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#include "internal.h"
int
io·seek(io·Header *io, intptr offset, int whence, intptr *pos)
{
intptr n,d,cap;
switch(io->state){
default:
fmt·fprint(2, "seek: unknown state %d\n", io->state);
return io·BufEof;
case io·BufEnd:
io->state = io·BufRdr;
io->ilen = 0;
io->g = io->e;
/* fallthrough */
case io·BufRdr:
n = offset;
if(whence == sys·SeekCur){
n += io·offset(io);
whence = sys·SeekSet;
}
/* can we seek inside our buffer */
if(whence == sys·SeekSet){
d = n - io·offset(io);
cap = io->e - io->g;
if(-cap <= d && d <= cap){
io->ilen += d;
if(d >= 0){
if(io->ilen <= 0){
*pos = n;
return 0;
}
}else{
if(io->e - io->g >= -io->ilen){
*pos = n;
return 0;
}
}
}
}
/* nope, call the kernel to do it for us */
sys·seek(io->fd, offset, whence, &n);
io->ilen = 0;
io->g = io->e;
break;
case io·BufWtr:
io·flush(io);
sys·seek(io->fd, offset, whence, &n);
break;
}
io->pos = *pos = n;
return 0;
}
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