runtime/interpreter.c

   1
   2 #include <stdio.h>
   3 #include <stdlib.h>
   4 #include "interpreter.h"
   5
   6 struct parse_stack_frame *init_new_stack_frame(struct parse_state *parse_state, struct rtn *rtn)
   7 {
   8     struct parse_stack_frame *frame = &parse_state->parse_stack[parse_state->parse_stack_length++];
   9     frame->rtn = rtn;
  10     frame->rtn_state = &rtn->states[0];
  11     frame->slots.rtn = rtn;
  12     frame->slots.num_slots = rtn->num_slots;
  13     frame->slots.slots = malloc(sizeof(struct parse_val)*frame->slots.num_slots);
  14     return frame;
  15 }
  16
  17 struct parse_stack_frame *pop_stack_frame(struct parse_state *parse_state)
  18 {
  19     struct parse_stack_frame *frame = &parse_state->parse_stack[parse_state->parse_stack_length-1];
  20     free(frame->slots.slots);
  21     parse_state->parse_stack_length--;
  22     if(parse_state->parse_stack_length == 0)
  23     {
  24         return NULL;  /* the parse is over */
  25     }
  26     else
  27     {
  28         frame--;
  29         frame->rtn_state = frame->rtn_transition->dest_state;
  30         return frame;
  31     }
  32 }
  33
  34 void reset_dfa_match(struct parse_state *parse_state)
  35 {
  36     struct parse_stack_frame *frame = &parse_state->parse_stack[parse_state->parse_stack_length-1];
  37     parse_state->dfa = frame->rtn_state->term_dfa;
  38     parse_state->dfa_state = &parse_state->dfa->states[0];
  39     parse_state->match_begin = parse_state->offset;
  40     parse_state->last_match_state = NULL;
  41 }
  42
  43 void do_rtn_transition(struct parse_state *parse_state, int match_begin, int match_len, char *terminal)
  44 {
  45     struct parse_stack_frame *frame = &parse_state->parse_stack[parse_state->parse_stack_length-1];
  46     struct parse_val val = {PARSE_VAL_TERMINAL, {.terminal = {match_begin, match_len}}};
  47     bool found_transition = false;
  48
  49     /* is this an ignored terminal?  if so, just skip it */
  50     for(int i = 0; i < frame->rtn->num_ignore; i++)
  51     {
  52         if(frame->rtn->ignore_terminals[i] == terminal)
  53         {
  54             reset_dfa_match(parse_state);
  55             return;
  56         }
  57     }
  58
  59     /* find a transition out of this RTN state on this terminal */
  60     for(int i = 0; i < frame->rtn_state->num_transitions; i++)
  61     {
  62         struct rtn_transition *t = &frame->rtn_state->transitions[i];
  63         if(t->transition_type == TERMINAL_TRANSITION && t->edge.terminal_name == terminal)
  64         {
  65             frame->slots.slots[t->slotnum] = val;
  66             frame->rtn_state = t->dest_state;
  67             found_transition = true;
  68             break;
  69         }
  70         else if(t->transition_type == DECISION && t->edge.decision->terminal_name == terminal)
  71         {
  72             struct decision *d = t->edge.decision;
  73
  74             for(int i = 0; i < d->num_actions; i++)
  75             {
  76                 struct rtn_transition *t2 = &frame->rtn_state->transitions[d->actions[i]];
  77
  78                 if(t2->transition_type == NONTERM_TRANSITION)
  79                 {
  80                     if(parse_state->parse_stack_length == parse_state->parse_stack_size)
  81                     {
  82                         printf("Need to reallocate parse stack!!\n");
  83                         exit(1);
  84                     }
  85                     frame->rtn_transition = t2;
  86                     frame = init_new_stack_frame(parse_state, t2->edge.nonterminal);
  87                 }
  88                 else if(t2->transition_type == TERMINAL_TRANSITION)
  89                 {
  90                     frame->slots.slots[t2->slotnum] = val;
  91                     frame->rtn_state = t2->dest_state;
  92                 }
  93             }
  94             found_transition = true;
  95             break;
  96         }
  97     }
  98
  99     if(found_transition)
 100     {
 101         while(parse_state->parse_stack_length > 0 && frame->rtn_state->is_final)
 102             frame = pop_stack_frame(parse_state);
 103
 104         if(parse_state->parse_stack_length > 0)
 105             reset_dfa_match(parse_state);
 106     }
 107     else
 108     {
 109         printf("Syntax error -- no RTN transition!!\n");
 110     }
 111 }
 112
 113
 114 void parse(struct parse_state *parse_state)
 115 {
 116     bool user_cancelled = false;
 117
 118     while(!parse_state->buffer->is_eof && !user_cancelled && parse_state->parse_stack_length > 0)
 119     {
 120         int ch = parse_state->buffer->buf[parse_state->offset];
 121         //printf("Offset: %d, char %c\n", parse_state->offset, ch);
 122         int found_transition = 0;
 123
 124         /* We've read one character, which should cause one transition in the DFA for terminals.
 125          * Find the appropriate transition, and put the DFA in its new state. */
 126         for(int i = 0; i < parse_state->dfa_state->num_transitions; i++)
 127         {
 128             struct intfa_transition *t = &parse_state->dfa_state->transitions[i];
 129
 130             if(ch >= t->ch_low && ch <= t->ch_high)
 131             {
 132                 parse_state->dfa_state = t->dest_state;
 133                 found_transition = 1;
 134                 break;
 135             }
 136         }
 137
 138         if(found_transition)
 139         {
 140             if(parse_state->dfa_state->final)
 141             {
 142                 parse_state->last_match_state = parse_state->dfa_state;
 143                 parse_state->last_match_end = parse_state->offset;
 144             }
 145             parse_state->offset++;
 146         }
 147         else
 148         {
 149             /* if there was a previous match, fall back to that.  otherwise this character represents
 150              * a syntax error. */
 151             if(parse_state->last_match_state)
 152             {
 153                 /* we have a terminal.  do RTN transitions as appropriate */
 154                 //int terminal_len = parse_state->last_match_end-parse_state->match_begin+1;
 155                 //char terminal[terminal_len];
 156                 //memcpy(terminal, parse_state->buffer->buf+parse_state->match_begin, terminal_len);
 157                 //terminal[terminal_len] = '\0';
 158                 //printf("Recognized a terminal (%s) (%s)\n", parse_state->last_match_state->final, terminal);
 159                 parse_state->offset = parse_state->last_match_end + 1;
 160                 do_rtn_transition(parse_state, parse_state->match_begin, parse_state->last_match_end,
 161                                   parse_state->last_match_state->final);
 162             }
 163             else
 164             {
 165                 printf("Syntax error!");
 166             }
 167         }
 168     }
 169 }
 170
 171 /*
 172  * Local Variables:
 173  * c-file-style: "bsd"
 174  * c-basic-offset: 4
 175  * indent-tabs-mode: nil
 176  * End:
 177  * vim:et:sts=4:sw=4
 178  */