C / C++ / MFC

4-Apr-02 22:47

I use this code:

ULONG size = finder.GetLength();

afile = fopen( strpath, "r+" );

char *list1 =(char *) malloc(size);
fread( list1 , sizeof( char ), size, afile );

CString str1=(CString )(list1);
str1.Format(str1 );
AfxMessageBox(str1);

Size of my file is something about 1.97Mb,but in message box it only 10 charachter(also when I debug and 'Watch' list1).Any suggestion?

Mazy

"The path you tread is narrow and the drop is shear and very high,
The ravens all are watching from a vantage point near by,
Apprehension creeping like a choo-train uo your spine,
Will the tightrope reach the end;will the final cuplet rhyme?"Cymbaline-Pink Floyd

jan larsen4-Apr-02 23:33

jan larsen

4-Apr-02 23:33

Just a suggestion: Test parameter size, it could be 10.
Or there could be a '\0' character in the file you read.
Oh, and you could also test if afile is actually opened, just in case...

Jan

"It could have been worse, it could have been ME!"

Mazdak5-Apr-02 0:28

5-Apr-02 0:28

jan larsen wrote:
there could be a '\0' character in the file you read.

I think this is the reason but how can I solve it?

Mazy

"The path you tread is narrow and the drop is shear and very high,
The ravens all are watching from a vantage point near by,
Apprehension creeping like a choo-train uo your spine,
Will the tightrope reach the end;will the final cuplet rhyme?"Cymbaline-Pink Floyd

Christian Graus5-Apr-02 0:33

5-Apr-02 0:33

You can't if you're trying to print/treat it as a C style string.

Christian

The tragedy of cyberspace - that so much can travel so far, and yet mean so little.

"I'm somewhat suspicious of STL though. My (test,experimental) program worked first time. Whats that all about??!?!
- Jon Hulatt, 22/3/2002

jan larsen5-Apr-02 2:57

jan larsen

5-Apr-02 2:57

As Christian is saying in this thread you cant't do anything about it if you want to print the raw char *.
But if the IO task went well then the pointer points to an array of size length and is an image of the data in the file.
If the file data are meant to be binary then you are misusing your pointer when you treat it as a string, i think that is one of the reasons why MS created the BYTE typedef so that you wont get confused.
If on the other hand the data is an array of zero terminated strings, then you could do something like this:
#include "stdio.h"
#include "string.h"

void PrintStrings(char * szString, int size)
{
   int i;
   char * pTmp;
   i = 0;
   pTmp = szString;
   while (i < size)
   {
      printf(pTmp);
      printf("\n");
      i += strlen(pTmp) + 1;
      pTmp = &szString[i];
   }
}

Jan

"It could have been worse, it could have been ME!"

alex.barylski4-Apr-02 23:34

alex.barylski

4-Apr-02 23:34

Take the address of your CString and enter it the memory window (debug). This will dump all of your memory including null characters, which i assume is causing your problems displaying all your data.

Cheers!

Smile | :)

"An expert is someone who has made all the mistakes in his or her field" - Niels Bohr

Christian Graus4-Apr-02 23:46

4-Apr-02 23:46

The first thing that's wrong with it is that it is ugly as all hell. Why on earth are you using malloc and fread when you're using MFC, so you must be using C++ ?

You should use iostreams in C++, you should ALWAYS prefer C++ code to C code unless you have a real reason not to, and NEVER use malloc/free.

Try this:

CFileStatus fs;

CFile::GetStatus("c:\\myfile.ext", fs);

CString s;
s.Format("File length = %d bytes", fs.m_szie);
AfxMessageBox(s);

Christian

The tragedy of cyberspace - that so much can travel so far, and yet mean so little.

"I'm somewhat suspicious of STL though. My (test,experimental) program worked first time. Whats that all about??!?!
- Jon Hulatt, 22/3/2002

Mazdak4-Apr-02 23:55

4-Apr-02 23:55

Thanks Christian Smile | :)

,The reason that I used AfxMessageBox and CString is JUST to test my 'char*' for myself not use in my application,I want to use 'char *' in my application and I want it as big as the size of my file,so what should I use instead malloc?

Mazy

"The path you tread is narrow and the drop is shear and very high,
The ravens all are watching from a vantage point near by,
Apprehension creeping like a choo-train uo your spine,
Will the tightrope reach the end;will the final cuplet rhyme?"Cymbaline-Pink Floyd

Christian Graus5-Apr-02 0:07

5-Apr-02 0:07

Every malloced pointer needs to be freed and every newed pointer needs to be deleted. You can't mix them up. new is better because it offers constructors and destructors, so there is good reason to just use new/delete, and thus never get them confused. The fact you're using AfxMessageBox & CString means you've got MFC available, yes ? So use the code I gave you to get the file length, and if you've got some reason to want to create a char* yourself of that size, use new to create it. There's no direct benefit in this case, but there's a benefit as I said in preferring the C++ to the C 'equivelant'. There's more to it, but I'd need to dig up my copy of 'Effective C++' to remind myself of it all.

If you're going to fill a char array with the contents of the file, why not read it into a std::string via an istringstream and an ifstream to read the file ? No messing around with pointers, memory is managed for you, and if you need a char * directly, use c_str() on the std::string to get it.

Christian

The tragedy of cyberspace - that so much can travel so far, and yet mean so little.

"I'm somewhat suspicious of STL though. My (test,experimental) program worked first time. Whats that all about??!?!
- Jon Hulatt, 22/3/2002

Mazdak5-Apr-02 0:19

5-Apr-02 0:19

Christian Graus wrote:
you're going to fill a char array with the contents of the file

Yes,thats exactly what I want to do,and after that I want to change the content of it character by character and write it again to that file.I think I can only do it with FILE structure.(Maybe you can point me to better thing)Can I do that with std::string?.

My C++ is really waek,Does your articles in CP have something about std::string?

Mazy

"The path you tread is narrow and the drop is shear and very high,
The ravens all are watching from a vantage point near by,
Apprehension creeping like a choo-train uo your spine,
Will the tightrope reach the end;will the final cuplet rhyme?"Cymbaline-Pink Floyd

Christian Graus5-Apr-02 0:30

5-Apr-02 0:30

I thought about it in the shower - don't use std::string, use a vector of unsigned chars instead. I have an article on vector, it's the first of my STL articles.

Basically you want to use an ifstream to read a file, and push the result into a vector. Like this:

This needs you to include fstream, vector, algorithm, iostream and maybe functional. I tacked it on the end of an existing project to test it. Give it the name of a real file, and it will read the file into the vector and then print it out to the console. Ignore the last line and the rest will give you a vector, which you can access with array notation, as in vec[0] = 5, etc. And it does not require you know before hand how big the file is, although knowing and preallocating the space in the vector would be an optimisation, as it stands, no MFC is required, nor do you need to manage any memory.

std::ifstream file("c:\\boot.ini");

std::vector<char> vec;

std::copy(std::istream_iterator<char>(file),std::istream_iterator<char>(), std::back_inserter(vec));

std::copy(vec.begin(), vec.end(), std::ostream_iterator<char>(cout, ""));

Christian

The tragedy of cyberspace - that so much can travel so far, and yet mean so little.

"I'm somewhat suspicious of STL though. My (test,experimental) program worked first time. Whats that all about??!?!
- <b>Jon Hulatt, 22/3/2002</b>

Mazdak5-Apr-02 0:59

5-Apr-02 0:59

hmmm,Its a little hard for me,its one of the first STL codes I faced. Smile | :)

But I can understand what it is.

I have a question about first line,I retrieve path of files with CFileFind,and it returns CString,How can I pass it to ifstream?

Mazy

"The path you tread is narrow and the drop is shear and very high,
The ravens all are watching from a vantage point near by,
Apprehension creeping like a choo-train uo your spine,
Will the tightrope reach the end;will the final cuplet rhyme?"Cymbaline-Pink Floyd

Mazdak5-Apr-02 1:46

5-Apr-02 1:46

Well,I think I found it. Smile | :)

:

string strfile=finder.GetFilePath();
ifstream file(strfile.c_str());

Mazy

"The path you tread is narrow and the drop is shear and very high,
The ravens all are watching from a vantage point near by,
Apprehension creeping like a choo-train uo your spine,
Will the tightrope reach the end;will the final cuplet rhyme?"Cymbaline-Pink Floyd

Christian Graus5-Apr-02 9:57

5-Apr-02 9:57

Yup - that will do it. If you had a CString, then you'd use GetBuffer & ReleaseBuffer.

Christian

The tragedy of cyberspace - that so much can travel so far, and yet mean so little.

"I'm somewhat suspicious of STL though. My (test,experimental) program worked first time. Whats that all about??!?!
- Jon Hulatt, 22/3/2002

Jon Hulatt5-Apr-02 5:51

Jon Hulatt

5-Apr-02 5:51

Whether it's the cause of the problem or not, i don't know, but this line is wrong:

CString str1=(CString )(list1);

you can't cast list1, which is a char* to CString.

However, CString has an operator designed for the job:

CString str1 = (LPCSTR) list1;

jon

Sorry to dissapoint you all with my lack of a witty or poignant signature.

Mazdak5-Apr-02 6:11

Netmessagebuffersend(): this is strange!

5-Apr-02 6:11

Jon Hulatt wrote:
CString str1 = (LPCSTR) list1;

hmmmm,thanks Smile | :)

Mazy

"The path you tread is narrow and the drop is shear and very high,
The ravens all are watching from a vantage point near by,
Apprehension creeping like a choo-train uo your spine,
Will the tightrope reach the end;will the final cuplet rhyme?"Cymbaline-Pink Floyd

Jörg Anslik4-Apr-02 21:42

Jörg Anslik

4-Apr-02 21:42

Hi,

I wrote a little tool for our current project here that automatically sends off messages to selected users using NetMessageBufferSend(). It works okay
when I sent off messages from my Win2000 system...every recipient gets the message. What's strange, the tool doesn't work on NT5.0 (SP6) machines -- I always get "NERR_NameNotFound" errors. I tried different ways to convert the relevant strings to UNICODE, but none of these does the trick:

(1)
#define MESGLEN 50000
WCHAR awcToName[MESGLEN*2];
ZeroMemory( awcToName, sizeof(WCHAR)*MESGLEN);
MultiByteToWideChar( CP_ACP, 0, strEmpf, strEmpf.GetLength(), awcToName, MESGLEN);

(2)
wchar_t name[256];
mbstowcs(name,strEmpf,256);
name[256 - 1] = L'\0';

(3)
_towchar(strEmpf) from TConvert.h written by Zoran M.Todorovic

Anyway, launching the usual "net send ..." from a CMD window works on the NT machines, so all required services, etc. seem to be up and running, so I believe it's a string converting problem, although I cannot see where the error might be, since any of the routines (1) - (3) mentioned above work perfectly under W2K.

Any suggestions anyone? I'd really appreciate your help with this.

Thanx in advance

--j

-----------------------------------------
There are three kinds of people:
Those who can count and those who cannot.

DirectShow StillCap problem

Ruzicka4-Apr-02 21:37

Ruzicka

4-Apr-02 21:37

Helo everyone

I'm trying to develop aplication that can capture still images from TV live source.

theese are my inputs...

I'm using DirectShow filters (DirectX 8.1 SDK)

Capture device is
ATI Rage Theater Video Capture chip

My still cap graph contains all needed upstream filters
up to Capture BaseFilter
I rendered preview pin to see Live Preview (works fine), then
I rendered capture pin to get video file (works fine),
I rendered VBI / CC pin (works fine).

Here comes the pain :
I use SampleGrabber filter to get still image
as used in StillCap SDK example.

I add Sample Grabber filter to graph (its connected to capture pin)
and render SampleGrabbers output pin, no errors returned,
but when I try run this still cap graph it returns
"A device atached to system is not funcionating"

Same error ocured in StillCap example, but when I use ATI TV program
It captures still images with no problem.

I've forced this problem for month , so any suggestions are very welcomed.

basic_string

Niklas L4-Apr-02 21:37

Niklas L

4-Apr-02 21:37

There must be a good reason why

operator const E*() const;<code><br />
isn't a member of basic_string. Has there been any discussions regarding this on this message board? I really can't come up with a good example where this might be harmful. Maybe just avoiding implicit type conversion is the stand alone reason? Could anyone give an example why this operator is omitted? I'm sure there is a good reason, just can't figure out why. :confused:

Niklas L4-Apr-02 21:39

Niklas L

4-Apr-02 21:39

...or maybe I'm just plain stupid. I can't even get the simple HTML tags right Smile | :)

Joaquín M López Muñoz4-Apr-02 22:32

Joaquín M López Muñoz

4-Apr-02 22:32

The main reason why operator const E*() const was banned out of the standard is simply that too many people were againt them. There's a general suspicion about implicit conversions as the can make call to overload functions ambiguous and make the code less clear (allegedly). But the subject is somewhat controversial, and not everybody agrees with the resolution taken by the standard commitee. The example against operator const E*() const that I find most convincing is this: suppose the conversion operator actually exists, then the following piece of code works just fine:

void f(const char *)
{
...
}
...
string s1="Code";
string s2="Project";
f(s1+s2); //create a temporary (s1+s2) and pass its internal const char *

But the following snippet will fail, although it seems an innocent version of the former:

string s1="Code";
string s2="Project";
const char *p=s1+s2;
f(p);

The reason why this fails is that p is no longer valid because the temporary (s1+s2) according to the standard rules might have been deleted when the call to f comes. Introducing c_str does not prevent this problem, but at least make you think twice about it ((s1+s2).c_str() is an eye-catching sentence, isn't it.)

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

Joao Vaz4-Apr-02 23:49

Joao Vaz

4-Apr-02 23:49

Joaquín M López Muñoz wrote:
The main reason why operator const E*() const was banned out of the standard is simply that too many people were againt them

Totally agree with them, but in the beginning I was totally against, until I discovered the reasons for this behaviour. Of course as you pinpoint, there are a quite few people that strongly disagree with this, but after all even the standard cannot please all of us.
Although this guys are cleaver , sometimes they just make nonsense decisions like the vector<bool> specialization returning a proxy object OMG | :OMG:

, of course this is just plain broken and will be fixed in next one, but this is a sample that this guys sometimes doesn't put the necessary thought on some things.Unfortunately even Stroustroup is against the ideia of incorporating in the C++ core proper multithreading support to do properly multithreading programming(and portable too). They could use policies to provide true thread safe capabilities to stl,not a difficult situation to deal with, and they also could provide true thread safe lazy initializion to c++, for instance in the case of the singleton pattern ..., but no, they don't want that ... lazy guys, and they are suprised that the guys on comp.lang.threads don't like them at all !!!

Joaquín M López Muñoz wrote:
(s1+s2).c_str() is an eye-catching sentence, isn't it

Definitely is ...

Cheers,

Joao Vaz