Never block when opening the port

[sojka/sterm.git] / sterm.c

diff --git a/sterm.c b/sterm.c
index 305a9855dd0998339f289210adb160dc006f1e8b..209f83c92df4d42ecd2a13d8c3c58d3e4a2ac73a 100644 (file)
--- a/sterm.c
+++ b/sterm.c
@@ -1,7 +1,7 @@
 /*
  * Simple serial terminal
  *
- * Copyright 2014 Michal Sojka <sojkam1@fel.cvut.cz>
+ * Copyright 2014, 2015 Michal Sojka <sojkam1@fel.cvut.cz>
  *
  * This program is free software: you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
@@ -31,6 +31,7 @@
 
 #define _BSD_SOURCE
 #include <sys/ioctl.h>
+#include <sys/types.h>
 #include <unistd.h>
 #include <fcntl.h>
 #include <termios.h>
@@ -41,20 +42,20 @@
 #include <stdbool.h>
 #include <string.h>
 #include <signal.h>
+#include <lockdev.h>
 
 #define STRINGIFY(val) #val
 #define TOSTRING(val) STRINGIFY(val)
 #define CHECK(cmd) ({ int ret = (cmd); if (ret == -1) { perror(#cmd " line " TOSTRING(__LINE__)); exit(1); }; ret; })
 #define CHECKPTR(cmd) ({ void *ptr = (cmd); if (ptr == (void*)-1) { perror(#cmd " line " TOSTRING(__LINE__)); exit(1); }; ptr; })
 
-#define VERBOSE(format, ...) do { if (verbose) fprintf(stderr, format, ##__VA_ARGS__); } while (0)
+#define VERBOSE(format, ...) do { if (verbose) fprintf(stderr, "sterm: " format, ##__VA_ARGS__); } while (0)
 
 bool verbose = false;
 bool exit_on_escape = true;
 
-char template[] = "/var/lock/TMPXXXXXX";
-char lockfile[100];
 struct termios stdin_tio_backup;
+char *dev = NULL;
 
 void rm_file(int status, void *arg)
 {
@@ -69,6 +70,11 @@ void restore_stdin_term()
        tcsetattr(0, TCSANOW, &stdin_tio_backup);
 }
 
+void unlock()
+{
+       dev_unlock(dev, getpid());
+}
+
 void sighandler(int arg)
 {
        exit(0); /* Invoke exit handlers */
@@ -95,14 +101,16 @@ void exit_on_escapeseq(const char *buf, int len)
        static const char escseq[] = "\r~.";
        static const char *state = escseq+1;
        int i;
-
        for (i = 0; i < len; i++) {
                if (buf[i] == *state) {
                        state++;
                        if (*state == 0)
                                exit(0);
-               } else
+               } else {
                        state = escseq;
+                       if (buf[i] == *state)
+                               state++;
+               }
        }
 }
 
@@ -121,7 +129,6 @@ void usage(const char* argv0)
 int main(int argc, char *argv[])
 {
        int fd;
-       char *dev = NULL;
        int opt;
        speed_t speed = 0;
        int dtr = 0, rts = 0;
@@ -192,42 +199,24 @@ int main(int argc, char *argv[])
        signal(SIGTERM, sighandler);
        signal(SIGHUP, sighandler);
 
-       if (strncmp(dev, "/dev/", 5) == 0 &&
-           strrchr(dev, '/') == dev + 4 &&
-           dev[5] != 0)
-       { /* Create lock file (to be inter-operable with other programs) */
-               /* This is racy, but what we can do - see also comments in uucp / cu */
-               int tmp = CHECK(mkstemp(template));
-               on_exit(rm_file, template);
-               char pid[20];
-               snprintf(pid, sizeof(pid), "%u", getpid());
-               CHECK(write(tmp, pid, strlen(pid)));
-               close(tmp);
-               snprintf(lockfile, sizeof(lockfile), "/var/lock/LCK..%s", dev + 5);
-       retry:
-               if (link(template, lockfile) == -1) {
-                       tmp = CHECK(open(lockfile, O_RDONLY));
-                       CHECK(read(tmp, pid, sizeof(pid)));
-                       close(tmp);
-                       int p = atoi(pid);
-                       char proc[50];
-                       snprintf(proc, sizeof(proc), "/proc/%d", p);
-                       if (access(proc, F_OK) == 0) {
-                               fprintf(stderr, "%s is used by PID %d\n", dev, p);
-                               exit(1);
-                       }
-                       fprintf(stderr, "Stale lock file %s (PID %d) - removing it!\n", lockfile, p);
-                       CHECK(unlink(lockfile));
-                       goto retry;
-               }
-               rm_file(0, template);
-               on_exit(rm_file, lockfile);
+       pid_t pid = dev_lock(dev);
+       if (pid > 0) {
+               fprintf(stderr, "%s is used by PID %d\n", dev, pid);
+               exit(1);
+       } else if (pid < 0) {
+               perror("dev_lock()");
+               exit(1);
        }
+       atexit(unlock);
 
-       if ((fd = open(dev, O_RDWR)) < 0) {
+       /* O_NONBLOCK is needed to not wait for the CDC signal. See tty_ioctl(4). */
+       if ((fd = open(dev, O_RDWR|O_NOCTTY|O_NONBLOCK)) < 0) {
                perror(dev);
                exit(1);
        }
+        /* Cancel the efect of O_NONBLOCK flag. */
+       int n = fcntl(fd, F_GETFL, 0);
+        fcntl(fd, F_SETFL, n & ~O_NDELAY);
 
        if (isatty(fd)) {
                CHECK(ioctl(fd, TIOCEXCL, NULL));
@@ -272,14 +261,17 @@ int main(int argc, char *argv[])
                CHECK(tcsetattr(0, TCSANOW, &tio));
        }
 
-       VERBOSE("Connected.\n");
+       VERBOSE("Connected.\r\n");
+       if (exit_on_escape)
+               VERBOSE("Use '<Enter>~.' sequence to exit.\r\n");
+
        while (1) {
                int r1, r2;
                CHECK(poll(fds, 2, -1));
                if (fds[0].revents & POLLIN) {
                        r1 = CHECK(read(0, buf, sizeof(buf)));
                        if (r1 == 0) {
-                               VERBOSE("EOF on stdin\n");
+                               VERBOSE("EOF on stdin\r\n");
                                break;
                        }
                        if (exit_on_escape)
@@ -293,7 +285,7 @@ int main(int argc, char *argv[])
                if (fds[1].revents & POLLIN) {
                        r1 = CHECK(read(fd, buf, sizeof(buf)));
                        if (r1 == 0) {
-                               VERBOSE("EOF on %s\n", dev);
+                               VERBOSE("EOF on %s\r\n", dev);
                                break;
                        }
                        r2 = CHECK(write(1, buf, r1));