perf tools: Introduce perf_session class

That does all the initialization boilerplate, opening the file,
reading the header, checking if it is valid, etc.

And that will as well have the threads list, kmap (now) global
variable, etc, so that we can handle two (or more) perf.data files
describing sessions to compare.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <1260573842-19720-1-git-send-email-acme@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 0e519c6..4decbd1 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -17,6 +17,7 @@
 #include "util/header.h"
 #include "util/event.h"
 #include "util/debug.h"
+#include "util/session.h"
 #include "util/symbol.h"
 
 #include <unistd.h>
@@ -62,7 +63,7 @@
 
 static int			file_new			=      1;
 
-struct perf_header		*header				=   NULL;
+static struct perf_session	*session;
 
 struct mmap_data {
 	int			counter;
@@ -216,12 +217,12 @@
 {
 	struct perf_header_attr *h_attr;
 
-	if (nr < header->attrs) {
-		h_attr = header->attr[nr];
+	if (nr < session->header.attrs) {
+		h_attr = session->header.attr[nr];
 	} else {
 		h_attr = perf_header_attr__new(a);
 		if (h_attr != NULL)
-			if (perf_header__add_attr(header, h_attr) < 0) {
+			if (perf_header__add_attr(&session->header, h_attr) < 0) {
 				perf_header_attr__delete(h_attr);
 				h_attr = NULL;
 			}
@@ -395,9 +396,9 @@
 
 static void atexit_header(void)
 {
-	header->data_size += bytes_written;
+	session->header.data_size += bytes_written;
 
-	perf_header__write(header, output, true);
+	perf_header__write(&session->header, output, true);
 }
 
 static int __cmd_record(int argc, const char **argv)
@@ -440,24 +441,24 @@
 		exit(-1);
 	}
 
-	header = perf_header__new();
-	if (header == NULL) {
+	session = perf_session__new(output_name, O_WRONLY, force);
+	if (session == NULL) {
 		pr_err("Not enough memory for reading perf file header\n");
 		return -1;
 	}
 
 	if (!file_new) {
-		err = perf_header__read(header, output);
+		err = perf_header__read(&session->header, output);
 		if (err < 0)
 			return err;
 	}
 
 	if (raw_samples) {
-		perf_header__set_feat(header, HEADER_TRACE_INFO);
+		perf_header__set_feat(&session->header, HEADER_TRACE_INFO);
 	} else {
 		for (i = 0; i < nr_counters; i++) {
 			if (attrs[i].sample_type & PERF_SAMPLE_RAW) {
-				perf_header__set_feat(header, HEADER_TRACE_INFO);
+				perf_header__set_feat(&session->header, HEADER_TRACE_INFO);
 				break;
 			}
 		}
@@ -481,7 +482,7 @@
 	}
 
 	if (file_new) {
-		err = perf_header__write(header, output, false);
+		err = perf_header__write(&session->header, output, false);
 		if (err < 0)
 			return err;
 	}