1 files changed, 130 insertions, 0 deletions
diff --git a/src/lock.c b/src/lock.c
new file mode 100644
index 0000000..465736c
--- /dev/null
+++ b/src/lock.c
@@ -0,0 +1,130 @@
+/* $Id$ */
+
+/*
+ * This file is part of ivcall.
+ *
+ * ivcall is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * ivcall is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with ivcall; if not, write to the Free Software Foundation,
+ * Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
+ */
+
+#include <unistd.h>
+#include <sys/stat.h>
+#include <stdio.h>
+#include <limits.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <signal.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+#include <pwd.h>
+
+#include "lock.h"
+#include "util.h"
+
+// Where do lockfiles reside?
+#define LOCK_PATH "/var/lock"
+
+static char* lockfile = NULL;
+
+// Tries to lock a TTY-device, returns 0 on success
+int device_lock(char *dev, char *appname) {
+    char buf[256], u[16];
+    char path[PATH_MAX];
+    int fd;
+    struct passwd *pwd;
+    char *username;
+
+    assert(dev && !lockfile);
+    
+    if (access(LOCK_PATH, W_OK) < 0)
+        return -1;
+        
+    snprintf(path, sizeof(path), "%s/LCK..%s", LOCK_PATH, basename(dev));
+      
+    if ((fd = open(path, O_RDONLY)) >= 0) {
+        int n = loop_read(fd, buf, sizeof(buf) - 1);
+        close(fd);
+
+        if (n > 0) {
+            int pid;
+            
+            if (n == 4)
+                pid = *(int*) buf;
+            else {
+                buf[n] = 0;
+                sscanf(buf, "%d", &pid);
+            }
+	      
+            if (pid > 0) {
+                if (kill((pid_t) pid, 0) < 0 && errno == ESRCH) {
+                    fprintf(stderr, "Lockfile is stale. Overriding it.\n");
+                    unlink(path);
+                } else
+                    return -1;
+            }
+        }
+    }
+
+    if ((fd = open(path, O_WRONLY | O_CREAT | O_EXCL, 0666)) < 0)
+        return -1;
+      
+    if ((pwd = getpwuid(getuid())))
+        username = pwd->pw_name;
+    else
+        snprintf(username = u, sizeof(u), "%u", getuid());
+
+    snprintf(buf, sizeof(buf), "%10ld %s %.20s\n", (long)getpid(), appname, username);
+    
+    if (loop_write(fd, buf, strlen(buf)) < 0) {
+        close(fd);
+        return -1;
+    }
+    
+    close(fd);
+
+    lockfile = strdup(path);
+    
+    return 0;
+}
+
+// Tries to lock the first free device, returns 0 on success
+int device_lock_first(char *appname, char *dev, size_t l) {
+    int i, found = 0;
+
+    for (i = 2; i <= 20; i++) {
+        snprintf(dev, l, "/dev/ttyI%i", i);
+        
+        if (!device_lock(dev, appname)) {
+            found = 1;
+            break;
+        }
+    }
+    
+    if (found)
+        return 0;
+    else {
+        fprintf(stderr, "Could not find free device.\n");
+        return -1;
+    }
+}
+
+// Deletes the lockfile
+void device_unlock(void) {
+    if (lockfile) {
+        unlink(lockfile);
+        free (lockfile);
+        lockfile = NULL;
+    }
+}