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authorDaniel Wilhelm <daniel@wili.li>2014-04-18 17:01:29 +0200
committerDaniel Wilhelm <daniel@wili.li>2014-04-18 17:01:29 +0200
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+////////////////////////////////////////////////////////////////////////////////
+// The Loki Library
+// Copyright (c) 2009 by Fedor Pikus & Rich Sposato
+// The copyright on this file is protected under the terms of the MIT license.
+//
+// Permission to use, copy, modify, distribute and sell this software for any
+// purpose is hereby granted without fee, provided that the above copyright
+// notice appear in all copies and that both that copyright notice and this
+// permission notice appear in supporting documentation.
+//
+// The author makes no claims about the suitability of this software for any
+// purpose. It is provided "as is" without express or implied warranty.
+////////////////////////////////////////////////////////////////////////////////
+
+// $Id$
+
+
+#ifndef LOKI_INCLUDED_SAFE_BIT_FIELDS_H
+#define LOKI_INCLUDED_SAFE_BIT_FIELDS_H
+
+#include <cstdlib>
+#include <assert.h>
+#include <loki/static_check.h>
+
+
+namespace Loki
+{
+
+/*
+ ==========================================================================================================================================
+ SafeBitField - type-safe class for bit fields.
+ SafeBitConst - type-safe class for bit constants.
+ SafeBitField is designed to be a [almost] drop-in replacement for integer flags and bit fields where individual bits are set and checked
+ using symbolic names for flags:
+
+ typedef unsigned long Labels_t;
+ Labels_t labels;
+ const Labels_t Label_A = 0x00000001;
+ const Labels_t Label_B = 0x00000002;
+ ...
+ labels |= Label_B;
+ if ( labels & Label_A ) { ... }
+
+ Such code offers no protection against mismatching bit constants and bit fields:
+
+ typedef unsigned long Kinds_t;
+ Kinds_t kinds;
+ const Kinds_t Kind_A = 0x00000004;
+ ...
+ if ( kinds & Label_A ) { ... } // Error but compiles
+
+ SafeBitField is a drop-in replacement which generates a unique type for each bit field. Bit fields of different types cannot be applied
+ to each other:
+
+ LOKI_BIT_FIELD( unsigned long ) Labels_t;
+ Labels_t labels;
+ LOKI_BIT_CONST( Labels_t, Label_A, 1 ); // 0x0001 - 1st bit is set
+ LOKI_BIT_CONST( Labels_t, Label_B, 2 ); // 0x0002 - 1st bit is set
+ ...
+ LOKI_BIT_FIELD( unsigned long ) Kinds_t;
+ Kinds_t kinds;
+ LOKI_BIT_CONST( Kinds_t, Kind_A, 3 ); // 0x0004 - 1st bit is set
+ ...
+ if ( kinds & Label_A ) { ... } // Does not compile
+
+ Several other kinds of bit field misuse are caught by safe bit fields:
+
+ if ( kinds & Kind_A == 0 ) { ... }
+ if ( kinds && Kind_A ) { ... }
+
+ There are few cases where drop-in replacement does not work:
+
+ 1. Operations involving bit fields and unnamed integers. Usually the integer in question is 0:
+
+ Labels_t labels = 0; // No longer compiles
+ if ( ( labels & Label_A ) == 0 ) { ... } // Also does not compile
+
+ The solution is to use named bit constants, including the one for 0:
+
+ LOKI_BIT_CONST( Labels_t, Label_None, 0 ); // 0x0000 - No bit is set
+ Labels_t labels = Label_None; // Or just Labels_t labels; - constructor initializes to 0
+ if ( ( labels & Label_A ) == Label_None ) { ... } // // Or just if ( labels & Label_A ) { ... }
+
+ 2. I/O and other operations which require integer variables and cannot be modified:
+
+ void write_to_db( unsigned int word );
+ Labels_t labels;
+ write_to_db( labels ); // No longer compiles
+
+ This problem is solved by reinterpreting the bit fields as an integer, the user is responsible for using the right
+ type of integer:
+
+ write_to_db( *((Labels_t::bit_word_t*)(&labels)) );
+
+ ==========================================================================================================================================
+*/
+
+/// @par Non-Templated Initialization.
+/// Not all compilers support template member functions where the template
+/// arguments are not deduced but explicitly specified. For these broken
+/// compilers, a non-template make_bit_const() function is provided instead of
+/// the template one. The only downside is that instead of compile-time checking
+/// of the index argument, it does runtime checking.
+#if defined(__SUNPRO_CC) || ( defined(__GNUC__) && (__GNUC__ < 3) )
+ #define LOKI_BIT_FIELD_NONTEMPLATE_INIT
+#endif
+
+/// @par Forbidding Conversions.
+/// This incomplete type prevents compilers from instantiating templates for
+/// type conversions which should not happen. This incomplete type must be a
+/// template: if the type is incomplete at the point of template definition,
+/// the template is illegal (although the standard allows compilers to accept
+/// or reject such code, ยง14.6/, so some compilers will not issue diagnostics
+/// unless template is instantiated). The standard-compliant way is to defer
+/// binding to the point of instantiation by making the incomplete type itself
+/// a template.
+template < typename > struct Forbidden_conversion; // This struct must not be defined!
+
+/// Forward declaration of the field type.
+template <
+ unsigned int unique_index,
+ typename word_t = unsigned long
+> class SafeBitField;
+
+////////////////////////////////////////////////////////////////////////////////
+/// \class SafeBitConst Bit constants.
+/// This class defines a bit-field constant - a collection of unchanging bits
+/// used to compare to bit-fields. Instances of this class are intended to act
+/// as labels for bit-fields.
+///
+/// \par Safety
+/// - This class provides operations used for comparisons and conversions, but
+/// no operations which may modify the value.
+/// - As a templated class, it provides type-safety so bit values and constants
+/// used for different reasons may not be unknowingly compared to each other.
+/// - The unique_index template parameter insures the unique type of each bit
+/// bit-field. It shares the unique_index with a similar SafeBitField.
+/// - Its operations only allow comparisons to other bit-constants and
+/// bit-fields of the same type.
+////////////////////////////////////////////////////////////////////////////////
+
+template
+<
+ unsigned int unique_index,
+ typename word_t = unsigned long
+>
+class SafeBitConst
+{
+public:
+
+ /// Type of the bit field is available if needed.
+ typedef word_t bit_word_t;
+ /// Corresponding field type.
+ typedef SafeBitField< unique_index, word_t > field_t;
+ /// Typedef is not allowed in friendship declaration.
+ friend class SafeBitField< unique_index, word_t >;
+
+ // Static factory constructor, creates a bit constant with one bit set. The position of the bit is given by the template parameter,
+ // bit 1 is the junior bit, i.e. make_bit_const<1>() returns 1. Bit index 0 is a special case and returns 0.
+ // This function should be used only to initialize the static bit constant objects.
+ // This function will not compile if the bit index is outside the vaild range.
+ // There is also a compile-time assert to make sure the size of the class is the same as the size of the underlaying integer type.
+ // This assert could go into the constructor, but aCC does not seem to understand sizeof(SafeBitConst) in the constructor.
+ //
+#ifndef LOKI_BIT_FIELD_NONTEMPLATE_INIT
+ template < unsigned int i > static SafeBitConst make_bit_const()
+ {
+ LOKI_STATIC_CHECK( i <= ( 8 * sizeof(word_t) ), Index_is_beyond_size_of_data );
+ LOKI_STATIC_CHECK( sizeof(SafeBitConst) == sizeof(word_t), Object_size_does_not_match_data_size );
+ // Why check for ( i > 0 ) again inside the shift if the shift
+ // can never be evaluated for i == 0? Some compilers see shift by ( i - 1 )
+ // and complain that for i == 0 the number is invalid, without
+ // checking that shift needs evaluating.
+ return SafeBitConst( ( i > 0 ) ? ( word_t(1) << ( ( i > 0 ) ? ( i - 1 ) : 0 ) ) : 0 );
+ }
+#else
+ static SafeBitConst make_bit_const( unsigned int i )
+ {
+ LOKI_STATIC_CHECK( sizeof(SafeBitConst) == sizeof(word_t), Object_size_does_not_match_data_size );
+ assert( i <= ( 8 * sizeof(word_t) ) ); // Index is beyond size of data.
+ // Why check for ( i > 0 ) again inside the shift if the shift
+ // can never be evaluated for i == 0? Some compilers see shift by ( i - 1 )
+ // and complain that for i == 0 the number is invalid, without
+ // checking that shift needs evaluating.
+ return SafeBitConst( ( i > 0 ) ? ( word_t(1) << ( ( i > 0 ) ? ( i - 1 ) : 0 ) ) : 0 );
+ }
+#endif
+
+ /// Default constructor allows client code to construct bit fields on the stack.
+ SafeBitConst() : word( 0 ) {}
+
+ /// Copy constructor.
+ SafeBitConst( const SafeBitConst& rhs ) : word( rhs.word ) {}
+
+ /// Comparison operators which take a constant bit value.
+ bool operator == ( const SafeBitConst & rhs ) const { return word == rhs.word; }
+ bool operator != ( const SafeBitConst & rhs ) const { return word != rhs.word; }
+ bool operator < ( const SafeBitConst & rhs ) const { return word < rhs.word; }
+ bool operator > ( const SafeBitConst & rhs ) const { return word > rhs.word; }
+ bool operator <= ( const SafeBitConst & rhs ) const { return word <= rhs.word; }
+ bool operator >= ( const SafeBitConst & rhs ) const { return word >= rhs.word; }
+
+ /// Comparision operators for mutable bit fields.
+ bool operator == ( const field_t & rhs ) const { return word == rhs.word; }
+ bool operator != ( const field_t & rhs ) const { return word != rhs.word; }
+ bool operator < ( const field_t & rhs ) const { return word < rhs.word; }
+ bool operator > ( const field_t & rhs ) const { return word > rhs.word; }
+ bool operator <= ( const field_t & rhs ) const { return word <= rhs.word; }
+ bool operator >= ( const field_t & rhs ) const { return word >= rhs.word; }
+
+ /// Bitwise operations. Operation-assignment operators are not needed,
+ /// since bit constants cannot be changed after they are initialized.
+ const SafeBitConst operator | ( const SafeBitConst & rhs ) const { return SafeBitConst( word | rhs.word ); }
+ const SafeBitConst operator & ( const SafeBitConst & rhs ) const { return SafeBitConst( word & rhs.word ); }
+ const SafeBitConst operator ^ ( const SafeBitConst & rhs ) const { return SafeBitConst( word ^ rhs.word ); }
+ const SafeBitConst operator ~ ( void ) const { return SafeBitConst( ~word ); }
+
+ /// These bitwise operators return a bit-field instead of a bit-const.
+ field_t operator | ( const field_t & rhs ) const { return field_t( word | rhs.word ); }
+ field_t operator & ( const field_t & rhs ) const { return field_t( word & rhs.word ); }
+ field_t operator ^ ( const field_t & rhs ) const { return field_t( word ^ rhs.word ); }
+
+ /// The shift operators move bits inside the bit field. These are useful in
+ /// loops which act over bit fields and increment them.
+ const SafeBitConst operator << ( unsigned int s ) const { return SafeBitConst( word << s ); }
+ const SafeBitConst operator >> ( unsigned int s ) const { return SafeBitConst( word >> s ); }
+
+ /// Word size is also the maximum number of different bit fields for a given word type.
+ static size_t size() { return ( 8 * sizeof( word_t ) ); }
+
+private:
+
+ /// Copy-assignment operator is not implemented since it does not make sense
+ /// for a constant object.
+ SafeBitConst operator = ( const SafeBitConst & rhs );
+
+ // Private constructor from an integer type.
+ explicit SafeBitConst( word_t init ) : word( init ) {}
+
+ /// This data stores a single bit value. It is declared const to enforce
+ // constness for all functions of this class.
+ const word_t word;
+
+ // Here comes the interesting stuff: all the operators designed to
+ // trap unintended conversions and make them not compile.
+ // Operators below handle code like this:
+ // SafeBitField<1> label1;
+ // SafeBitField<2> label2;
+ // if ( label1 & label2 ) { ... }
+
+ // These operators are private, and will not instantiate in any
+ // event because of the incomplete Forbidden_conversion struct.
+ template < typename T > SafeBitConst operator|( T ) const { Forbidden_conversion< T > wrong; return *this; }
+ template < typename T > SafeBitConst operator&( T ) const { Forbidden_conversion< T > wrong; return *this; }
+ template < typename T > SafeBitConst operator^( T ) const { Forbidden_conversion< T > wrong; return *this; }
+ template < typename T > SafeBitConst operator|=( T ) const { Forbidden_conversion< T > wrong; return *this; }
+ template < typename T > SafeBitConst operator&=( T ) const { Forbidden_conversion< T > wrong; return *this; }
+ template < typename T > SafeBitConst operator^=( T ) const { Forbidden_conversion< T > wrong; return *this; }
+
+ // And the same thing for comparisons: private and unusable.
+ // if ( label1 == label2 ) { ... }
+ template < typename T > bool operator==( const T ) const { Forbidden_conversion< T > wrong; return true; }
+ template < typename T > bool operator!=( const T ) const { Forbidden_conversion< T > wrong; return true; }
+ template < typename T > bool operator<( const T ) const { Forbidden_conversion< T > wrong; return true; }
+ template < typename T > bool operator>( const T ) const { Forbidden_conversion< T > wrong; return true; }
+ template < typename T > bool operator<=( const T ) const { Forbidden_conversion< T > wrong; return true; }
+ template < typename T > bool operator>=( const T ) const { Forbidden_conversion< T > wrong; return true; }
+};
+
+
+////////////////////////////////////////////////////////////////////////////////
+/// \class SafeBitConst Bit constants.
+/// This class defines a bit-field constant - a collection of unchanging bits
+/// used to compare to bit-fields. Instances of this class are intended to
+/// store bit values.
+///
+/// \par Safety
+/// - This class provides operations used for comparisons and conversions, and
+/// also operations which may safely modify the value.
+/// - As a templated class, it provides type-safety so bit values and constants
+/// used for different reasons may not be unknowingly compared to each other.
+/// - The unique_index template parameter insures the unique type of each bit
+/// bit-field. It shares the unique_index with a similar SafeBitConst.
+/// - Its operations only allow comparisons to other bit-constants and
+/// bit-fields of the same type.
+////////////////////////////////////////////////////////////////////////////////
+
+template
+<
+ unsigned int unique_index,
+ typename word_t
+>
+class SafeBitField
+{
+public:
+
+ /// Type of the bit field is available if needed.
+ typedef word_t bit_word_t;
+ /// Corresponding field type.
+ typedef SafeBitConst< unique_index, word_t > const_t;
+ /// Typedef is not allowed in friendship declaration.
+ friend class SafeBitConst<unique_index, word_t>;
+
+ /// Default constructor allows client code to construct bit fields on the stack.
+ SafeBitField() : word( 0 ) {}
+
+ /// Copy constructor and assignment operators.
+ SafeBitField( const SafeBitField & rhs ) : word( rhs.word ) {}
+ SafeBitField & operator = ( const SafeBitField & rhs ) { word = rhs.word; return *this; }
+
+ /// Copy constructor and assignment operators from constant bit fields.
+ SafeBitField( const const_t & rhs ) : word( rhs.word ) {}
+ SafeBitField & operator = ( const const_t & rhs ) { word = rhs.word; return *this; }
+
+ /// These comparison operators act on bit-fields of the same type.
+ bool operator == ( const SafeBitField & rhs ) const { return word == rhs.word; }
+ bool operator != ( const SafeBitField & rhs ) const { return word != rhs.word; }
+ bool operator < ( const SafeBitField & rhs ) const { return word < rhs.word; }
+ bool operator > ( const SafeBitField & rhs ) const { return word > rhs.word; }
+ bool operator <= ( const SafeBitField & rhs ) const { return word <= rhs.word; }
+ bool operator >= ( const SafeBitField & rhs ) const { return word >= rhs.word; }
+
+ /// These comparison operators act on bit-constants of a similar type.
+ bool operator == ( const const_t & rhs ) const { return word == rhs.word; }
+ bool operator != ( const const_t & rhs ) const { return word != rhs.word; }
+ bool operator < ( const const_t & rhs ) const { return word < rhs.word; }
+ bool operator > ( const const_t & rhs ) const { return word > rhs.word; }
+ bool operator <= ( const const_t & rhs ) const { return word <= rhs.word; }
+ bool operator >= ( const const_t & rhs ) const { return word >= rhs.word; }
+
+ /// Bitwise operations that use bit-fields.
+ SafeBitField operator | ( const SafeBitField & rhs ) const { return SafeBitField( word | rhs.word ); }
+ SafeBitField operator & ( const SafeBitField & rhs ) const { return SafeBitField( word & rhs.word ); }
+ SafeBitField operator ^ ( const SafeBitField & rhs ) const { return SafeBitField( word ^ rhs.word ); }
+ SafeBitField operator ~ ( void ) const { return SafeBitField( ~word ); }
+ SafeBitField operator |= ( const SafeBitField & rhs ) { word |= rhs.word; return SafeBitField( *this ); }
+ SafeBitField operator &= ( const SafeBitField & rhs ) { word &= rhs.word; return SafeBitField( *this ); }
+ SafeBitField operator ^= ( const SafeBitField & rhs ) { word ^= rhs.word; return SafeBitField( *this ); }
+
+ /// Bitwise operators that use bit-constants.
+ SafeBitField operator | ( const_t rhs ) const { return SafeBitField( word | rhs.word ); }
+ SafeBitField operator & ( const_t rhs ) const { return SafeBitField( word & rhs.word ); }
+ SafeBitField operator ^ ( const_t rhs ) const { return SafeBitField( word ^ rhs.word ); }
+ SafeBitField operator |= ( const_t rhs ) { word |= rhs.word; return SafeBitField( *this ); }
+ SafeBitField operator &= ( const_t rhs ) { word &= rhs.word; return SafeBitField( *this ); }
+ SafeBitField operator ^= ( const_t rhs ) { word ^= rhs.word; return SafeBitField( *this ); }
+
+ // Conversion to bool.
+ // This is a major source of headaches, but it's required to support code like this:
+ // const static SafeBitConst<1> Label_value = SafeBitConst<1>::make_bit_const<1>();
+ // SafeBitField<1> label;
+ // if ( label & Label_value ) { ... } // Nice...
+ //
+ // The downside is that this allows all sorts of nasty conversions. Without additional precautions, bit fields of different types
+ // can be converted to bool and then compared or operated on:
+ // SafeBitField<1> label1;
+ // SafeBitField<2> label2;
+ // if ( label1 == label2 ) { ... } // Yuck!
+ // if ( label1 & label2 ) { ... } // Blech!
+ //
+ // It is somewhat safer to convert to a pointer, at least pointers to different types cannot be readilly compared, and there are no
+ // bitwise operations on pointers, but the conversion from word_t to a pointer can have run-time cost if they are of different size.
+ //
+ operator const bool() const { return ( 0 != word ); }
+
+ // Shift operators shift bits inside the bit field. Does not make
+ // sense, most of the time, except perhaps to loop over labels and
+ // increment them.
+ SafeBitField operator << ( unsigned int s ) { return SafeBitField( word << s ); }
+ SafeBitField operator >> ( unsigned int s ) { return SafeBitField( word >> s ); }
+ SafeBitField operator <<= ( unsigned int s ) { word <<= s; return *this; }
+ SafeBitField operator >>= ( unsigned int s ) { word >>= s; return *this; }
+
+ // Word size is also the maximum number of different bit fields for
+ // a given word type.
+ static size_t size( void ) { return ( 8 * sizeof( word_t ) ); }
+
+private:
+
+ /// Private constructor from an integer type. Don't put too much stock into
+ /// explicit declaration, it's better than nothing but does not solve all
+ /// problems with undesired conversions because SafeBitField coverts to bool.
+ explicit SafeBitField( word_t init ) : word( init ) {}
+
+ /// This stores the bits.
+ word_t word;
+
+ // Here comes the interesting stuff: all the operators designed to
+ // trap unintended conversions and make them not compile.
+ // Operators below handle code like this:
+ // SafeBitField<1> label1;
+ // SafeBitField<2> label2;
+ // if ( label1 & label2 ) { ... }
+
+ // These operators are private, and will not instantiate in any
+ // event because of the incomplete Forbidden_conversion struct.
+ template < typename T > SafeBitField operator | ( T ) const { Forbidden_conversion< T > wrong; return *this; }
+ template < typename T > SafeBitField operator & ( T ) const { Forbidden_conversion< T > wrong; return *this; }
+ template < typename T > SafeBitField operator ^ ( T ) const { Forbidden_conversion< T > wrong; return *this; }
+ template < typename T > SafeBitField operator |= ( T ) const { Forbidden_conversion< T > wrong; return *this; }
+ template < typename T > SafeBitField operator &= ( T ) const { Forbidden_conversion< T > wrong; return *this; }
+ template < typename T > SafeBitField operator ^= ( T ) const { Forbidden_conversion< T > wrong; return *this; }
+
+ // And the same thing for comparisons:
+ // if ( label1 == label2 ) { ... }
+ template < typename T > bool operator == ( const T ) const { Forbidden_conversion< T > wrong; return true; }
+ template < typename T > bool operator != ( const T ) const { Forbidden_conversion< T > wrong; return true; }
+ template < typename T > bool operator < ( const T ) const { Forbidden_conversion< T > wrong; return true; }
+ template < typename T > bool operator > ( const T ) const { Forbidden_conversion< T > wrong; return true; }
+ template < typename T > bool operator <= ( const T ) const { Forbidden_conversion< T > wrong; return true; }
+ template < typename T > bool operator >= ( const T ) const { Forbidden_conversion< T > wrong; return true; }
+};
+
+// The above template member operators catch errors when the first
+// argument to a binary operator is a label, but they don't work when
+// the first argument is an integer and the second one is a label: the
+// label converts to bool and the operator is performed on two integers.
+// These operators catch errors like this:
+// SafeBitField<1> label1;
+// SafeBitField<2> label2;
+// if ( !label1 & label2 ) { ... }
+// where the first label is converted to bool (these errors cannot be
+// caught by member operators of SafeBitField class because the first
+// argument is not SafeBitField but bool.
+//
+// If used, these operators will not instantiate because of the
+// incomplete Forbidden_conversion struct.
+
+template < unsigned int unique_index, typename word_t >
+inline SafeBitField< unique_index, word_t > operator & ( bool, SafeBitField< unique_index, word_t > rhs )
+{
+ Forbidden_conversion<word_t> wrong;
+ return rhs;
+}
+
+template < unsigned int unique_index, typename word_t >
+inline SafeBitField< unique_index, word_t > operator | ( bool, SafeBitField< unique_index, word_t > rhs )
+{
+ Forbidden_conversion< word_t > wrong;
+ return rhs;
+}
+
+template < unsigned int unique_index, typename word_t >
+inline SafeBitField< unique_index, word_t > operator ^ ( bool, SafeBitField< unique_index, word_t > rhs )
+{
+ Forbidden_conversion< word_t > wrong;
+ return rhs;
+}
+
+template < unsigned int unique_index, typename word_t >
+inline SafeBitField< unique_index, word_t > operator == ( bool, SafeBitField< unique_index, word_t > rhs )
+{
+ Forbidden_conversion< word_t > wrong;
+ return rhs;
+}
+
+template < unsigned int unique_index, typename word_t >
+inline SafeBitField< unique_index, word_t > operator != ( bool, SafeBitField< unique_index, word_t > rhs )
+{
+ Forbidden_conversion< word_t > wrong;
+ return rhs;
+}
+
+// Finally, few macros. All macros are conditionally defined to use the SafeBitField classes if LOKI_SAFE_BIT_FIELD is defined. Otherwise,
+// the macros fall back on the use of typedefs and integer constants. This provides no addititonal safety but allows the code to support the
+// mixture of compilers which are broken to different degrees.
+#define LOKI_SAFE_BIT_FIELD
+
+// The first macro helps to declare new bit field types:
+// LOKI_BIT_FIELD( ulong ) field_t;
+// This creates a typedef field_t for SafeBitField<unique_index, ulong> where index is the current line number. Since line numbers __LINE__ are counted
+// separately for all header files, this ends up being the same type in all files using the header which defines field_t.
+#ifdef LOKI_SAFE_BIT_FIELD
+ #define LOKI_BIT_FIELD( word_t ) typedef SafeBitField<__LINE__, word_t>
+#else
+ #define LOKI_BIT_FIELD( word_t ) typedef word_t
+#endif // LOKI_SAFE_BIT_FIELD
+
+// The second macro helps to declare static bit constants:
+// LOKI_BIT_CONST( field_t, Label_1, 1 );
+// creates new bit field object named Label_1 of type field_t which represents the field with the 1st (junior) bit set.
+#ifdef LOKI_SAFE_BIT_FIELD
+ #ifndef LOKI_BIT_FIELD_NONTEMPLATE_INIT
+ #define LOKI_BIT_CONST( field_t, label, bit_index ) \
+ static const field_t::const_t label = field_t::const_t::make_bit_const<bit_index>()
+ #else
+ #define LOKI_BIT_CONST( field_t, label, bit_index ) \
+ static const field_t::const_t label = field_t::const_t::make_bit_const( bit_index )
+ #endif // LOKI_BIT_FIELD_NONTEMPLATE_INIT
+#else
+ inline size_t make_bit_const( size_t i ) { return ( i > 0 ) ? ( size_t(1) << ( ( i > 0 ) ? ( i - 1 ) : 0 ) ) : 0; }
+ #define LOKI_BIT_CONST( field_t, label, bit_index ) static const field_t label = make_bit_const( bit_index )
+#endif // LOKI_SAFE_BIT_FIELD
+
+// The third macro helps to declare complex bit constants which are combination of several bits:
+// LOKI_BIT_CONSTS( field_t, Label12 ) = Label_1 | Label_2;
+#ifdef LOKI_SAFE_BIT_FIELD
+ #define LOKI_BIT_CONSTS( field_t, label ) static const field_t::const_t label
+#else
+ #define LOKI_BIT_CONSTS( field_t, label ) static const field_t label
+#endif // LOKI_SAFE_BIT_FIELD
+
+// The fourth macro helps to declare the maximum number of bit constants for a given type:
+// static const size_t count = LOKI_BIT_FIELD_COUNT( field_t );
+// declared a variable "count" initialized to field_t::size()
+#ifdef LOKI_SAFE_BIT_FIELD
+ #define LOKI_BIT_FIELD_COUNT( field_t ) field_t::size()
+#else
+ #define LOKI_BIT_FIELD_COUNT( field_t ) ( 8 * sizeof(field_t) )
+#endif // LOKI_SAFE_BIT_FIELD
+
+} // namespace Loki
+
+#endif // LOKI_INCLUDED_SAFE_BIT_FIELDS_H
bgstack15