1 | |
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2 | // Copyright 2005-2009 Daniel James. |
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3 | // Distributed under the Boost Software License, Version 1.0. (See accompanying |
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4 | // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) |
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5 | |
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6 | #if !defined(BOOST_FUNCTIONAL_HASH_DETAIL_FLOAT_FUNCTIONS_HPP) |
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7 | #define BOOST_FUNCTIONAL_HASH_DETAIL_FLOAT_FUNCTIONS_HPP |
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8 | |
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9 | #include <boost/config.hpp> |
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10 | #include <boost/config/no_tr1/cmath.hpp> |
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11 | |
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12 | #if defined(_MSC_VER) && (_MSC_VER >= 1020) |
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13 | # pragma once |
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14 | #endif |
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15 | |
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16 | // The C++ standard requires that the C float functions are overloarded |
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17 | // for float, double and long double in the std namespace, but some of the older |
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18 | // library implementations don't support this. On some that don't, the C99 |
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19 | // float functions (frexpf, frexpl, etc.) are available. |
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20 | // |
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21 | // The following tries to automatically detect which are available. |
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22 | |
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23 | namespace boost { |
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24 | namespace hash_detail { |
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25 | |
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26 | // Returned by dummy versions of the float functions. |
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27 | |
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28 | struct not_found { |
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29 | // Implicitly convertible to float and long double in order to avoid |
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30 | // a compile error when the dummy float functions are used. |
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31 | |
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32 | inline operator float() const { return 0; } |
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33 | inline operator long double() const { return 0; } |
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34 | }; |
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35 | |
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36 | // A type for detecting the return type of functions. |
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37 | |
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38 | template <typename T> struct is; |
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39 | template <> struct is<float> { char x[10]; }; |
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40 | template <> struct is<double> { char x[20]; }; |
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41 | template <> struct is<long double> { char x[30]; }; |
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42 | template <> struct is<boost::hash_detail::not_found> { char x[40]; }; |
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43 | |
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44 | // Used to convert the return type of a function to a type for sizeof. |
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45 | |
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46 | template <typename T> is<T> float_type(T); |
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47 | |
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48 | // call_ldexp |
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49 | // |
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50 | // This will get specialized for float and long double |
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51 | |
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52 | template <typename Float> struct call_ldexp |
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53 | { |
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54 | typedef double float_type; |
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55 | |
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56 | inline double operator()(double a, int b) const |
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57 | { |
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58 | using namespace std; |
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59 | return ldexp(a, b); |
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60 | } |
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61 | }; |
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62 | |
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63 | // call_frexp |
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64 | // |
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65 | // This will get specialized for float and long double |
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66 | |
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67 | template <typename Float> struct call_frexp |
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68 | { |
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69 | typedef double float_type; |
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70 | |
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71 | inline double operator()(double a, int* b) const |
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72 | { |
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73 | using namespace std; |
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74 | return frexp(a, b); |
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75 | } |
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76 | }; |
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77 | } |
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78 | } |
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79 | |
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80 | // A namespace for dummy functions to detect when the actual function we want |
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81 | // isn't available. ldexpl, ldexpf etc. might be added tby the macros below. |
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82 | // |
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83 | // AFAICT these have to be outside of the boost namespace, as if they're in |
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84 | // the boost namespace they'll always be preferable to any other function |
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85 | // (since the arguments are built in types, ADL can't be used). |
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86 | |
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87 | namespace boost_hash_detect_float_functions { |
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88 | template <class Float> boost::hash_detail::not_found ldexp(Float, int); |
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89 | template <class Float> boost::hash_detail::not_found frexp(Float, int*); |
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90 | } |
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91 | |
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92 | // Macros for generating specializations of call_ldexp and call_frexp. |
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93 | // |
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94 | // check_cpp and check_c99 check if the C++ or C99 functions are available. |
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95 | // |
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96 | // Then the call_* functions select an appropriate implementation. |
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97 | // |
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98 | // I used c99_func in a few places just to get a unique name. |
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99 | // |
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100 | // Important: when using 'using namespace' at namespace level, include as |
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101 | // little as possible in that namespace, as Visual C++ has an odd bug which |
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102 | // can cause the namespace to be imported at the global level. This seems to |
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103 | // happen mainly when there's a template in the same namesapce. |
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104 | |
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105 | #define BOOST_HASH_CALL_FLOAT_FUNC(cpp_func, c99_func, type1, type2) \ |
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106 | namespace boost_hash_detect_float_functions { \ |
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107 | template <class Float> \ |
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108 | boost::hash_detail::not_found c99_func(Float, type2); \ |
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109 | } \ |
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110 | \ |
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111 | namespace boost { \ |
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112 | namespace hash_detail { \ |
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113 | namespace c99_func##_detect { \ |
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114 | using namespace std; \ |
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115 | using namespace boost_hash_detect_float_functions; \ |
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116 | \ |
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117 | struct check { \ |
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118 | static type1 x; \ |
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119 | static type2 y; \ |
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120 | BOOST_STATIC_CONSTANT(bool, cpp = \ |
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121 | sizeof(float_type(cpp_func(x,y))) \ |
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122 | == sizeof(is<type1>)); \ |
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123 | BOOST_STATIC_CONSTANT(bool, c99 = \ |
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124 | sizeof(float_type(c99_func(x,y))) \ |
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125 | == sizeof(is<type1>)); \ |
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126 | }; \ |
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127 | } \ |
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128 | \ |
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129 | template <bool x> \ |
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130 | struct call_c99_##c99_func : \ |
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131 | boost::hash_detail::call_##cpp_func<double> {}; \ |
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132 | \ |
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133 | template <> \ |
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134 | struct call_c99_##c99_func<true> { \ |
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135 | typedef type1 float_type; \ |
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136 | \ |
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137 | template <typename T> \ |
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138 | inline type1 operator()(type1 a, T b) const \ |
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139 | { \ |
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140 | using namespace std; \ |
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141 | return c99_func(a, b); \ |
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142 | } \ |
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143 | }; \ |
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144 | \ |
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145 | template <bool x> \ |
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146 | struct call_cpp_##c99_func : \ |
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147 | call_c99_##c99_func< \ |
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148 | ::boost::hash_detail::c99_func##_detect::check::c99 \ |
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149 | > {}; \ |
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150 | \ |
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151 | template <> \ |
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152 | struct call_cpp_##c99_func<true> { \ |
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153 | typedef type1 float_type; \ |
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154 | \ |
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155 | template <typename T> \ |
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156 | inline type1 operator()(type1 a, T b) const \ |
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157 | { \ |
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158 | using namespace std; \ |
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159 | return cpp_func(a, b); \ |
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160 | } \ |
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161 | }; \ |
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162 | \ |
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163 | template <> \ |
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164 | struct call_##cpp_func<type1> : \ |
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165 | call_cpp_##c99_func< \ |
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166 | ::boost::hash_detail::c99_func##_detect::check::cpp \ |
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167 | > {}; \ |
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168 | } \ |
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169 | } |
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170 | |
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171 | #define BOOST_HASH_CALL_FLOAT_MACRO(cpp_func, c99_func, type1, type2) \ |
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172 | namespace boost { \ |
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173 | namespace hash_detail { \ |
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174 | \ |
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175 | template <> \ |
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176 | struct call_##cpp_func<type1> { \ |
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177 | typedef type1 float_type; \ |
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178 | inline type1 operator()(type1 x, type2 y) const { \ |
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179 | return c99_func(x, y); \ |
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180 | } \ |
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181 | }; \ |
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182 | } \ |
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183 | } |
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184 | |
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185 | #if defined(ldexpf) |
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186 | BOOST_HASH_CALL_FLOAT_MACRO(ldexp, ldexpf, float, int) |
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187 | #else |
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188 | BOOST_HASH_CALL_FLOAT_FUNC(ldexp, ldexpf, float, int) |
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189 | #endif |
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190 | |
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191 | #if defined(ldexpl) |
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192 | BOOST_HASH_CALL_FLOAT_MACRO(ldexp, ldexpl, long double, int) |
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193 | #else |
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194 | BOOST_HASH_CALL_FLOAT_FUNC(ldexp, ldexpl, long double, int) |
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195 | #endif |
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196 | |
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197 | #if defined(frexpf) |
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198 | BOOST_HASH_CALL_FLOAT_MACRO(frexp, frexpf, float, int*) |
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199 | #else |
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200 | BOOST_HASH_CALL_FLOAT_FUNC(frexp, frexpf, float, int*) |
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201 | #endif |
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202 | |
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203 | #if defined(frexpl) |
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204 | BOOST_HASH_CALL_FLOAT_MACRO(frexp, frexpl, long double, int*) |
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205 | #else |
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206 | BOOST_HASH_CALL_FLOAT_FUNC(frexp, frexpl, long double, int*) |
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207 | #endif |
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208 | |
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209 | #undef BOOST_HASH_CALL_FLOAT_MACRO |
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210 | #undef BOOST_HASH_CALL_FLOAT_FUNC |
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211 | |
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212 | |
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213 | namespace boost |
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214 | { |
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215 | namespace hash_detail |
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216 | { |
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217 | template <typename Float1, typename Float2> |
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218 | struct select_hash_type_impl { |
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219 | typedef double type; |
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220 | }; |
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221 | |
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222 | template <> |
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223 | struct select_hash_type_impl<float, float> { |
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224 | typedef float type; |
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225 | }; |
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226 | |
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227 | template <> |
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228 | struct select_hash_type_impl<long double, long double> { |
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229 | typedef long double type; |
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230 | }; |
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231 | |
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232 | |
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233 | // select_hash_type |
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234 | // |
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235 | // If there is support for a particular floating point type, use that |
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236 | // otherwise use double (there's always support for double). |
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237 | |
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238 | template <typename Float> |
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239 | struct select_hash_type : select_hash_type_impl< |
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240 | BOOST_DEDUCED_TYPENAME call_ldexp<Float>::float_type, |
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241 | BOOST_DEDUCED_TYPENAME call_frexp<Float>::float_type |
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242 | > {}; |
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243 | } |
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244 | } |
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245 | |
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246 | #endif |
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