Mirror of roytam1's UXP fork just in case Moonchild and Tobin decide to go after him
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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/. */
/* 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