSocket *pListenSocket = (CAsyncSocket*)lpParameter;<br />
//some processing here<br />
}<br />

Amjath Rahman4-Nov-07 16:01

Amjath Rahman

4-Nov-07 16:01

Thank u very much dude
im new to vc++, sorry for asking such a small question
from where v can get this variable buddy "ListenThreadID"

David Crow4-Nov-07 16:19

4-Nov-07 16:19

Amjath Rahman wrote:
im new to vc++,

So why are you trying to tackle a project that is not for beginners? Sockets or threads is a medium-difficulty project at best, but doing them in tandem is no trivial task.

Llasus4-Nov-07 16:48

A question about exit codes

4-Nov-07 16:48

Its a DWORD which holds the ID for the ListenThread.

Llasus4-Nov-07 14:08

4-Nov-07 14:08

Hello and good day! I created an application using VS 2005 which simply loads an image from a bitmap using a picture box (there are other functionalities involved though but that is its main function). And I was earlier told that it crashed on a different PC even though on tests it did not crash at all (2 test PCs). I can only guess that that PC's set-up could cause it to crash but still I'm looking for other reasons. One is the exit code. The application when opened and closed displays this on the output:
Program '[2788] Application.exe: Native' has exited with Code 2 (0x2).
Based on my research it said that code 2 indicates that "The system cannot find the file specified.". On start I only open a file but I don't think that was the cause of code 2. Can anyone explain to me or help me about this? Thank you for the time and help Smile | :)

FtpPutFile problem

dellthinker4-Nov-07 10:16

dellthinker

4-Nov-07 10:16

Hi all. I've tried to use this but it doesnt seem to work. One time i tried it and it worked very well. The second time i tried it it didnt work. What it does is it connects well and sends the file. But problem is that there is nothing in the text file. Here is what i have so far.

<br />
#include <iostream><br />
#include <windows.h><br />
#include <wininet.h><br />
using namespace std;<br />
<br />
<br />
<br />
void FileSubmit()<br />
{<br />
    char *user="user";<br />
    char *pass="password";<br />
    char *ftpserver="ftp.server.com";<br />
    HINTERNET hInternet;<br />
    HINTERNET hFtpSession;<br />
    hInternet = InternetOpen(NULL,INTERNET_OPEN_TYPE_DIRECT,NULL,NULL,0);<br />
    hFtpSession = InternetConnect(hInternet,ftpserver , INTERNET_DEFAULT_FTP_PORT, user, pass, INTERNET_SERVICE_FTP, 0, 0);<br />
    if(FtpPutFile(hFtpSession, "C:\\test.txt", "file.txt", FTP_TRANSFER_TYPE_ASCII, 0) == TRUE){<br />
        cout << "File Sent! " << endl;<br />
        Sleep(1000);<br />
        InternetCloseHandle(hFtpSession);<br />
        InternetCloseHandle(hInternet);<br />
    }<br />
    else{<br />
        cout << "File didnt send " << endl;<br />
    }<br />
}<br />
<br />
int main(){<br />
    FileSubmit();<br />
    return 0;<br />
}<br />

I know text files need to be sent in ASCII mode so i switched to that and it still didnt work. It uploads the file but the file is empty. Whats going on??? Thanx in advance!

Re: FtpPutFile problem

Peter Weyzen4-Nov-07 13:13

Peter Weyzen

4-Nov-07 13:13

Try opening the connection in passive mode..... I had the same problem.... worked for me.

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Staff Engineer<br />
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Re: FtpPutFile problem

David Crow4-Nov-07 16:20