Write/Read a struct into a file...;-)

[Ludovic Lemoine]

Hi,
I would like to be able to write and "later!!" read a struct in a file.
This is my structure :
struct {
CString Rep;
int Size;
int NbFile;
}
I have tried many solutions like with CFile but all the times unsuccessfully :-(

Thanks i.a. for your help.

[email protected]

[herbieII]

Your structure needs a "tag" or name then you can write it to a file using basic, low level I/O.

[Ludovic Lemoine]

Thanks,
But I already know that, I just want by writing this structure explain that I use a CString inside.
The real source is this one :
struct Record {
CString R_rep;
int R_size;
int R_nbfile;
};
char* pFileName = "test3.dat";
Record Enregistrement;
f.Open( pFileName, CFile::modeCreate | CFile::modeWrite, &e ) ;
Enregistrement.R_rep = Direct;
Enregistrement.R_size = size;
Enregistrement.R_nbfile = nbFile;
// Ecriture dans le fichier
f.Write((struct Record *) &Enregistrement, sizeof(Enregistrement));
f.Close();
// For reading :
Record Lecture;
f.Read((struct Record *) &Lecture, sizeof(struct Record));
f.Close();
That's all...
Thanks i.a for any help...
Ludo

[Rail Jon Rogut]

When you use a CString in a structure, you can't use sizeof to find out how many bytes you want to save or read - I would recommend that instead of using a CString, you use a char[MAX_LENGTH] -- that way your structure will have a constant size and you can use sizeof. An alternative, is to have the first member of the structure be an integer which holds the structure's size:

struct Record
{
int R_iSize;
CString R_rep;
int R_size;
int R_nbfile;
};

Then set R_iSize equal to the size of the structure:

R_iSize = R_rep.GetLength() + sizeof(R_size) + sizeof(R_nbfile);

after you set the CString value... then use R_iSize as the length parameter in your CFile::Read() or CFile::Write() calls.

Generally though I use my first suggestion:

#define MAX_RECORD_STRING 256

struct Record
{
char R_rep[MAX_RECORD_STRING];
int R_size;
int R_nbfile;
};



Rail

------------
Recording Engineer/Software Developer
Rail Jon Rogut Software
http://home.earthlink.net/~railro/
[email protected]