Add granular file tracing.
R=thestig@chromium.org,nduca@chromium.org
BUG=480665
Review URL: https://codereview.chromium.org/1072133006
Cr-Commit-Position: refs/heads/master@{#329114}
CrOS-Libchrome-Original-Commit: 492dc31b433656444c9c74213a133c19c8ebfa21
diff --git a/base/files/file_tracing.h b/base/files/file_tracing.h
new file mode 100644
index 0000000..8452037
--- /dev/null
+++ b/base/files/file_tracing.h
@@ -0,0 +1,95 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_FILES_FILE_TRACING_H_
+#define BASE_FILES_FILE_TRACING_H_
+
+#include "base/base_export.h"
+#include "base/basictypes.h"
+#include "base/macros.h"
+
+#define FILE_TRACING_PREFIX "File"
+
+#define SCOPED_FILE_TRACE_WITH_SIZE(name, size) \
+ FileTracing::ScopedTrace scoped_file_trace; \
+ if (scoped_file_trace.ShouldInitialize()) \
+ scoped_file_trace.Initialize(FILE_TRACING_PREFIX "::" name, this, size)
+
+#define SCOPED_FILE_TRACE(name) SCOPED_FILE_TRACE_WITH_SIZE(name, 0)
+
+namespace base {
+
+class File;
+class FilePath;
+
+class BASE_EXPORT FileTracing {
+ public:
+ class Provider {
+ public:
+ // Whether the file tracing category is currently enabled.
+ virtual bool FileTracingCategoryIsEnabled() const = 0;
+
+ // Enables file tracing for |id|. Must be called before recording events.
+ virtual void FileTracingEnable(void* id) = 0;
+
+ // Disables file tracing for |id|.
+ virtual void FileTracingDisable(void* id) = 0;
+
+ // Begins an event for |id| with |name|. |path| tells where in the directory
+ // structure the event is happening (and may be blank). |size| is reported
+ // if not 0.
+ virtual void FileTracingEventBegin(
+ const char* name, void* id, const FilePath& path, int64 size) = 0;
+
+ // Ends an event for |id| with |name|. |path| tells where in the directory
+ // structure the event is happening (and may be blank). |size| is reported
+ // if not 0.
+ virtual void FileTracingEventEnd(
+ const char* name, void* id, const FilePath& path, int64 size) = 0;
+ };
+
+ // Sets a global file tracing provider to query categories and record events.
+ static void SetProvider(Provider* provider);
+
+ // Enables file tracing while in scope.
+ class ScopedEnabler {
+ public:
+ ScopedEnabler();
+ ~ScopedEnabler();
+ };
+
+ class ScopedTrace {
+ public:
+ ScopedTrace();
+ ~ScopedTrace();
+
+ // Whether this trace should be initialized or not.
+ bool ShouldInitialize() const;
+
+ // Called only if the tracing category is enabled.
+ void Initialize(const char* event, File* file, int64 size);
+
+ private:
+ // True if |Initialize()| has been called. Don't touch |path_|, |event_|,
+ // or |bytes_| if |initialized_| is false.
+ bool initialized_;
+
+ // The event name to trace (e.g. "Read", "Write"). Prefixed with "File".
+ const char* name_;
+
+ // The file being traced. Must outlive this class.
+ File* file_;
+
+ // The size (in bytes) of this trace. Not reported if 0.
+ int64 size_;
+
+ DISALLOW_COPY_AND_ASSIGN(ScopedTrace);
+ };
+
+ DISALLOW_COPY_AND_ASSIGN(FileTracing);
+};
+
+} // namespace base
+
+#endif // BASE_FILES_FILE_TRACING_H_