base/win/event_trace_consumer.h

   1 // Copyright (c) 2012 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 // Declaration of a Windows event trace consumer base class.
   6 #ifndef BASE_WIN_EVENT_TRACE_CONSUMER_H_
   7 #define BASE_WIN_EVENT_TRACE_CONSUMER_H_
   8 #pragma once
   9
  10 #include <windows.h>
  11 #include <wmistr.h>
  12 #include <evntrace.h>
  13 #include <vector>
  14 #include "base/basictypes.h"
  15
  16 namespace base {
  17 namespace win {
  18
  19 // This class is a base class that makes it easier to consume events
  20 // from realtime or file sessions. Concrete consumers need to sublass
  21 // a specialization of this class and override the ProcessEvent and/or
  22 // the ProcessBuffer methods to implement the event consumption logic.
  23 // Usage might look like:
  24 // class MyConsumer: public EtwTraceConsumerBase<MyConsumer, 1> {
  25 //  protected:
  26 //    static VOID WINAPI ProcessEvent(PEVENT_TRACE event);
  27 // };
  28 //
  29 // MyConsumer consumer;
  30 // consumer.OpenFileSession(file_path);
  31 // consumer.Consume();
  32 template <class ImplClass>
  33 class EtwTraceConsumerBase {
  34  public:
  35   // Constructs a closed consumer.
  36   EtwTraceConsumerBase() {
  37   }
  38
  39   ~EtwTraceConsumerBase() {
  40     Close();
  41   }
  42
  43   // Opens the named realtime session, which must be existent.
  44   // Note: You can use OpenRealtimeSession or OpenFileSession
  45   //    to open as many as MAXIMUM_WAIT_OBJECTS (63) sessions at
  46   //    any one time, though only one of them may be a realtime
  47   //    session.
  48   HRESULT OpenRealtimeSession(const wchar_t* session_name);
  49
  50   // Opens the event trace log in "file_name", which must be a full or
  51   // relative path to an existing event trace log file.
  52   // Note: You can use OpenRealtimeSession or OpenFileSession
  53   //    to open as many as kNumSessions at any one time.
  54   HRESULT OpenFileSession(const wchar_t* file_name);
  55
  56   // Consume all open sessions from beginning to end.
  57   HRESULT Consume();
  58
  59   // Close all open sessions.
  60   HRESULT Close();
  61
  62  protected:
  63   // Override in subclasses to handle events.
  64   static void ProcessEvent(EVENT_TRACE* event) {
  65   }
  66   // Override in subclasses to handle buffers.
  67   static bool ProcessBuffer(EVENT_TRACE_LOGFILE* buffer) {
  68     return true;  // keep going
  69   }
  70
  71  protected:
  72   // Currently open sessions.
  73   std::vector<TRACEHANDLE> trace_handles_;
  74
  75  private:
  76   // These delegate to ImplClass callbacks with saner signatures.
  77   static void WINAPI ProcessEventCallback(EVENT_TRACE* event) {
  78     ImplClass::ProcessEvent(event);
  79   }
  80   static ULONG WINAPI ProcessBufferCallback(PEVENT_TRACE_LOGFILE buffer) {
  81     return ImplClass::ProcessBuffer(buffer);
  82   }
  83
  84   DISALLOW_COPY_AND_ASSIGN(EtwTraceConsumerBase);
  85 };
  86
  87 template <class ImplClass> inline
  88 HRESULT EtwTraceConsumerBase<ImplClass>::OpenRealtimeSession(
  89     const wchar_t* session_name) {
  90   EVENT_TRACE_LOGFILE logfile = {};
  91   logfile.LoggerName = const_cast<wchar_t*>(session_name);
  92   logfile.LogFileMode = EVENT_TRACE_REAL_TIME_MODE;
  93   logfile.BufferCallback = &ProcessBufferCallback;
  94   logfile.EventCallback = &ProcessEventCallback;
  95   logfile.Context = this;
  96   TRACEHANDLE trace_handle = ::OpenTrace(&logfile);
  97   if (reinterpret_cast<TRACEHANDLE>(INVALID_HANDLE_VALUE) == trace_handle)
  98     return HRESULT_FROM_WIN32(::GetLastError());
  99
 100   trace_handles_.push_back(trace_handle);
 101   return S_OK;
 102 }
 103
 104 template <class ImplClass> inline
 105 HRESULT EtwTraceConsumerBase<ImplClass>::OpenFileSession(
 106     const wchar_t* file_name) {
 107   EVENT_TRACE_LOGFILE logfile = {};
 108   logfile.LogFileName = const_cast<wchar_t*>(file_name);
 109   logfile.BufferCallback = &ProcessBufferCallback;
 110   logfile.EventCallback = &ProcessEventCallback;
 111   logfile.Context = this;
 112   TRACEHANDLE trace_handle = ::OpenTrace(&logfile);
 113   if (reinterpret_cast<TRACEHANDLE>(INVALID_HANDLE_VALUE) == trace_handle)
 114     return HRESULT_FROM_WIN32(::GetLastError());
 115
 116   trace_handles_.push_back(trace_handle);
 117   return S_OK;
 118 }
 119
 120 template <class ImplClass> inline
 121 HRESULT EtwTraceConsumerBase<ImplClass>::Consume() {
 122   ULONG err = ::ProcessTrace(&trace_handles_[0],
 123                              trace_handles_.size(),
 124                              NULL,
 125                              NULL);
 126   return HRESULT_FROM_WIN32(err);
 127 }
 128
 129 template <class ImplClass> inline
 130 HRESULT EtwTraceConsumerBase<ImplClass>::Close() {
 131   HRESULT hr = S_OK;
 132   for (size_t i = 0; i < trace_handles_.size(); ++i) {
 133     if (NULL != trace_handles_[i]) {
 134       ULONG ret = ::CloseTrace(trace_handles_[i]);
 135       trace_handles_[i] = NULL;
 136
 137       if (FAILED(HRESULT_FROM_WIN32(ret)))
 138         hr = HRESULT_FROM_WIN32(ret);
 139     }
 140   }
 141   trace_handles_.clear();
 142
 143   return hr;
 144 }
 145
 146 }  // namespace win
 147 }  // namespace base
 148
 149 #endif  // BASE_WIN_EVENT_TRACE_CONSUMER_H_