 static int mem_write(jas_stream_obj_t *obj, char *buf, int cnt)
 {
	size_t n;
 	int ret;
 	jas_stream_memobj_t *m = (jas_stream_memobj_t *)obj;
	size_t newbufsize;
	size_t newpos;
 
 	assert(buf);
 	assert(cnt >= 0);

	JAS_DBGLOG(100, ("mem_write(%p, %p, %d)\n", obj, buf, cnt));
	newpos = m->pos_ + cnt;
 	if (newpos > m->bufsize_ && m->growable_) {
 		newbufsize = m->bufsize_;
 		while (newbufsize < newpos) {
			//newbufsize <<= 1;
			if (!jas_safe_size_mul(newbufsize, 2, &newbufsize)) {
				JAS_DBGLOG(100, ("new buffer size would cause overflow\n"));
				return -1;
			}
 		}
		JAS_DBGLOG(100, ("mem_write resizing from %d to %zu\n", m->bufsize_,
 		  newbufsize));
		assert(newbufsize > 0);
 		if (mem_resize(m, newbufsize)) {
 			return -1;
 		}
	}
	if (m->pos_ > m->len_) {
		/* The current position is beyond the end of the file, so
		  pad the file to the current position with zeros. */
		n = JAS_MIN(m->pos_, m->bufsize_) - m->len_;
		if (n > 0) {
			memset(&m->buf_[m->len_], 0, n);
			m->len_ += n;
		}
		if (m->pos_ != m->len_) {
			/* The buffer is not big enough. */
			return 0;
		}
	}
	n = m->bufsize_ - m->pos_;
	ret = JAS_MIN(n, cnt);
	if (ret > 0) {
		memcpy(&m->buf_[m->pos_], buf, ret);
		m->pos_ += ret;
	}
	if (m->pos_ > m->len_) {
		m->len_ = m->pos_;
	}
	assert(ret == cnt);
	return ret;
}

The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.