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