-int
-bdirect_write_prepare(struct fastbuf *f, byte **buf)
-{
- if (f->bptr == f->bufend)
- f->spout(f);
- *buf = f->bptr;
- return f->bufend - f->bptr;
+ favail = bdirect_read_prepare(f, &fptr);
+ if (!favail)
+ {
+ if (l == ~0U)
+ return;
+ die("bbcopy: source exhausted");
+ }
+ tavail = bdirect_write_prepare(t, &tptr);
+ n = MIN(l, favail);
+ n = MIN(n, tavail);
+ memcpy(tptr, fptr, n);
+ bdirect_read_commit(f, fptr + n);
+ bdirect_write_commit(t, tptr + n);
+ if (l != ~0U)
+ l -= n;
+ }