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      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 <stdint.h>
      9 
     10 #include "base/base_export.h"
     11 #include "base/macros.h"
     12 
     13 #define FILE_TRACING_PREFIX "File"
     14 
     15 #define SCOPED_FILE_TRACE_WITH_SIZE(name, size) \
     16     FileTracing::ScopedTrace scoped_file_trace; \
     17     if (FileTracing::IsCategoryEnabled()) \
     18       scoped_file_trace.Initialize(FILE_TRACING_PREFIX "::" name, this, size)
     19 
     20 #define SCOPED_FILE_TRACE(name) SCOPED_FILE_TRACE_WITH_SIZE(name, 0)
     21 
     22 namespace base {
     23 
     24 class File;
     25 class FilePath;
     26 
     27 class BASE_EXPORT FileTracing {
     28  public:
     29   // Whether the file tracing category is enabled.
     30   static bool IsCategoryEnabled();
     31 
     32   class Provider {
     33    public:
     34     virtual ~Provider() = default;
     35 
     36     // Whether the file tracing category is currently enabled.
     37     virtual bool FileTracingCategoryIsEnabled() const = 0;
     38 
     39     // Enables file tracing for |id|. Must be called before recording events.
     40     virtual void FileTracingEnable(const void* id) = 0;
     41 
     42     // Disables file tracing for |id|.
     43     virtual void FileTracingDisable(const void* id) = 0;
     44 
     45     // Begins an event for |id| with |name|. |path| tells where in the directory
     46     // structure the event is happening (and may be blank). |size| is the number
     47     // of bytes involved in the event.
     48     virtual void FileTracingEventBegin(const char* name,
     49                                        const void* id,
     50                                        const FilePath& path,
     51                                        int64_t size) = 0;
     52 
     53     // Ends an event for |id| with |name|.
     54     virtual void FileTracingEventEnd(const char* name, const void* id) = 0;
     55   };
     56 
     57   // Sets a global file tracing provider to query categories and record events.
     58   static void SetProvider(Provider* provider);
     59 
     60   // Enables file tracing while in scope.
     61   class ScopedEnabler {
     62    public:
     63     ScopedEnabler();
     64     ~ScopedEnabler();
     65   };
     66 
     67   class ScopedTrace {
     68    public:
     69     ScopedTrace();
     70     ~ScopedTrace();
     71 
     72     // Called only if the tracing category is enabled. |name| is the name of the
     73     // event to trace (e.g. "Read", "Write") and must have an application
     74     // lifetime (e.g. static or literal). |file| is the file being traced; must
     75     // outlive this class. |size| is the size (in bytes) of this event.
     76     void Initialize(const char* name, const File* file, int64_t size);
     77 
     78    private:
     79     // The ID of this trace. Based on the |file| passed to |Initialize()|. Must
     80     // outlive this class.
     81     const void* id_;
     82 
     83     // The name of the event to trace (e.g. "Read", "Write"). Prefixed with
     84     // "File".
     85     const char* name_;
     86 
     87     DISALLOW_COPY_AND_ASSIGN(ScopedTrace);
     88   };
     89 
     90   DISALLOW_COPY_AND_ASSIGN(FileTracing);
     91 };
     92 
     93 }  // namespace base
     94 
     95 #endif  // BASE_FILES_FILE_TRACING_H_
     96