extension/dynamic_image/dynamic_at_c.hpp

0001 //
0002 // Copyright 2005-2007 Adobe Systems Incorporated
0003 //
0004 // Distributed under the Boost Software License, Version 1.0
0005 // See accompanying file LICENSE_1_0.txt or copy at
0006 // http://www.boost.org/LICENSE_1_0.txt
0007 //
0008 #ifndef BOOST_GIL_EXTENSION_DYNAMIC_IMAGE_DYNAMIC_AT_C_HPP
0009 #define BOOST_GIL_EXTENSION_DYNAMIC_IMAGE_DYNAMIC_AT_C_HPP
0010
0011 #include <boost/gil/detail/mp11.hpp>
0012
0013 #include <boost/preprocessor/facilities/empty.hpp>
0014 #include <boost/preprocessor/repetition/repeat.hpp>
0015
0016 #include <stdexcept>
0017
0018 namespace boost { namespace gil {
0019
0020 // Constructs for static-to-dynamic integer convesion
0021
0022 #define BOOST_GIL_AT_C_VALUE(z, N, text) mp11::mp_at_c<IntTypes, S+N>::value,
0023 #define BOOST_GIL_DYNAMIC_AT_C_LIMIT 226 // size of the maximum vector to handle
0024
0025 #define BOOST_GIL_AT_C_LOOKUP(z, NUM, text)                                   \
0026     template<std::size_t S>                                             \
0027     struct at_c_fn<S,NUM> {                                             \
0028     template <typename IntTypes, typename ValueType> inline           \
0029         static ValueType apply(std::size_t index) {                    \
0030             static ValueType table[] = {                               \
0031                 BOOST_PP_REPEAT(NUM, BOOST_GIL_AT_C_VALUE, BOOST_PP_EMPTY)    \
0032             };                                                          \
0033             return table[index];                                        \
0034         }                                                               \
0035     };
0036
0037 namespace detail {
0038     namespace at_c {
0039         template <std::size_t START, std::size_t NUM> struct at_c_fn;
0040         BOOST_PP_REPEAT(BOOST_GIL_DYNAMIC_AT_C_LIMIT, BOOST_GIL_AT_C_LOOKUP, BOOST_PP_EMPTY)
0041
0042         template <std::size_t QUOT> struct at_c_impl;
0043
0044         template <>
0045         struct at_c_impl<0> {
0046             template <typename IntTypes, typename ValueType> inline
0047             static ValueType apply(std::size_t index) {
0048                 return at_c_fn<0, mp11::mp_size<IntTypes>::value>::template apply<IntTypes,ValueType>(index);
0049             }
0050         };
0051
0052         template <>
0053         struct at_c_impl<1> {
0054             template <typename IntTypes, typename ValueType> inline
0055             static ValueType apply(std::size_t index) {
0056                 const std::size_t SIZE = mp11::mp_size<IntTypes>::value;
0057                 const std::size_t REM = SIZE % BOOST_GIL_DYNAMIC_AT_C_LIMIT;
0058                 switch (index / BOOST_GIL_DYNAMIC_AT_C_LIMIT) {
0059                     case 0: return at_c_fn<0                   ,BOOST_GIL_DYNAMIC_AT_C_LIMIT-1>::template apply<IntTypes,ValueType>(index);
0060                     case 1: return at_c_fn<BOOST_GIL_DYNAMIC_AT_C_LIMIT  ,REM                 >::template apply<IntTypes,ValueType>(index - BOOST_GIL_DYNAMIC_AT_C_LIMIT);
0061                 };
0062                 throw;
0063             }
0064         };
0065
0066         template <>
0067         struct at_c_impl<2> {
0068             template <typename IntTypes, typename ValueType> inline
0069             static ValueType apply(std::size_t index) {
0070                 const std::size_t SIZE = mp11::mp_size<IntTypes>::value;
0071                 const std::size_t REM = SIZE % BOOST_GIL_DYNAMIC_AT_C_LIMIT;
0072                 switch (index / BOOST_GIL_DYNAMIC_AT_C_LIMIT) {
0073                     case 0: return at_c_fn<0                   ,BOOST_GIL_DYNAMIC_AT_C_LIMIT-1>::template apply<IntTypes,ValueType>(index);
0074                     case 1: return at_c_fn<BOOST_GIL_DYNAMIC_AT_C_LIMIT  ,BOOST_GIL_DYNAMIC_AT_C_LIMIT-1>::template apply<IntTypes,ValueType>(index - BOOST_GIL_DYNAMIC_AT_C_LIMIT);
0075                     case 2: return at_c_fn<BOOST_GIL_DYNAMIC_AT_C_LIMIT*2,REM                 >::template apply<IntTypes,ValueType>(index - BOOST_GIL_DYNAMIC_AT_C_LIMIT*2);
0076                 };
0077                 throw;
0078             }
0079         };
0080
0081         template <>
0082         struct at_c_impl<3> {
0083             template <typename IntTypes, typename ValueType> inline
0084             static ValueType apply(std::size_t index) {
0085                 const std::size_t SIZE = mp11::mp_size<IntTypes>::value;
0086                 const std::size_t REM = SIZE % BOOST_GIL_DYNAMIC_AT_C_LIMIT;
0087                 switch (index / BOOST_GIL_DYNAMIC_AT_C_LIMIT) {
0088                     case 0: return at_c_fn<0                   ,BOOST_GIL_DYNAMIC_AT_C_LIMIT-1>::template apply<IntTypes,ValueType>(index);
0089                     case 1: return at_c_fn<BOOST_GIL_DYNAMIC_AT_C_LIMIT  ,BOOST_GIL_DYNAMIC_AT_C_LIMIT-1>::template apply<IntTypes,ValueType>(index - BOOST_GIL_DYNAMIC_AT_C_LIMIT);
0090                     case 2: return at_c_fn<BOOST_GIL_DYNAMIC_AT_C_LIMIT*2,BOOST_GIL_DYNAMIC_AT_C_LIMIT-1>::template apply<IntTypes,ValueType>(index - BOOST_GIL_DYNAMIC_AT_C_LIMIT*2);
0091                     case 3: return at_c_fn<BOOST_GIL_DYNAMIC_AT_C_LIMIT*3,REM                 >::template apply<IntTypes,ValueType>(index - BOOST_GIL_DYNAMIC_AT_C_LIMIT*3);
0092                 };
0093                 throw;
0094             }
0095         };
0096     }
0097 }
0098
0099 ////////////////////////////////////////////////////////////////////////////////////
0100 ///
0101 /// \brief Given an Boost.MP11-compatible list and a dynamic index n,
0102 /// returns the value of the n-th element.
0103 /// It constructs a lookup table at compile time.
0104 ///
0105 ////////////////////////////////////////////////////////////////////////////////////
0106
0107 template <typename IntTypes, typename ValueType> inline
0108 ValueType at_c(std::size_t index) {
0109     const std::size_t Size=mp11::mp_size<IntTypes>::value;
0110     return detail::at_c::at_c_impl<Size/BOOST_GIL_DYNAMIC_AT_C_LIMIT>::template apply<IntTypes,ValueType>(index);
0111 }
0112
0113 #undef BOOST_GIL_AT_C_VALUE
0114 #undef BOOST_GIL_DYNAMIC_AT_C_LIMIT
0115 #undef BOOST_GIL_AT_C_LOOKUP
0116
0117 }} // namespace boost::gil
0118
0119 #endif