base/trace_event/trace_event_win.h

// 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.

// This file contains the Windows-specific declarations for trace_event.h.
#ifndef BASE_TRACE_EVENT_TRACE_EVENT_WIN_H_
#define BASE_TRACE_EVENT_TRACE_EVENT_WIN_H_

#include <string>

#include "base/base_export.h"
#include "base/trace_event/trace_event.h"
#include "base/win/event_trace_provider.h"

// Fwd.
template <typename Type>
struct StaticMemorySingletonTraits;

namespace base {
namespace trace_event {

// This EtwTraceProvider subclass implements ETW logging
// for the macros above on Windows.
class BASE_EXPORT TraceEventETWProvider : public base::win::EtwTraceProvider {
 public:
   static const size_t kUseStrlen = static_cast<size_t>(-1);

  // Start logging trace events.
  // This is a noop in this implementation.
  static bool StartTracing();

  // Trace begin/end/instant events, this is the bottleneck implementation
  // all the others defer to.
  // Allowing the use of std::string for name or extra is a convenience,
  // whereas passing name or extra as a const char* avoids the construction
  // of temporary std::string instances.
  // If kUseStrlen is passed for name_len or extra_len, the strlen of the string
  // will be used for length.
  static void Trace(const char* name,
                    size_t name_len,
                    char type,
                    const void* id,
                    const char* extra,
                    size_t extra_len);

  // Allows passing extra as a std::string for convenience.
  static void Trace(const char* name,
                    char type,
                    const void* id,
                    const std::string& extra) {
    return Trace(name, kUseStrlen, type, id, extra.c_str(), extra.length());
  }

  // Allows passing extra as a const char* to avoid constructing temporary
  // std::string instances where not needed.
  static void Trace(const char* name,
                    char type,
                    const void* id,
                    const char* extra) {
    return Trace(name, kUseStrlen, type, id, extra, kUseStrlen);
  }

  // Retrieves the singleton.
  // Note that this may return NULL post-AtExit processing.
  static TraceEventETWProvider* GetInstance();

  // Returns true iff tracing is turned on.
  bool IsTracing() {
    return enable_level() >= TRACE_LEVEL_INFORMATION;
  }

  // Emit a trace of type |type| containing |name|, |id|, and |extra|.
  // Note: |name| and |extra| must be NULL, or a zero-terminated string of
  //    length |name_len| or |extra_len| respectively.
  // Note: if name_len or extra_len are kUseStrlen, the length of the
  //    corresponding string will be used.
  void TraceEvent(const char* name,
                  size_t name_len,
                  char type,
                  const void* id,
                  const char* extra,
                  size_t extra_len);

  // Exposed for unittesting only, allows resurrecting our
  // singleton instance post-AtExit processing.
  static void Resurrect();

 private:
  // Ensure only the provider can construct us.
  friend struct StaticMemorySingletonTraits<TraceEventETWProvider>;
  TraceEventETWProvider();

  DISALLOW_COPY_AND_ASSIGN(TraceEventETWProvider);
};

// The ETW trace provider GUID.
BASE_EXPORT extern const GUID kChromeTraceProviderName;

// The ETW event class GUID for 32 bit events.
BASE_EXPORT extern const GUID kTraceEventClass32;

// The ETW event class GUID for 64 bit events.
BASE_EXPORT extern const GUID kTraceEventClass64;

// The ETW event types, IDs 0x00-0x09 are reserved, so start at 0x10.
const base::win::EtwEventType kTraceEventTypeBegin = 0x10;
const base::win::EtwEventType kTraceEventTypeEnd = 0x11;
const base::win::EtwEventType kTraceEventTypeInstant = 0x12;

// If this flag is set in enable flags
enum TraceEventETWFlags {
  CAPTURE_STACK_TRACE = 0x0001,
};

// The event format consists of:
// The "name" string as a zero-terminated ASCII string.
// The id pointer in the machine bitness.
// The "extra" string as a zero-terminated ASCII string.
// Optionally the stack trace, consisting of a DWORD "depth", followed
//    by an array of void* (machine bitness) of length "depth".

}  // namespace trace_event
}  // namespace base

#endif  // BASE_TRACE_EVENT_TRACE_EVENT_WIN_H_