fscomch--communication between multiple chess processes

11 files changed, 144 insertions, 1 deletions

diff --git a/Makefile b/Makefile
index 9aa92fd..64b3196 100644
--- a/Makefile
+++ b/Makefile
@@ -2,7 +2,7 @@ CC=gcc
 CFLAGS=-I.
 
 generate:
-	$(CC) -o chess chess.c vector.c chesshelpers.c console.c $(CFLAGS)
+	$(CC) -o chess src/chess.c src/vector.c src/chesshelpers.c src/console.c src/fscomch.c $(CFLAGS)
 
 install:
 	cp chess /usr/local/bin/
diff --git a/chess.c b/src/chess.c
index f5881fe..530bc79 100644
--- a/chess.c
+++ b/src/chess.c
@@ -4,6 +4,7 @@
 #include "vector.h"
 #include "console.h"
 #include "chesshelpers.h"
+#include "fscomch.h"
 #include "chess.h"
 
 int main(int argc, char **argv) {
@@ -33,6 +34,27 @@ int main(int argc, char **argv) {
 		}
 	}
 	board_t board = init_board(pieces);
+	/* try to acquire a lock on the local matchfile */
+	FILE* matchFile = try_lock_match();
+	match_t match;
+	if (matchFile != NULL) {
+		/* we are acting as the host--await a connection */
+		printf("awaiting connection\n");
+		match = await_match(matchFile, NULL);
+		printf("connection completed. match is %s\n", match.uuid);
+	}
+	else {
+		/* we are joining an existing match */
+		printf("attempting to join existing match\n");
+		match = join_match();
+		if (match.uuid != NULL) {
+			printf("joined match %s\n", match.uuid);
+		}
+		else {
+			printf("error joining match. reload the program\n");
+		}
+	}
+	exit(0);
 	int turn = 0;
 	while(1) {
 		//draw the board, write some info
diff --git a/chess.h b/src/chess.h
index 1d88a6e..1d88a6e 100644
--- a/chess.h
+++ b/src/chess.h
diff --git a/chesshelpers.c b/src/chesshelpers.c
index b64a0f4..b64a0f4 100644
--- a/chesshelpers.c
+++ b/src/chesshelpers.c
diff --git a/chesshelpers.h b/src/chesshelpers.h
index b3a3d21..b3a3d21 100644
--- a/chesshelpers.h
+++ b/src/chesshelpers.h
diff --git a/console.c b/src/console.c
index e675ba2..e675ba2 100644
--- a/console.c
+++ b/src/console.c
diff --git a/console.h b/src/console.h
index c0ca9f7..c0ca9f7 100644
--- a/console.h
+++ b/src/console.h
diff --git a/src/fscomch.c b/src/fscomch.c
new file mode 100644
index 0000000..a9fc27b
--- /dev/null
+++ b/src/fscomch.c
@@ -0,0 +1,97 @@
+#include <fcntl.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <time.h>
+#include <sys/stat.h>
+#include "fscomch.h"
+
+match_t init_match(char* uuid, FILE* streamIn, FILE* streamOut) {
+	match_t match;
+	match.uuid = uuid;
+	match.streamIn = streamIn;
+	match.streamOut = streamOut;
+	return match;
+}
+void destroy_match(match_t match) {
+	free(match.uuid);
+	fclose(match.streamIn);
+	fclose(match.streamOut);
+}
+FILE* try_lock_match() {
+	mkdir("/tmp/chess/", 0777);
+	mode_t mode = S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH;
+	int fd = open("/tmp/chess/match", O_RDONLY | O_CREAT | O_EXCL, mode);
+	if (fd == -1) {
+		return NULL;
+	}
+	return fdopen(fd, "r");
+}
+match_t await_match(FILE* matchFile, char* cancelToken) {
+	/* await match UUID */
+	char* uuid = calloc(37, sizeof(char));
+	while (cancelToken == NULL || *cancelToken) {
+		if (fgets(uuid, 37, matchFile) != NULL) {
+			break;
+		}
+		fseek(matchFile, 0, SEEK_SET);
+		struct timespec req;
+		req.tv_sec = 0;
+		req.tv_nsec = awaitMatchNs;
+		printf("sleeping\n");
+		nanosleep(&req, NULL);
+	}
+	/* connect to files created by joining player */
+	char aName[256];
+	char bName[256];
+	snprintf(aName, 256, "/tmp/chess/%s.a", uuid);
+	snprintf(bName, 256, "/tmp/chess/%s.b", uuid);
+	FILE* streamIn = fopen(aName, "r");
+	FILE* streamOut = fopen(bName, "w");
+	/* 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 join_match() {
+	/* create a join lock so that no one else can join this match */
+	mode_t mode = S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH;
+	int fd = open("/tmp/chess/matchjoin", O_WRONLY | O_CREAT | O_EXCL, mode);
+	if (fd == -1) {
+		/* another process is in the process of joining this game */
+		match_t match;
+		return match;
+	}
+	/* this is definitely the only process joining the game
+	proceed to generate a uuid */
+	char* uuid = make_uuid();
+	/* make the .a and .b files based on the uuid */
+	char aName[256];
+	char bName[256];
+	snprintf(aName, 256, "/tmp/chess/%s.a", uuid);
+	snprintf(bName, 256, "/tmp/chess/%s.b", uuid);
+	FILE* streamIn = fopen(bName, "w+");
+	FILE* streamOut = fopen(aName, "w");
+	match_t match = init_match(uuid, streamIn, streamOut);
+	/* send uuid to the host */
+	FILE* matchFile = fopen("/tmp/chess/match", "a");
+	fputs(uuid, matchFile);
+	/* joining match complete, close the descriptor */
+	close(fd);
+	return match;
+}
+char* make_uuid() {
+	char sym[] = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '0', 'a', 'b', 'c', 'd', 'e', 'f'};
+	char* out = calloc(37, sizeof(char));
+	srand(time(NULL));
+	for (int i = 0; i < 36; i++) {
+		if (i == 8 || i == 13 || i == 18 || i == 23) {
+			out[i] = '-';
+		}
+		else {
+			out[i] = sym[rand() % 16];
+		}
+	}
+	out[37] = '\0';
+	return out;
+}
diff --git a/src/fscomch.h b/src/fscomch.h
new file mode 100644
index 0000000..b7900e3
--- /dev/null
+++ b/src/fscomch.h
@@ -0,0 +1,24 @@
+#include <stdio.h>
+#ifndef FSCOMCH
+#define FSCOMCH
+
+/* 1/2 second */
+static const unsigned long int awaitMatchNs = 500000000L;
+/* 1/4 second */
+static const unsigned long int awaitMoveNs = 250000000L;
+
+typedef struct Match {
+	char* uuid;
+	FILE* streamIn;
+	FILE* streamOut;
+} match_t;
+match_t init_match(char* uuid, FILE* streamIn, FILE* streamOut);
+void destroy_match(match_t match);
+/* returns null if the matchfile is already extant */
+FILE* try_lock_match();
+/* creates a new match, waits for it to be joined by another player */
+match_t await_match(FILE* matchFile, char* cancelToken);
+/* joins an existing match */
+match_t join_match();
+char* make_uuid();
+#endif
diff --git a/vector.c b/src/vector.c
index 6ab3bf2..6ab3bf2 100644
--- a/vector.c
+++ b/src/vector.c
diff --git a/vector.h b/src/vector.h
index ea2ddcd..ea2ddcd 100644
--- a/vector.h
+++ b/src/vector.h