static int32_t
read(int ispread, int fd, void *p, int32_t n, int64_t off)
{
Proc *up = externup();
int32_t nn, nnn;
Chan *c;
p = validaddr(p, n, 1);
c = fdtochan(fd, OREAD, 1, 1);
if(waserror()){
cclose(c);
nexterror();
}
/*
* The offset is passed through on directories, normally.
* Sysseek complains, but pread is used by servers like exportfs,
* that shouldn't need to worry about this issue.
*
* Notice that c->devoffset is the offset that c's dev is seeing.
* The number of bytes read on this fd (c->offset) may be different
* due to rewritings in mountfix.
*/
if(ispread){
if(off == ~0LL){ /* use and maintain channel's offset */
off = c->offset;
ispread = 0;
}
}
else
off = c->offset;
if(c->qid.type & QTDIR){
/*
* Directory read:
* rewind to the beginning of the file if necessary;
* try to fill the buffer via mountrockread;
* clear ispread to always maintain the Chan offset.
*/
if(off == 0LL){
if(!ispread){
c->offset = 0;
c->devoffset = 0;
}
mountrewind(c);
unionrewind(c);
}
if(!mountrockread(c, p, n, &nn)){
if(c->umh)
nn = unionread(c, p, n);
else{
if(off != c->offset)
error(Edirseek);
nn = c->dev->read(c, p, n, c->devoffset);
}
}
nnn = mountfix(c, p, nn, n);
ispread = 0;
}
else
nnn = nn = c->dev->read(c, p, n, off);
if(!ispread){
lock(&c->r.l);
c->devoffset += nn;
c->offset += nnn;
unlock(&c->r.l);
}
poperror();
cclose(c);
return nnn;
}
static long
read(ulong *arg, vlong *offp)
{
long n, nn, nnn;
uchar *p;
Chan *c;
vlong off;
n = arg[2];
validaddr(arg[1], n, 1);
p = (void*)arg[1];
c = fdtochan(arg[0], OREAD, 1, 1);
if(waserror()){
cclose(c);
nexterror();
}
/*
* The offset is passed through on directories, normally.
* Sysseek complains, but pread is used by servers like exportfs,
* that shouldn't need to worry about this issue.
*
* Notice that c->devoffset is the offset that c's dev is seeing.
* The number of bytes read on this fd (c->offset) may be different
* due to rewritings in rockfix.
*/
if(offp == nil) /* use and maintain channel's offset */
off = c->offset;
else
off = *offp;
if(off < 0)
error(Enegoff);
if(off == 0){ /* rewind to the beginning of the directory */
if(offp == nil){
c->offset = 0;
c->devoffset = 0;
}
mountrewind(c);
unionrewind(c);
}
if(c->qid.type & QTDIR){
if(mountrockread(c, p, n, &nn)){
/* do nothing: mountrockread filled buffer */
}else if(c->umh)
nn = unionread(c, p, n);
else{
if(off != c->offset)
error(Edirseek);
nn = devtab[c->type]->read(c, p, n, c->devoffset);
}
nnn = mountfix(c, p, nn, n);
}else
nnn = nn = devtab[c->type]->read(c, p, n, off);
lock(c);
c->devoffset += nn;
c->offset += nnn;
unlock(c);
poperror();
cclose(c);
return nnn;
}
