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// Copyright Catch2 Authors
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE.txt or copy at
// https://www.boost.org/LICENSE_1_0.txt)
// SPDX-License-Identifier: BSL-1.0
#ifndef CATCH_RANDOM_INTEGER_HELPERS_HPP_INCLUDED
#define CATCH_RANDOM_INTEGER_HELPERS_HPP_INCLUDED
#include <climits>
#include <cstddef>
#include <cstdint>
#include <type_traits>
// Note: We use the usual enable-disable-autodetect dance here even though
// we do not support these in CMake configuration options (yet?).
// It is highly unlikely that we will need to make these actually
// user-configurable, but this will make it simpler if weend up needing
// it, and it provides an escape hatch to the users who need it.
#if defined( __SIZEOF_INT128__ )
# define CATCH_CONFIG_INTERNAL_UINT128
// Unlike GCC, MSVC does not polyfill umul as mulh + mul pair on ARM machines.
// Currently we do not bother doing this ourselves, but we could if it became
// important for perf.
#elif defined( _MSC_VER ) && defined( _M_X64 )
# define CATCH_CONFIG_INTERNAL_MSVC_UMUL128
#endif
#if defined( CATCH_CONFIG_INTERNAL_UINT128 ) && \
!defined( CATCH_CONFIG_NO_UINT128 ) && \
!defined( CATCH_CONFIG_UINT128 )
#define CATCH_CONFIG_UINT128
#endif
#if defined( CATCH_CONFIG_INTERNAL_MSVC_UMUL128 ) && \
!defined( CATCH_CONFIG_NO_MSVC_UMUL128 ) && \
!defined( CATCH_CONFIG_MSVC_UMUL128 )
# define CATCH_CONFIG_MSVC_UMUL128
# include <intrin.h>
#endif
namespace Catch {
namespace Detail {
template <std::size_t>
struct SizedUnsignedType;
#define SizedUnsignedTypeHelper( TYPE ) \
template <> \
struct SizedUnsignedType<sizeof( TYPE )> { \
using type = TYPE; \
}
SizedUnsignedTypeHelper( std::uint8_t );
SizedUnsignedTypeHelper( std::uint16_t );
SizedUnsignedTypeHelper( std::uint32_t );
SizedUnsignedTypeHelper( std::uint64_t );
#undef SizedUnsignedTypeHelper
template <std::size_t sz>
using SizedUnsignedType_t = typename SizedUnsignedType<sz>::type;
template <typename T>
using DoubleWidthUnsignedType_t = SizedUnsignedType_t<2 * sizeof( T )>;
template <typename T>
struct ExtendedMultResult {
T upper;
T lower;
constexpr bool operator==( ExtendedMultResult const& rhs ) const {
return upper == rhs.upper && lower == rhs.lower;
}
};
/**
* Returns 128 bit result of lhs * rhs using portable C++ code
*
* This implementation is almost twice as fast as naive long multiplication,
* and unlike intrinsic-based approach, it supports constexpr evaluation.
*/
constexpr ExtendedMultResult<std::uint64_t>
extendedMultPortable(std::uint64_t lhs, std::uint64_t rhs) {
#define CarryBits( x ) ( x >> 32 )
#define Digits( x ) ( x & 0xFF'FF'FF'FF )
std::uint64_t lhs_low = Digits( lhs );
std::uint64_t rhs_low = Digits( rhs );
std::uint64_t low_low = ( lhs_low * rhs_low );
std::uint64_t high_high = CarryBits( lhs ) * CarryBits( rhs );
// We add in carry bits from low-low already
std::uint64_t high_low =
( CarryBits( lhs ) * rhs_low ) + CarryBits( low_low );
// Note that we can add only low bits from high_low, to avoid
// overflow with large inputs
std::uint64_t low_high =
( lhs_low * CarryBits( rhs ) ) + Digits( high_low );
return { high_high + CarryBits( high_low ) + CarryBits( low_high ),
( low_high << 32 ) | Digits( low_low ) };
#undef CarryBits
#undef Digits
}
//! Returns 128 bit result of lhs * rhs
inline ExtendedMultResult<std::uint64_t>
extendedMult( std::uint64_t lhs, std::uint64_t rhs ) {
#if defined( CATCH_CONFIG_UINT128 )
auto result = __uint128_t( lhs ) * __uint128_t( rhs );
return { static_cast<std::uint64_t>( result >> 64 ),
static_cast<std::uint64_t>( result ) };
#elif defined( CATCH_CONFIG_MSVC_UMUL128 )
std::uint64_t high;
std::uint64_t low = _umul128( lhs, rhs, &high );
return { high, low };
#else
return extendedMultPortable( lhs, rhs );
#endif
}
template <typename UInt>
constexpr ExtendedMultResult<UInt> extendedMult( UInt lhs, UInt rhs ) {
static_assert( std::is_unsigned<UInt>::value,
"extendedMult can only handle unsigned integers" );
static_assert( sizeof( UInt ) < sizeof( std::uint64_t ),
"Generic extendedMult can only handle types smaller "
"than uint64_t" );
using WideType = DoubleWidthUnsignedType_t<UInt>;
auto result = WideType( lhs ) * WideType( rhs );
return {
static_cast<UInt>( result >> ( CHAR_BIT * sizeof( UInt ) ) ),
static_cast<UInt>( result & UInt( -1 ) ) };
}
template <typename TargetType,
typename Generator>
std::enable_if_t<sizeof(typename Generator::result_type) >= sizeof(TargetType),
TargetType> fillBitsFrom(Generator& gen) {
using gresult_type = typename Generator::result_type;
static_assert( std::is_unsigned<TargetType>::value, "Only unsigned integers are supported" );
static_assert( Generator::min() == 0 &&
Generator::max() == static_cast<gresult_type>( -1 ),
"Generator must be able to output all numbers in its result type (effectively it must be a random bit generator)" );
// We want to return the top bits from a generator, as they are
// usually considered higher quality.
constexpr auto generated_bits = sizeof( gresult_type ) * CHAR_BIT;
constexpr auto return_bits = sizeof( TargetType ) * CHAR_BIT;
return static_cast<TargetType>( gen() >>
( generated_bits - return_bits) );
}
template <typename TargetType,
typename Generator>
std::enable_if_t<sizeof(typename Generator::result_type) < sizeof(TargetType),
TargetType> fillBitsFrom(Generator& gen) {
using gresult_type = typename Generator::result_type;
static_assert( std::is_unsigned<TargetType>::value,
"Only unsigned integers are supported" );
static_assert( Generator::min() == 0 &&
Generator::max() == static_cast<gresult_type>( -1 ),
"Generator must be able to output all numbers in its result type (effectively it must be a random bit generator)" );
constexpr auto generated_bits = sizeof( gresult_type ) * CHAR_BIT;
constexpr auto return_bits = sizeof( TargetType ) * CHAR_BIT;
std::size_t filled_bits = 0;
TargetType ret = 0;
do {
ret <<= generated_bits;
ret |= gen();
filled_bits += generated_bits;
} while ( filled_bits < return_bits );
return ret;
}
/*
* Transposes numbers into unsigned type while keeping their ordering
*
* This means that signed types are changed so that the ordering is
* [INT_MIN, ..., -1, 0, ..., INT_MAX], rather than order we would
* get by simple casting ([0, ..., INT_MAX, INT_MIN, ..., -1])
*/
template <typename OriginalType, typename UnsignedType>
constexpr
std::enable_if_t<std::is_signed<OriginalType>::value, UnsignedType>
transposeToNaturalOrder( UnsignedType in ) {
static_assert(
sizeof( OriginalType ) == sizeof( UnsignedType ),
"reordering requires the same sized types on both sides" );
static_assert( std::is_unsigned<UnsignedType>::value,
"Input type must be unsigned" );
// Assuming 2s complement (standardized in current C++), the
// positive and negative numbers are already internally ordered,
// and their difference is in the top bit. Swapping it orders
// them the desired way.
constexpr auto highest_bit =
UnsignedType( 1 ) << ( sizeof( UnsignedType ) * CHAR_BIT - 1 );
return static_cast<UnsignedType>( in ^ highest_bit );
}
template <typename OriginalType,
typename UnsignedType>
constexpr
std::enable_if_t<std::is_unsigned<OriginalType>::value, UnsignedType>
transposeToNaturalOrder(UnsignedType in) {
static_assert(
sizeof( OriginalType ) == sizeof( UnsignedType ),
"reordering requires the same sized types on both sides" );
static_assert( std::is_unsigned<UnsignedType>::value, "Input type must be unsigned" );
// No reordering is needed for unsigned -> unsigned
return in;
}
} // namespace Detail
} // namespace Catch
#endif // CATCH_RANDOM_INTEGER_HELPERS_HPP_INCLUDED
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