1 /*

     2  * (c) 2003 Mario de Sousa

     3  *

     4  * Offered to the public under the terms of the GNU General Public License

     5  * as published by the Free Software Foundation; either version 2 of the

     6  * License, or (at your option) any later version.

     7  *

     8  * This program is distributed in the hope that it will be useful, but

     9  * WITHOUT ANY WARRANTY; without even the implied warranty of

    10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General

    11  * Public License for more details.

    12  *

    13  * This code is made available on the understanding that it will not be

    14  * used in safety-critical situations without a full and competent review.

    15  */

    16 

    17 /*

    18  * An IEC 61131-3 IL and ST compiler.

    19  *

    20  * Based on the

    21  * FINAL DRAFT - IEC 61131-3, 2nd Ed. (2001-12-10)

    22  *

    23  */

    24 

    25 

    26 

    27 /* Determine the data type of a variable.

    28  * The variable may be a simple variable, a function block instance, a

    29  * struture element within a data structured type (a struct or a fb), or

    30  * an array element.

    31  * A mixture of array element of a structure element of a structure element

    32  * of a .... is also suported!

    33  *

    34  * A reference to the relevant base type __definition__ is returned.

    35  * This means that if we find that the variable is of type MY_INT,

    36  * which was previously declared to be

    37  * TYPE MY_INT: INT := 9;

    38  * this class wil return INT, and __not__ MY_INT !!

    39  *

    40  *

    41  *  example:

    42  *    window.points[1].coordinate.x

    43  *    window.points[1].colour

    44  *    etc... ARE ALLOWED!

    45  *

    46  * This class must be passed the scope within which the

    47  * variable was declared, and the variable name...

    48  */

    49 class search_varfb_instance_type_c: public search_base_type_c {

    50   private:

    51     search_var_instance_decl_c search_var_instance_decl;

    52     decompose_var_instance_name_c *decompose_var_instance_name;

    53     symbol_c *current_structelement_name;

    54 

    55   public:

    56     search_varfb_instance_type_c(symbol_c *search_scope): search_var_instance_decl(search_scope) {

    57       this->decompose_var_instance_name = NULL;

    58       this->current_structelement_name = NULL;

    59     }

    60 

    61 

    62     symbol_c *get_type(symbol_c *variable_name) {

    63       this->current_structelement_name = NULL;

    64       this->decompose_var_instance_name = new decompose_var_instance_name_c(variable_name);

    65       if (NULL == decompose_var_instance_name) ERROR;

    66 

    67       /* find the part of the variable name that will appear in the

    68        * variable declaration, for e.g., in window.point.x, this would be

    69        * window!

    70        */

    71       symbol_c *var_name_part = decompose_var_instance_name->next_part();

    72       if (NULL == var_name_part) ERROR;

    73 

    74       /* Now we try to find the variable instance declaration, to determine its type... */

    75       symbol_c *var_decl = search_var_instance_decl.get_decl(var_name_part);

    76       if (NULL == var_decl) {

    77         /* variable instance declaration not found! */

    78  	return NULL;

    79       }

    80 

    81       /* if it is a struct or function block, we must search the type

    82        * of the struct or function block member.

    83        * This is done by this class visiting the var_decl.

    84        * This class, while visiting, will recursively call

    85        * decompose_var_instance_name->get_next() when and if required...

    86        */

    87       symbol_c *res = (symbol_c *)var_decl->accept(*this);

    88       if (NULL == res) ERROR;

    89 

    90       /* make sure that we have decomposed all strcuture elements of the variable name */

    91       symbol_c *var_name = decompose_var_instance_name->next_part();

    92       if (NULL != var_name) ERROR;

    93 

    94       return res;

    95     }

    96 

    97   private:

    98     /* a helper function... */

    99     void *visit_list(list_c *list)	{

   100       if (NULL == current_structelement_name) ERROR;

   101 

   102       for(int i = 0; i < list->n; i++) {

   103         void *res = list->elements[i]->accept(*this);

   104         if (res != NULL)

   105           return res;

   106       }

   107       /* not found! */

   108       return NULL;

   109     }

   110 

   111     /* a helper function... */

   112     void *base_type(symbol_c *symbol)	{

   113         search_base_type_c search_base_type;

   114 	return symbol->accept(search_base_type);

   115     }

   116 

   117 

   118   private:

   119     /* We override the base class' visitor to identifier_c.

   120      * This is so because the base class does not consider a function block

   121      * to be a type, unlike this class that allows a variable instance

   122      * of a function block type...

   123      */

   124     void *visit(identifier_c *type_name) {

   125       /* look up the type declaration... */

   126       symbol_c *fb_decl = function_block_type_symtable.find_value(type_name);

   127       if (fb_decl != function_block_type_symtable.end_value())

   128         /* Type declaration found!! */

   129 	return fb_decl->accept(*this);

   130 

   131       /* No. It is not a function block, so we let

   132        * the base class take care of it...

   133        */

   134       return search_base_type_c::visit(type_name);

   135     }

   136 

   137 /********************************/

   138 /* B 1.3.3 - Derived data types */

   139 /********************************/

   140 /*  structure_type_name ':' structure_specification */

   141     void *visit(structure_type_declaration_c *symbol) {

   142       return symbol->structure_specification->accept(*this);

   143       /* NOTE: structure_specification will point to either a

   144        *       initialized_structure_c

   145        *       OR A

   146        *       structure_element_declaration_list_c

   147        */

   148     }

   149 

   150 /* structure_type_name ASSIGN structure_initialization */

   151 /* structure_initialization may be NULL ! */

   152 // SYM_REF2(initialized_structure_c, structure_type_name, structure_initialization)

   153     void *visit(initialized_structure_c *symbol)	{

   154       /* make sure that we have decomposed all strcuture elements of the variable name */

   155       symbol_c *var_name = decompose_var_instance_name->next_part();

   156       if (NULL == var_name) {

   157         /* this is it... !

   158 	  * No need to look any further...

   159 	 */

   160 	/* NOTE: we could simply do a

   161 	 *   return (void *)symbol;

   162 	 *       nevertheless, note that this search_varfb_instance_type_c

   163 	 *       class inherits from the search_base_type_c class,

   164 	 *       which means that it will usually return the base type,

   165 	 *       and not the derived type (*). If we are to be consistent,

   166 	 *       we should guarantee that we always return the base type.

   167 	 *       To do this we could use

   168 	 *   return (void *)symbol->accept(*this);

   169 	 *       since this class inherits from the search_base_type_c.

   170 	 *       However, in this case we don't want it to follow

   171 	 *       the structs as this search_varfb_instance_type_c does.

   172 	 *       We therefore have to create a new search_base_type_c

   173 	 *       instance to search through this type without going

   174 	 *       through the structs...

   175 	 */

   176         return base_type(symbol->structure_type_name);

   177       }

   178 

   179       /* now search the structure declaration */

   180       current_structelement_name = var_name;

   181       /* recursively find out the data type of var_name... */

   182       return symbol->structure_type_name->accept(*this);

   183     }

   184 

   185 /* helper symbol for structure_declaration */

   186 /* structure_declaration:  STRUCT structure_element_declaration_list END_STRUCT */

   187 /* structure_element_declaration_list structure_element_declaration ';' */

   188     void *visit(structure_element_declaration_list_c *symbol)	{return visit_list(symbol);}

   189 

   190 /*  structure_element_name ':' spec_init */

   191     void *visit(structure_element_declaration_c *symbol) {

   192       if (NULL == current_structelement_name) ERROR;

   193 

   194       if (compare_identifiers(symbol->structure_element_name, current_structelement_name) == 0)

   195         return symbol->spec_init->accept(*this);

   196 

   197       return NULL;

   198     }

   199 

   200 /* helper symbol for structure_initialization */

   201 /* structure_initialization: '(' structure_element_initialization_list ')' */

   202 /* structure_element_initialization_list ',' structure_element_initialization */

   203     void *visit(structure_element_initialization_list_c *symbol) {ERROR; return NULL;} /* should never get called... */

   204 /*  structure_element_name ASSIGN value */

   205     void *visit(structure_element_initialization_c *symbol) {ERROR; return NULL;} /* should never get called... */

   206 

   207 

   208 

   209 /**************************************/

   210 /* B.1.5 - Program organization units */

   211 /**************************************/

   212 /*****************************/

   213 /* B 1.5.2 - Function Blocks */

   214 /*****************************/

   215 /*  FUNCTION_BLOCK derived_function_block_name io_OR_other_var_declarations function_block_body END_FUNCTION_BLOCK */

   216 // SYM_REF4(function_block_declaration_c, fblock_name, var_declarations, fblock_body, unused)

   217     void *visit(function_block_declaration_c *symbol) {

   218       /* make sure that we have decomposed all strcuture elements of the variable name */

   219 

   220       symbol_c *var_name = decompose_var_instance_name->next_part();

   221       if (NULL == var_name) {

   222         /* this is it... !

   223 	 * No need to look any further...

   224 	 * Note also that, unlike for the struct types, a function block may

   225 	 * not be defined based on another (i.e. no inheritance is allowed),

   226 	 * so this function block is already the most base type.

   227 	 * We simply return it.

   228 	 */

   229 	return (void *)symbol;

   230       }

   231 

   232       /* now search the function block declaration for the variable... */

   233       search_var_instance_decl_c search_decl(symbol);

   234       symbol_c *var_decl = search_decl.get_decl(var_name);

   235       if (NULL == var_decl) {

   236         /* variable instance declaration not found! */

   237  	return NULL;

   238       }

   239 

   240       /* We have found the declaration.

   241        * Should we look any further?

   242        */

   243       var_name = decompose_var_instance_name->next_part();

   244       if (NULL == var_name) {

   245         /* this is it... ! */

   246 	return base_type(var_decl);

   247       }

   248 

   249       current_structelement_name = var_name;

   250       /* recursively find out the data type of var_name... */

   251       return symbol->var_declarations->accept(*this);

   252     }

   253 

   254 };

   255 

   256 

   257 

   258 

   259