Add fcatomic.c

1 files changed, 183 insertions, 0 deletions

diff --git a/src/fcatomic.c b/src/fcatomic.c
new file mode 100644
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--- /dev/null
+++ b/src/fcatomic.c
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+/*
+ * $XFree86: $
+ *
+ * Copyright © 2002 Keith Packard, member of The XFree86 Project, Inc.
+ *
+ * Permission to use, copy, modify, distribute, and sell this software and its
+ * documentation for any purpose is hereby granted without fee, provided that
+ * the above copyright notice appear in all copies and that both that
+ * copyright notice and this permission notice appear in supporting
+ * documentation, and that the name of Keith Packard not be used in
+ * advertising or publicity pertaining to distribution of the software without
+ * specific, written prior permission.  Keith Packard makes no
+ * representations about the suitability of this software for any purpose.  It
+ * is provided "as is" without express or implied warranty.
+ *
+ * KEITH PACKARD DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
+ * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
+ * EVENT SHALL KEITH PACKARD BE LIABLE FOR ANY SPECIAL, INDIRECT OR
+ * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
+ * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
+ * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+ * PERFORMANCE OF THIS SOFTWARE.
+ */
+
+/*
+ * fcatomic.c
+ *
+ * Lock cache and configuration files for atomic update
+ *
+ * Uses only regular filesystem calls so it should
+ * work even in the absense of functioning file locking
+ *
+ *  Four files:
+ *	file	    - the data file accessed by other apps.
+ *	new	    - a new version of the data file while it's being written
+ *	lck	    - the lock file
+ *	tmp	    - a temporary file made unique with mkstemp
+ *
+ *  Here's how it works:
+ *	Create 'tmp' and store our PID in it
+ *	Attempt to link it to 'lck'
+ *	Unlink 'tmp'
+ *	If the link succeeded, the lock is held
+ */
+
+#include "fcint.h"
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <time.h>
+
+#define NEW_NAME	".NEW"
+#define LCK_NAME	".LCK"
+#define TMP_NAME	".TMP-XXXXXX"
+
+FcAtomic *
+FcAtomicCreate (const FcChar8   *file)
+{
+    int	    file_len = strlen ((char *) file);
+    int	    new_len = file_len + sizeof (NEW_NAME);
+    int	    lck_len = file_len + sizeof (LCK_NAME);
+    int	    tmp_len = file_len + sizeof (TMP_NAME);
+    int	    total_len = (sizeof (FcAtomic) +
+			 file_len + 1 +
+			 new_len + 1 +
+			 lck_len + 1 +
+			 tmp_len + 1);
+    FcAtomic	*atomic = malloc (total_len);
+    if (!atomic)
+	return 0;
+    
+    atomic->file = (FcChar8 *) (atomic + 1);
+    strcpy ((char *) atomic->file, (char *) file);
+
+    atomic->new = atomic->file + file_len + 1;
+    strcpy ((char *) atomic->new, (char *) file);
+    strcat ((char *) atomic->new, NEW_NAME);
+
+    atomic->lck = atomic->new + new_len + 1;
+    strcpy ((char *) atomic->lck, (char *) file);
+    strcat ((char *) atomic->lck, LCK_NAME);
+
+    atomic->tmp = atomic->lck + lck_len + 1;
+
+    return atomic;
+}
+
+FcBool
+FcAtomicLock (FcAtomic *atomic)
+{
+    int		fd = -1;
+    FILE	*f = 0;
+    int		ret;
+    struct stat	lck_stat;
+
+    strcpy ((char *) atomic->tmp, (char *) atomic->file);
+    strcat ((char *) atomic->tmp, TMP_NAME);
+    fd = mkstemp ((char *) atomic->tmp);
+    if (fd < 0)
+	return FcFalse;
+    f = fdopen (fd, "w");
+    if (!f)
+    {
+    	close (fd);
+	unlink ((char *) atomic->tmp);
+	return FcFalse;
+    }
+    ret = fprintf (f, "%d\n", getpid());
+    if (ret <= 0)
+    {
+	fclose (f);
+	unlink ((char *) atomic->tmp);
+	return FcFalse;
+    }
+    if (fclose (f) == EOF)
+    {
+	unlink ((char *) atomic->tmp);
+	return FcFalse;
+    }
+    ret = link ((char *) atomic->tmp, (char *) atomic->lck);
+    (void) unlink ((char *) atomic->tmp);
+    if (ret < 0)
+    {
+	/*
+	 * If the file is around and old (> 10 minutes),
+	 * assume the lock is stale.  This assumes that any
+	 * machines sharing the same filesystem will have clocks
+	 * reasonably close to each other.
+	 */
+	if (stat ((char *) atomic->lck, &lck_stat) >= 0)
+	{
+	    time_t  now = time (0);
+	    if ((long int) (now - lck_stat.st_mtime) > 10 * 60)
+	    {
+		if (unlink ((char *) atomic->lck) == 0)
+		    return FcAtomicLock (atomic);
+	    }
+	}
+	return FcFalse;
+    }
+    (void) unlink ((char *) atomic->new);
+    return FcTrue;
+}
+
+FcChar8 *
+FcAtomicNewFile (FcAtomic *atomic)
+{
+    return atomic->new;
+}
+
+FcChar8 *
+FcAtomicOrigFile (FcAtomic *atomic)
+{
+    return atomic->file;
+}
+
+FcBool
+FcAtomicReplaceOrig (FcAtomic *atomic)
+{
+    if (rename ((char *) atomic->new, (char *) atomic->file) < 0)
+	return FcFalse;
+    return FcTrue;
+}
+
+void
+FcAtomicDeleteNew (FcAtomic *atomic)
+{
+    unlink ((char *) atomic->new);
+}
+
+void
+FcAtomicUnlock (FcAtomic *atomic)
+{
+    unlink ((char *) atomic->lck);
+}
+
+void
+FcAtomicDestroy (FcAtomic *atomic)
+{
+    free (atomic);
+}