[RFC PATCH 2/4] libtracefs: Transform tracefs_hist_add_sort_key()

["Yordan Karadzhov (VMware)" <y.karadz@gmail.com>]

The current version of the API makes it hard to add multiple sort keys
to a histogram. The only way to do this is to use the variadic arguments,
however in order to do this the caller have to know the number of sort
keys at compile time, because the method overwrite all previously added
keys. The problem is addressed by splitting tracefs_hist_add_sort_key()
into two methods - one that overwrite and one that does not.

Signed-off-by: Yordan Karadzhov (VMware) <y.karadz@gmail.com>
---
 include/tracefs.h  |  4 +++-
 src/tracefs-hist.c | 21 +++++++++++++++++++--
 2 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/include/tracefs.h b/include/tracefs.h
index 64fbb3f..c3fa1d6 100644
--- a/include/tracefs.h
+++ b/include/tracefs.h
@@ -303,7 +303,9 @@ int tracefs_hist_add_key(struct tracefs_hist *hist, const char *key,
 			 enum tracefs_hist_key_type type);
 int tracefs_hist_add_value(struct tracefs_hist *hist, const char *value);
 int tracefs_hist_add_sort_key(struct tracefs_hist *hist,
-			      const char *sort_key, ...);
+			      char *sort_key);
+int tracefs_hist_sort_key(struct tracefs_hist *hist,
+			  const char *sort_key, ...);
 int tracefs_hist_sort_key_direction(struct tracefs_hist *hist,
 				    const char *sort_key,
 				    enum tracefs_hist_sort_direction dir);
diff --git a/src/tracefs-hist.c b/src/tracefs-hist.c
index 8501d64..2ea90d9 100644
--- a/src/tracefs-hist.c
+++ b/src/tracefs-hist.c
@@ -453,6 +453,23 @@ add_sort_key(struct tracefs_hist *hist, const char *sort_key, char **list)
 	return tracefs_list_add(list, sort_key);
 }
 
+int tracefs_hist_add_sort_key(struct tracefs_hist *hist,
+			      char *sort_key)
+{
+	char **list = hist->sort;
+
+	if (!hist || !sort_key)
+		return -1;
+
+	list = add_sort_key(hist, sort_key, hist->sort);
+	if (!list)
+		return -1;
+
+	hist->sort = list;
+
+	return 0;
+}
+
 /**
  * tracefs_hist_add_sort_key - add a key for sorting the histogram
  * @hist: The histogram to add the sort key to
@@ -464,8 +481,8 @@ add_sort_key(struct tracefs_hist *hist, const char *sort_key, char **list)
  *
  * Returns 0 on success, -1 on error.
  */
-int tracefs_hist_add_sort_key(struct tracefs_hist *hist,
-			      const char *sort_key, ...)
+int tracefs_hist_sort_key(struct tracefs_hist *hist,
+			  const char *sort_key, ...)
 {
 	char **list = NULL;
 	char **tmp;
-- 
2.30.2