Re: A89: fwrite function
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Re: A89: fwrite function
...man I suck, I apologize for emailing this three times... but I think
I have reviewed the code in source enough times to say that I think
Zeljko overlooked a lot (or got tired of it) when he hacked together
ANSI FILE support. The *crosses fingers* correct implementation should
be like this, and similar check should be added to fputs:
unsigned __fwrite(int(*fnc)(int,FILE*),void *ptr,unsigned size,unsigned
n,FILE *f)
{
unsigned i,j,free,needed;
int saveflags=f->flags;
char *base=f->base,*oldbase=base;
if(f->flags&_F_ERR) return EOF;
if(!(f->flags&_F_WRIT)) __FERROR(f);
f->flags|=_F_BIN;
if((needed = size*n) > (free = f->alloc - f->fpos - f->base))
{
HeapUnlock(f->handle);
if(!HeapRealloc(f->handle,f->alloc+=needed-free)) __FERROR(f);
base=f->base=HLock(f->handle);
f->fpos+=base-oldbase;
oldbase=base;
}
for(i=0;i<n;i++)
for(j=0;j<size;j++)
if(fnc(*(char*)ptr++,f)<0) goto exit;
exit:
f->flags=saveflags;
return i;
}
Scott Dial wrote:
>
> I wanna make a correction to a mistake I made.... f->pos should be
> f->fpos, note below the change
>
> Scott Dial wrote:
> >
> > This is my third time writing this email (don't ask), so this is the
> > abrigded version of this email. fwrite is "buggy" or rather implemented
> > badly. fwrite does no memory checking, thus does not allocate the space
> > nessecary for the data being wrote. I suggest that the fwrite
> > implementation be changed to something similar to this: (btw, fputs has
> > a similar problem... which I don't have time to rewrite)
> >
> > unsigned __fwrite(int(*fnc)(int,FILE*),void *ptr,unsigned size,unsigned
> > n,FILE *f)
> > {
> > unsigned i,j,free,needed;
> > int saveflags=f->flags;
> > f->flags|=_F_BIN;
> free = f->alloc - f->fpos - f->base;
> > needed = size*n;
> > if(needed>free)
> > {
> > HeapUnlock(f->handle);
> > if(!HeapRealloc(f->handle,f->alloc+=needed-free)) __FERROR(f);
> > base=f->base=HLock(f->handle);
> > f->fpos+=base-oldbase;
> > oldbase=base;
> > }
> > for(i=0;i<n;i++)
> > for(j=0;j<size;j++)
> > if(fnc(*(char*)ptr++,f)<0) goto exit;
> > exit:
> > f->flags=saveflags;
> > return i;
> > }
> >
> > Michael Cowart wrote:
> > >
> > > Ok, what is wrong here?
> > >
> > > FILE *fp = fopen("example","wb");
> > > fwrite (vplane0,3840,1,fp); /*vplane is a pointer to a 3840
> > > byte screen buffer*/
> > > fputc(0,fp);
> > > fputs("PNT",fp);
> > > fputc(0,fp);
> > > fputc(OTH_TAG,fp);
> > > fclose(fp);
> > >
> > > When I create this file, it's only 371 bytes long... Is fwrite buggy, or am
> > > I just insane : ) ?
> > >
> > > Thanx,
> > > Michael Cowart
> >
> > --
> > Scott "Wrath" Dial
> > wrath@calc.org
> > ICQ#3608935
> > Member of TCPA - tcpa.calc.org
> > PGP key available
> >
> > _____NetZero Free Internet Access and Email______
> > http://www.netzero.net/download/index.html
>
> --
> Scott "Wrath" Dial
> wrath@calc.org
> ICQ#3608935
> Member of TCPA - tcpa.calc.org
> PGP key available
> _______________________________________________
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--
Scott "Wrath" Dial
wrath@calc.org
ICQ#3608935
Member of TCPA - tcpa.calc.org
PGP key available
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