virfile: Introduce virDirIsEmpty()

There might be cases where we want to know whether given
directory is empty or not. Introduce a helper for that:
virDirIsEmpty().

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>

src/libvirt_private.syms

@@ -2271,6 +2271,7 @@ safezero;
 virBuildPathInternal;
 virDirClose;
 virDirCreate;
+virDirIsEmpty;
 virDirOpen;
 virDirOpenIfExists;
 virDirOpenQuiet;

src/util/virfile.c

@@ -3036,6 +3036,45 @@ void virDirClose(DIR *dirp)
     closedir(dirp); /* exempt from syntax-check */
 }
 
+/**
+ * virDirIsEmpty:
+ * @path: path to the directory
+ * @hidden: whether hidden files matter
+ *
+ * Check whether given directory (@path) is empty, i.e. it
+ * contains just the usual entries '.' and '..'. Hidden files are
+ * ignored unless @hidden is true. IOW, a directory containing
+ * nothing but hidden files is considered empty if @hidden is
+ * false and not empty if @hidden is true.
+ *
+ * Returns: 1 if the directory is empty,
+ *          0 if the directory is not empty,
+ *         -1 otherwise (no error reported).
+ */
+int virDirIsEmpty(const char *path,
+                  bool hidden)
+{
+    g_autoptr(DIR) dir = NULL;
+    struct dirent *ent;
+    int direrr;
+
+    if (virDirOpenQuiet(&dir, path) < 0)
+        return -1;
+
+    while ((direrr = virDirRead(dir, &ent, NULL)) > 0) {
+        /* virDirRead() skips over '.' and '..' so here we have
+         * actual directory entry. */
+        if (!hidden ||
+            (hidden && ent->d_name[0] != '.'))
+            return 0;
+    }
+
+    if (direrr < 0)
+        return -1;
+
+    return 1;
+}
+
 
 /*
  * virFileChownFiles:

src/util/virfile.h

@@ -283,6 +283,9 @@ int virDirRead(DIR *dirp, struct dirent **ent, const char *dirname)
     ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2) G_GNUC_WARN_UNUSED_RESULT;
 void virDirClose(DIR *dirp);
 G_DEFINE_AUTOPTR_CLEANUP_FUNC(DIR, virDirClose);
+int virDirIsEmpty(const char *path,
+                  bool hidden)
+    ATTRIBUTE_NONNULL(1) G_GNUC_WARN_UNUSED_RESULT;
 
 int virFileMakeParentPath(const char *path) G_GNUC_WARN_UNUSED_RESULT;