Clean up backend detection flow.

adsbus.c

@@ -18,18 +18,11 @@ struct opts {
 	char *backend_service;
 };
 
-typedef bool (*parser)(struct buf *, struct packet *, void *);
 static parser parsers[] = {
 	airspy_adsb_parse,
 };
 #define NUM_PARSERS (sizeof(parsers) / sizeof(*parsers))
 
-struct backend {
-	struct buf buf;
-	char parser_state[PARSER_STATE_LEN];
-	parser parser;
-};
-
 struct client {
 	int placeholder;
 };
@@ -47,14 +40,7 @@ struct peer {
 };
 #define PEER_BACKEND_INIT { \
 	.type = BACKEND, \
-	.backend = { \
-		.buf = { \
-			.start = 0, \
-			.length = 0, \
-		}, \
-		.parser_state = { 0 }, \
-		.parser = NULL, \
-	}, \
+	.backend = BACKEND_INIT, \
 }
 
 
@@ -77,7 +63,6 @@ static int parse_opts(int argc, char *argv[], struct opts *opts) {
 	return 0;
 }
 
-
 static int connect_backend(struct opts *opts) {
 	struct addrinfo hints = {
 		.ai_family = AF_UNSPEC,
@@ -124,6 +109,15 @@ static int connect_backend(struct opts *opts) {
 	return bfd;
 }
 
+bool backend_autodetect_parse(struct backend *backend, struct packet *packet) {
+	for (int i = 0; i < NUM_PARSERS; i++) {
+		if (parsers[i](backend, packet)) {
+			backend->parser = parsers[i];
+			return true;
+		}
+	}
+	return false;
+}
 
 static int loop(int bfd) {
 	struct peer backend = PEER_BACKEND_INIT;
@@ -167,19 +161,7 @@ static int loop(int bfd) {
 					}
 
 					struct packet packet;
-					if (!peer->backend.parser) {
-						// Attempt to autodetect format
-						for (int i = 0; i < NUM_PARSERS; i++) {
-							if (parsers[i](&peer->backend.buf, &packet, peer->backend.parser_state)) {
-								peer->backend.parser = parsers[i];
-								break;
-							}
-						}
-					}
-
-					if (peer->backend.parser) {
-						while (peer->backend.parser(&peer->backend.buf, &packet, peer->backend.parser_state)) {
-						}
+					while (peer->backend.parser(&peer->backend, &packet)) {
 					}
 
 					if (peer->backend.buf.length == BUF_LEN_MAX) {
@@ -196,7 +178,6 @@ static int loop(int bfd) {
 	}
 }
 
-
 int main(int argc, char *argv[]) {
 	hex_init();
 	airspy_adsb_init();

airspy_adsb.c

@@ -6,24 +6,26 @@
 #include "common.h"
 #include "airspy_adsb.h"
 
-struct backend_state {
+struct airspy_adsb_parser_state {
 	uint64_t mlat_timestamp_last;
 	uint64_t mlat_timestamp_generation;
 };
 
-static bool airspy_adsb_parse_common(char *, struct packet *, struct backend_state *);
+static bool airspy_adsb_parse_common(char *, struct packet *, struct airspy_adsb_parser_state *);
 
 
 void airspy_adsb_init() {
-	assert(sizeof(struct backend_state) <= PARSER_STATE_LEN);
+	assert(sizeof(struct airspy_adsb_parser_state) <= PARSER_STATE_LEN);
 }
 
-bool airspy_adsb_parse(struct buf *buf, struct packet *packet, void *state_in) {
+bool airspy_adsb_parse(struct backend *backend, struct packet *packet) {
+	struct buf *buf = &backend->buf;
+	struct airspy_adsb_parser_state *state = (struct airspy_adsb_parser_state *) backend->parser_state;
+
 	if (buf->length < 35 ||
 	    buf_chr(buf, 0) != '*') {
 		return false;
 	}
-	struct backend_state *state = state_in;
 	if (buf->length >= 35 &&
 	    buf_chr(buf, 33) == '\r' &&
 	    buf_chr(buf, 34) == '\n' &&
@@ -51,7 +53,7 @@ bool airspy_adsb_parse(struct buf *buf, struct packet *packet, void *state_in) {
 	return false;
 }
 
-static bool airspy_adsb_parse_common(char *in, struct packet *packet, struct backend_state *state) {
+static bool airspy_adsb_parse_common(char *in, struct packet *packet, struct airspy_adsb_parser_state *state) {
 	if (in[8] != ';' ||
 	    in[11] != ';' ||
 			in[16] != ';') {

airspy_adsb.h

@@ -1,4 +1,4 @@
 #include <stdbool.h>
 
 void airspy_adsb_init();
-bool airspy_adsb_parse(struct buf *, struct packet *, void *);
+bool airspy_adsb_parse(struct backend *, struct packet *);

common.h

@@ -1,12 +1,8 @@
+#include <stdbool.h>
 #include <stdint.h>
 #include <unistd.h>
 
 
-//////// misc
-
-#define PARSER_STATE_LEN 256
-
-
 //////// buf
 
 #define BUF_LEN_MAX 256
@@ -15,6 +11,10 @@ struct buf {
 	size_t start;
 	size_t length;
 };
+#define BUF_INIT { \
+	.start = 0, \
+	.length = 0, \
+}
 
 #define buf_chr(buff, at) ((buff)->buf[(buff)->start + (at)])
 #define buf_at(buff, at) (&buf_chr(buff, at))
@@ -40,6 +40,23 @@ struct packet {
 };
 
 
+//////// backend
+
+#define PARSER_STATE_LEN 256
+struct backend;
+typedef bool (*parser)(struct backend *, struct packet *);
+struct backend {
+	struct buf buf;
+	char parser_state[PARSER_STATE_LEN];
+	parser parser;
+};
+#define BACKEND_INIT { \
+	.buf = BUF_INIT, \
+	.parser_state = { 0 }, \
+	.parser = backend_autodetect_parse, \
+}
+
+
 //////// hex
 void hex_init();
 void hex_to_bin(char *, char *, size_t);