#ifndef __BASE_BITFIELD_HH__
#define __BASE_BITFIELD_HH__
-#include <inttypes.h>
+#include "base/types.hh"
/**
* Generate a 64-bit mask of 'nbits' 1s, right justified.
return (val >> last) & mask(nbits);
}
+/**
+ * Extract the bit from this position from 'val' and right justify it.
+ */
+template <class T>
+inline
+T
+bits(T val, int bit)
+{
+ return bits(val, bit, bit);
+}
+
/**
* Mask off the given bits in place like bits() but without shifting.
* msb = 63, lsb = 0
T
insertBits(T val, int first, int last, B bit_val)
{
+ T t_bit_val = bit_val;
T bmask = mask(first - last + 1) << last;
- return ((bit_val << last) & bmask) | (val & ~bmask);
+ return ((t_bit_val << last) & bmask) | (val & ~bmask);
+}
+
+/**
+ * Overloaded for access to only one bit in value
+ */
+template <class T, class B>
+inline
+T
+insertBits(T val, int bit, B bit_val)
+{
+ return insertBits(val, bit, bit, bit_val);
}
/**
val = insertBits(val, first, last, bit_val);
}
+/** Overloaded function to allow to access only 1 bit*/
+template <class T, class B>
+inline
+void
+replaceBits(T& val, int bit, B bit_val)
+{
+ val = insertBits(val, bit, bit, bit_val);
+}
/**
* Returns the bit position of the MSB that is set in the input
*/
return msb;
}
-// 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;
- }
- };
+/**
+ * Returns the bit position of the LSB that is set in the input
+ */
+inline int
+findLsbSet(uint64_t val) {
+ int lsb = 0;
+ if (!val)
+ return sizeof(val) * 8;
+ if (!bits(val, 31,0)) { lsb += 32; val >>= 32; }
+ if (!bits(val, 15,0)) { lsb += 16; val >>= 16; }
+ if (!bits(val, 7,0)) { lsb += 8; val >>= 8; }
+ if (!bits(val, 3,0)) { lsb += 4; val >>= 4; }
+ if (!bits(val, 1,0)) { lsb += 2; val >>= 2; }
+ if (!bits(val, 0,0)) { lsb += 1; }
+ return lsb;
}
-//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_BITFIELD_HH__
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