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 /* Decomposes a variable instance name into its constituents,

    27  * example:

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

    29  *

    30  *  will succesfully return

    31  *        - window

    32  *        - points

    33  *        - coordinate

    34  *        - x

    35  * on succesive calls to decompose_var_instance_name_c::next_part()

    36  */

    37 

    38 

    39 

    40 #include "decompose_var_instance_name.hh"

    41 

    42 decompose_var_instance_name_c::decompose_var_instance_name_c(symbol_c *variable_instance_name) {

    43   variable_name = variable_instance_name;

    44   next_variable_name = NULL;

    45   current_recursive_variable_name = NULL;

    46   previously_returned_variable_name = NULL;

    47 }

    48 

    49 symbol_c *decompose_var_instance_name_c::next_part(void) {

    50   /* We must always start from the top!

    51    * See note in the structured_variable_c visitor

    52    * to understand why...

    53    */

    54   symbol_c *res = (symbol_c *)variable_name->accept(*this);

    55   next_variable_name = current_recursive_variable_name;

    56 

    57   if (previously_returned_variable_name == res)

    58     return NULL;

    59   previously_returned_variable_name = res;

    60   return res;

    61 }

    62 

    63 /*********************/

    64 /* B 1.4 - Variables */

    65 /*********************/

    66 void *decompose_var_instance_name_c::visit(symbolic_variable_c *symbol) {return (void *)(symbol->var_name);}

    67 

    68 /********************************************/

    69 /* B.1.4.1   Directly Represented Variables */

    70 /********************************************/

    71 void *decompose_var_instance_name_c::visit(direct_variable_c *symbol) {return (void *)symbol;}

    72 

    73 /*************************************/

    74 /* B.1.4.2   Multi-element Variables */

    75 /*************************************/

    76 /*  subscripted_variable '[' subscript_list ']' */

    77 // SYM_REF2(array_variable_c, subscripted_variable, subscript_list)

    78 void *decompose_var_instance_name_c::visit(array_variable_c *symbol) {

    79   /* NOTE: the subscripted_variable may itself be a structure!,

    80    * so we must recursevily visit!

    81    */

    82   return symbol->subscripted_variable->accept(*this);

    83 }

    84 

    85 /*  record_variable '.' field_selector */

    86 /*  WARNING: input and/or output variables of function blocks

    87  *           may be accessed as fields of a tructured variable!

    88  *           Code handling a structured_variable_c must take

    89  *           this into account!

    90  */

    91 //SYM_REF2(structured_variable_c, record_variable, field_selector)

    92 void *decompose_var_instance_name_c::visit(structured_variable_c *symbol) {

    93   /* NOTE: The following code will not work, as structured_variable_c

    94    *       are grouped on the left, and not on the right!

    95    *

    96    *       example: window.origin.x

    97    *       will result in

    98    *       s1 = structured_variable_c("window, "origin");

    99    *       s2 = structured_variable_c(s1, "x");

   100    *       AND NOT

   101    *       s1 = structured_variable_c("origin", "x");

   102    *       s2 = structured_variable_c("window", s1);

   103    *

   104    *       as the following code assumes!!

   105    *

   106   current_variable_name = symbol->field_selector;

   107   return symbol->record_variable->accept(*this);

   108    */

   109 

   110   /* The correct code, is therefore more complex... */

   111   if (next_variable_name == symbol) {

   112     /* NOTE: field_selector is always an identifier_c,

   113      * so we do not have to recursevily visit it again...

   114      * return (void *)symbol->field_selector->accept(*this);  -> NOT REQUIRED!!

   115      */

   116      return (void *)symbol->field_selector;

   117   }

   118 

   119   current_recursive_variable_name = symbol;

   120   return symbol->record_variable->accept(*this);

   121 }

   122 

   123 

   124 

   125