added proper cancellation token handling; cleanup when host is found to be unresponsive

1 files changed, 55 insertions, 8 deletions

diff --git a/src/fscomch.c b/src/fscomch.c
index 412f9cf..16dcdcf 100644
--- a/src/fscomch.c
+++ b/src/fscomch.c
@@ -5,8 +5,25 @@
 #include <time.h>
 #include <sys/stat.h>
 #include <string.h>
+#include <pthread.h>
 #include "fscomch.h"
 
+cancelToken_t init_cancel_token_timeout(int seconds) {
+	cancelToken_t token;
+	token.timeout = seconds;
+	token.value = calloc(1, sizeof(char));
+	pthread_t cancelTimer;
+	cancelToken_t* memToken = malloc(sizeof(cancelToken_t));
+	*memToken = token;
+	pthread_create(&cancelTimer, NULL, cancel_in_secs, (void*)memToken);
+	return token;
+}
+cancelToken_t init_cancel_token_never() {
+	cancelToken_t token;
+	token.timeout = -1;
+	token.value = NULL;
+	return token;
+}
 match_t init_match(char* uuid, FILE* streamIn, FILE* streamOut) {
 	match_t match;
 	match.uuid = uuid;
@@ -28,10 +45,10 @@ FILE* try_lock_match() {
 	}
 	return fdopen(fd, "r");
 }
-match_t await_match(FILE* matchFile, char* cancelToken) {
+match_t await_match(FILE* matchFile, cancelToken_t cancelToken) {
 	/* await match UUID */
 	char* uuid = calloc(37, sizeof(char));
-	while (cancelToken == NULL || *cancelToken) {
+	while (cancelToken.value == NULL || !*cancelToken.value) {
 		if (fgets(uuid, 37, matchFile) != NULL) {
 			break;
 		}
@@ -51,7 +68,9 @@ match_t await_match(FILE* matchFile, char* cancelToken) {
 	/* connection complete, delete the match file and the join lock */
 	remove("/tmp/chess/match");
 	remove("/tmp/chess/matchjoin");
-	return init_match(uuid, streamIn, streamOut);
+	match_t match = init_match(uuid, streamIn, streamOut);
+	send_message("ping", match);
+	return match;
 }
 match_t join_match() {
 	/* create a join lock so that no one else can join this match */
@@ -62,6 +81,7 @@ match_t join_match() {
 		match_t match;
 		return match;
 	}
+	close(fd);
 	/* this is definitely the only process joining the game
 	proceed to generate a uuid */
 	char* uuid = make_uuid();
@@ -77,17 +97,34 @@ match_t join_match() {
 	FILE* matchFile = fopen("/tmp/chess/match", "a");
 	fputs(uuid, matchFile);
 	fclose(matchFile);
-	/* joining match complete, close the descriptor */
-	close(fd);
-	return match;
+	/* handshake */
+	cancelToken_t token = init_cancel_token_timeout(2);
+	char* message = read_message(match, token);
+	if (message != NULL) {
+		if (strcmp(message, "ping") == 0) {
+			return match;
+		}
+		else {
+			printf("Extreme de-sync. Aborting\n");
+			exit(1);
+		}
+	}
+	printf("Host is dead. Cleaning up\n");
+	fclose(streamIn);
+	fclose(streamOut);
+	remove("/tmp/chess/match");
+	remove("/tmp/chess/matchjoin");
+	remove(aName);
+	remove(bName);
+	exit(1);
 }
 void send_message(char* content, match_t match) {
 	fprintf(match.streamOut, "%s\n", content);
 	fflush(match.streamOut);
 }
-char* read_message(match_t match, char* cancelToken) {
+char* read_message(match_t match, cancelToken_t cancelToken) {
 	char* buffer = calloc(256, sizeof(char));
-	while (cancelToken == NULL || *cancelToken) {
+	while (cancelToken.value == NULL || !*cancelToken.value) {
 		if (fgets(buffer, 256, match.streamIn) != NULL) {
 			break;
 		}
@@ -98,6 +135,11 @@ char* read_message(match_t match, char* cancelToken) {
 		req.tv_nsec = awaitMoveNs;
 		nanosleep(&req, NULL);
 	}
+	/* if we cancelled via token, return NULL */
+	if (cancelToken.value != NULL && *cancelToken.value == 1) {
+		free(buffer);
+		return NULL;
+	}
 	/* overwrite potential newline */
 	buffer[strlen(buffer) - 1] = '\0';
 	return buffer;
@@ -117,3 +159,8 @@ char* make_uuid() {
 	out[37] = '\0';
 	return out;
 }
+void* cancel_in_secs(void* token) {
+	sleep(((cancelToken_t*)token)->timeout);
+	*(((cancelToken_t*)token)->value) = 1;
+	free(token);
+}