a928a438b8
Used cppclean to help identify useless includes and removed them. This involved erroneously included headers, but also cases where forward declarations could have been used rather than a full include.
333 lines
12 KiB
C++
333 lines
12 KiB
C++
/*
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* Copyright (c) 2007-2008 The Regents of The University of Michigan
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are
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* met: redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer;
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* redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution;
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* neither the name of the copyright holders nor the names of its
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* contributors may be used to endorse or promote products derived from
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* this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* Authors: Gabe Black
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*/
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#ifndef __BASE_BITUNION_HH__
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#define __BASE_BITUNION_HH__
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#include "base/bitfield.hh"
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// The following implements the BitUnion system of defining bitfields
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//on top of an underlying class. This is done through the pervasive use of
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//both named and unnamed unions which all contain the same actual storage.
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//Since they're unioned with each other, all of these storage locations
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//overlap. This allows all of the bitfields to manipulate the same data
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//without having to have access to each other. More details are provided with
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//the individual components.
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//This namespace is for classes which implement the backend of the BitUnion
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//stuff. Don't use any of these directly, except for the Bitfield classes in
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//the *BitfieldTypes class(es).
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namespace BitfieldBackend
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{
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//A base class for all bitfields. It instantiates the actual storage,
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//and provides getBits and setBits functions for manipulating it. The
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//Data template parameter is type of the underlying storage.
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template<class Data>
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class BitfieldBase
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{
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protected:
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Data __data;
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//This function returns a range of bits from the underlying storage.
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//It relies on the "bits" function above. It's the user's
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//responsibility to make sure that there is a properly overloaded
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//version of this function for whatever type they want to overlay.
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inline uint64_t
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getBits(int first, int last) const
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{
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return bits(__data, first, last);
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}
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//Similar to the above, but for settings bits with replaceBits.
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inline void
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setBits(int first, int last, uint64_t val)
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{
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replaceBits(__data, first, last, val);
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}
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};
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//This class contains all the "regular" bitfield classes. It is inherited
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//by all BitUnions which give them access to those types.
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template<class Type>
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class RegularBitfieldTypes
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{
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protected:
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//This class implements ordinary bitfields, that is a span of bits
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//who's msb is "first", and who's lsb is "last".
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template<int first, int last=first>
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class Bitfield : public BitfieldBase<Type>
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{
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static_assert(first >= last,
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"Bitfield ranges must be specified as <msb, lsb>");
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public:
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operator uint64_t () const
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{
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return this->getBits(first, last);
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}
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uint64_t
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operator=(const uint64_t _data)
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{
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this->setBits(first, last, _data);
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return _data;
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}
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uint64_t
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operator=(Bitfield<first, last> const & other)
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{
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return *this = (uint64_t)other;
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}
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};
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//A class which specializes the above so that it can only be read
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//from. This is accomplished explicitly making sure the assignment
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//operator is blocked. The conversion operator is carried through
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//inheritance. This will unfortunately need to be copied into each
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//bitfield type due to limitations with how templates work
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template<int first, int last=first>
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class BitfieldRO : public Bitfield<first, last>
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{
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private:
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uint64_t
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operator=(const uint64_t _data);
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uint64_t
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operator=(const Bitfield<first, last>& other);
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};
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//Similar to the above, but only allows writing.
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template<int first, int last=first>
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class BitfieldWO : public Bitfield<first, last>
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{
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private:
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operator uint64_t () const;
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public:
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using Bitfield<first, last>::operator=;
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};
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};
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//This class contains all the "regular" bitfield classes. It is inherited
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//by all BitUnions which give them access to those types.
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template<class Type>
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class SignedBitfieldTypes
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{
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protected:
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//This class implements ordinary bitfields, that is a span of bits
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//who's msb is "first", and who's lsb is "last".
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template<int first, int last=first>
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class SignedBitfield : public BitfieldBase<Type>
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{
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public:
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operator int64_t () const
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{
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return sext<first - last + 1>(this->getBits(first, last));
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}
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int64_t
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operator=(const int64_t _data)
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{
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this->setBits(first, last, _data);
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return _data;
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}
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int64_t
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operator=(SignedBitfield<first, last> const & other)
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{
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return *this = (int64_t)other;
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}
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};
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//A class which specializes the above so that it can only be read
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//from. This is accomplished explicitly making sure the assignment
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//operator is blocked. The conversion operator is carried through
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//inheritance. This will unfortunately need to be copied into each
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//bitfield type due to limitations with how templates work
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template<int first, int last=first>
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class SignedBitfieldRO : public SignedBitfield<first, last>
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{
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private:
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int64_t
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operator=(const int64_t _data);
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int64_t
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operator=(const SignedBitfield<first, last>& other);
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};
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//Similar to the above, but only allows writing.
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template<int first, int last=first>
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class SignedBitfieldWO : public SignedBitfield<first, last>
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{
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private:
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operator int64_t () const;
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public:
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using SignedBitfield<first, last>::operator=;
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};
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};
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template<class Type>
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class BitfieldTypes : public RegularBitfieldTypes<Type>,
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public SignedBitfieldTypes<Type>
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{};
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//When a BitUnion is set up, an underlying class is created which holds
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//the actual union. This class then inherits from it, and provids the
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//implementations for various operators. Setting things up this way
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//prevents having to redefine these functions in every different BitUnion
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//type. More operators could be implemented in the future, as the need
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//arises.
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template <class Type, class Base>
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class BitUnionOperators : public Base
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{
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public:
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BitUnionOperators(Type const & _data)
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{
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Base::__data = _data;
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}
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BitUnionOperators() {}
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operator const Type () const
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{
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return Base::__data;
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}
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Type
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operator=(Type const & _data)
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{
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Base::__data = _data;
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return _data;
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}
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Type
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operator=(BitUnionOperators const & other)
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{
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Base::__data = other;
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return Base::__data;
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}
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bool
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operator<(Base const & base) const
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{
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return Base::__data < base.__data;
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}
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bool
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operator==(Base const & base) const
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{
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return Base::__data == base.__data;
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}
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};
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}
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//This macro is a backend for other macros that specialize it slightly.
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//First, it creates/extends a namespace "BitfieldUnderlyingClasses" and
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//sticks the class which has the actual union in it, which
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//BitfieldOperators above inherits from. Putting these classes in a special
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//namespace ensures that there will be no collisions with other names as long
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//as the BitUnion names themselves are all distinct and nothing else uses
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//the BitfieldUnderlyingClasses namespace, which is unlikely. The class itself
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//creates a typedef of the "type" parameter called __DataType. This allows
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//the type to propagate outside of the macro itself in a controlled way.
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//Finally, the base storage is defined which BitfieldOperators will refer to
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//in the operators it defines. This macro is intended to be followed by
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//bitfield definitions which will end up inside it's union. As explained
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//above, these is overlayed the __data member in its entirety by each of the
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//bitfields which are defined in the union, creating shared storage with no
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//overhead.
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#define __BitUnion(type, name) \
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class BitfieldUnderlyingClasses##name : \
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public BitfieldBackend::BitfieldTypes<type> \
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{ \
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public: \
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typedef type __DataType; \
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union { \
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type __data;\
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//This closes off the class and union started by the above macro. It is
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//followed by a typedef which makes "name" refer to a BitfieldOperator
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//class inheriting from the class and union just defined, which completes
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//building up the type for the user.
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#define EndBitUnion(name) \
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}; \
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}; \
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typedef BitfieldBackend::BitUnionOperators< \
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BitfieldUnderlyingClasses##name::__DataType, \
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BitfieldUnderlyingClasses##name> name;
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//This sets up a bitfield which has other bitfields nested inside of it. The
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//__data member functions like the "underlying storage" of the top level
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//BitUnion. Like everything else, it overlays with the top level storage, so
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//making it a regular bitfield type makes the entire thing function as a
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//regular bitfield when referred to by itself.
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#define __SubBitUnion(fieldType, first, last, name) \
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class : public BitfieldBackend::BitfieldTypes<__DataType> \
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{ \
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public: \
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union { \
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fieldType<first, last> __data;
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//This closes off the union created above and gives it a name. Unlike the top
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//level BitUnion, we're interested in creating an object instead of a type.
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//The operators are defined in the macro itself instead of a class for
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//technical reasons. If someone determines a way to move them to one, please
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//do so.
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#define EndSubBitUnion(name) \
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}; \
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inline operator __DataType () const \
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{ return __data; } \
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\
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inline __DataType operator = (const __DataType & _data) \
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{ return __data = _data;} \
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} name;
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//Regular bitfields
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//These define macros for read/write regular bitfield based subbitfields.
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#define SubBitUnion(name, first, last) \
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__SubBitUnion(Bitfield, first, last, name)
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//Regular bitfields
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//These define macros for read/write regular bitfield based subbitfields.
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#define SignedSubBitUnion(name, first, last) \
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__SubBitUnion(SignedBitfield, first, last, name)
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//Use this to define an arbitrary type overlayed with bitfields.
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#define BitUnion(type, name) __BitUnion(type, name)
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//Use this to define conveniently sized values overlayed with bitfields.
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#define BitUnion64(name) __BitUnion(uint64_t, name)
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#define BitUnion32(name) __BitUnion(uint32_t, name)
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#define BitUnion16(name) __BitUnion(uint16_t, name)
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#define BitUnion8(name) __BitUnion(uint8_t, name)
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#endif // __BASE_BITUNION_HH__
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