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#include <arpa/inet.h>
#include <endian.h>
#include <poll.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>
#include "midimcast.h"
bool midimcast_debug;
// Container of messsage to be relayed
struct baton {
struct baton *next;
size_t midi_size;
struct msg msg;
};
static void env_read_client(long *const delay, const char **const soundfont)
{
const char *const delay_str = getenv("RELAY_DELAY");
if (delay_str) {
errno = 0;
*delay = strtol(delay_str, NULL, 0);
if (errno)
err_std_nchk(strtol);
} else {
*delay = 3000;
}
debug("Using intentional relay delay %ld ms", *delay);
*soundfont = getenv("SOUNDFONT");
if (!soundfont)
err("`$SOUNDFONT` unset");
debug("Using soundfont %s", *soundfont);
}
static int in_sock_init(struct sockaddr_in *const addr,
const char *const group,
const uint16_t port) {
const int sock = err_std_neg(socket, AF_INET, SOCK_DGRAM, 0);
// Allow immediate address reuse
int reuse_addr = true;
err_std(setsockopt,
sock,
SOL_SOCKET,
SO_REUSEADDR,
(void *)&reuse_addr,
sizeof(reuse_addr));
// Bind address to socket
memset(addr, 0, sizeof(*addr));
addr->sin_family = AF_INET;
addr->sin_addr.s_addr = htonl(INADDR_ANY);
addr->sin_port = htons(port);
err_std(bind, sock, (struct sockaddr *)addr, sizeof(*addr));
// Join multicast group
struct ip_mreq mreq;
mreq.imr_multiaddr.s_addr = inet_addr(group);
mreq.imr_interface.s_addr = htonl(INADDR_ANY);
err_std(setsockopt,
sock,
IPPROTO_IP,
IP_ADD_MEMBERSHIP,
(void *)&mreq,
sizeof(mreq));
return sock;
}
static size_t msg_read(struct msg *const msg,
const int sock,
const struct sockaddr_in *const addr) {
socklen_t addr_size = sizeof(*addr); // Overwritten below
const ssize_t nread = err_std_neg(recvfrom,
sock,
msg,
sizeof(*msg),
0,
(struct sockaddr *)addr,
&addr_size);
debug("Message length %zu", nread);
if (nread > (ssize_t)sizeof(*msg))
err("Message longer than %zu", sizeof(*msg));
const size_t header_size = ((void *)&msg->midi - (void *)&msg->ts);
if (nread < (ssize_t)header_size)
err("Message shorter than %zu", header_size);
msg->ts = le64toh(msg->ts);
return nread - header_size;
}
void baton_read(struct baton *const baton,
const int in_sock,
const struct sockaddr_in *const addr) {
baton->midi_size = msg_read(&baton->msg, in_sock, addr);
const uint64_t ts_dst = now();
int64_t latency = (int64_t)ts_dst - (int64_t)baton->msg.ts;
debug("Message received: ts_src = %lu, ts_dst = %lu, latency = %ld, midi_size = %lu",
baton->msg.ts,
ts_dst,
latency,
baton->midi_size);
if (latency < 0)
warn("Clocks unsynchronised by over %lu ms", -latency);
}
void baton_put(struct baton *baton, struct baton **const first_baton)
{
// TODO: Simplify conditionals
struct baton *prev_baton = *first_baton;
struct baton *next_baton = *first_baton ? (**first_baton).next : NULL;
while (next_baton && next_baton->msg.ts < baton->msg.ts) {
prev_baton = next_baton;
next_baton = next_baton->next;
}
baton->next = next_baton;
if (prev_baton)
prev_baton->next = baton;
else
*first_baton = baton;
}
int timeout(const struct baton *const first_baton, const long delay)
{
if (first_baton) {
uint64_t have = now(), want = first_baton->msg.ts + delay;
if (have < want) {
const int timeout = want - have;
debug("Relaying in %d ms", timeout);
return timeout;
} else {
warn("Relaying %lu ms late", have - want);
return 0;
}
} else {
debug("Nothing to relay right now");
return -1;
}
}
void baton_write(const struct baton *const baton, FILE *const out_file)
{
size_t write_count = fwrite(baton->msg.midi,
1,
baton->midi_size,
out_file);
if (write_count < baton->midi_size)
err_std_nchk(fwrite);
err_std(fflush, out_file);
}
struct baton *baton_take(struct baton **const first_baton)
{
struct baton *const first_baton_old = *first_baton;
*first_baton = (**first_baton).next;
return first_baton_old;
}
void batons_relay(const char *const mcast_group,
const uint16_t mcast_port,
const long delay,
const int out_fd) {
struct sockaddr_in addr;
const int in_sock = in_sock_init(&addr, mcast_group, mcast_port);
struct pollfd in_sock_poll = {.fd = in_sock, .events = POLLIN};
struct baton *first_baton = NULL;
FILE *const out_file = err_std_null(fdopen, out_fd, "w");
for (;;) {
if (err_std_neg(poll, &in_sock_poll, 1, timeout(first_baton, delay))) {
struct baton *baton = err_std_null(malloc, sizeof(*baton));
baton_read(baton, in_sock, &addr);
baton_put(baton, &first_baton);
} else {
baton_write(first_baton, out_file);
free(baton_take(&first_baton));
}
}
}
void synthesise(const int fd, const char *const soundfont)
{
err_std(dup2, fd, STDIN_FILENO);
debug("Starting synthesiser");
err_std(execlp,
"fluidsynth",
"fluidsynth",
"--no-shell",
"--server",
"--gain=1",
"--audio-driver=pulseaudio",
"-o", "midi.driver=oss",
"-o", "midi.oss.device=/dev/stdin",
soundfont,
NULL);
}
int main()
{
const char *mcast_group;
uint16_t mcast_port;
long delay;
const char *soundfont;
env_read_common(&mcast_group, &mcast_port);
env_read_client(&delay, &soundfont);
int pipes_fds[2];
err_std(pipe, pipes_fds);
if (err_std_neg(fork))
batons_relay(mcast_group, mcast_port, delay, pipes_fds[1]);
else
synthesise(pipes_fds[0], soundfont);
}
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