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authorMatt A. Tobin <mattatobin@localhost.localdomain>2018-02-02 04:16:08 -0500
committerMatt A. Tobin <mattatobin@localhost.localdomain>2018-02-02 04:16:08 -0500
commit5f8de423f190bbb79a62f804151bc24824fa32d8 (patch)
tree10027f336435511475e392454359edea8e25895d /mfbt/Saturate.h
parent49ee0794b5d912db1f95dce6eb52d781dc210db5 (diff)
downloaduxp-5f8de423f190bbb79a62f804151bc24824fa32d8.tar.gz
Add m-esr52 at 52.6.0
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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/. */
+
+/* Provides saturation arithmetics for scalar types. */
+
+#ifndef mozilla_Saturate_h
+#define mozilla_Saturate_h
+
+#include "mozilla/Attributes.h"
+#include "mozilla/Move.h"
+#include "mozilla/TypeTraits.h"
+
+#include <limits>
+
+namespace mozilla {
+namespace detail {
+
+/**
+ * |SaturateOp<T>| wraps scalar values for saturation arithmetics. Usage:
+ *
+ * uint32_t value = 1;
+ *
+ * ++SaturateOp<uint32_t>(value); // value is 2
+ * --SaturateOp<uint32_t>(value); // value is 1
+ * --SaturateOp<uint32_t>(value); // value is 0
+ * --SaturateOp<uint32_t>(value); // value is still 0
+ *
+ * Please add new operators when required.
+ *
+ * |SaturateOp<T>| will saturate at the minimum and maximum values of
+ * type T. If you need other bounds, implement a clamped-type class and
+ * specialize the type traits accordingly.
+ */
+template <typename T>
+class SaturateOp
+{
+public:
+ explicit SaturateOp(T& aValue)
+ : mValue(aValue)
+ {
+ // We should actually check for |std::is_scalar<T>::value| to be
+ // true, but this type trait is not available everywhere. Relax
+ // this assertion if you want to use floating point values as well.
+ static_assert(IsIntegral<T>::value,
+ "Integral type required in instantiation");
+ }
+
+ // Add and subtract operators
+
+ T operator+(const T& aRhs) const
+ {
+ return T(mValue) += aRhs;
+ }
+
+ T operator-(const T& aRhs) const
+ {
+ return T(mValue) -= aRhs;
+ }
+
+ // Compound operators
+
+ const T& operator+=(const T& aRhs) const
+ {
+ const T min = std::numeric_limits<T>::min();
+ const T max = std::numeric_limits<T>::max();
+
+ if (aRhs > static_cast<T>(0)) {
+ mValue = (max - aRhs) < mValue ? max : mValue + aRhs;
+ } else {
+ mValue = (min - aRhs) > mValue ? min : mValue + aRhs;
+ }
+ return mValue;
+ }
+
+ const T& operator-=(const T& aRhs) const
+ {
+ const T min = std::numeric_limits<T>::min();
+ const T max = std::numeric_limits<T>::max();
+
+ if (aRhs > static_cast<T>(0)) {
+ mValue = (min + aRhs) > mValue ? min : mValue - aRhs;
+ } else {
+ mValue = (max + aRhs) < mValue ? max : mValue - aRhs;
+ }
+ return mValue;
+ }
+
+ // Increment and decrement operators
+
+ const T& operator++() const // prefix
+ {
+ return operator+=(static_cast<T>(1));
+ }
+
+ T operator++(int) const // postfix
+ {
+ const T value(mValue);
+ operator++();
+ return value;
+ }
+
+ const T& operator--() const // prefix
+ {
+ return operator-=(static_cast<T>(1));
+ }
+
+ T operator--(int) const // postfix
+ {
+ const T value(mValue);
+ operator--();
+ return value;
+ }
+
+private:
+ SaturateOp(const SaturateOp<T>&) = delete;
+ SaturateOp(SaturateOp<T>&&) = delete;
+ SaturateOp& operator=(const SaturateOp<T>&) = delete;
+ SaturateOp& operator=(SaturateOp<T>&&) = delete;
+
+ T& mValue;
+};
+
+/**
+ * |Saturate<T>| is a value type for saturation arithmetics. It's
+ * build on top of |SaturateOp<T>|.
+ */
+template <typename T>
+class Saturate
+{
+public:
+ Saturate() = default;
+ MOZ_IMPLICIT Saturate(const Saturate<T>&) = default;
+
+ MOZ_IMPLICIT Saturate(Saturate<T>&& aValue)
+ {
+ mValue = Move(aValue.mValue);
+ }
+
+ explicit Saturate(const T& aValue)
+ : mValue(aValue)
+ { }
+
+ const T& value() const
+ {
+ return mValue;
+ }
+
+ // Compare operators
+
+ bool operator==(const Saturate<T>& aRhs) const
+ {
+ return mValue == aRhs.mValue;
+ }
+
+ bool operator!=(const Saturate<T>& aRhs) const
+ {
+ return !operator==(aRhs);
+ }
+
+ bool operator==(const T& aRhs) const
+ {
+ return mValue == aRhs;
+ }
+
+ bool operator!=(const T& aRhs) const
+ {
+ return !operator==(aRhs);
+ }
+
+ // Assignment operators
+
+ Saturate<T>& operator=(const Saturate<T>&) = default;
+
+ Saturate<T>& operator=(Saturate<T>&& aRhs)
+ {
+ mValue = Move(aRhs.mValue);
+ return *this;
+ }
+
+ // Add and subtract operators
+
+ Saturate<T> operator+(const Saturate<T>& aRhs) const
+ {
+ Saturate<T> lhs(mValue);
+ return lhs += aRhs.mValue;
+ }
+
+ Saturate<T> operator+(const T& aRhs) const
+ {
+ Saturate<T> lhs(mValue);
+ return lhs += aRhs;
+ }
+
+ Saturate<T> operator-(const Saturate<T>& aRhs) const
+ {
+ Saturate<T> lhs(mValue);
+ return lhs -= aRhs.mValue;
+ }
+
+ Saturate<T> operator-(const T& aRhs) const
+ {
+ Saturate<T> lhs(mValue);
+ return lhs -= aRhs;
+ }
+
+ // Compound operators
+
+ Saturate<T>& operator+=(const Saturate<T>& aRhs)
+ {
+ SaturateOp<T>(mValue) += aRhs.mValue;
+ return *this;
+ }
+
+ Saturate<T>& operator+=(const T& aRhs)
+ {
+ SaturateOp<T>(mValue) += aRhs;
+ return *this;
+ }
+
+ Saturate<T>& operator-=(const Saturate<T>& aRhs)
+ {
+ SaturateOp<T>(mValue) -= aRhs.mValue;
+ return *this;
+ }
+
+ Saturate<T>& operator-=(const T& aRhs)
+ {
+ SaturateOp<T>(mValue) -= aRhs;
+ return *this;
+ }
+
+ // Increment and decrement operators
+
+ Saturate<T>& operator++() // prefix
+ {
+ ++SaturateOp<T>(mValue);
+ return *this;
+ }
+
+ Saturate<T> operator++(int) // postfix
+ {
+ return Saturate<T>(SaturateOp<T>(mValue)++);
+ }
+
+ Saturate<T>& operator--() // prefix
+ {
+ --SaturateOp<T>(mValue);
+ return *this;
+ }
+
+ Saturate<T> operator--(int) // postfix
+ {
+ return Saturate<T>(SaturateOp<T>(mValue)--);
+ }
+
+private:
+ T mValue;
+};
+
+} // namespace detail
+
+typedef detail::Saturate<int8_t> SaturateInt8;
+typedef detail::Saturate<int16_t> SaturateInt16;
+typedef detail::Saturate<int32_t> SaturateInt32;
+typedef detail::Saturate<uint8_t> SaturateUint8;
+typedef detail::Saturate<uint16_t> SaturateUint16;
+typedef detail::Saturate<uint32_t> SaturateUint32;
+
+} // namespace mozilla
+
+template<typename LhsT, typename RhsT>
+bool
+operator==(LhsT aLhs, const mozilla::detail::Saturate<RhsT>& aRhs)
+{
+ return aRhs.operator==(static_cast<RhsT>(aLhs));
+}
+
+template<typename LhsT, typename RhsT>
+bool
+operator!=(LhsT aLhs, const mozilla::detail::Saturate<RhsT>& aRhs)
+{
+ return !(aLhs == aRhs);
+}
+
+#endif // mozilla_Saturate_h