include/basebmp/metafunctions.hxx

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  17  *   the License at http://www.apache.org/licenses/LICENSE-2.0 .
  18  */
  19
  20 #ifndef INCLUDED_BASEBMP_METAFUNCTIONS_HXX
  21 #define INCLUDED_BASEBMP_METAFUNCTIONS_HXX
  22
  23 #include <boost/mpl/integral_c.hpp>
  24 #include <vigra/metaprogramming.hxx>
  25 #include <vigra/numerictraits.hxx>
  26
  27 #include <functional>
  28
  29 namespace basebmp
  30 {
  31
  32 // TODO(Q3): move to generic place (o3tl?)
  33
  34 /** template meta function: add const qualifier to 2nd type, if given
  35     1st type has it
  36 */
  37 template<typename A, typename B> struct clone_const
  38 {
  39     typedef B type;
  40 };
  41 template<typename A, typename B> struct clone_const<const A,B>
  42 {
  43     typedef const B type;
  44 };
  45
  46 /** template meta function: add const qualifier to plain type (if not
  47     already there)
  48  */
  49 template <typename T> struct add_const
  50 {
  51     typedef const T type;
  52 };
  53 template <typename T> struct add_const<const T>
  54 {
  55     typedef const T type;
  56 };
  57
  58 /// template meta function: remove const qualifier from plain type
  59 template <typename T> struct remove_const
  60 {
  61     typedef T type;
  62 };
  63 template <typename T> struct remove_const<const T>
  64 {
  65     typedef T type;
  66 };
  67
  68 //--------------------------------------------------------------
  69
  70 /// Base class for an adaptable ternary functor
  71 template< typename A1, typename A2, typename A3, typename R > struct TernaryFunctorBase
  72 {
  73     typedef A1 first_argument_type;
  74     typedef A2 second_argument_type;
  75     typedef A3 third_argument_type;
  76     typedef R  result_type;
  77 };
  78
  79 //--------------------------------------------------------------
  80
  81 /** template meta function: ensure that given integer type is unsigned
  82
  83     If given integer type is already unsigned, return as-is -
  84     otherwise, convert to unsigned type of same or greater range.
  85  */
  86 template< typename T > struct make_unsigned;
  87
  88 #define BASEBMP_MAKE_UNSIGNED(T,U)        \
  89     template<> struct make_unsigned<T> { \
  90         typedef U type; \
  91     };
  92
  93 BASEBMP_MAKE_UNSIGNED(signed char,unsigned char)
  94 BASEBMP_MAKE_UNSIGNED(unsigned char,unsigned char)
  95 BASEBMP_MAKE_UNSIGNED(short,unsigned short)
  96 BASEBMP_MAKE_UNSIGNED(unsigned short,unsigned short)
  97 BASEBMP_MAKE_UNSIGNED(int,unsigned int)
  98 BASEBMP_MAKE_UNSIGNED(unsigned int,unsigned int)
  99 BASEBMP_MAKE_UNSIGNED(long,unsigned long)
 100 BASEBMP_MAKE_UNSIGNED(unsigned long,unsigned long)
 101
 102 #undef BASEBMP_MAKE_UNSIGNED
 103
 104 /// cast integer to unsigned type of similar size
 105 template< typename T > inline typename make_unsigned<T>::type unsigned_cast( T value )
 106 {
 107     return static_cast< typename make_unsigned<T>::type >(value);
 108 }
 109
 110 //--------------------------------------------------------------
 111
 112 /// returns true, if given number is strictly less than 0
 113 template< typename T > inline bool is_negative( T x )
 114 {
 115     return x < 0;
 116 }
 117
 118 /// Overload for ints (branch-free)
 119 inline bool is_negative( int x )
 120 {
 121     // force logic shift (result for signed shift right is undefined)
 122     return static_cast<unsigned int>(x) >> (sizeof(int)*8-1);
 123 }
 124
 125 //--------------------------------------------------------------
 126
 127 /// Results in VigraTrueType, if T is of integer type and scalar
 128 template< typename T, typename trueCase, typename falseCase >
 129 struct ifScalarIntegral
 130 {
 131     typedef
 132     typename vigra::If<
 133         typename vigra::NumericTraits< T >::isIntegral,
 134         typename vigra::If<
 135             typename vigra::NumericTraits< T >::isScalar,
 136             trueCase,
 137             falseCase >::type,
 138         falseCase >::type type;
 139 };
 140
 141 /// Results in VigraTrueType, if T is of non-integer type and scalar
 142 template< typename T, typename trueCase, typename falseCase >
 143 struct ifScalarNonIntegral
 144 {
 145     typedef
 146     typename vigra::If<
 147         typename vigra::NumericTraits< T >::isIntegral,
 148         falseCase,
 149         typename vigra::If<
 150             typename vigra::NumericTraits< T >::isScalar,
 151             trueCase,
 152             falseCase >::type >::type type;
 153 };
 154
 155 /// Results in VigraTrueType, if both T1 and T2 are of integer type and scalar
 156 template< typename T1, typename T2, typename trueCase, typename falseCase >
 157 struct ifBothScalarIntegral
 158 {
 159     typedef
 160     typename ifScalarIntegral<
 161         T1,
 162         typename ifScalarIntegral<
 163             T2,
 164             trueCase,
 165             falseCase >::type,
 166         falseCase >::type type;
 167 };
 168
 169 //--------------------------------------------------------------
 170
 171 /// Count number of trailing zeros
 172 template< unsigned int val > struct numberOfTrailingZeros
 173 {
 174     enum { next = val >> 1 };
 175     enum { value = vigra::IfBool< (val & 1) == 0,
 176                                   numberOfTrailingZeros<next>,
 177                                   boost::mpl::integral_c< int,-1 > > ::type::value + 1 };
 178 };
 179
 180 template<> struct numberOfTrailingZeros<0>
 181 {
 182     enum { value = 0 };
 183 };
 184
 185 //--------------------------------------------------------------
 186
 187 /// Count number of one bits
 188 template< unsigned int val > struct bitcount
 189 {
 190     enum { next = val >> 1 };
 191     enum { value = bitcount<next>::value + (val & 1) };
 192 };
 193
 194 template<> struct bitcount<0>
 195 {
 196     enum { value = 0 };
 197 };
 198
 199 //--------------------------------------------------------------
 200
 201 /// Shift left for positive shift value, and right otherwise
 202 template< typename T > inline T shiftLeft( T v, int shift )
 203 {
 204     return shift > 0 ? v << shift : v >> (-shift);
 205 }
 206
 207 /// Shift right for positive shift value, and left otherwise
 208 template< typename T > inline T shiftRight( T v, int shift )
 209 {
 210     return shift > 0 ? v >> shift : v << (-shift);
 211 }
 212
 213 //--------------------------------------------------------------
 214
 215 /// Replace non-std project2nd from SGI extensions
 216 template< typename T1, typename T2 >
 217 struct project2nd : public std::binary_function<T1, T2, T2>
 218 {
 219     T2 operator() (const T1&, const T2& v) const { return v; }
 220 };
 221
 222 } // namespace basebmp
 223
 224 #endif /* INCLUDED_BASEBMP_METAFUNCTIONS_HXX */
 225
 226 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */