data/variant.hh

   1 # C++ skeleton for Bison
   2
   3 # Copyright (C) 2002-2010 Free Software Foundation, Inc.
   4
   5 # This program is free software: you can redistribute it and/or modify
   6 # it under the terms of the GNU General Public License as published by
   7 # the Free Software Foundation, either version 3 of the License, or
   8 # (at your option) any later version.
   9 #
  10 # This program is distributed in the hope that it will be useful,
  11 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 # GNU General Public License for more details.
  14 #
  15 # You should have received a copy of the GNU General Public License
  16 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
  17
  18
  19 ## --------- ##
  20 ## variant.  ##
  21 ## --------- ##
  22
  23 # b4_symbol_variant(YYTYPE, YYVAL, ACTION, [ARGS])
  24 # ------------------------------------------------
  25 # Run some ACTION ("build", or "destroy") on YYVAL of symbol type
  26 # YYTYPE.
  27 m4_define([b4_symbol_variant],
  28 [m4_pushdef([b4_dollar_dollar],
  29             [$2.$3< $][3 >(m4_shift3($@))])dnl
  30   switch ($1)
  31     {
  32 b4_type_foreach([b4_type_action_])[]dnl
  33       default:
  34         break;
  35     }
  36 m4_popdef([b4_dollar_dollar])dnl
  37 ])
  38
  39
  40 # _b4_char_sizeof_counter
  41 # -----------------------
  42 # A counter used by _b4_char_sizeof_dummy to create fresh symbols.
  43 m4_define([_b4_char_sizeof_counter],
  44 [0])
  45
  46 # _b4_char_sizeof_dummy
  47 # ---------------------
  48 # At each call return a new C++ identifier.
  49 m4_define([_b4_char_sizeof_dummy],
  50 [m4_define([_b4_char_sizeof_counter], m4_incr(_b4_char_sizeof_counter))dnl
  51 dummy[]_b4_char_sizeof_counter])
  52
  53
  54 # b4_char_sizeof_(SYMBOL-NUM)
  55 # ---------------------------
  56 # A comment describing this symbol.
  57 m4_define([b4_char_sizeof_],
  58 [      // b4_symbol([$1], [tag])
  59 ])
  60
  61 # b4_char_sizeof(SYMBOL-NUMS)
  62 # ---------------------------
  63 # To be mapped on the list of type names to produce:
  64 #
  65 #    char dummy1[sizeof(type_name_1)];
  66 #    char dummy2[sizeof(type_name_2)];
  67 #
  68 # for defined type names.
  69 m4_define([b4_char_sizeof],
  70 [b4_symbol_if([$1], [has_type],
  71 [
  72 m4_map([b4_char_sizeof_], [$@])dnl
  73       char _b4_char_sizeof_dummy@{sizeof([b4_symbol([$1], [type])])@};
  74 ])])
  75
  76
  77 # b4_variant_define
  78 # -----------------
  79 # Define "variant".
  80 m4_define([b4_variant_define],
  81 [[
  82   /// A char[S] buffer to store and retrieve objects.
  83   ///
  84   /// Sort of a variant, but does not keep track of the nature
  85   /// of the stored data, since that knowledge is available
  86   /// via the current state.
  87   template <size_t S>
  88   struct variant
  89   {]b4_parse_assert_if([
  90     /// Whether something is contained.
  91     bool built;
  92 ])[
  93     /// Empty construction.
  94     inline
  95     variant ()]b4_parse_assert_if([
  96       : built (false)])[
  97     {}
  98
  99     /// Instantiate a \a T in here.
 100     template <typename T>
 101     inline T&
 102     build ()
 103     {]b4_parse_assert_if([
 104       assert (!built);
 105       built = true;])[
 106       return *new (buffer.raw) T;
 107     }
 108
 109     /// Instantiate a \a T in here from \a t.
 110     template <typename T>
 111     inline T&
 112     build (const T& t)
 113     {]b4_parse_assert_if([
 114       assert(!built);
 115       built = true;])[
 116       return *new (buffer.raw) T(t);
 117     }
 118
 119     /// Construct and fill.
 120     template <typename T>
 121     inline
 122     variant (const T& t)]b4_parse_assert_if([
 123       : built (true)])[
 124     {
 125       new (buffer.raw) T(t);
 126     }
 127
 128     /// Accessor to a built \a T.
 129     template <typename T>
 130     inline T&
 131     as ()
 132     {]b4_parse_assert_if([
 133       assert (built);])[
 134       return reinterpret_cast<T&>(buffer.raw);
 135     }
 136
 137     /// Const accessor to a built \a T (for %printer).
 138     template <typename T>
 139     inline const T&
 140     as () const
 141     {]b4_parse_assert_if([
 142       assert(built);])[
 143       return reinterpret_cast<const T&>(buffer.raw);
 144     }
 145
 146     /// Swap the content with \a other.
 147     template <typename T>
 148     inline void
 149     swap (variant<S>& other)
 150     {
 151       std::swap (as<T>(), other.as<T>());
 152     }
 153
 154     /// Assign the content of \a other to this.
 155     /// Destroys \a other.
 156     template <typename T>
 157     inline void
 158     build (variant<S>& other)
 159     {
 160       build<T>();
 161       swap<T>(other);
 162       other.destroy<T>();
 163     }
 164
 165     /// Destroy the stored \a T.
 166     template <typename T>
 167     inline void
 168     destroy ()
 169     {
 170       as<T>().~T();]b4_parse_assert_if([
 171       built = false;])[
 172     }
 173
 174     /// A buffer large enough to store any of the semantic values.
 175     /// Long double is chosen as it has the strongest alignment
 176     /// constraints.
 177     union
 178     {
 179       long double align_me;
 180       char raw[S];
 181     } buffer;
 182   };
 183 ]])
 184
 185
 186 ## -------------------------- ##
 187 ## Adjustments for variants.  ##
 188 ## -------------------------- ##
 189
 190
 191 # b4_semantic_type_declare
 192 # ------------------------
 193 # Declare semantic_type.
 194 m4_define([b4_semantic_type_declare],
 195 [    /// An auxiliary type to compute the largest semantic type.
 196     union union_type
 197     {]b4_type_foreach([b4_char_sizeof])[};
 198
 199     /// Symbol semantic values.
 200     typedef variant<sizeof(union_type)> semantic_type;])
 201
 202
 203 # How the semantic value is extracted when using variants.
 204
 205 # b4_symbol_value(VAL, [TYPE])
 206 # ----------------------------
 207 m4_define([b4_symbol_value],
 208 [m4_ifval([$2],
 209           [$1.as< $2 >()],
 210           [$1])])
 211
 212 # b4_symbol_value_template(VAL, [TYPE])
 213 # -------------------------------------
 214 # Same as b4_symbol_value, but used in a template method.
 215 m4_define([b4_symbol_value_template],
 216 [m4_ifval([$2],
 217           [$1.template as< $2 >()],
 218           [$1])])
 219
 220
 221
 222 ## ------------- ##
 223 ## make_SYMBOL.  ##
 224 ## ------------- ##
 225
 226
 227 # b4_symbol_constructor_declare_(SYMBOL-NUMBER)
 228 # ---------------------------------------------
 229 # Declare the overloaded version of make_symbol for the (common) type of
 230 # these SYMBOL-NUMBERS.  Use at class-level.
 231 m4_define([b4_symbol_constructor_declare_],
 232 [b4_symbol_if([$1], [is_token], [b4_symbol_if([$1], [has_id],
 233 [    static inline
 234     symbol_type
 235     make_[]b4_symbol_([$1], [id]) (dnl
 236 b4_args(b4_symbol_if([$1], [has_type],
 237                      [const b4_symbol([$1], [type])& v]),
 238         b4_locations_if([const location_type& l])));
 239
 240 ])])])
 241
 242
 243 # b4_symbol_constructor_declare
 244 # -----------------------------
 245 # Declare symbol constructors for all the value types.
 246 # Use at class-level.
 247 m4_define([b4_symbol_constructor_declare],
 248 [    // Symbol constructors declarations.
 249 b4_symbol_foreach([b4_symbol_constructor_declare_])])
 250
 251
 252
 253 # b4_symbol_constructor_define_(SYMBOL-NUMBER)
 254 # --------------------------------------------
 255 # Define symbol constructor for this SYMBOL-NUMBER.
 256 m4_define([b4_symbol_constructor_define_],
 257 [b4_symbol_if([$1], [is_token], [b4_symbol_if([$1], [has_id],
 258 [  b4_parser_class_name::symbol_type
 259   b4_parser_class_name::make_[]b4_symbol_([$1], [id]) (dnl
 260 b4_args(b4_symbol_if([$1], [has_type],
 261                      [const b4_symbol([$1], [type])& v]),
 262         b4_locations_if([const location_type& l])))
 263   {
 264     return symbol_type (b4_args([token::b4_symbol([$1], [id])],
 265                                 b4_symbol_if([$1], [has_type], [v]),
 266                                 b4_locations_if([l])));
 267   }
 268
 269 ])])])
 270
 271
 272 # b4_symbol_constructor_define
 273 # ----------------------------
 274 # Define the overloaded versions of make_symbol for all the value types.
 275 m4_define([b4_symbol_constructor_define],
 276 [  // Implementation of make_symbol for each symbol type.
 277 b4_symbol_foreach([b4_symbol_constructor_define_])])