perf tools: Add perf_data_file__open interface to data object

Adding perf_data_file__open interface to data object to open the
perf.data file for both read and write.

Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1381847254-28809-3-git-send-email-jolsa@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/util/data.h b/tools/perf/util/data.h
index ffa0186..d6c262e 100644
--- a/tools/perf/util/data.h
+++ b/tools/perf/util/data.h
@@ -13,6 +13,7 @@
 	int fd;
 	bool is_pipe;
 	bool force;
+	unsigned long size;
 	enum perf_data_mode mode;
 };
 
@@ -26,4 +27,7 @@
 	return file->mode == PERF_DATA_MODE_WRITE;
 }
 
+int perf_data_file__open(struct perf_data_file *file);
+void perf_data_file__close(struct perf_data_file *file);
+
 #endif /* __PERF_DATA_H */