Factor out backend handling code.

backend.c

@@ -0,0 +1,109 @@
+#include <stdio.h>
+#include <assert.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netdb.h>
+#include <sys/epoll.h>
+
+#include "airspy_adsb.h"
+#include "backend.h"
+
+
+static parser parsers[] = {
+	airspy_adsb_parse,
+};
+#define NUM_PARSERS (sizeof(parsers) / sizeof(*parsers))
+
+
+bool backend_connect(char *node, char *service, struct backend *backend, int epoll_fd) {
+	assert(backend->type == PEER_BACKEND);
+
+	struct addrinfo *addrs;
+
+	{
+		struct addrinfo hints = {
+			.ai_family = AF_UNSPEC,
+			.ai_socktype = SOCK_STREAM,
+		};
+
+		int gai_err = getaddrinfo(node, service, &hints, &addrs);
+		if (gai_err) {
+			fprintf(stderr, "getaddrinfo(%s/%s): %s\n", node, service, gai_strerror(gai_err));
+			return false;
+		}
+	}
+
+	{
+		struct addrinfo *addr;
+  	for (addr = addrs; addr != NULL; addr = addr->ai_next) {
+			backend->fd = socket(addr->ai_family, addr->ai_socktype, addr->ai_protocol);
+			if (backend->fd == -1) {
+				perror("socket");
+				continue;
+			}
+
+			if (connect(backend->fd, addr->ai_addr, addr->ai_addrlen) != -1) {
+				break;
+			}
+
+			close(backend->fd);
+		}
+
+		if (addr == NULL) {
+			freeaddrinfo(addrs);
+			fprintf(stderr, "Can't connect to %s/%s\n", node, service);
+			return false;
+		}
+
+  	char hbuf[NI_MAXHOST], sbuf[NI_MAXSERV];
+  	if (getnameinfo(addr->ai_addr, addr->ai_addrlen, hbuf, sizeof(hbuf), sbuf, sizeof(sbuf), NI_NUMERICHOST | NI_NUMERICSERV) == 0) {
+			fprintf(stderr, "Connected to %s/%s\n", hbuf, sbuf);
+		}
+	}
+
+	freeaddrinfo(addrs);
+
+	{
+		struct epoll_event ev = {
+			.events = EPOLLIN,
+			.data = {
+				.ptr = backend,
+			},
+		};
+		if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, backend->fd, &ev) == -1) {
+			perror("epoll_ctl");
+			return false;
+		}
+	}
+
+	return true;
+}
+
+bool backend_read(struct backend *backend) {
+	if (buf_fill(&backend->buf, backend->fd) < 0) {
+		fprintf(stderr, "Connection closed by backend\n");
+		return false;
+	}
+
+	struct packet packet;
+	while (backend->parser(backend, &packet)) {
+	}
+
+	if (backend->buf.length == BUF_LEN_MAX) {
+		fprintf(stderr, "Input buffer overrun. This probably means that adsbus doesn't understand the protocol that this source is speaking.\n");
+		return false;
+	}
+	return true;
+}
+
+bool backend_autodetect_parse(struct backend *backend, struct packet *packet) {
+	assert(backend->type == PEER_BACKEND);
+
+	for (int i = 0; i < NUM_PARSERS; i++) {
+		if (parsers[i](backend, packet)) {
+			backend->parser = parsers[i];
+			return true;
+		}
+	}
+	return false;
+}