/**
* returns -1 on error, or size on success
*/
static int do_send(struct libvchan *ctrl, const void *data, size_t size)
{
int real_idx = wr_prod(ctrl) & (wr_ring_size(ctrl) - 1);
int avail_contig = wr_ring_size(ctrl) - real_idx;
if (VCHAN_DEBUG) {
char metainfo[32];
struct iovec iov[2];
iov[0].iov_base = metainfo;
iov[0].iov_len = snprintf(metainfo, 32, "vchan wr %d/%d", ctrl->other_domain_id, ctrl->device_number);
iov[1].iov_base = (void *)data;
iov[1].iov_len = size;
writev(-1, iov, 2);
}
if (avail_contig > size)
avail_contig = size;
memcpy(wr_ring(ctrl) + real_idx, data, avail_contig);
if (avail_contig < size)
{
// we rolled across the end of the ring
memcpy(wr_ring(ctrl), data + avail_contig, size - avail_contig);
}
barrier(); // data must be in the ring prior to increment
wr_prod(ctrl) += size;
barrier(); // increment must happen prior to notify
if (do_notify(ctrl) < 0)
return -1;
return size;
}
/**
* returns -1 on error, or size on success
*/
static int do_send(struct libxenvchan *ctrl, const void *data, size_t size)
{
int real_idx = wr_prod(ctrl) & (wr_ring_size(ctrl) - 1);
int avail_contig = wr_ring_size(ctrl) - real_idx;
if (avail_contig > size)
avail_contig = size;
xen_mb(); /* read indexes /then/ write data */
memcpy(wr_ring(ctrl) + real_idx, data, avail_contig);
if (avail_contig < size)
{
// we rolled across the end of the ring
memcpy(wr_ring(ctrl), data + avail_contig, size - avail_contig);
}
xen_wmb(); /* write data /then/ notify */
wr_prod(ctrl) += size;
if (send_notify(ctrl, VCHAN_NOTIFY_WRITE))
return -1;
return size;
}
