Generalize the net module's LoadLog facility from a passive container, to an event stream (NetLog).

net/base/load_log_util.h

-// Copyright (c) 2009 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.
-
-#ifndef NET_BASE_LOAD_LOG_UTIL_H_
-#define NET_BASE_LOAD_LOG_UTIL_H_
-
-#include <string>
-#include <vector>
-
-#include "base/basictypes.h"
-#include "net/base/load_log.h"
-
-namespace net {
-
-// The LoadLogUtil utility class contains methods to analyze and visualize
-// LoadLogs.
-
-class LoadLogUtil {
- public:
-  struct EventDuration {
-    LoadLog::EventType event;
-    base::TimeDelta duration;
-  };
-  typedef std::vector<EventDuration> EventDurationList;
-
-  // Builds a pretty printed ASCII tree showing the chronological order
-  // of events.
-  //
-  // The indentation reflects hiearchy, with the duration of each indented
-  // block noted on the right. The timestamp (tick count in milliseconds)
-  // is noted in the left column.
-  //
-  // This detailed view of what went into servicing a request can be used
-  // in logs, and is copy-pastable by users, for attaching to bug reports.
-  //
-  // Example A:
-  //
-  //     t=0: +Event1       [dt = 8]
-  //     t=1:   +Event2     [dt = 0]
-  //     t=1:      EventX
-  //     t=1:   -Event2
-  //     t=4:   +Event3     [dt = 2]
-  //     t=6:   -Event3
-  //     t=6:   +Event2     [dt = 1]
-  //     t=7:   -Event2
-  //     t=8:    EventY
-  //     t=8: -Event1
-  //
-  // Here we can see that:
-  //   - Event1 started at t=0 and ended at t=8; the duration was 8 time units.
-  //   - Event2 took place while Event1 was in progress, and was repeated
-  //     at t=1 and t=6.
-  //   - EventX took place while (the first) Event2 was in progress.
-  //   - Event3 started and ended at the same time, taking 0 time.
-  //   - EventY took place right before Event1 finished, at t=8
-  //
-  // In general the rules are:
-  //   - Log entries added by BeginEvent() are prefixed with a '+' and
-  //     start an indentation block.
-  //   - Log entries added by EndEvent() are prefixed with a '-' and
-  //     finish an indentation block.
-  //   - Log entries added by AddEvent() have no prefix.
-  //   - Time units are given as milliseconds.
-  //
-  static std::string PrettyPrintAsEventTree(const LoadLog* log);
-
- private:
-  DISALLOW_IMPLICIT_CONSTRUCTORS(LoadLogUtil);
-};
-
-}  // namespace net
-
-#endif  // NET_BASE_LOAD_LOG_UTIL_H_