mirror of
https://github.com/mozilla/gecko-dev.git
synced 2024-11-05 08:35:26 +00:00
139 lines
3.6 KiB
C++
139 lines
3.6 KiB
C++
/* -*- 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<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
|