WINSIZE
next->dict = out - beg > WINSIZE ? WINSIZE : (unsigned)(out - beg);
unsigned recent = WINSIZE - index->strm.avail_out;
memcpy(next->window, window + WINSIZE - copy, copy);
unsigned char win[WINSIZE] = {0}; // output sliding window
unsigned char discard[WINSIZE];
index->strm.avail_out = offset < WINSIZE ? (unsigned)offset :
WINSIZE;
index->strm.avail_out = WINSIZE;