xpcom/ds/TimeStamp.cpp

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim:set ts=2 sw=2 sts=2 et cindent: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 /*
   8  * Implementation of the OS-independent methods of the TimeStamp class
   9  */
  10
  11 #include "mozilla/TimeStamp.h"
  12 #include "prenv.h"
  13
  14 namespace mozilla {
  15
  16 /**
  17  * Wrapper class used to initialize static data used by the TimeStamp class
  18  */
  19 struct TimeStampInitialization
  20 {
  21   /**
  22    * First timestamp taken when the class static initializers are run. This
  23    * timestamp is used to sanitize timestamps coming from different sources.
  24    */
  25   TimeStamp mFirstTimeStamp;
  26
  27   /**
  28    * Timestamp representing the time when the process was created. This field
  29    * is populated lazily the first time this information is required and is
  30    * replaced every time the process is restarted.
  31    */
  32   TimeStamp mProcessCreation;
  33
  34   TimeStampInitialization()
  35   {
  36     TimeStamp::Startup();
  37     mFirstTimeStamp = TimeStamp::Now();
  38   };
  39
  40   ~TimeStampInitialization()
  41   {
  42     TimeStamp::Shutdown();
  43   };
  44 };
  45
  46 static TimeStampInitialization sInitOnce;
  47
  48 TimeStamp
  49 TimeStamp::ProcessCreation(bool& aIsInconsistent)
  50 {
  51   aIsInconsistent = false;
  52
  53   if (sInitOnce.mProcessCreation.IsNull()) {
  54     char* mozAppRestart = PR_GetEnv("MOZ_APP_RESTART");
  55     TimeStamp ts;
  56
  57     /* When calling PR_SetEnv() with an empty value the existing variable may
  58      * be unset or set to the empty string depending on the underlying platform
  59      * thus we have to check if the variable is present and not empty. */
  60     if (mozAppRestart && (strcmp(mozAppRestart, "") != 0)) {
  61       /* Firefox was restarted, use the first time-stamp we've taken as the new
  62        * process startup time. */
  63       ts = sInitOnce.mFirstTimeStamp;
  64     } else {
  65       TimeStamp now = Now();
  66       uint64_t uptime = ComputeProcessUptime();
  67
  68       ts = now - TimeDuration::FromMicroseconds(uptime);
  69
  70       if ((ts > sInitOnce.mFirstTimeStamp) || (uptime == 0)) {
  71         /* If the process creation timestamp was inconsistent replace it with
  72          * the first one instead and notify that a telemetry error was
  73          * detected. */
  74         aIsInconsistent = true;
  75         ts = sInitOnce.mFirstTimeStamp;
  76       }
  77     }
  78
  79     sInitOnce.mProcessCreation = ts;
  80   }
  81
  82   return sInitOnce.mProcessCreation;
  83 }
  84
  85 void
  86 TimeStamp::RecordProcessRestart()
  87 {
  88   sInitOnce.mProcessCreation = TimeStamp();
  89 }
  90
  91 } // namespace mozilla