base/files/file_tracing.h

   1 // Copyright 2015 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef BASE_FILES_FILE_TRACING_H_
   6 #define BASE_FILES_FILE_TRACING_H_
   7
   8 #include "base/base_export.h"
   9 #include "base/basictypes.h"
  10 #include "base/macros.h"
  11
  12 #define FILE_TRACING_PREFIX "File"
  13
  14 #define SCOPED_FILE_TRACE_WITH_SIZE(name, size) \
  15     FileTracing::ScopedTrace scoped_file_trace; \
  16     if (FileTracing::IsCategoryEnabled()) \
  17       scoped_file_trace.Initialize(FILE_TRACING_PREFIX "::" name, this, size)
  18
  19 #define SCOPED_FILE_TRACE(name) SCOPED_FILE_TRACE_WITH_SIZE(name, 0)
  20
  21 namespace base {
  22
  23 class File;
  24 class FilePath;
  25
  26 class BASE_EXPORT FileTracing {
  27  public:
  28   // Whether the file tracing category is enabled.
  29   static bool IsCategoryEnabled();
  30
  31   class Provider {
  32    public:
  33     virtual ~Provider() = default;
  34
  35     // Whether the file tracing category is currently enabled.
  36     virtual bool FileTracingCategoryIsEnabled() const = 0;
  37
  38     // Enables file tracing for |id|. Must be called before recording events.
  39     virtual void FileTracingEnable(void* id) = 0;
  40
  41     // Disables file tracing for |id|.
  42     virtual void FileTracingDisable(void* id) = 0;
  43
  44     // Begins an event for |id| with |name|. |path| tells where in the directory
  45     // structure the event is happening (and may be blank). |size| is the number
  46     // of bytes involved in the event.
  47     virtual void FileTracingEventBegin(
  48         const char* name, void* id, const FilePath& path, int64 size) = 0;
  49
  50     // Ends an event for |id| with |name|.
  51     virtual void FileTracingEventEnd(const char* name, void* id) = 0;
  52   };
  53
  54   // Sets a global file tracing provider to query categories and record events.
  55   static void SetProvider(Provider* provider);
  56
  57   // Enables file tracing while in scope.
  58   class ScopedEnabler {
  59    public:
  60     ScopedEnabler();
  61     ~ScopedEnabler();
  62   };
  63
  64   class ScopedTrace {
  65    public:
  66     ScopedTrace();
  67     ~ScopedTrace();
  68
  69     // Called only if the tracing category is enabled. |name| is the name of the
  70     // event to trace (e.g. "Read", "Write") and must have an application
  71     // lifetime (e.g. static or literal). |file| is the file being traced; must
  72     // outlive this class. |size| is the size (in bytes) of this event.
  73     void Initialize(const char* name, File* file, int64 size);
  74
  75    private:
  76     // The ID of this trace. Based on the |file| passed to |Initialize()|. Must
  77     // outlive this class.
  78     void* id_;
  79
  80     // The name of the event to trace (e.g. "Read", "Write"). Prefixed with
  81     // "File".
  82     const char* name_;
  83
  84     DISALLOW_COPY_AND_ASSIGN(ScopedTrace);
  85   };
  86
  87   DISALLOW_COPY_AND_ASSIGN(FileTracing);
  88 };
  89
  90 }  // namespace base
  91
  92 #endif  // BASE_FILES_FILE_TRACING_H_