lcm_buf_t *
lcm_buf_allocate_data(lcm_buf_queue_t * inbufs_empty, lcm_ringbuf_t **ringbuf) {
lcm_buf_t * lcmb = NULL;
// first allocate a buffer struct for the packet metadata
if (lcm_buf_queue_is_empty(inbufs_empty)) {
// allocate additional buffer structs if needed
int i;
for (i = 0; i < LCM_DEFAULT_RECV_BUFS; i++) {
lcm_buf_t * nbuf = (lcm_buf_t *) calloc(1, sizeof(lcm_buf_t));
lcm_buf_enqueue(inbufs_empty, nbuf);
}
}
lcmb = lcm_buf_dequeue(inbufs_empty);
assert(lcmb);
// allocate space on the ringbuffer for the packet data.
// give it the maximum possible size for an unfragmented packet
lcmb->buf = lcm_ringbuf_alloc(*ringbuf, LCM_MAX_UNFRAGMENTED_PACKET_SIZE);
if (lcmb->buf == NULL) {
// ringbuffer is full. allocate a larger ringbuffer
// Can't free the old ringbuffer yet because it's in use (i.e., full)
// Must wait until later to free it.
assert(lcm_ringbuf_used(*ringbuf) > 0);
dbg(DBG_LCM, "Orphaning ringbuffer %p\n", *ringbuf);
unsigned int old_capacity = lcm_ringbuf_capacity(*ringbuf);
unsigned int new_capacity = (unsigned int) (old_capacity * 1.5);
// replace the passed in ringbuf with the new one
*ringbuf = lcm_ringbuf_new(new_capacity);
lcmb->buf = lcm_ringbuf_alloc(*ringbuf, 65536);
assert(lcmb->buf);
dbg(DBG_LCM, "Allocated new ringbuffer size %u\n", new_capacity);
}
// save a pointer to the ringbuf, in case it gets replaced by another call
lcmb->ringbuf = *ringbuf;
// zero the last byte so that strlen never segfaults
lcmb->buf[65535] = 0;
return lcmb;
}
// read continuously until a complete message arrives
static lcm_buf_t *
udp_read_packet (lcm_udpm_t *lcm)
{
lcm_buf_t *lcmb = NULL;
int sz = 0;
g_static_rec_mutex_lock (&lcm->mutex);
double buf_avail = lcm_ringbuf_available(lcm->ringbuf);
g_static_rec_mutex_unlock (&lcm->mutex);
if (buf_avail < lcm->udp_low_watermark)
lcm->udp_low_watermark = buf_avail;
GTimeVal tv;
g_get_current_time(&tv);
int elapsedsecs = tv.tv_sec - lcm->udp_last_report_secs;
if (elapsedsecs > 2) {
uint32_t total_bad = lcm->udp_discarded_lcmb +
lcm->udp_discarded_buf +
lcm->udp_discarded_bad;
if (total_bad > 0 || lcm->udp_low_watermark < 0.5) {
fprintf(stderr,
"%d.%03d LCM loss %4.1f%% : %5d lcmb, %5d buf, %5d err, "
"buf avail %4.1f%%\n",
(int) tv.tv_sec, (int) tv.tv_usec/1000,
total_bad * 100.0 / (lcm->udp_rx + total_bad),
lcm->udp_discarded_lcmb,
lcm->udp_discarded_buf,
lcm->udp_discarded_bad,
100.0 * lcm->udp_low_watermark);
lcm->udp_rx = 0;
lcm->udp_discarded_lcmb = 0;
lcm->udp_discarded_buf = 0;
lcm->udp_discarded_bad = 0;
lcm->udp_last_report_secs = tv.tv_sec;
lcm->udp_low_watermark = HUGE;
}
}
int got_complete_message = 0;
while (!got_complete_message) {
// wait for either incoming UDP data, or for an abort message
fd_set fds;
FD_ZERO (&fds);
FD_SET (lcm->recvfd, &fds);
FD_SET (lcm->thread_msg_pipe[0], &fds);
SOCKET maxfd = MAX(lcm->recvfd, lcm->thread_msg_pipe[0]);
if (select (maxfd + 1, &fds, NULL, NULL, NULL) <= 0) {
perror ("udp_read_packet -- select:");
continue;
}
if (FD_ISSET (lcm->thread_msg_pipe[0], &fds)) {
// received an exit command.
dbg (DBG_LCM, "read thread received exit command\n");
if (lcmb) {
// lcmb is not on one of the memory managed buffer queues. We could
// either put it back on one of the queues, or just free it here. Do the
// latter.
//
// Can also just free its lcm_buf_t here. Its data buffer is
// managed either by the ring buffer or the fragment buffer, so
// we can ignore it.
free (lcmb);
}
return NULL;
}
// there is incoming UDP data ready.
assert (FD_ISSET (lcm->recvfd, &fds));
if (!lcmb) {
// try to allocate space on the ringbuffer for the new data
// first allocate a buffer struct
g_static_rec_mutex_lock (&lcm->mutex);
lcmb = lcm_buf_dequeue (lcm->inbufs_empty);
if (!lcmb) {
g_static_rec_mutex_unlock (&lcm->mutex);
udp_discard_packet (lcm);
continue;
}
lcmb->buf_from_ringbuf = 1;
// next allocate space on the ringbuffer.
// give it the maximum possible size for an unfragmented packet
lcmb->buf = lcm_ringbuf_alloc(lcm->ringbuf, 65536);
g_static_rec_mutex_unlock (&lcm->mutex);
if (!lcmb->buf) {
// ringbuffer is full. discard the packet, put lcmb back on the
// empty queue, and start waiting again
udp_discard_packet (lcm);
lcm_buf_enqueue (lcm->inbufs_empty, lcmb);
lcmb = NULL;
continue;
}
// zero the last byte so that strlen never segfaults
lcmb->buf[65535] = 0;
}
struct iovec vec;
vec.iov_base = lcmb->buf;
vec.iov_len = 65535;
#ifdef MSG_EXT_HDR
// operating systems that provide SO_TIMESTAMP allow us to obtain more
// accurate timestamps by having the kernel produce timestamps as soon
// as packets are received.
char controlbuf[64];
#endif
struct msghdr msg;
msg.msg_name = &lcmb->from;
msg.msg_namelen = sizeof (struct sockaddr);
msg.msg_iov = &vec;
msg.msg_iovlen = 1;
#ifdef MSG_EXT_HDR
msg.msg_control = controlbuf;
msg.msg_controllen = sizeof (controlbuf);
msg.msg_flags = 0;
#endif
sz = recvmsg (lcm->recvfd, &msg, 0);
if (sz < 0) {
perror ("udp_read_packet -- recvmsg");
lcm->udp_discarded_bad++;
continue;
}
if (sz < sizeof(lcm2_header_short_t)) {
// packet too short to be LCM
lcm->udp_discarded_bad++;
continue;
}
lcmb->fromlen = msg.msg_namelen;
int got_utime = 0;
#ifdef SO_TIMESTAMP
struct cmsghdr * cmsg = CMSG_FIRSTHDR (&msg);
/* Get the receive timestamp out of the packet headers if possible */
while (!lcmb->recv_utime && cmsg) {
if (cmsg->cmsg_level == SOL_SOCKET &&
cmsg->cmsg_type == SCM_TIMESTAMP) {
// GTimeVal is identical to struct timeval, so this cast is ok
GTimeVal * t = (GTimeVal*) CMSG_DATA (cmsg);
lcmb->recv_utime = (int64_t) t->tv_sec * 1000000 + t->tv_usec;
got_utime = 1;
break;
}
cmsg = CMSG_NXTHDR (&msg, cmsg);
}
#endif
if (!got_utime)
lcmb->recv_utime = _timestamp_now ();
lcm2_header_short_t *hdr2 = (lcm2_header_short_t*) lcmb->buf;
uint32_t rcvd_magic = ntohl(hdr2->magic);
if (rcvd_magic == LCM2_MAGIC_SHORT)
got_complete_message = _recv_short_message (lcm, lcmb, sz);
else if (rcvd_magic == LCM2_MAGIC_LONG)
got_complete_message = _recv_message_fragment (lcm, lcmb, sz);
else {
dbg (DBG_LCM, "LCM: bad magic\n");
lcm->udp_discarded_bad++;
continue;
}
}
// if the newly received packet is a short packet, then resize the space
// allocated to it on the ringbuffer to exactly match the amount of space
// required. That way, we do not use 64k of the ringbuffer for every
// incoming message.
if (lcmb->buf_from_ringbuf) {
g_static_rec_mutex_lock (&lcm->mutex);
lcm_ringbuf_shrink_last(lcm->ringbuf, lcmb->buf, sz);
g_static_rec_mutex_unlock (&lcm->mutex);
}
return lcmb;
}
