[Libguestfs] [RFC nbdkit PATCH 4/5] file: Utilize nbdkit_string_intern

[Eric Blake]

Instead of needing to provide .unload, we can let nbdkit manage the
lifetime for us.  However, if we like this approach, it may be wiser
to introduce new variants of nbdkit_realpath/absolute_path which
return const char * already intern'd.

Signed-off-by: Eric Blake <eblake at redhat.com>
---

See the cover letter: if we like this, there are several other plugins
that could also reduce their .unload, or maybe we want to add
convenience functions to make the combo
'nbdkit_realpath/nbdkit_string_intern' simpler.

 plugins/file/file.c | 20 ++++++--------------
 1 file changed, 6 insertions(+), 14 deletions(-)

diff --git a/plugins/file/file.c b/plugins/file/file.c
index 08418194..6a0aad93 100644
--- a/plugins/file/file.c
+++ b/plugins/file/file.c
@@ -64,8 +64,8 @@
 #define fdatasync fsync
 #endif

-static char *filename = NULL;
-static char *directory = NULL;
+static const char *filename = NULL;
+static const char *directory = NULL;

 /* posix_fadvise mode: -1 = don't set it, or POSIX_FADV_*. */
 static int fadvise_mode =
@@ -91,13 +91,6 @@ is_enotsup (int err)
   return err == ENOTSUP || err == EOPNOTSUPP;
 }

-static void
-file_unload (void)
-{
-  free (filename);
-  free (directory);
-}
-
 /* Called for each key=value passed on the command line.  This plugin
  * only accepts file=<filename> and dir=<dirname>, where exactly
  * one is required.
@@ -111,15 +104,15 @@ file_config (const char *key, const char *value)
    * existence checks to the last possible moment.
    */
   if (strcmp (key, "file") == 0) {
-    free (filename);
-    filename = nbdkit_realpath (value);
+    CLEANUP_FREE char *tmp = nbdkit_realpath (value);
+    filename = nbdkit_string_intern (tmp);
     if (!filename)
       return -1;
   }
   else if (strcmp (key, "directory") == 0 ||
            strcmp (key, "dir") == 0) {
-    free (directory);
-    directory = nbdkit_realpath (value);
+    CLEANUP_FREE char *tmp = nbdkit_realpath (value);
+    directory = nbdkit_string_intern (value);
     if (!directory)
       return -1;
   }
@@ -812,7 +805,6 @@ static struct nbdkit_plugin plugin = {
   .name              = "file",
   .longname          = "nbdkit file plugin",
   .version           = PACKAGE_VERSION,
-  .unload            = file_unload,
   .config            = file_config,
   .config_complete   = file_config_complete,
   .config_help       = file_config_help,
-- 
2.28.0