-
- if (last_shift)
- last_shift->next = p;
- else
- first_shift = p;
- last_shift = p;
-}
-
-
-/*------------------------------------------------------------------.
-| Subroutine of augment_automaton. Create the next-to-final state, |
-| to which a shift has already been made in the initial state. |
-| |
-| The task of this state consists in shifting (actually, it's a |
-| goto, but shifts and gotos are both stored in SHIFTS) the start |
-| symbols, hence the name. |
-`------------------------------------------------------------------*/
-
-static void
-insert_start_shifting_state (void)
-{
- state_t *statep;
- shifts *sp;
-
- statep = STATE_ALLOC (0);
- statep->number = nstates;
-
- /* The distinctive feature of this state from the
- eof_shifting_state, is that it is labeled as post-start-symbol
- shifting. I fail to understand why this state, and the
- post-start-start can't be merged into one. But it does fail if
- you try. --akim */
- statep->accessing_symbol = start_symbol;
-
- last_state->next = statep;
- last_state = statep;
-
- /* Make a shift from this state to (what will be) the final state. */
- sp = shifts_new (1);
- statep->shifts = sp;
- sp->number = nstates++;
- sp->shifts[0] = nstates;
-
- last_shift->next = sp;
- last_shift = sp;
-}
-
-
-/*-----------------------------------------------------------------.
-| Subroutine of augment_automaton. Create the final state, which |
-| shifts `0', the end of file. The initial state shifts the start |
-| symbol, and goes to here. |
-`-----------------------------------------------------------------*/
-
-static void
-insert_eof_shifting_state (void)
-{
- state_t *statep;
- shifts *sp;
-
- /* Make the final state--the one that follows a shift from the
- next-to-final state.
- The symbol for that shift is 0 (end-of-file). */
- statep = STATE_ALLOC (0);
- statep->number = nstates;
-
- last_state->next = statep;
- last_state = statep;
-
- /* Make the shift from the final state to the termination state. */
- sp = shifts_new (1);
- statep->shifts = sp;
- sp->number = nstates++;
- sp->shifts[0] = nstates;
-
- last_shift->next = sp;
- last_shift = sp;
-}
-
-
-/*---------------------------------------------------------------.
-| Subroutine of augment_automaton. Create the accepting state. |
-`---------------------------------------------------------------*/
-
-static void
-insert_accepting_state (void)
-{
- state_t *statep;
-
- /* Note that the variable `final_state' refers to what we sometimes
- call the termination state. */
- final_state = nstates;
-
- /* Make the termination state. */
- statep = STATE_ALLOC (0);
- statep->number = nstates++;
- last_state->next = statep;
- last_state = statep;
-}
-
-
-
-
-
-/*------------------------------------------------------------------.
-| Make sure that the initial state has a shift that accepts the |
-| grammar's start symbol and goes to the next-to-final state, which |
-| has a shift going to the final state, which has a shift to the |
-| termination state. Create such states and shifts if they don't |
-| happen to exist already. |
-`------------------------------------------------------------------*/
-
-static void
-augment_automaton (void)
-{
- if (!first_shift->nshifts)
- {
- /* There are no shifts for any state. Make one shift, from the
- initial state to the next-to-final state. */
-
- shifts *sp = shifts_new (1);
- first_state->shifts = sp;
- sp->shifts[0] = nstates;
-
- /* Initialize the chain of shifts with sp. */
- first_shift = sp;
- last_shift = sp;
-
- /* Create the next-to-final state, with shift to
- what will be the final state. */
- insert_start_shifting_state ();
- }
- else if (first_shift->number == 0)
- {
- state_t *statep = first_state->next;
- shifts *sp = first_shift;
- shifts *sp1 = NULL;
- /* The states reached by shifts from FIRST_STATE are numbered
- 1..(SP->NSHIFTS). Look for one reached by START_SYMBOL. */
- while (statep->accessing_symbol != start_symbol
- && statep->number < sp->nshifts)
- statep = statep->next;
-
- if (statep->accessing_symbol == start_symbol)
- {
- /* We already have a next-to-final state.
- Make sure it has a shift to what will be the final state. */
- while (sp && sp->number < statep->number)
- {
- sp1 = sp;
- sp = sp->next;
- }
-
- if (sp && sp->number == statep->number)
- {
- int i;
- shifts *sp2 = shifts_new (sp->nshifts + 1);
- sp2->number = statep->number;
- statep->shifts = sp2;
- sp2->shifts[0] = nstates;
- for (i = sp->nshifts; i > 0; i--)
- sp2->shifts[i] = sp->shifts[i - 1];
-
- /* Patch sp2 into the chain of shifts in place of sp,
- following sp1. */
- sp2->next = sp->next;
- sp1->next = sp2;
- if (sp == last_shift)
- last_shift = sp2;
- XFREE (sp);
- }
- else
- {
- shifts *sp2 = shifts_new (1);
- sp2->number = statep->number;
- statep->shifts = sp2;
- sp2->shifts[0] = nstates;
-
- /* Patch sp2 into the chain of shifts between sp1 and sp. */
- sp2->next = sp;
- sp1->next = sp2;
- if (sp == 0)
- last_shift = sp2;
- }
- }
- else
- {
- int i, k;
- shifts *sp2;
- sp = first_shift;
-
- /* There is no next-to-final state as yet. */
- /* Add one more shift in first_shift,
- going to the next-to-final state (yet to be made). */
- sp2 = shifts_new (sp->nshifts + 1);
- first_state->shifts = sp2;
- /* Stick this shift into the vector at the proper place. */
- statep = first_state->next;
- for (k = 0, i = 0; i < sp->nshifts; k++, i++)
- {
- if (statep->accessing_symbol > start_symbol && i == k)
- sp2->shifts[k++] = nstates;
- sp2->shifts[k] = sp->shifts[i];
- statep = statep->next;
- }
- if (i == k)
- sp2->shifts[k++] = nstates;
-
- /* Patch sp2 into the chain of shifts
- in place of sp, at the beginning. */
- sp2->next = sp->next;
- first_shift = sp2;
- if (last_shift == sp)
- last_shift = sp2;
-
- XFREE (sp);
-
- /* Create the next-to-final state, with shift to
- what will be the final state. */
- insert_start_shifting_state ();
- }
- }
- else
- {
- /* The initial state didn't even have any shifts.
- Give it one shift, to the next-to-final state. */
- shifts *sp = shifts_new (1);
- first_state->shifts = sp;
- sp->shifts[0] = nstates;
-
- /* Patch sp into the chain of shifts at the beginning. */
- sp->next = first_shift;
- first_shift = sp;
-
- /* Create the next-to-final state, with shift to
- what will be the final state. */
- insert_start_shifting_state ();
- }
-
- insert_eof_shifting_state ();
- insert_accepting_state ();
projects / bison.git / blobdiff