}
// The following implements the BitUnion system of defining bitfields
-//on top of an underlying class. This is done through the extensive use of
+//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 know about each other. More details are provided with the
+//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 this directly! Use the macros at the end instead.
+//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,
}
};
- //A class which specializes a given base so that it can only be read
- //from. This is accomplished by only passing through the conversion
- //operator and explicitly making sure the assignment operator is blocked.
- template<class Type, class Base>
- class _BitfieldRO : public Base
+ //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
{
- private:
- const Type
- operator=(const Type & _data);
-
- public:
- operator const Type ()
+ 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>
{
- return *((Base *)this);
- }
- };
-
- //Similar to the above, but only allows writing.
- template<class Type, class Base>
- class _BitfieldWO : public Base
- {
- private:
- operator const Type ();
-
- public:
- const Type operator=(const Type & _data)
+ public:
+ operator const Type ()
+ {
+ return this->getBits(first, last);
+ }
+
+ const Type
+ operator=(const Type & _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>
{
- *((Base *)this) = _data;
- return _data;
- }
- };
-
- //This class implements ordinary bitfields, that is a span of bits
- //who's msb is "first", and who's lsb is "last".
- template<class Data, int first, int last=first>
- class _Bitfield : public BitfieldBase<Data>
- {
- public:
- operator const Data ()
- {
- return this->getBits(first, last);
- }
-
- const Data
- operator=(const Data & _data)
+ private:
+ const Type
+ operator=(const Type & _data);
+ };
+
+ //Similar to the above, but only allows writing.
+ template<int first, int last=first>
+ class BitfieldWO : public Bitfield<first, last>
{
- this->setBits(first, last, _data);
- return _data;
- }
+ private:
+ operator const Type ();
+
+ public:
+ const Type operator=(const Type & _data)
+ {
+ *((Bitfield<first, last> *)this) = _data;
+ return _data;
+ }
+ };
};
+ template<class Type>
+ class BitfieldTypes : public RegularBitfieldTypes<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
{ \
class name; \
} \
- class BitfieldUnderlyingClasses::name { \
+ class BitfieldUnderlyingClasses::name : \
+ public BitfieldBackend::BitfieldTypes<type> \
+ { \
public: \
typedef type __DataType; \
union { \
//__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. 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 __SubBitUnion(type, name) \
+//regular bitfield when referred to by itself.
+#define __SubBitUnion(fieldType, first, last, name) \
+ class : public BitfieldBackend::BitfieldTypes<__DataType> \
+ { \
+ public: \
union { \
- type __data; \
- inline operator const __DataType () \
- { return __data; } \
- \
- inline const __DataType operator = (const __DataType & _data) \
- { __data = _data; }
+ 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.
-#define EndSubBitUnion(name) } name;
-
-//The preprocessor will treat everything inside of parenthesis as a single
-//argument even if it has commas in it. This is used to pass in templated
-//classes which typically have commas to seperate their parameters.
-#define wrap(guts) guts
-
-//Read only bitfields
-//This wraps another bitfield class inside a _BitfieldRO class using
-//inheritance. As explained above, the _BitfieldRO class only passes through
-//the conversion operator, so the underlying bitfield can then only be read
-//from.
-#define __BitfieldRO(base) \
- BitfieldBackend::_BitfieldRO<__DataType, base>
-#define __SubBitUnionRO(name, base) \
- __SubBitUnion(wrap(_BitfieldRO<__DataType, base>), name)
-
-//Write only bitfields
-//Similar to above, but for making write only versions of bitfields with
-//_BitfieldWO.
-#define __BitfieldWO(base) \
- BitfieldBackend::_BitfieldWO<__DataType, base>
-#define __SubBitUnionWO(name, base) \
- __SubBitUnion(wrap(_BitfieldWO<__DataType, base>), name)
+//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
-//This uses all of the above to define macros for read/write, read only, and
-//write only versions of regular bitfields.
-#define Bitfield(first, last) \
- BitfieldBackend::_Bitfield<__DataType, first, last>
+//These define macros for read/write regular bitfield based subbitfields.
#define SubBitUnion(name, first, last) \
- __SubBitUnion(Bitfield(first, last), name)
-#define BitfieldRO(first, last) __BitfieldRO(Bitfield(first, last))
-#define SubBitUnionRO(name, first, last) \
- __SubBitUnionRO(Bitfield(first, last), name)
-#define BitfieldWO(first, last) __BitfieldWO(Bitfield(first, last))
-#define SubBitUnionWO(name, first, last) \
- __SubBitUnionWO(Bitfield(first, last), name)
+ __SubBitUnion(Bitfield, first, last, name)
//Use this to define an arbitrary type overlayed with bitfields.
#define BitUnion(type, name) __BitUnion(type, name)
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