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/*
* Copyright (c) 2007-2008 The Regents of The University of Michigan
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met: redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer;
* redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution;
* neither the name of the copyright holders nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* Authors: Gabe Black
*/
#ifndef __BASE_BITUNION_HH__
#define __BASE_BITUNION_HH__
#include <functional>
#include <type_traits>
#include "base/bitfield.hh"
// The following implements the BitUnion system of defining bitfields
//on top of an underlying class. This is done through the pervasive use of
//both named and unnamed unions which all contain the same actual storage.
//Since they're unioned with each other, all of these storage locations
//overlap. This allows all of the bitfields to manipulate the same data
//without having to have access to each other. More details are provided with
//the individual components.
//This class wraps around another which defines getter/setter functions which
//manipulate the underlying data. The type of the underlying data and the type
//of the bitfield itself are inferred from the argument types of the setter
//function.
template<class Base>
class BitfieldTypeImpl : public Base
{
static_assert(std::is_empty<Base>::value,
"Bitfield base class must be empty.");
private:
struct TypeDeducer
{
template<typename>
struct T;
template<typename C, typename Type1, typename Type2>
struct T<void (C::*)(Type1 &, Type2)>
{
typedef Type1 Storage;
typedef Type2 Type;
};
struct Wrapper : public Base
{
using Base::setter;
};
typedef typename T<decltype(&Wrapper::setter)>::Storage Storage;
typedef typename T<decltype(&Wrapper::setter)>::Type Type;
};
protected:
typedef typename TypeDeducer::Storage Storage;
typedef typename TypeDeducer::Type Type;
Type getter(const Storage &storage) const = delete;
void setter(Storage &storage, Type val) = delete;
Storage __storage;
operator Type () const
{
return Base::getter(__storage);
}
Type
operator=(const Type val)
{
Base::setter(__storage, val);
return val;
}
Type
operator=(BitfieldTypeImpl<Base> const & other)
{
return *this = (Type)other;
}
};
//A wrapper for the above class which allows setting and getting.
template<class Base>
class BitfieldType : public BitfieldTypeImpl<Base>
{
protected:
using Impl = BitfieldTypeImpl<Base>;
using typename Impl::Type;
public:
operator Type () const { return Impl::operator Type(); }
Type operator=(const Type val) { return Impl::operator=(val); }
Type
operator=(BitfieldType<Base> const & other)
{
return Impl::operator=(other);
}
};
//A wrapper which only supports getting.
template<class Base>
class BitfieldROType : public BitfieldTypeImpl<Base>
{
public:
using Impl = BitfieldTypeImpl<Base>;
using typename Impl::Type;
Type operator=(BitfieldROType<Base> const &other) = delete;
operator Type () const { return Impl::operator Type(); }
};
//A wrapper which only supports setting.
template <class Base>
class BitfieldWOType : public BitfieldTypeImpl<Base>
{
protected:
using Impl = BitfieldTypeImpl<Base>;
using typename Impl::Type;
public:
Type operator=(const Type val) { return Impl::operator=(val); }
Type
operator=(BitfieldWOType<Base> const & other)
{
return Impl::operator=(other);
}
};
//This namespace is for classes which implement the backend of the BitUnion
//stuff. Don't use any of these directly.
namespace BitfieldBackend
{
template<class Storage, int first, int last>
class Unsigned
{
static_assert(first >= last,
"Bitfield ranges must be specified as <msb, lsb>");
protected:
uint64_t
getter(const Storage &storage) const
{
return bits(storage, first, last);
}
void
setter(Storage &storage, uint64_t val)
{
replaceBits(storage, first, last, val);
}
};
template<class Storage, int first, int last>
class Signed
{
static_assert(first >= last,
"Bitfield ranges must be specified as <msb, lsb>");
protected:
int64_t
getter(const Storage &storage) const
{
return sext<first - last + 1>(bits(storage, first, last));
}
void
setter(Storage &storage, int64_t val)
{
replaceBits(storage, first, last, val);
}
};
//This class contains the basic bitfield types which are automatically
//available within a BitUnion. They inherit their Storage type from the
//containing BitUnion.
template<class Storage>
class BitfieldTypes
{
protected:
template<int first, int last=first>
using Bitfield = BitfieldType<Unsigned<Storage, first, last> >;
template<int first, int last=first>
using BitfieldRO =
BitfieldROType<Unsigned<Storage, first, last> >;
template<int first, int last=first>
using BitfieldWO =
BitfieldWOType<Unsigned<Storage, first, last> >;
template<int first, int last=first>
using SignedBitfield =
BitfieldType<Signed<Storage, first, last> >;
template<int first, int last=first>
using SignedBitfieldRO =
BitfieldROType<Signed<Storage, first, last> >;
template<int first, int last=first>
using SignedBitfieldWO =
BitfieldWOType<Signed<Storage, first, last> >;
};
//When a BitUnion is set up, an underlying class is created which holds
//the actual union. This class then inherits from it, and provids the
//implementations for various operators. Setting things up this way
//prevents having to redefine these functions in every different BitUnion
//type. More operators could be implemented in the future, as the need
//arises.
template <class Base>
class BitUnionOperators : public Base
{
static_assert(sizeof(Base) == sizeof(typename Base::__StorageType),
"BitUnion larger than its storage type.");
public:
BitUnionOperators(typename Base::__StorageType const &val)
{
Base::__storage = val;
}
BitUnionOperators() {}
operator const typename Base::__StorageType () const
{
return Base::__storage;
}
typename Base::__StorageType
operator=(typename Base::__StorageType const &val)
{
Base::__storage = val;
return val;
}
typename Base::__StorageType
operator=(BitUnionOperators const &other)
{
Base::__storage = other;
return Base::__storage;
}
bool
operator<(Base const &base) const
{
return Base::__storage < base.__storage;
}
bool
operator==(Base const &base) const
{
return Base::__storage == base.__storage;
}
};
}
//This macro is a backend for other macros that specialize it slightly.
//First, it creates/extends a namespace "BitfieldUnderlyingClasses" and
//sticks the class which has the actual union in it, which
//BitfieldOperators above inherits from. Putting these classes in a special
//namespace ensures that there will be no collisions with other names as long
//as the BitUnion names themselves are all distinct and nothing else uses
//the BitfieldUnderlyingClasses namespace, which is unlikely. The class itself
//creates a typedef of the "type" parameter called __StorageType. This allows
//the type to propagate outside of the macro itself in a controlled way.
//Finally, the base storage is defined which BitfieldOperators will refer to
//in the operators it defines. This macro is intended to be followed by
//bitfield definitions which will end up inside it's union. As explained
//above, these is overlayed the __storage member in its entirety by each of the
//bitfields which are defined in the union, creating shared storage with no
//overhead.
#define __BitUnion(type, name) \
class BitfieldUnderlyingClasses##name : \
public BitfieldBackend::BitfieldTypes<type> \
{ \
protected: \
typedef type __StorageType; \
friend BitfieldBackend::BitUnionBaseType< \
BitfieldBackend::BitUnionOperators< \
BitfieldUnderlyingClasses##name> >; \
friend BitfieldBackend::BitUnionBaseType< \
BitfieldUnderlyingClasses##name>; \
public: \
union { \
type __storage;
//This closes off the class and union started by the above macro. It is
//followed by a typedef which makes "name" refer to a BitfieldOperator
//class inheriting from the class and union just defined, which completes
//building up the type for the user.
#define EndBitUnion(name) \
}; \
}; \
typedef BitfieldBackend::BitUnionOperators< \
BitfieldUnderlyingClasses##name> name;
//This sets up a bitfield which has other bitfields nested inside of it. The
//__storage member functions like the "underlying storage" of the top level
//BitUnion. Like everything else, it overlays with the top level storage, so
//making it a regular bitfield type makes the entire thing function as a
//regular bitfield when referred to by itself.
#define __SubBitUnion(name, fieldType, ...) \
class \
{ \
public: \
union { \
fieldType<__VA_ARGS__> __storage;
//This closes off the union created above and gives it a name. Unlike the top
//level BitUnion, we're interested in creating an object instead of a type.
//The operators are defined in the macro itself instead of a class for
//technical reasons. If someone determines a way to move them to one, please
//do so.
#define EndSubBitUnion(name) \
}; \
inline operator __StorageType () const \
{ return __storage; } \
\
inline __StorageType operator = (const __StorageType & _storage) \
{ return __storage = _storage;} \
} name;
//Regular bitfields
//These define macros for read/write regular bitfield based subbitfields.
#define SubBitUnion(name, first, last) \
__SubBitUnion(name, Bitfield, first, last)
//Regular bitfields
//These define macros for read/write regular bitfield based subbitfields.
#define SignedSubBitUnion(name, first, last) \
__SubBitUnion(name, SignedBitfield, first, last)
//Use this to define an arbitrary type overlayed with bitfields.
#define BitUnion(type, name) __BitUnion(type, name)
//Use this to define conveniently sized values overlayed with bitfields.
#define BitUnion64(name) __BitUnion(uint64_t, name)
#define BitUnion32(name) __BitUnion(uint32_t, name)
#define BitUnion16(name) __BitUnion(uint16_t, name)
#define BitUnion8(name) __BitUnion(uint8_t, name)
//These templates make it possible to define other templates related to
//BitUnions without having to refer to internal typedefs or the BitfieldBackend
//namespace.
//To build a template specialization which works for all BitUnions, accept a
//template argument T, and then use BitUnionType<T> as an argument in the
//template. To refer to the basic type the BitUnion wraps, use
//BitUnionBaseType<T>.
//For example:
//template <typename T>
//void func(BitUnionType<T> u) { BitUnionBaseType<T> b = u; }
//Also, BitUnionBaseType can be used on a BitUnion type directly.
template <typename T>
using BitUnionType = BitfieldBackend::BitUnionOperators<T>;
namespace BitfieldBackend
{
template<typename T>
struct BitUnionBaseType
{
typedef typename BitUnionType<T>::__StorageType Type;
};
template<typename T>
struct BitUnionBaseType<BitUnionType<T> >
{
typedef typename BitUnionType<T>::__StorageType Type;
};
}
template <typename T>
using BitUnionBaseType = typename BitfieldBackend::BitUnionBaseType<T>::Type;
//An STL style hash structure for hashing BitUnions based on their base type.
namespace std
{
template <typename T>
struct hash<BitUnionType<T> > : public hash<BitUnionBaseType<T> >
{
size_t
operator() (const BitUnionType<T> &val) const
{
return hash<BitUnionBaseType<T> >::operator()(val);
}
};
}
#endif // __BASE_BITUNION_HH__