1// Copyright (c) 2011 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 controller class.
6// The controller takes care of creating and manipulating event trace
7// sessions.
8//
9// Event tracing for Windows is a system-provided service that provides
10// logging control and high-performance transport for generic, binary trace
11// events. Event trace providers register with the system by their name,
12// which is a GUID, and can from that point forward receive callbacks that
13// start or end tracing and that change their trace level and enable mask.
14//
15// A trace controller can create an event tracing session, which either
16// sends events to a binary file, or to a realtime consumer, or both.
17//
18// A trace consumer consumes events from zero or one realtime session,
19// as well as potentially from multiple binary trace files.
20#ifndef BASE_WIN_EVENT_TRACE_CONTROLLER_H_
21#define BASE_WIN_EVENT_TRACE_CONTROLLER_H_
22#pragma once
23
24#include <windows.h>
25#include <wmistr.h>
26#include <evntrace.h>
27#include <string>
28
29#include "base/base_api.h"
30#include "base/basictypes.h"
31
32namespace base {
33namespace win {
34
35// Utility class to make it easier to work with EVENT_TRACE_PROPERTIES.
36// The EVENT_TRACE_PROPERTIES structure contains information about an
37// event tracing session.
38class BASE_API EtwTraceProperties {
39 public:
40  EtwTraceProperties();
41
42  EVENT_TRACE_PROPERTIES* get() {
43    return &properties_;
44  }
45
46  const EVENT_TRACE_PROPERTIES* get() const {
47    return reinterpret_cast<const EVENT_TRACE_PROPERTIES*>(&properties_);
48  }
49
50  const wchar_t* GetLoggerName() const {
51    return reinterpret_cast<const wchar_t *>(buffer_ + get()->LoggerNameOffset);
52  }
53
54  // Copies logger_name to the properties structure.
55  HRESULT SetLoggerName(const wchar_t* logger_name);
56  const wchar_t* GetLoggerFileName() const {
57    return reinterpret_cast<const wchar_t*>(buffer_ + get()->LogFileNameOffset);
58  }
59
60  // Copies logger_file_name to the properties structure.
61  HRESULT SetLoggerFileName(const wchar_t* logger_file_name);
62
63  // Max string len for name and session name is 1024 per documentation.
64  static const size_t kMaxStringLen = 1024;
65  // Properties buffer allocates space for header and for
66  // max length for name and session name.
67  static const size_t kBufSize = sizeof(EVENT_TRACE_PROPERTIES)
68      + 2 * sizeof(wchar_t) * (kMaxStringLen);
69
70 private:
71  // The EVENT_TRACE_PROPERTIES structure needs to be overlaid on a
72  // larger buffer to allow storing the logger name and logger file
73  // name contiguously with the structure.
74  union {
75   public:
76    // Our properties header.
77    EVENT_TRACE_PROPERTIES properties_;
78    // The actual size of the buffer is forced by this member.
79    char buffer_[kBufSize];
80  };
81
82  DISALLOW_COPY_AND_ASSIGN(EtwTraceProperties);
83};
84
85// This class implements an ETW controller, which knows how to start and
86// stop event tracing sessions, as well as controlling ETW provider
87// log levels and enable bit masks under the session.
88class BASE_API EtwTraceController {
89 public:
90  EtwTraceController();
91  ~EtwTraceController();
92
93  // Start a session with given name and properties.
94  HRESULT Start(const wchar_t* session_name, EtwTraceProperties* prop);
95
96  // Starts a session tracing to a file with some default properties.
97  HRESULT StartFileSession(const wchar_t* session_name,
98                           const wchar_t* logfile_path,
99                           bool realtime = false);
100
101  // Starts a realtime session with some default properties.
102  HRESULT StartRealtimeSession(const wchar_t* session_name,
103                               size_t buffer_size);
104
105  // Enables "provider" at "level" for this session.
106  // This will cause all providers registered with the GUID
107  // "provider" to start tracing at the new level, systemwide.
108  HRESULT EnableProvider(const GUID& provider, UCHAR level,
109                         ULONG flags = 0xFFFFFFFF);
110  // Disables "provider".
111  HRESULT DisableProvider(const GUID& provider);
112
113  // Stops our session and retrieve the new properties of the session,
114  // properties may be NULL.
115  HRESULT Stop(EtwTraceProperties* properties);
116
117  // Flushes our session and retrieve the current properties,
118  // properties may be NULL.
119  HRESULT Flush(EtwTraceProperties* properties);
120
121  // Static utility functions for controlling
122  // sessions we don't necessarily own.
123  static HRESULT Start(const wchar_t* session_name,
124                       EtwTraceProperties* properties,
125                       TRACEHANDLE* session_handle);
126
127  static HRESULT Query(const wchar_t* session_name,
128                       EtwTraceProperties* properties);
129
130  static HRESULT Update(const wchar_t* session_name,
131                        EtwTraceProperties* properties);
132
133  static HRESULT Stop(const wchar_t* session_name,
134                      EtwTraceProperties* properties);
135  static HRESULT Flush(const wchar_t* session_name,
136                       EtwTraceProperties* properties);
137
138  // Accessors.
139  TRACEHANDLE session() const { return session_; }
140  const wchar_t* session_name() const { return session_name_.c_str(); }
141
142 private:
143  std::wstring session_name_;
144  TRACEHANDLE session_;
145
146  DISALLOW_COPY_AND_ASSIGN(EtwTraceController);
147};
148
149}  // namespace win
150}  // namespace base
151
152#endif  // BASE_WIN_EVENT_TRACE_CONTROLLER_H_
153