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// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
//
// Declaration of a Windows event trace consumer base class.
#ifndef BASE_WIN_EVENT_TRACE_CONSUMER_H_
#define BASE_WIN_EVENT_TRACE_CONSUMER_H_
#include <windows.h>
#include <wmistr.h>
#include <evntrace.h>
#include <stddef.h>
#include <vector>
#include "base/macros.h"
namespace base {
namespace win {
// This class is a base class that makes it easier to consume events
// from realtime or file sessions. Concrete consumers need to subclass
// a specialization of this class and override the ProcessEvent and/or
// the ProcessBuffer methods to implement the event consumption logic.
// Usage might look like:
// class MyConsumer: public EtwTraceConsumerBase<MyConsumer, 1> {
// protected:
// static VOID WINAPI ProcessEvent(PEVENT_TRACE event);
// };
//
// MyConsumer consumer;
// consumer.OpenFileSession(file_path);
// consumer.Consume();
template <class ImplClass>
class EtwTraceConsumerBase {
public:
// Constructs a closed consumer.
EtwTraceConsumerBase() {
}
~EtwTraceConsumerBase() {
Close();
}
// Opens the named realtime session, which must be existent.
// Note: You can use OpenRealtimeSession or OpenFileSession
// to open as many as MAXIMUM_WAIT_OBJECTS (63) sessions at
// any one time, though only one of them may be a realtime
// session.
HRESULT OpenRealtimeSession(const wchar_t* session_name);
// Opens the event trace log in "file_name", which must be a full or
// relative path to an existing event trace log file.
// Note: You can use OpenRealtimeSession or OpenFileSession
// to open as many as kNumSessions at any one time.
HRESULT OpenFileSession(const wchar_t* file_name);
// Consume all open sessions from beginning to end.
HRESULT Consume();
// Close all open sessions.
HRESULT Close();
protected:
// Override in subclasses to handle events.
static void ProcessEvent(EVENT_TRACE* event) {
}
// Override in subclasses to handle buffers.
static bool ProcessBuffer(EVENT_TRACE_LOGFILE* buffer) {
return true; // keep going
}
protected:
// Currently open sessions.
std::vector<TRACEHANDLE> trace_handles_;
private:
// These delegate to ImplClass callbacks with saner signatures.
static void WINAPI ProcessEventCallback(EVENT_TRACE* event) {
ImplClass::ProcessEvent(event);
}
static ULONG WINAPI ProcessBufferCallback(PEVENT_TRACE_LOGFILE buffer) {
return ImplClass::ProcessBuffer(buffer);
}
DISALLOW_COPY_AND_ASSIGN(EtwTraceConsumerBase);
};
template <class ImplClass> inline
HRESULT EtwTraceConsumerBase<ImplClass>::OpenRealtimeSession(
const wchar_t* session_name) {
EVENT_TRACE_LOGFILE logfile = {};
logfile.LoggerName = const_cast<wchar_t*>(session_name);
logfile.LogFileMode = EVENT_TRACE_REAL_TIME_MODE;
logfile.BufferCallback = &ProcessBufferCallback;
logfile.EventCallback = &ProcessEventCallback;
logfile.Context = this;
TRACEHANDLE trace_handle = ::OpenTrace(&logfile);
if (reinterpret_cast<TRACEHANDLE>(INVALID_HANDLE_VALUE) == trace_handle)
return HRESULT_FROM_WIN32(::GetLastError());
trace_handles_.push_back(trace_handle);
return S_OK;
}
template <class ImplClass> inline
HRESULT EtwTraceConsumerBase<ImplClass>::OpenFileSession(
const wchar_t* file_name) {
EVENT_TRACE_LOGFILE logfile = {};
logfile.LogFileName = const_cast<wchar_t*>(file_name);
logfile.BufferCallback = &ProcessBufferCallback;
logfile.EventCallback = &ProcessEventCallback;
logfile.Context = this;
TRACEHANDLE trace_handle = ::OpenTrace(&logfile);
if (reinterpret_cast<TRACEHANDLE>(INVALID_HANDLE_VALUE) == trace_handle)
return HRESULT_FROM_WIN32(::GetLastError());
trace_handles_.push_back(trace_handle);
return S_OK;
}
template <class ImplClass> inline
HRESULT EtwTraceConsumerBase<ImplClass>::Consume() {
ULONG err = ::ProcessTrace(&trace_handles_[0],
static_cast<ULONG>(trace_handles_.size()),
NULL,
NULL);
return HRESULT_FROM_WIN32(err);
}
template <class ImplClass> inline
HRESULT EtwTraceConsumerBase<ImplClass>::Close() {
HRESULT hr = S_OK;
for (size_t i = 0; i < trace_handles_.size(); ++i) {
if (NULL != trace_handles_[i]) {
ULONG ret = ::CloseTrace(trace_handles_[i]);
trace_handles_[i] = NULL;
if (FAILED(HRESULT_FROM_WIN32(ret)))
hr = HRESULT_FROM_WIN32(ret);
}
}
trace_handles_.clear();
return hr;
}
} // namespace win
} // namespace base
#endif // BASE_WIN_EVENT_TRACE_CONSUMER_H_
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