on_gosub.c

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/*****************************************************************************
 * ugBASIC - an isomorphic BASIC language compiler for retrocomputers        *
 *****************************************************************************
 * Copyright 2021-2026 Marco Spedaletti (asimov@mclink.it)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
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/****************************************************************************
 * INCLUDE SECTION 
 ****************************************************************************/
 
#include "../../ugbc.h"
 
/****************************************************************************
 * CODE SECTION 
 ****************************************************************************/

/* <usermanual>
@keyword ON...GOSUB
 
@english
This command is used to force a unconditional jump with returning to a pre-defined position when a 
specific expression is calculated. The choice is done against several positions,
and it depends on what value is held by the expression at the time it is spotted.
 
To work properly, the expression must have a value from 1 up to the number of 
the highest possible destination. If the expression has a value of 0 or 
greater than the highest possibile destination, no jump will be performed.
 
@italian
Questo comando viene utilizzato per forzare un salto incondizionato a una
posizione predefinita (con ritorno), calcolata da un'espressione. La scelta è tra le posizioni
elencate, e dipende dal valore dell'espressione al momento in cui viene 
calcolata.
 
Per funzionare correttamente, l'espressione deve avere un valore compreso 
tra 1 e il numero di destinazioni. Se l'espressione ha un valore di 0 o
maggiore della destinazione più alta possibile, non sarà eseguito alcun salto.
 
@syntax ON expression GOSUB label1[, label2 [, ... ] ]
 
@example ON level GOSUB level1, level2, level3
@usedInExample control_by_expression_01.bas
 
@target all
</usermanual> */
void on_gosub( Environment * _environment, char * _expression ) {
 
    MAKE_LABEL
 
    Variable * expression = variable_retrieve( _environment, _expression );
 
    char newLabel[MAX_TEMPORARY_STORAGE]; sprintf(newLabel, "gosub%d", UNIQUE_ID );
 
    Conditional * conditional = malloc( sizeof( Conditional ) );
    conditional->label = strdup( newLabel );
    conditional->type = CT_ON_GOSUB;
    conditional->expression = variable_cast( _environment, expression->name, expression->type );
    conditional->expression->locked = 1;
    conditional->index = 1;
    conditional->next = _environment->conditionals;
    _environment->conditionals = conditional;
 
}

void on_gosub_index( Environment * _environment, char * _label ) {
 
    Conditional * conditional = _environment->conditionals;
 
    if ( ! conditional ) {
        CRITICAL_INTERNAL_ERROR("on_gosub_index called out of order (1)");
    }
 
    if ( conditional->type != CT_ON_GOSUB ) {
        CRITICAL_INTERNAL_ERROR("on_gosub_index called out of order (2)");
    }
 
    char realLabel[MAX_TEMPORARY_STORAGE];
    if (strcmp(_label, "q" ) == 0 && _environment->vestigialConfig.rchack_ostra_1172 ) {
        sprintf( realLabel, "lbl%s", _label );
    } else {
        strcpy( realLabel, _label );
    }
    label_referred_define_named( _environment, realLabel );
 
    Variable * index = variable_resident( _environment, VT_BYTE, "(index)");
    
    variable_store( _environment, index->name, conditional->index );
 
    Variable * expression = variable_retrieve( _environment, conditional->expression->name );
 
    char newLabel[MAX_TEMPORARY_STORAGE]; sprintf(newLabel, "%s%d", conditional->label, (conditional->index+1) );
 
    cpu_bveq( _environment, variable_compare( _environment, expression->name, index->name )->realName, newLabel );
 
    cpu_call( _environment, realLabel );
 
    char newLabel2[MAX_TEMPORARY_STORAGE]; sprintf(newLabel2, "%sfinal", conditional->label );
 
    cpu_jump( _environment, newLabel2 );
 
    cpu_label( _environment, newLabel );
 
    ++conditional->index;
 
};

void on_gosub_number( Environment * _environment, int _number ) {
 
    label_referred_define_numeric( _environment, _number );
 
    char label[MAX_TEMPORARY_STORAGE]; sprintf( label, "_linenumber%d", _number );
 
    on_gosub_index( _environment, label );
 
};
 

void on_gosub_end( Environment * _environment ) {
 
    Conditional * conditional = _environment->conditionals;
 
    if ( ! conditional ) {
        CRITICAL_INTERNAL_ERROR("on_gosub_end called out of order (1)");
    }
 
    if ( conditional->type != CT_ON_GOSUB ) {
        CRITICAL_INTERNAL_ERROR("on_gosub_end called out of order (2)");
    }
 
    char newLabel2[MAX_TEMPORARY_STORAGE]; sprintf(newLabel2, "%sfinal", conditional->label );
 
    cpu_label( _environment, newLabel2 );
 
    _environment->conditionals->expression->locked = 0;
 
    _environment->conditionals = _environment->conditionals->next;
 
};