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 (scoped_file_trace.ShouldInitialize()) \
  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   class Provider {
  29    public:
  30     // Whether the file tracing category is currently enabled.
  31     virtual bool FileTracingCategoryIsEnabled() const = 0;
  32
  33     // Enables file tracing for |id|. Must be called before recording events.
  34     virtual void FileTracingEnable(void* id) = 0;
  35
  36     // Disables file tracing for |id|.
  37     virtual void FileTracingDisable(void* id) = 0;
  38
  39     // Begins an event for |id| with |name|. |path| tells where in the directory
  40     // structure the event is happening (and may be blank). |size| is the number
  41     // of bytes involved in the event.
  42     virtual void FileTracingEventBegin(
  43         const char* name, void* id, const FilePath& path, int64 size) = 0;
  44
  45     // Ends an event for |id| with |name|.
  46     virtual void FileTracingEventEnd(const char* name, void* id) = 0;
  47   };
  48
  49   // Sets a global file tracing provider to query categories and record events.
  50   static void SetProvider(Provider* provider);
  51
  52   // Enables file tracing while in scope.
  53   class ScopedEnabler {
  54    public:
  55     ScopedEnabler();
  56     ~ScopedEnabler();
  57   };
  58
  59   class ScopedTrace {
  60    public:
  61     ScopedTrace();
  62     ~ScopedTrace();
  63
  64     // Whether this trace should be initialized or not.
  65     bool ShouldInitialize() const;
  66
  67     // Called only if the tracing category is enabled. |name| is the name of the
  68     // event to trace (e.g. "Read", "Write") and must have an application
  69     // lifetime (e.g. static or literal). |file| is the file being traced; must
  70     // outlive this class. |size| is the size (in bytes) of this event.
  71     void Initialize(const char* name, File* file, int64 size);
  72
  73    private:
  74     // The ID of this trace. Based on the |file| passed to |Initialize()|. Must
  75     // outlive this class.
  76     void* id_;
  77
  78     // The name of the event to trace (e.g. "Read", "Write"). Prefixed with
  79     // "File".
  80     const char* name_;
  81
  82     DISALLOW_COPY_AND_ASSIGN(ScopedTrace);
  83   };
  84
  85   DISALLOW_COPY_AND_ASSIGN(FileTracing);
  86 };
  87
  88 }  // namespace base
  89
  90 #endif  // BASE_FILES_FILE_TRACING_H_