1 files changed, 432 insertions, 0 deletions
diff --git a/dom/media/TimeUnits.cpp b/dom/media/TimeUnits.cpp
new file mode 100644
index 0000000000..e5865bb3c4
--- /dev/null
+++ b/dom/media/TimeUnits.cpp
@@ -0,0 +1,432 @@
+/* -*- 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/. */
+
+#include <cstdint>
+#include <cmath>
+#include <inttypes.h>
+#include <limits>
+#include <type_traits>
+
+#include "TimeUnits.h"
+#include "Intervals.h"
+#include "mozilla/CheckedInt.h"
+#include "mozilla/FloatingPoint.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/TimeStamp.h"
+#include "mozilla/IntegerPrintfMacros.h"
+#include "nsDebug.h"
+#include "nsPrintfCString.h"
+#include "nsStringFwd.h"
+
+namespace mozilla::media {
+class TimeIntervals;
+}  // namespace mozilla::media
+
+namespace mozilla {
+
+namespace media {
+
+TimeUnit TimeUnit::FromSeconds(double aValue, int64_t aBase) {
+  MOZ_ASSERT(!std::isnan(aValue));
+  MOZ_ASSERT(aBase > 0);
+
+  if (std::isinf(aValue)) {
+    return aValue > 0 ? FromInfinity() : FromNegativeInfinity();
+  }
+  // Warn that a particular value won't be able to be roundtrip at the same
+  // base -- we can keep this for some time until we're confident this is
+  // stable.
+  double inBase = aValue * static_cast<double>(aBase);
+  if (std::abs(inBase) >
+      static_cast<double>(std::numeric_limits<int64_t>::max())) {
+    NS_WARNING(
+        nsPrintfCString("Warning: base %" PRId64
+                        " is too high to represent %lfs, returning Infinity.",
+                        aBase, aValue)
+            .get());
+    if (inBase > 0) {
+      return TimeUnit::FromInfinity();
+    }
+    return TimeUnit::FromNegativeInfinity();
+  }
+
+  // inBase can large enough that it doesn't map to an exact integer, warn in
+  // this case. This happens if aBase is large, and so the loss of precision is
+  // likely small.
+  if (inBase > std::pow(2, std::numeric_limits<double>::digits) - 1) {
+    NS_WARNING(nsPrintfCString("Warning: base %" PRId64
+                               " is too high to represent %lfs accurately.",
+                               aBase, aValue)
+                   .get());
+  }
+  return TimeUnit(static_cast<int64_t>(std::round(inBase)), aBase);
+}
+
+TimeUnit TimeUnit::FromInfinity() { return TimeUnit(INT64_MAX); }
+
+TimeUnit TimeUnit::FromNegativeInfinity() { return TimeUnit(INT64_MIN); }
+
+TimeUnit TimeUnit::FromTimeDuration(const TimeDuration& aDuration) {
+  // This could be made to choose the base
+  return TimeUnit(AssertedCast<int64_t>(aDuration.ToMicroseconds()),
+                  USECS_PER_S);
+}
+
+TimeUnit TimeUnit::Invalid() {
+  TimeUnit ret;
+  ret.mTicks = CheckedInt64(INT64_MAX);
+  // Force an overflow to render the CheckedInt invalid.
+  ret.mTicks += 1;
+  return ret;
+}
+
+int64_t TimeUnit::ToMilliseconds() const { return ToCommonUnit(MSECS_PER_S); }
+
+int64_t TimeUnit::ToMicroseconds() const { return ToCommonUnit(USECS_PER_S); }
+
+int64_t TimeUnit::ToNanoseconds() const { return ToCommonUnit(NSECS_PER_S); }
+
+int64_t TimeUnit::ToTicksAtRate(int64_t aRate) const {
+  // Common case
+  if (aRate == mBase) {
+    return mTicks.value();
+  }
+  // Approximation
+  return mTicks.value() * aRate / mBase;
+}
+
+bool TimeUnit::IsBase(int64_t aBase) const { return aBase == mBase; }
+
+double TimeUnit::ToSeconds() const {
+  if (IsPosInf()) {
+    return PositiveInfinity<double>();
+  }
+  if (IsNegInf()) {
+    return NegativeInfinity<double>();
+  }
+  return static_cast<double>(mTicks.value()) / static_cast<double>(mBase);
+}
+
+nsCString TimeUnit::ToString() const {
+  nsCString dump;
+  if (mTicks.isValid()) {
+    dump += nsPrintfCString("{%" PRId64 ",%" PRId64 "}", mTicks.value(), mBase);
+  } else {
+    dump += nsLiteralCString("{invalid}"_ns);
+  }
+  return dump;
+}
+
+TimeDuration TimeUnit::ToTimeDuration() const {
+  return TimeDuration::FromSeconds(ToSeconds());
+}
+
+bool TimeUnit::IsInfinite() const { return IsPosInf() || IsNegInf(); }
+
+bool TimeUnit::IsPositive() const { return mTicks.value() > 0; }
+
+bool TimeUnit::IsPositiveOrZero() const { return mTicks.value() >= 0; }
+
+bool TimeUnit::IsZero() const { return mTicks.value() == 0; }
+
+bool TimeUnit::IsNegative() const { return mTicks.value() < 0; }
+
+// Returns true if the fractions are equal when converted to the smallest
+// base.
+bool TimeUnit::EqualsAtLowestResolution(const TimeUnit& aOther) const {
+  MOZ_ASSERT(IsValid() && aOther.IsValid());
+  if (aOther.mBase == mBase) {
+    return mTicks == aOther.mTicks;
+  }
+  if (mBase > aOther.mBase) {
+    TimeUnit thisInBase = ToBase(aOther.mBase);
+    return thisInBase.mTicks == aOther.mTicks;
+  }
+  TimeUnit otherInBase = aOther.ToBase(mBase);
+  return otherInBase.mTicks == mTicks;
+}
+
+// Strict equality -- the fractions must be exactly equal
+bool TimeUnit::operator==(const TimeUnit& aOther) const {
+  MOZ_ASSERT(IsValid() && aOther.IsValid());
+  if (aOther.mBase == mBase) {
+    return mTicks == aOther.mTicks;
+  }
+  // debatable mathematically
+  if ((IsPosInf() && aOther.IsPosInf()) || (IsNegInf() && aOther.IsNegInf())) {
+    return true;
+  }
+  if ((IsPosInf() && !aOther.IsPosInf()) ||
+      (IsNegInf() && !aOther.IsNegInf())) {
+    return false;
+  }
+  CheckedInt<int64_t> lhs = mTicks * aOther.mBase;
+  CheckedInt<int64_t> rhs = aOther.mTicks * mBase;
+  if (lhs.isValid() && rhs.isValid()) {
+    return lhs == rhs;
+  }
+  // Reduce the fractions and try again
+  const TimeUnit a = Reduced();
+  const TimeUnit b = aOther.Reduced();
+  lhs = a.mTicks * b.mBase;
+  rhs = b.mTicks * a.mBase;
+
+  if (lhs.isValid() && rhs.isValid()) {
+    return lhs.value() == rhs.value();
+  }
+  // last ditch, convert the reduced fractions to doubles
+  double lhsFloating =
+      static_cast<double>(a.mTicks.value()) * static_cast<double>(a.mBase);
+  double rhsFloating =
+      static_cast<double>(b.mTicks.value()) * static_cast<double>(b.mBase);
+
+  return lhsFloating == rhsFloating;
+}
+bool TimeUnit::operator!=(const TimeUnit& aOther) const {
+  MOZ_ASSERT(IsValid() && aOther.IsValid());
+  return !(aOther == *this);
+}
+bool TimeUnit::operator>=(const TimeUnit& aOther) const {
+  MOZ_ASSERT(IsValid() && aOther.IsValid());
+  if (aOther.mBase == mBase) {
+    return mTicks.value() >= aOther.mTicks.value();
+  }
+  if ((!IsPosInf() && aOther.IsPosInf()) ||
+      (IsNegInf() && !aOther.IsNegInf())) {
+    return false;
+  }
+  if ((IsPosInf() && !aOther.IsPosInf()) ||
+      (!IsNegInf() && aOther.IsNegInf())) {
+    return true;
+  }
+  CheckedInt<int64_t> lhs = mTicks * aOther.mBase;
+  CheckedInt<int64_t> rhs = aOther.mTicks * mBase;
+  if (lhs.isValid() && rhs.isValid()) {
+    return lhs.value() >= rhs.value();
+  }
+  // Reduce the fractions and try again
+  const TimeUnit a = Reduced();
+  const TimeUnit b = aOther.Reduced();
+  lhs = a.mTicks * b.mBase;
+  rhs = b.mTicks * a.mBase;
+
+  if (lhs.isValid() && rhs.isValid()) {
+    return lhs.value() >= rhs.value();
+  }
+  // last ditch, convert the reduced fractions to doubles
+  return ToSeconds() >= aOther.ToSeconds();
+}
+bool TimeUnit::operator>(const TimeUnit& aOther) const {
+  return !(*this <= aOther);
+}
+bool TimeUnit::operator<=(const TimeUnit& aOther) const {
+  MOZ_ASSERT(IsValid() && aOther.IsValid());
+  if (aOther.mBase == mBase) {
+    return mTicks.value() <= aOther.mTicks.value();
+  }
+  if ((!IsPosInf() && aOther.IsPosInf()) ||
+      (IsNegInf() && !aOther.IsNegInf())) {
+    return true;
+  }
+  if ((IsPosInf() && !aOther.IsPosInf()) ||
+      (!IsNegInf() && aOther.IsNegInf())) {
+    return false;
+  }
+  CheckedInt<int64_t> lhs = mTicks * aOther.mBase;
+  CheckedInt<int64_t> rhs = aOther.mTicks * mBase;
+  if (lhs.isValid() && rhs.isValid()) {
+    return lhs.value() <= rhs.value();
+  }
+  // Reduce the fractions and try again
+  const TimeUnit a = Reduced();
+  const TimeUnit b = aOther.Reduced();
+  lhs = a.mTicks * b.mBase;
+  rhs = b.mTicks * a.mBase;
+  if (lhs.isValid() && rhs.isValid()) {
+    return lhs.value() <= rhs.value();
+  }
+  // last ditch, convert the reduced fractions to doubles
+  return ToSeconds() <= aOther.ToSeconds();
+}
+bool TimeUnit::operator<(const TimeUnit& aOther) const {
+  return !(*this >= aOther);
+}
+
+TimeUnit TimeUnit::operator%(const TimeUnit& aOther) const {
+  MOZ_ASSERT(IsValid() && aOther.IsValid());
+  if (aOther.mBase == mBase) {
+    return TimeUnit(mTicks % aOther.mTicks, mBase);
+  }
+  // This path can be made better if need be.
+  double a = ToSeconds();
+  double b = aOther.ToSeconds();
+  return TimeUnit::FromSeconds(fmod(a, b), mBase);
+}
+
+TimeUnit TimeUnit::operator+(const TimeUnit& aOther) const {
+  if (IsInfinite() || aOther.IsInfinite()) {
+    // When adding at least one infinite value, the result is either
+    // +/-Inf, or NaN. So do the calculation in floating point for
+    // simplicity.
+    double result = ToSeconds() + aOther.ToSeconds();
+    return std::isnan(result) ? TimeUnit::Invalid() : FromSeconds(result);
+  }
+  if (aOther.mBase == mBase) {
+    return TimeUnit(mTicks + aOther.mTicks, mBase);
+  }
+  if (aOther.IsZero()) {
+    return *this;
+  }
+  if (IsZero()) {
+    return aOther;
+  }
+
+  double error;
+  TimeUnit inBase = aOther.ToBase(mBase, error);
+  if (error == 0.0) {
+    return *this + inBase;
+  }
+
+  // Last ditch: not exact
+  double a = ToSeconds();
+  double b = aOther.ToSeconds();
+  return TimeUnit::FromSeconds(a + b, mBase);
+}
+
+TimeUnit TimeUnit::operator-(const TimeUnit& aOther) const {
+  if (IsInfinite() || aOther.IsInfinite()) {
+    // When subtracting at least one infinite value, the result is either
+    // +/-Inf, or NaN. So do the calculation in floating point for
+    // simplicity.
+    double result = ToSeconds() - aOther.ToSeconds();
+    return std::isnan(result) ? TimeUnit::Invalid() : FromSeconds(result);
+  }
+  if (aOther.mBase == mBase) {
+    return TimeUnit(mTicks - aOther.mTicks, mBase);
+  }
+  if (aOther.IsZero()) {
+    return *this;
+  }
+
+  if (IsZero()) {
+    return TimeUnit(-aOther.mTicks, aOther.mBase);
+  }
+
+  double error = 0.0;
+  TimeUnit inBase = aOther.ToBase(mBase, error);
+  if (error == 0) {
+    return *this - inBase;
+  }
+
+  // Last ditch: not exact
+  double a = ToSeconds();
+  double b = aOther.ToSeconds();
+  return TimeUnit::FromSeconds(a - b, mBase);
+}
+TimeUnit& TimeUnit::operator+=(const TimeUnit& aOther) {
+  if (aOther.mBase == mBase) {
+    mTicks += aOther.mTicks;
+    return *this;
+  }
+  *this = *this + aOther;
+  return *this;
+}
+TimeUnit& TimeUnit::operator-=(const TimeUnit& aOther) {
+  if (aOther.mBase == mBase) {
+    mTicks -= aOther.mTicks;
+    return *this;
+  }
+  *this = *this - aOther;
+  return *this;
+}
+
+TimeUnit TimeUnit::MultDouble(double aVal) const {
+  double multiplied = AssertedCast<double>(mTicks.value()) * aVal;
+  // Check is the result of the multiplication can be represented exactly as
+  // an integer, in a double.
+  if (multiplied > std::pow(2, std::numeric_limits<double>::digits) - 1) {
+    printf_stderr("TimeUnit tick count after multiplication %" PRId64
+                  " * %lf is too"
+                  " high for the result to be exact",
+                  mTicks.value(), aVal);
+    MOZ_CRASH();
+  }
+  // static_cast is ok, the magnitude of the number has been checked just above.
+  return TimeUnit(static_cast<int64_t>(multiplied), mBase);
+}
+
+bool TimeUnit::IsValid() const { return mTicks.isValid(); }
+
+bool TimeUnit::IsPosInf() const {
+  return mTicks.isValid() && mTicks.value() == INT64_MAX;
+}
+bool TimeUnit::IsNegInf() const {
+  return mTicks.isValid() && mTicks.value() == INT64_MIN;
+}
+
+int64_t TimeUnit::ToCommonUnit(int64_t aRatio) const {
+  CheckedInt<int64_t> rv = mTicks;
+  // Avoid the risk overflowing in common cases, e.g. converting a TimeUnit
+  // with a base of 1e9 back to nanoseconds.
+  if (mBase == aRatio) {
+    return rv.value();
+  }
+  // Avoid overflowing in other common cases, e.g. converting a TimeUnit with
+  // a base of 1e9 to microseconds: the denominator is divisible by the target
+  // unit so we can reorder the computation and keep the number within int64_t
+  // range.
+  if (aRatio < mBase && (mBase % aRatio) == 0) {
+    int64_t exactDivisor = mBase / aRatio;
+    rv /= exactDivisor;
+    return rv.value();
+  }
+  rv *= aRatio;
+  rv /= mBase;
+  if (rv.isValid()) {
+    return rv.value();
+  }
+  // Last ditch, perform the computation in floating point.
+  double ratioFloating = AssertedCast<double>(aRatio);
+  double baseFloating = AssertedCast<double>(mBase);
+  double ticksFloating = static_cast<double>(mTicks.value());
+  double approx = ticksFloating * (ratioFloating / baseFloating);
+  // Clamp to a valid range. If this is clamped it's outside any usable time
+  // value even in nanoseconds (thousands of years).
+  if (approx > static_cast<double>(std::numeric_limits<int64_t>::max())) {
+    return std::numeric_limits<int64_t>::max();
+  }
+  if (approx < static_cast<double>(std::numeric_limits<int64_t>::lowest())) {
+    return std::numeric_limits<int64_t>::lowest();
+  }
+  return static_cast<int64_t>(approx);
+}
+
+// Reduce a TimeUnit to the smallest possible ticks and base. This is useful
+// to comparison with big time values that can otherwise overflow.
+TimeUnit TimeUnit::Reduced() const {
+  int64_t gcd = GCD(mTicks.value(), mBase);
+  return TimeUnit(mTicks.value() / gcd, mBase / gcd);
+}
+
+double RoundToMicrosecondResolution(double aSeconds) {
+  return std::round(aSeconds * USECS_PER_S) / USECS_PER_S;
+}
+
+TimeRanges TimeRanges::ToMicrosecondResolution() const {
+  TimeRanges output;
+
+  for (const auto& interval : mIntervals) {
+    TimeRange reducedPrecision{RoundToMicrosecondResolution(interval.mStart),
+                               RoundToMicrosecondResolution(interval.mEnd),
+                               RoundToMicrosecondResolution(interval.mFuzz)};
+    output += reducedPrecision;
+  }
+  return output;
+}
+
+};  // namespace media
+
+}  // namespace mozilla