Re: Overwriting a portion of a binary file

mohammad.nabil.h@xxxxxxxxx wrote:

> I've been working on a database management system, and i have met a
> problem when i update a row, i found that fwrite() and _write, writes
> to the end of the file, even if i hade rewind() the file before it. As
> far as i can guess, they `append', i am looking for something that
> overwrites. of course i can't load the 'whole' file in memory, change
> it, then resave it again. the whole memory might not be enough.
>
> my code always insists on storing 'bar' after 'foo'. i want to save
> 'bar' instead of 'foo'
>
> here is a peek of my code :

We don't want a peek, we want a long, lingering look at the whole thing.


> void add_record(record* rec)
> {
> // m_db is a FILE*

Where is the code that created this FILE*?

> //fseek(m_db,0,SEEK_END);
> //fwrite(rec,record_size(),1,m_db);
> _write(fileno(m_db),rec,record_size()); // both function result in
> the same output

There is no _write() function in the C language.

> any help greatly appreciated

Post a complete, minimal, compilable program that demonstrates the
problem.



Brian

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