Move bitunion code into it's own file.

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extra : convert_revision : 8d55ca9645ee4e357b7f4595435542eb72490331

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diff --git a/src/base/bitunion.hh b/src/base/bitunion.hh
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+/*
+ * Copyright (c) 2003-2005 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 <inttypes.h>
+#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 namespace is for classes which implement the backend of the BitUnion
+//stuff. Don't use any of these directly, except for the Bitfield classes in
+//the *BitfieldTypes class(es).
+namespace BitfieldBackend
+{
+    //A base class for all bitfields. It instantiates the actual storage,
+    //and provides getBits and setBits functions for manipulating it. The
+    //Data template parameter is type of the underlying storage.
+    template<class Data>
+    class BitfieldBase
+    {
+      protected:
+        Data __data;
+
+        //This function returns a range of bits from the underlying storage.
+        //It relies on the "bits" function above. It's the user's
+        //responsibility to make sure that there is a properly overloaded
+        //version of this function for whatever type they want to overlay.
+        inline uint64_t
+        getBits(int first, int last) const
+        {
+            return bits(__data, first, last);
+        }
+
+        //Similar to the above, but for settings bits with replaceBits.
+        inline void
+        setBits(int first, int last, uint64_t val)
+        {
+            replaceBits(__data, first, last, val);
+        }
+    };
+
+    //This class contains all the "regular" bitfield classes. It is inherited
+    //by all BitUnions which give them access to those types.
+    template<class Type>
+    class RegularBitfieldTypes
+    {
+      protected:
+        //This class implements ordinary bitfields, that is a span of bits
+        //who's msb is "first", and who's lsb is "last".
+        template<int first, int last=first>
+        class Bitfield : public BitfieldBase<Type>
+        {
+          public:
+            operator uint64_t () const
+            {
+                return this->getBits(first, last);
+            }
+
+            uint64_t
+            operator=(const uint64_t _data)
+            {
+                this->setBits(first, last, _data);
+                return _data;
+            }
+        };
+
+        //A class which specializes the above so that it can only be read
+        //from. This is accomplished explicitly making sure the assignment
+        //operator is blocked. The conversion operator is carried through
+        //inheritance. This will unfortunately need to be copied into each
+        //bitfield type due to limitations with how templates work
+        template<int first, int last=first>
+        class BitfieldRO : public Bitfield<first, last>
+        {
+          private:
+            uint64_t
+            operator=(const uint64_t _data);
+        };
+
+        //Similar to the above, but only allows writing.
+        template<int first, int last=first>
+        class BitfieldWO : public Bitfield<first, last>
+        {
+          private:
+            operator uint64_t () const;
+
+          public:
+            using Bitfield<first, last>::operator=;
+        };
+    };
+
+    //This class contains all the "regular" bitfield classes. It is inherited
+    //by all BitUnions which give them access to those types.
+    template<class Type>
+    class SignedBitfieldTypes
+    {
+      protected:
+        //This class implements ordinary bitfields, that is a span of bits
+        //who's msb is "first", and who's lsb is "last".
+        template<int first, int last=first>
+        class SignedBitfield : public BitfieldBase<Type>
+        {
+          public:
+            operator int64_t () const
+            {
+                return sext<first - last + 1>(this->getBits(first, last));
+            }
+
+            int64_t
+            operator=(const int64_t _data)
+            {
+                this->setBits(first, last, _data);
+                return _data;
+            }
+        };
+
+        //A class which specializes the above so that it can only be read
+        //from. This is accomplished explicitly making sure the assignment
+        //operator is blocked. The conversion operator is carried through
+        //inheritance. This will unfortunately need to be copied into each
+        //bitfield type due to limitations with how templates work
+        template<int first, int last=first>
+        class SignedBitfieldRO : public SignedBitfield<first, last>
+        {
+          private:
+            int64_t
+            operator=(const int64_t _data);
+        };
+
+        //Similar to the above, but only allows writing.
+        template<int first, int last=first>
+        class SignedBitfieldWO : public SignedBitfield<first, last>
+        {
+          private:
+            operator int64_t () const;
+
+          public:
+            int64_t operator=(const int64_t _data)
+            {
+                *((SignedBitfield<first, last> *)this) = _data;
+                return _data;
+            }
+        };
+    };
+
+    template<class Type>
+    class BitfieldTypes : public RegularBitfieldTypes<Type>,
+                          public SignedBitfieldTypes<Type>
+    {};
+
+    //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 Type, class Base>
+    class BitUnionOperators : public Base
+    {
+      public:
+        operator Type () const
+        {
+            return Base::__data;
+        }
+
+        Type
+        operator=(const Type & _data)
+        {
+            Base::__data = _data;
+            return _data;
+        }
+
+        bool
+        operator<(const Base & base) const
+        {
+            return Base::__data < base.__data;
+        }
+
+        bool
+        operator==(const Base & base) const
+        {
+            return Base::__data == base.__data;
+        }
+    };
+}
+
+//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 __DataType. 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 __data 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) \
+    namespace BitfieldUnderlyingClasses \
+    { \
+        class name; \
+    } \
+    class BitfieldUnderlyingClasses::name : \
+        public BitfieldBackend::BitfieldTypes<type> \
+    { \
+      public: \
+        typedef type __DataType; \
+        union { \
+            type __data;\
+
+//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::__DataType, \
+        BitfieldUnderlyingClasses::name> name;
+
+//This sets up a bitfield which has other bitfields nested inside of it. The
+//__data 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(fieldType, first, last, name) \
+    class : public BitfieldBackend::BitfieldTypes<__DataType> \
+    { \
+      public: \
+        union { \
+            fieldType<first, last> __data;
+
+//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 const __DataType () \
+        { return __data; } \
+        \
+        inline const __DataType operator = (const __DataType & _data) \
+        { __data = _data; } \
+    } name;
+
+//Regular bitfields
+//These define macros for read/write regular bitfield based subbitfields.
+#define SubBitUnion(name, first, last) \
+    __SubBitUnion(Bitfield, first, last, name)
+
+//Regular bitfields
+//These define macros for read/write regular bitfield based subbitfields.
+#define SignedSubBitUnion(name, first, last) \
+    __SubBitUnion(SignedBitfield, first, last, name)
+
+//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)
+
+#endif // __BASE_BITUNION_HH__