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-rw-r--r--mozglue/misc/TimeStamp.cpp115
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * Implementation of the OS-independent methods of the TimeStamp class
+ */
+
+#include "mozilla/TimeStamp.h"
+#include "mozilla/Uptime.h"
+#include <string.h>
+#include <stdlib.h>
+
+namespace mozilla {
+
+/**
+ * Wrapper class used to initialize static data used by the TimeStamp class
+ */
+struct TimeStampInitialization {
+ /**
+ * First timestamp taken when the class static initializers are run. This
+ * timestamp is used to sanitize timestamps coming from different sources.
+ */
+ TimeStamp mFirstTimeStamp;
+
+ /**
+ * Timestamp representing the time when the process was created. This field
+ * is populated lazily the first time this information is required and is
+ * replaced every time the process is restarted.
+ */
+ TimeStamp mProcessCreation;
+
+ TimeStampInitialization() {
+ TimeStamp::Startup();
+ mFirstTimeStamp = TimeStamp::Now();
+ // On Windows < 10, initializing the uptime requires `mFirstTimeStamp` to be
+ // valid.
+ mozilla::InitializeUptime();
+ }
+
+ ~TimeStampInitialization() { TimeStamp::Shutdown(); }
+};
+
+static TimeStampInitialization sInitOnce;
+
+MFBT_API TimeStamp TimeStamp::ProcessCreation() {
+ if (sInitOnce.mProcessCreation.IsNull()) {
+ char* mozAppRestart = getenv("MOZ_APP_RESTART");
+ TimeStamp ts;
+
+ /* When calling PR_SetEnv() with an empty value the existing variable may
+ * be unset or set to the empty string depending on the underlying platform
+ * thus we have to check if the variable is present and not empty. */
+ if (mozAppRestart && (strcmp(mozAppRestart, "") != 0)) {
+ /* Firefox was restarted, use the first time-stamp we've taken as the new
+ * process startup time. */
+ ts = sInitOnce.mFirstTimeStamp;
+ } else {
+ TimeStamp now = Now();
+ uint64_t uptime = ComputeProcessUptime();
+
+ ts = now - TimeDuration::FromMicroseconds(static_cast<double>(uptime));
+
+ if ((ts > sInitOnce.mFirstTimeStamp) || (uptime == 0)) {
+ ts = sInitOnce.mFirstTimeStamp;
+ }
+ }
+
+ sInitOnce.mProcessCreation = ts;
+ }
+
+ return sInitOnce.mProcessCreation;
+}
+
+void TimeStamp::RecordProcessRestart() {
+ sInitOnce.mProcessCreation = TimeStamp();
+}
+
+MFBT_API TimeStamp TimeStamp::FirstTimeStamp() {
+ return sInitOnce.mFirstTimeStamp;
+}
+
+class TimeStampTests {
+ // Check that nullity is set/not set correctly.
+ static_assert(TimeStamp{TimeStampValue{0}}.IsNull());
+ static_assert(!TimeStamp{TimeStampValue{1}}.IsNull());
+
+ // Check that some very basic comparisons work correctly.
+ static constexpr uint64_t sMidTime = (uint64_t)1 << 63;
+ static_assert(TimeStampValue{sMidTime + 5} > TimeStampValue{sMidTime - 5});
+ static_assert(TimeStampValue{sMidTime + 5} >= TimeStampValue{sMidTime - 5});
+ static_assert(TimeStampValue{sMidTime - 5} < TimeStampValue{sMidTime + 5});
+ static_assert(TimeStampValue{sMidTime - 5} <= TimeStampValue{sMidTime + 5});
+ static_assert(TimeStampValue{sMidTime} == TimeStampValue{sMidTime});
+ static_assert(TimeStampValue{sMidTime} >= TimeStampValue{sMidTime});
+ static_assert(TimeStampValue{sMidTime} <= TimeStampValue{sMidTime});
+ static_assert(TimeStampValue{sMidTime - 5} != TimeStampValue{sMidTime + 5});
+
+ // Check that comparisons involving very large and very small TimeStampValue's
+ // work correctly. This may seem excessive, but these asserts would have
+ // failed in the past due to a comparison such as "a > b" being implemented as
+ // "<cast to signed 64-bit value>(a - b) > 0". When a-b didn't fit into a
+ // signed 64-bit value, this would have given an incorrect result.
+ static_assert(TimeStampValue{UINT64_MAX} > TimeStampValue{1});
+ static_assert(TimeStampValue{1} < TimeStampValue{UINT64_MAX});
+
+ // NOTE/TODO: It would be nice to add some additional tests here that involve
+ // arithmetic between TimeStamps and TimeDurations (and verifying some of the
+ // special behaviors in some cases such as not wrapping around below zero) but
+ // that is not possible right now because those operators are not constexpr.
+};
+
+} // namespace mozilla