etisserant@0: /*
etisserant@0:  * (c) 2003 Mario de Sousa
etisserant@0:  *
etisserant@0:  * Offered to the public under the terms of the GNU General Public License
etisserant@0:  * as published by the Free Software Foundation; either version 2 of the
etisserant@0:  * License, or (at your option) any later version.
etisserant@0:  *
etisserant@0:  * This program is distributed in the hope that it will be useful, but
etisserant@0:  * WITHOUT ANY WARRANTY; without even the implied warranty of
etisserant@0:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
etisserant@0:  * Public License for more details.
etisserant@0:  *
etisserant@0:  * This code is made available on the understanding that it will not be
etisserant@0:  * used in safety-critical situations without a full and competent review.
etisserant@0:  */
etisserant@0: 
etisserant@0: /*
etisserant@0:  * An IEC 61131-3 IL and ST compiler.
etisserant@0:  *
etisserant@0:  * Based on the
etisserant@0:  * FINAL DRAFT - IEC 61131-3, 2nd Ed. (2001-12-10)
etisserant@0:  *
etisserant@0:  */
etisserant@0: 
etisserant@0: 
etisserant@0: /* Decomposes a variable instance name into its constituents,
etisserant@0:  * example:
etisserant@0:  *    window.points[1].coordinate.x
etisserant@0:  *
etisserant@0:  *  will succesfully return
etisserant@0:  *        - window
etisserant@0:  *        - points
etisserant@0:  *        - coordinate
etisserant@0:  *        - x
etisserant@0:  * on succesive calls to decompose_var_instance_name_c::next_part()
etisserant@0:  */
etisserant@0: class decompose_var_instance_name_c: null_visitor_c {
etisserant@0: 
etisserant@0:   private:
etisserant@0:     symbol_c *variable_name;
etisserant@0:     symbol_c *next_variable_name;
etisserant@0:     symbol_c *current_recursive_variable_name;
etisserant@0:     symbol_c *previously_returned_variable_name;
etisserant@0: 
etisserant@0:   public:
etisserant@0:     decompose_var_instance_name_c(symbol_c *variable_instance_name) {
etisserant@0:       variable_name = variable_instance_name;
etisserant@0:       next_variable_name = NULL;
etisserant@0:       current_recursive_variable_name = NULL;
etisserant@0:       previously_returned_variable_name = NULL;
etisserant@0:     }
etisserant@0: 
etisserant@0:   public:
etisserant@0:     symbol_c *next_part(void) {
etisserant@0:       /* We must always start from the top!
etisserant@0:        * See note in the structured_variable_c visitor
etisserant@0:        * to understand why...
etisserant@0:        */
etisserant@0:       symbol_c *res = (symbol_c *)variable_name->accept(*this);
etisserant@0:       next_variable_name = current_recursive_variable_name;
etisserant@0: 
etisserant@0:       if (previously_returned_variable_name == res)
etisserant@0:         return NULL;
etisserant@0:       previously_returned_variable_name = res;
etisserant@0:       return res;
etisserant@0:     }
etisserant@0: 
etisserant@0:   public:
etisserant@0: /*********************/
etisserant@0: /* B 1.4 - Variables */
etisserant@0: /*********************/
etisserant@0:     void *visit(symbolic_variable_c *symbol) {return (void *)(symbol->var_name);}
etisserant@0: 
etisserant@0: /********************************************/
etisserant@0: /* B.1.4.1   Directly Represented Variables */
etisserant@0: /********************************************/
etisserant@0:     void *visit(direct_variable_c *symbol) {return (void *)symbol;}
etisserant@0: 
etisserant@0: /*************************************/
etisserant@0: /* B.1.4.2   Multi-element Variables */
etisserant@0: /*************************************/
etisserant@0: /*  subscripted_variable '[' subscript_list ']' */
etisserant@0: // SYM_REF2(array_variable_c, subscripted_variable, subscript_list)
etisserant@0:     void *visit(array_variable_c *symbol) {
etisserant@0:       /* NOTE: the subscripted_variable may itself be a structure!,
etisserant@0:        * so we must recursevily visit!
etisserant@0:        */
etisserant@0:       return symbol->subscripted_variable->accept(*this);
etisserant@0:     }
etisserant@0: 
etisserant@0: /*  record_variable '.' field_selector */
etisserant@0: /*  WARNING: input and/or output variables of function blocks
etisserant@0:  *           may be accessed as fields of a tructured variable!
etisserant@0:  *           Code handling a structured_variable_c must take
etisserant@0:  *           this into account!
etisserant@0:  */
etisserant@0: //SYM_REF2(structured_variable_c, record_variable, field_selector)
etisserant@0:     void *visit(structured_variable_c *symbol) {
etisserant@0:       /* NOTE: The following code will not work, as structured_variable_c
etisserant@0:        *       are grouped on the left, and not on the right!
etisserant@0:        *
etisserant@0:        *       example: window.origin.x
etisserant@0:        *       will result in
etisserant@0:        *       s1 = structured_variable_c("window, "origin");
etisserant@0:        *       s2 = structured_variable_c(s1, "x");
etisserant@0:        *       AND NOT
etisserant@0:        *       s1 = structured_variable_c("origin", "x");
etisserant@0:        *       s2 = structured_variable_c("window", s1);
etisserant@0:        *
etisserant@0:        *       as the following code assumes!!
etisserant@0:        *
etisserant@0:       current_variable_name = symbol->field_selector;
etisserant@0:       return symbol->record_variable->accept(*this);
etisserant@0:        */
etisserant@0: 
etisserant@0:       /* The correct code, is therefore more complex... */
etisserant@0:       if (next_variable_name == symbol) {
etisserant@0:         /* NOTE: field_selector is always an identifier_c,
etisserant@0: 	 * so we do not have to recursevily visit it again...
etisserant@0: 	 * return (void *)symbol->field_selector->accept(*this);  -> NOT REQUIRED!!
etisserant@0: 	 */
etisserant@0: 	return (void *)symbol->field_selector;
etisserant@0:       }
etisserant@0: 
etisserant@0:       current_recursive_variable_name = symbol;
etisserant@0:       return symbol->record_variable->accept(*this);
etisserant@0:     }
etisserant@0: };
etisserant@0: 
etisserant@0: 
etisserant@0: 
etisserant@0: