Add granular file tracing.

base/files/file.h

 // Copyright (c) 2012 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_H_
 #define BASE_FILES_FILE_H_
 
 #include "build/build_config.h"
 #if defined(OS_WIN)
 #include <windows.h>
 #endif
 
 #if defined(OS_POSIX)
 #include <sys/stat.h>
 #endif
 
 #include <string>
 
 #include "base/base_export.h"
 #include "base/basictypes.h"
+#include "base/files/file_path.h"
 #include "base/files/scoped_file.h"
 #include "base/gtest_prod_util.h"
 #include "base/move.h"
 #include "base/time/time.h"
 
 #if defined(OS_WIN)
 #include "base/win/scoped_handle.h"
 #endif
 
 FORWARD_DECLARE_TEST(FileTest, MemoryCorruption);
 
 namespace base {
 
-class FilePath;
-
 #if defined(OS_WIN)
 typedef HANDLE PlatformFile;
 #elif defined(OS_POSIX)
 typedef int PlatformFile;
 
 #if defined(OS_BSD) || defined(OS_MACOSX) || defined(OS_NACL)
 typedef struct stat stat_wrapper_t;
 #else
 typedef struct stat64 stat_wrapper_t;
 #endif
@@ skipping 109 matching lines @@
     // The last accessed time of a file.
     Time last_accessed;
 
     // The creation time of a file.
     Time creation_time;
   };
 
   File();
 
   // Creates or opens the given file. This will fail with 'access denied' if the
-  // |name| contains path traversal ('..') components.
-  File(const FilePath& name, uint32 flags);
+  // |path| contains path traversal ('..') components.
+  File(const FilePath& path, uint32 flags);
 
   // Takes ownership of |platform_file|.
   explicit File(PlatformFile platform_file);
 
   // Creates an object with a specific error_details code.
   explicit File(Error error_details);
 
   // Move constructor for C++03 move emulation of this type.
   File(RValue other);
 
   ~File();
 
   // Move operator= for C++03 move emulation of this type.
   File& operator=(RValue other);
 
   // Creates or opens the given file.
-  void Initialize(const FilePath& name, uint32 flags);
+  void Initialize(const FilePath& path, uint32 flags);
 
   bool IsValid() const;
 
   // Returns true if a new file was created (or an old one truncated to zero
   // length to simulate a new file, which can happen with
   // FLAG_CREATE_ALWAYS), and false otherwise.
   bool created() const { return created_; }
 
   // Returns the OS result of opening this file. Note that the way to verify
   // the success of the operation is to use IsValid(), not this method:
-  //   File file(name, flags);
+  //   File file(path, flags);
   //   if (!file.IsValid())
   //     return;
   Error error_details() const { return error_details_; }
 
   PlatformFile GetPlatformFile() const;
   PlatformFile TakePlatformFile();
 
   // Destroying this object closes the file automatically.
   void Close();
 
@@ skipping 93 matching lines @@
 #elif defined(OS_POSIX)
   static Error OSErrorToFileError(int saved_errno);
 #endif
 
   // Converts an error value to a human-readable form. Used for logging.
   static std::string ErrorToString(Error error);
 
  private:
   FRIEND_TEST_ALL_PREFIXES(::FileTest, MemoryCorruption);
 
+  // The tracing group file traces will show up as.
+  static const char kTraceGroup[];

[Sami, 2015/04/28 11:10:39]

nit: Usually we just write the trace category explicitly in each trace event. It
makes it easier to grep where trace events are coming from, and the compiler
will fold the identical strings into one anyway.

[Dan Beam, 2015/04/28 15:47:58]

I guess I can do this, it's just... TRACE_DISABLED_BY_DEFAULT("file") is pretty
long.

[Sami, 2015/04/28 15:51:05]

I don't think it's a hard rule, so I'll leave it up to you to decide.

[groby-ooo-7-16, 2015/04/28 20:26:54]

I don't have a specific preference, but consider naming it kFileTraceGroup -
this way we can still grep somewhat reliably.

[Dan Beam, 2015/04/29 02:48:03]

  $ git grep \\bkTraceGroup\\b

yields only these results reliably

+
 #if defined(OS_POSIX)
   // Encloses a single ScopedFD, saving a cheap tamper resistent memory checksum
   // alongside it. This checksum is validated at every access, allowing early
   // detection of memory corruption.
 
   // TODO(gavinp): This is in place temporarily to help us debug
   // https://crbug.com/424562 , which can't be reproduced in valgrind. Remove
   // this code after we have fixed this issue.
   class MemoryCheckingScopedFD {
    public:
@@ skipping 25 matching lines @@
     // failing a CHECK if they do not.
     void Check() const;
 
     void UpdateChecksum();
 
     ScopedFD file_;
     unsigned int file_memory_checksum_;
   };
 #endif
 
-  // Creates or opens the given file. Only called if |name| has no traversal
+  // Creates or opens the given file. Only called if |path_| has no traversal
   // ('..') components.
-  void DoInitialize(const FilePath& name, uint32 flags);
+  void DoInitialize(uint32 flags);
 
   // TODO(tnagel): Reintegrate into Flush() once histogram isn't needed anymore,
   // cf. issue 473337.
   bool DoFlush();
 
   void SetPlatformFile(PlatformFile file);
 
 #if defined(OS_WIN)
   win::ScopedHandle file_;
 #elif defined(OS_POSIX)
   MemoryCheckingScopedFD file_;
 #endif
 

[groby-ooo-7-16, 2015/04/28 20:26:54]

|unsafe_path_|, then?

[Dan Beam, 2015/04/29 02:48:02]

Done.

+  // Path that |Initialize()| was called with. Can be unsafe (e.g. have '..').
+  FilePath path_;
+
   Error error_details_;
   bool created_;
   bool async_;
 };
 
 }  // namespace base
 
 #endif  // BASE_FILES_FILE_H_