int nstates;
int final_state;
-state_t *first_state = NULL;
-shifts *first_shift = NULL;
+static state_t *first_state = NULL;
static state_t *this_state = NULL;
static state_t *last_state = NULL;
-static shifts *last_shift = NULL;
static int nshifts;
static short *shift_symbol = NULL;
save_shifts (void)
{
shifts *p = shifts_new (nshifts);
-
- p->number = this_state->number;
-
shortcpy (p->shifts, shiftset, nshifts);
-
- if (last_shift)
- last_shift->next = p;
- else
- first_shift = p;
- last_shift = p;
+ this_state->shifts = 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_shift (void)
+insert_start_shifting_state (void)
{
state_t *statep;
shifts *sp;
statep = STATE_ALLOC (0);
- statep->number = nstates;
+ 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;
/* Make a shift from this state to (what will be) the final state. */
sp = shifts_new (1);
- sp->number = nstates++;
+ statep->shifts = sp;
sp->shifts[0] = nstates;
+}
+
+
+/*-----------------------------------------------------------------.
+| 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. |
+`-----------------------------------------------------------------*/
- last_shift->next = sp;
- last_shift = sp;
+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->shifts[0] = nstates;
+}
+
+
+/*---------------------------------------------------------------.
+| 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 |
static void
augment_automaton (void)
{
- state_t *statep;
- shifts *sp;
- shifts *sp1 = NULL;
-
- sp = first_shift;
-
- if (!sp->nshifts)
+ if (!first_state->shifts->nshifts)
{
- /* There are no shifts for any state. Make one shift, from the
+ /* The first state has no shifts. Make one shift, from the
initial state to the next-to-final state. */
- sp = shifts_new (1);
+ 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_shift ();
+ insert_start_shifting_state ();
}
- else if (sp->number == 0)
+ else
{
- statep = first_state->next;
-
+ state_t *statep = first_state->next;
/* 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)
+ 1..(SP->NSHIFTS). Look for one reached by START_SYMBOL.
+ This is typical of `start: start ... ;': there is a state
+ with the item `start: start . ...'. We want to add a `shift
+ on EOF to eof-shifting state here. */
+ while (statep->accessing_symbol != start_symbol
+ && statep->number < first_state->shifts->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;
- }
+ /* We already have STATEP, a next-to-final state for `start:
+ start . ...'. Make sure it has a shift to what will be
+ the final state. */
+ int i;
- if (sp && sp->number == statep->number)
- {
- int i;
- shifts *sp2 = shifts_new (sp->nshifts + 1);
- sp2->number = statep->number;
- 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;
- 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;
- }
+ /* Find the shift of the inital state that leads to STATEP. */
+ shifts *sp = statep->shifts;
+
+ shifts *sp1 = shifts_new (sp->nshifts + 1);
+ statep->shifts = sp1;
+ sp1->shifts[0] = nstates;
+ for (i = sp->nshifts; i > 0; i--)
+ sp1->shifts[i] = sp->shifts[i - 1];
+
+ XFREE (sp);
+
+ insert_eof_shifting_state ();
}
else
{
+ /* There is no state for `start: start . ...'. */
int i, k;
- shifts *sp2;
-
- /* 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). */
- sp = first_shift;
-
- sp2 = shifts_new (sp->nshifts + 1);
+ shifts *sp = first_state->shifts;
+ shifts *sp1 = NULL;
+ /* Add one more shift to the initial state, going to the
+ next-to-final state (yet to be made). */
+ sp1 = shifts_new (sp->nshifts + 1);
+ first_state->shifts = sp1;
/* 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];
+ sp1->shifts[k++] = nstates;
+ sp1->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;
+ sp1->shifts[k++] = nstates;
XFREE (sp);
- /* Create the next-to-final state, with shift to
- what will be the final state. */
- insert_start_shift ();
+ /* Create the next-to-final state, with shift to what will
+ be the final state. Corresponds to `start: start . ...'. */
+ insert_start_shifting_state ();
}
}
- else
- {
- /* The initial state didn't even have any shifts.
- Give it one shift, to the next-to-final state. */
- sp = shifts_new (1);
- 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_shift ();
- }
- /* 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);
- sp->number = nstates++;
- sp->shifts[0] = nstates;
- last_shift->next = sp;
- last_shift = sp;
-
- /* 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;
+ insert_accepting_state ();
}
}
\f
+/*--------------------.
+| Build STATE_TABLE. |
+`--------------------*/
+
+static void
+set_state_table (void)
+{
+ /* NSTATES + 1 because lookahead for the pseudo state number NSTATES
+ might be used (see conflicts.c). It is too opaque for me to
+ provide a probably less hacky implementation. --akim */
+ state_table = XCALLOC (state_t *, nstates + 1);
+
+ {
+ state_t *sp;
+ for (sp = first_state; sp; sp = sp->next)
+ state_table[sp->number] = sp;
+ }
+
+ /* Pessimization, but simplification of the code: make sure all the
+ states have a shifts, even if reduced to 0 shifts. */
+ {
+ int i;
+ for (i = 0; i < nstates; i++)
+ if (!state_table[i]->shifts)
+ state_table[i]->shifts = shifts_new (0);
+ }
+}
+
/*-------------------------------------------------------------------.
| Compute the nondeterministic finite state machine (see state.h for |
| details) from the grammar. |
/* set up initial and final states as parser wants them */
augment_automaton ();
+
+ /* Set up STATE_TABLE. */
+ set_state_table ();
}
projects / bison.git / blobdiff