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util/dotlock.c

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+/* dotlock.c - dotfile locking
+ *	Copyright (C) 1998 Free Software Foundation, Inc.
+ *
+ * This file is part of GNUPG.
+ *
+ * GNUPG 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.
+ *
+ * GNUPG 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 this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
+ */
+
+#include <config.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <ctype.h>
+#include "types.h"
+#include "util.h"
+#include "memory.h"
+
+
+
+
+#if 0
+/****************
+ * Create a lockfile with the given name. A TIMEOUT of 0
+ * returns immediately, -1 waits forever (hopefully not), other
+ * values are timeouts in milliseconds.
+ * Returns: a char pointer used as handle for reelase lock
+ *	    or NULL in case of an error.
+ *
+ * Notes: This function creates a lock file in the same directory
+ *	  as file_to_lock with the name "file_to_lock.lock"
+ *	  A temporary file ".#lk.<pid>.<hostname> is used.
+ *	  This function does nothing for Windoze.
+ */
+int
+make_dotlock( const char *file_to_lock, long timeout )
+{
+    int rc=-1, fd=-1, pid;
+    char pidstr[16];
+    char *tname = NULL;
+    char *p;
+
+    log_debug("dotlock_make: lock='%s'\n", lockfile );
+    sprintf( pidstr, "%10d\n", getpid() );
+    /* add the hostname to the second line (FQDN or IP addr?) */
+
+    /* create a temporary file */
+    tname = CreateTmpFile2( p, ".#lk" );
+    free(p);
+    if( !tname )
+	log_fatal( "could not create temporary lock file '%s'\n");
+    log_debug( "dotlock_make: tmpname='%s'\n", tname );
+    chmod( tname, 0644 ); /* just in case an "umask" is set */
+    if( !(fd = open( tname, O_WRONLY )) )
+	log_fatal( "could not open temporary lock file '%s'\n", tname);
+    if( write(fd, pidstr, 11 ) != 11 )
+	log_fatal( "error writing to temporary lock file '%s'\n", tname);
+    if( close(fd) ) {
+	log_fatal( "error closing '%s'\n", tname);
+
+  retry:
+    if( !link(tname, lockfile) )
+	rc = 0; /* okay */
+    else if( errno != EEXIST )
+	log_error( "lock not made: link() failed: %s\n", strerror(errno) );
+    else { /* lock file already there */
+	if( (pid = read_lockfile(lockfile)) == -1 ) {
+	    if( errno == ENOENT ) {
+		log_debug( "lockfile disappeared\n");
+		goto retry;
+	    }
+	    log_debug("cannot read lockfile\n");
+	}
+	else if( pid == getpid() ) {
+	    log_info( "Oops: lock already hold by us\n");
+	    rc = 0;  /* okay */
+	}
+	else if( kill(pid, 0) && errno == ESRCH ) {
+	    log_info( "removing stale lockfile (created by %d)", (int)pid );
+	    remove( lockfile );
+	    goto retry;
+	}
+	log_debug( "lock not made: lock file exists\n" );
+    }
+
+    if( tname ) {
+	remove(tname);
+	free(tname);
+    }
+    if( !rc )
+	log_debug( "lock made\n");
+    return rc;
+}
+
+/****************
+ * Create a lockfile for a existing file
+ * Returns: a char pointer used as handle for release lock
+ *	    or NULL in case of an error.
+ *
+ * Notes: This function creates a lock file in the same directory
+ *	  as file_to_lock with the name "lock.<inode-no>"
+ *
+ * int
+ * make_inodelock( const char *file_to_lock )
+ *
+ */
+
+
+
+
+/****************
+ * release a lock
+ * Returns: 0 := success
+ */
+int
+release_dotlock( const char *lockfile )
+{
+    int pid = ReadLockfile( lockfile );
+    if( pid == -1 ) {
+	Log_printf( LERROR, "ReleaseLock: lockfile error");
+	return -1;
+    }
+    if( pid != getpid() ) {
+	Log_printf( LERROR, "ReleaseLock: not our lock (pid=%d)", pid);
+	return -1;
+    }
+    if( remove(lockfile) ) {
+	Log_printf( LERROR, "ReleaseLock: error removing lockfile '%s'",
+							    lockfile);
+	return -1;
+    }
+    Log_printf( LMESG, "ReleaseLock: released lockfile '%s'", lockfile);
+    return 0;
+}
+
+
+/****************
+ * Read the lock file and return the pid, returns -1 on error.
+ */
+static int
+read_lockfile( const char *name )
+{
+    int fd, pid;
+    char pidstr[16];
+
+    if( (fd = open(name, O_RDONLY)) == -1 ) {
+	int e = errno;
+	Log_printf(LJUNK, "error opening lockfile '%s'", name );
+	errno = e;  /* restore errno */
+	return -1;
+    }
+    if( read(fd, pidstr, 10 ) != 10 ) {
+	Log_printf(LNOISE, "error reading lockfile '%s'", name );
+	close(fd);
+	errno = 0;
+	return -1;
+    }
+    close(fd);
+    pid = atoi(pidstr);
+    if( !pid || pid == -1 ) {
+	Log_printf(LERROR, "invalid pid %d in lockfile '%s'", pid, name );
+	errno = 0;
+	return -1;
+    }
+    return pid;
+}
+#endif