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