/* -*- 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/. */ /* Helpers to manipulate integer types that don't fit in TypeTraits.h */ #ifndef mozilla_IntegerTypeTraits_h #define mozilla_IntegerTypeTraits_h #include "mozilla/TypeTraits.h" #include <stdint.h> namespace mozilla { namespace detail { /** * StdintTypeForSizeAndSignedness returns the stdint integer type * of given size (can be 1, 2, 4 or 8) and given signedness * (false means unsigned, true means signed). */ template<size_t Size, bool Signedness> struct StdintTypeForSizeAndSignedness; template<> struct StdintTypeForSizeAndSignedness<1, true> { typedef int8_t Type; }; template<> struct StdintTypeForSizeAndSignedness<1, false> { typedef uint8_t Type; }; template<> struct StdintTypeForSizeAndSignedness<2, true> { typedef int16_t Type; }; template<> struct StdintTypeForSizeAndSignedness<2, false> { typedef uint16_t Type; }; template<> struct StdintTypeForSizeAndSignedness<4, true> { typedef int32_t Type; }; template<> struct StdintTypeForSizeAndSignedness<4, false> { typedef uint32_t Type; }; template<> struct StdintTypeForSizeAndSignedness<8, true> { typedef int64_t Type; }; template<> struct StdintTypeForSizeAndSignedness<8, false> { typedef uint64_t Type; }; } // namespace detail template<size_t Size> struct UnsignedStdintTypeForSize : detail::StdintTypeForSizeAndSignedness<Size, false> {}; template<size_t Size> struct SignedStdintTypeForSize : detail::StdintTypeForSizeAndSignedness<Size, true> {}; template<typename IntegerType> struct PositionOfSignBit { static_assert(IsIntegral<IntegerType>::value, "PositionOfSignBit is only for integral types"); // 8 here should be CHAR_BIT from limits.h, but the world has moved on. static const size_t value = 8 * sizeof(IntegerType) - 1; }; /** * MinValue returns the minimum value of the given integer type as a * compile-time constant, which std::numeric_limits<IntegerType>::min() * cannot do in c++98. */ template<typename IntegerType> struct MinValue { private: static_assert(IsIntegral<IntegerType>::value, "MinValue is only for integral types"); typedef typename MakeUnsigned<IntegerType>::Type UnsignedIntegerType; static const size_t PosOfSignBit = PositionOfSignBit<IntegerType>::value; public: // Bitwise ops may return a larger type, that's why we cast explicitly. // In C++, left bit shifts on signed values is undefined by the standard // unless the shifted value is representable. // Notice that signed-to-unsigned conversions are always well-defined in // the standard as the value congruent to 2**n, as expected. By contrast, // unsigned-to-signed is only well-defined if the value is representable. static const IntegerType value = IsSigned<IntegerType>::value ? IntegerType(UnsignedIntegerType(1) << PosOfSignBit) : IntegerType(0); }; /** * MaxValue returns the maximum value of the given integer type as a * compile-time constant, which std::numeric_limits<IntegerType>::max() * cannot do in c++98. */ template<typename IntegerType> struct MaxValue { static_assert(IsIntegral<IntegerType>::value, "MaxValue is only for integral types"); // Tricksy, but covered by the CheckedInt unit test. // Relies on the type of MinValue<IntegerType>::value // being IntegerType. static const IntegerType value = ~MinValue<IntegerType>::value; }; } // namespace mozilla #endif // mozilla_IntegerTypeTraits_h