lbessard@70: /*
lbessard@70:  * (c) 2003 Mario de Sousa
lbessard@70:  *
lbessard@70:  * Offered to the public under the terms of the GNU General Public License
lbessard@70:  * as published by the Free Software Foundation; either version 2 of the
lbessard@70:  * License, or (at your option) any later version.
lbessard@70:  *
lbessard@70:  * This program is distributed in the hope that it will be useful, but
lbessard@70:  * WITHOUT ANY WARRANTY; without even the implied warranty of
lbessard@70:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
lbessard@70:  * Public License for more details.
lbessard@70:  *
lbessard@70:  * This code is made available on the understanding that it will not be
lbessard@70:  * used in safety-critical situations without a full and competent review.
lbessard@70:  */
lbessard@70: 
lbessard@70: /*
lbessard@70:  * An IEC 61131-3 IL and ST compiler.
lbessard@70:  *
lbessard@70:  * Based on the
lbessard@70:  * FINAL DRAFT - IEC 61131-3, 2nd Ed. (2001-12-10)
lbessard@70:  *
lbessard@70:  */
lbessard@70: 
lbessard@70: 
lbessard@70: /* Decomposes a variable instance name into its constituents,
lbessard@70:  * example:
lbessard@70:  *    window.points[1].coordinate.x
lbessard@70:  *
lbessard@70:  *  will succesfully return
lbessard@70:  *        - window
lbessard@70:  *        - points
lbessard@70:  *        - coordinate
lbessard@70:  *        - x
lbessard@70:  * on succesive calls to decompose_var_instance_name_c::next_part()
lbessard@70:  */
lbessard@70: class decompose_var_instance_name_c: null_visitor_c {
lbessard@70: 
lbessard@70:   private:
lbessard@70:     symbol_c *variable_name;
lbessard@70:     symbol_c *next_variable_name;
lbessard@70:     symbol_c *current_recursive_variable_name;
lbessard@70:     symbol_c *previously_returned_variable_name;
lbessard@70: 
lbessard@70:   public:
lbessard@70:     decompose_var_instance_name_c(symbol_c *variable_instance_name) {
lbessard@70:       variable_name = variable_instance_name;
lbessard@70:       next_variable_name = NULL;
lbessard@70:       current_recursive_variable_name = NULL;
lbessard@70:       previously_returned_variable_name = NULL;
lbessard@70:     }
lbessard@70: 
lbessard@70:   public:
lbessard@70:     symbol_c *next_part(void) {
lbessard@70:       /* We must always start from the top!
lbessard@70:        * See note in the structured_variable_c visitor
lbessard@70:        * to understand why...
lbessard@70:        */
lbessard@70:       symbol_c *res = (symbol_c *)variable_name->accept(*this);
lbessard@70:       next_variable_name = current_recursive_variable_name;
lbessard@70: 
lbessard@70:       if (previously_returned_variable_name == res)
lbessard@70:         return NULL;
lbessard@70:       previously_returned_variable_name = res;
lbessard@70:       return res;
lbessard@70:     }
lbessard@70: 
lbessard@70:   public:
lbessard@70: /*********************/
lbessard@70: /* B 1.4 - Variables */
lbessard@70: /*********************/
lbessard@70:     void *visit(symbolic_variable_c *symbol) {return (void *)(symbol->var_name);}
lbessard@70: 
lbessard@70: /********************************************/
lbessard@70: /* B.1.4.1   Directly Represented Variables */
lbessard@70: /********************************************/
lbessard@70:     void *visit(direct_variable_c *symbol) {return (void *)symbol;}
lbessard@70: 
lbessard@70: /*************************************/
lbessard@70: /* B.1.4.2   Multi-element Variables */
lbessard@70: /*************************************/
lbessard@70: /*  subscripted_variable '[' subscript_list ']' */
lbessard@70: // SYM_REF2(array_variable_c, subscripted_variable, subscript_list)
lbessard@70:     void *visit(array_variable_c *symbol) {
lbessard@70:       /* NOTE: the subscripted_variable may itself be a structure!,
lbessard@70:        * so we must recursevily visit!
lbessard@70:        */
lbessard@70:       return symbol->subscripted_variable->accept(*this);
lbessard@70:     }
lbessard@70: 
lbessard@70: /*  record_variable '.' field_selector */
lbessard@70: /*  WARNING: input and/or output variables of function blocks
lbessard@70:  *           may be accessed as fields of a tructured variable!
lbessard@70:  *           Code handling a structured_variable_c must take
lbessard@70:  *           this into account!
lbessard@70:  */
lbessard@70: //SYM_REF2(structured_variable_c, record_variable, field_selector)
lbessard@70:     void *visit(structured_variable_c *symbol) {
lbessard@70:       /* NOTE: The following code will not work, as structured_variable_c
lbessard@70:        *       are grouped on the left, and not on the right!
lbessard@70:        *
lbessard@70:        *       example: window.origin.x
lbessard@70:        *       will result in
lbessard@70:        *       s1 = structured_variable_c("window, "origin");
lbessard@70:        *       s2 = structured_variable_c(s1, "x");
lbessard@70:        *       AND NOT
lbessard@70:        *       s1 = structured_variable_c("origin", "x");
lbessard@70:        *       s2 = structured_variable_c("window", s1);
lbessard@70:        *
lbessard@70:        *       as the following code assumes!!
lbessard@70:        *
lbessard@70:       current_variable_name = symbol->field_selector;
lbessard@70:       return symbol->record_variable->accept(*this);
lbessard@70:        */
lbessard@70: 
lbessard@70:       /* The correct code, is therefore more complex... */
lbessard@70:       if (next_variable_name == symbol) {
lbessard@70:         /* NOTE: field_selector is always an identifier_c,
lbessard@98:          * so we do not have to recursevily visit it again...
lbessard@98:          * return (void *)symbol->field_selector->accept(*this);  -> NOT REQUIRED!!
lbessard@98:          */
lbessard@98:          return (void *)symbol->field_selector;
lbessard@70:       }
lbessard@70: 
lbessard@70:       current_recursive_variable_name = symbol;
lbessard@70:       return symbol->record_variable->accept(*this);
lbessard@70:     }
lbessard@70: };
lbessard@70: 
lbessard@70: 
lbessard@70: 
lbessard@70: