perf callchain: Add callchain_cursor_snapshot()

The callchain_cursor_snapshot() is for saving current status of the
callchain.  It'll be used to accumulate callchain information for each node.
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arun Sharma <asharma@fb.com>
Tested-by: Rodrigo Campos <rodrigo@sdfg.com.ar>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/1401335910-16832-9-git-send-email-namhyung@kernel.orgSigned-off-by: Jiri Olsa <jolsa@kernel.org>

tools/perf/util/callchain.h

@@ -167,4 +167,13 @@ int fill_callchain_info(struct addr_location *al, struct callchain_cursor_node *
 
 extern const char record_callchain_help[];
 int parse_callchain_report_opt(const char *arg);
+
+static inline void callchain_cursor_snapshot(struct callchain_cursor *dest,
+					     struct callchain_cursor *src)
+{
+	*dest = *src;
+
+	dest->first = src->curr;
+	dest->nr -= src->pos;
+}
 #endif	/* __PERF_CALLCHAIN_H */