michael@0: /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
michael@0: /* vim: set ts=8 sts=2 et sw=2 tw=80: */
michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: /* Helpers to manipulate integer types that don't fit in TypeTraits.h */
michael@0: 
michael@0: #ifndef mozilla_IntegerTypeTraits_h
michael@0: #define mozilla_IntegerTypeTraits_h
michael@0: 
michael@0: #include "mozilla/TypeTraits.h"
michael@0: #include <stdint.h>
michael@0: 
michael@0: namespace mozilla {
michael@0: 
michael@0: namespace detail {
michael@0: 
michael@0: /**
michael@0:  * StdintTypeForSizeAndSignedness returns the stdint integer type
michael@0:  * of given size (can be 1, 2, 4 or 8) and given signedness
michael@0:  * (false means unsigned, true means signed).
michael@0:  */
michael@0: template<size_t Size, bool Signedness>
michael@0: struct StdintTypeForSizeAndSignedness;
michael@0: 
michael@0: template<>
michael@0: struct StdintTypeForSizeAndSignedness<1, true>
michael@0: { typedef int8_t   Type; };
michael@0: 
michael@0: template<>
michael@0: struct StdintTypeForSizeAndSignedness<1, false>
michael@0: { typedef uint8_t  Type; };
michael@0: 
michael@0: template<>
michael@0: struct StdintTypeForSizeAndSignedness<2, true>
michael@0: { typedef int16_t  Type; };
michael@0: 
michael@0: template<>
michael@0: struct StdintTypeForSizeAndSignedness<2, false>
michael@0: { typedef uint16_t Type; };
michael@0: 
michael@0: template<>
michael@0: struct StdintTypeForSizeAndSignedness<4, true>
michael@0: { typedef int32_t  Type; };
michael@0: 
michael@0: template<>
michael@0: struct StdintTypeForSizeAndSignedness<4, false>
michael@0: { typedef uint32_t Type; };
michael@0: 
michael@0: template<>
michael@0: struct StdintTypeForSizeAndSignedness<8, true>
michael@0: { typedef int64_t  Type; };
michael@0: 
michael@0: template<>
michael@0: struct StdintTypeForSizeAndSignedness<8, false>
michael@0: { typedef uint64_t Type; };
michael@0: 
michael@0: } // namespace detail
michael@0: 
michael@0: template<size_t Size>
michael@0: struct UnsignedStdintTypeForSize
michael@0:   : detail::StdintTypeForSizeAndSignedness<Size, false>
michael@0: {};
michael@0: 
michael@0: template<typename IntegerType>
michael@0: struct PositionOfSignBit
michael@0: {
michael@0:   static_assert(IsIntegral<IntegerType>::value, "PositionOfSignBit is only for integral types");
michael@0:   // 8 here should be CHAR_BIT from limits.h, but the world has moved on.
michael@0:   static const size_t value = 8 * sizeof(IntegerType) - 1;
michael@0: };
michael@0: 
michael@0: /**
michael@0:  * MinValue returns the minimum value of the given integer type as a
michael@0:  * compile-time constant, which std::numeric_limits<IntegerType>::min()
michael@0:  * cannot do in c++98.
michael@0:  */
michael@0: template<typename IntegerType>
michael@0: struct MinValue
michael@0: {
michael@0:   private:
michael@0:     static_assert(IsIntegral<IntegerType>::value, "MinValue is only for integral types");
michael@0: 
michael@0:     typedef typename MakeUnsigned<IntegerType>::Type UnsignedIntegerType;
michael@0:     static const size_t PosOfSignBit = PositionOfSignBit<IntegerType>::value;
michael@0: 
michael@0:   public:
michael@0:     // Bitwise ops may return a larger type, that's why we cast explicitly.
michael@0:     // In C++, left bit shifts on signed values is undefined by the standard
michael@0:     // unless the shifted value is representable.
michael@0:     // Notice that signed-to-unsigned conversions are always well-defined in
michael@0:     // the standard as the value congruent to 2**n, as expected. By contrast,
michael@0:     // unsigned-to-signed is only well-defined if the value is representable.
michael@0:     static const IntegerType value =
michael@0:         IsSigned<IntegerType>::value
michael@0:         ? IntegerType(UnsignedIntegerType(1) << PosOfSignBit)
michael@0:         : IntegerType(0);
michael@0: };
michael@0: 
michael@0: /**
michael@0:  * MaxValue returns the maximum value of the given integer type as a
michael@0:  * compile-time constant, which std::numeric_limits<IntegerType>::max()
michael@0:  * cannot do in c++98.
michael@0:  */
michael@0: template<typename IntegerType>
michael@0: struct MaxValue
michael@0: {
michael@0:     static_assert(IsIntegral<IntegerType>::value, "MaxValue is only for integral types");
michael@0: 
michael@0:     // Tricksy, but covered by the CheckedInt unit test.
michael@0:     // Relies on the type of MinValue<IntegerType>::value
michael@0:     // being IntegerType.
michael@0:     static const IntegerType value = ~MinValue<IntegerType>::value;
michael@0: };
michael@0: 
michael@0: } // namespace mozilla
michael@0: 
michael@0: #endif // mozilla_IntegerTypeTraits_h