/*
read len bytes without advancing the read pointer
*/
uint32_t ByteBuffer::peekbytes(uint8_t *data, uint32_t len)
{
if (len > available()) {
len = available();
}
if (len == 0) {
return 0;
}
uint32_t n;
const uint8_t *b = readptr(n);
if (n > len) {
n = len;
}
// perform first memcpy
memcpy(data, b, n);
data += n;
if (len > n) {
// possible second memcpy, must be from front of buffer
memcpy(data, buf, len-n);
}
return len;
}
static long
segmentread(Chan *c, void *a, long n, vlong voff)
{
Globalseg *g;
Zseg *zs;
uintptr va;
char *p, *s;
long tot;
char buf[64];
if(c->qid.type == QTDIR)
return devdirread(c, a, n, (Dirtab *)0, 0L, segmentgen);
g = c->aux;
switch(TYPE(c)){
case Qfree:
if(g->s == nil)
error("segment not yet allocated");
if(n < PTRSIZE)
error("read buffer too small");
zs = &g->s->zseg;
qlock(&g->s->lk);
if(waserror()){
qunlock(&g->s->lk);
nexterror();
}
while((va = zgetaddr(g->s)) == 0ULL){
qunlock(&g->s->lk);
sleep(&zs->rr, znotempty, zs);
qlock(&g->s->lk);
}
p = a;
for(tot = 0; n-tot > PTRSIZE; tot += PTRSIZE){
p += readptr(p, n, va);
if((va = zgetaddr(g->s)) == 0ULL)
break;
}
poperror();
qunlock(&g->s->lk);
return tot;
case Qctl:
if(g->s == nil)
error("segment not yet allocated");
if(g->s->type&SG_KZIO)
s = "kmsg";
else if(g->s->type&SG_ZIO)
s = "umsg";
else
s = "addr";
snprint(buf, sizeof(buf), "%s %#p %#p\n",
s, g->s->base, (uintptr)(g->s->top-g->s->base));
return readstr(voff, a, n, buf);
case Qdata:
if(voff < 0)
error(Enegoff);
if(voff + n > g->s->top - g->s->base){
n = g->s->top - voff;
if(n <= 0)
break;
}
qlock(&g->l);
if(waserror()){
qunlock(&g->l);
nexterror();
}
g->off = voff + g->s->base;
g->data = smalloc(n);
if(waserror()){
free(g->data);
nexterror();
}
g->dlen = n;
docmd(g, Cread);
memmove(a, g->data, g->dlen);
poperror();
free(g->data);
poperror();
qunlock(&g->l);
return g->dlen;
default:
panic("segmentread");
}
return 0; /* not reached */
}
