state. These symbols at these items are the allowable inputs that
can follow now.
- A core represents one state. States are numbered in the number
+ A core represents one state. States are numbered in the NUMBER
field. When generate_states is finished, the starting state is
- state 0 and nstates is the number of states. (A transition to a
- state whose state number is nstates indicates termination.) All
- the cores are chained together and first_state points to the first
- one (state 0).
+ state 0 and NSTATES is the number of states. (FIXME: This sentence
+ is no longer true: A transition to a state whose state number is
+ NSTATES indicates termination.) All the cores are chained together
+ and FIRST_STATE points to the first one (state 0).
For each state there is a particular symbol which must have been
the last thing accepted to reach that state. It is the
- accessing_symbol of the core.
+ ACCESSING_SYMBOL of the core.
- Each core contains a vector of nitems items which are the indices
- in the ritems vector of the items that are selected in this state.
+ Each core contains a vector of NITEMS items which are the indices
+ in the RITEMS vector of the items that are selected in this state.
- The link field is used for chaining buckets that hash states by
- their itemsets. This is for recognizing equivalent states and
- combining them when the states are generated.
+ The two types of actions are shifts/gotos (push the lookahead token
+ and read another/goto to the state designated by a nterm) and
+ reductions (combine the last n things on the stack via a rule,
+ replace them with the symbol that the rule derives, and leave the
+ lookahead token alone). When the states are generated, these
+ actions are represented in two other lists.
- The two types of transitions are shifts (push the lookahead token
- and read another) and reductions (combine the last n things on the
- stack via a rule, replace them with the symbol that the rule
- derives, and leave the lookahead token alone). When the states are
- generated, these transitions are represented in two other lists.
+ Each transition_t structure describes the possible transitions out
+ of one state, the state whose number is in the number field. Each
+ contains a vector of numbers of the states that transitions can go
+ to. The accessing_symbol fields of those states' cores say what
+ kind of input leads to them.
- Each shifts structure describes the possible shift transitions out
- of one state, the state whose number is in the number field. The
- shifts structures are linked through next and first_shift points to
- them. Each contains a vector of numbers of the states that shift
- transitions can go to. The accessing_symbol fields of those
- states' cores say what kind of input leads to them.
-
- A shift to state zero should be ignored. Conflict resolution
- deletes shifts by changing them to zero.
+ A transition to state zero should be ignored: conflict resolution
+ deletes transitions by having them point to zero.
Each reductions structure describes the possible reductions at the
state whose number is in the number field. The data is a list of
Conflict resolution can decide that certain tokens in certain
states should explicitly be errors (for implementing %nonassoc).
For each state, the tokens that are errors for this reason are
- recorded in an errs structure, which has the state number in its
- number field. The rest of the errs structure is full of token
- numbers.
+ recorded in an errs structure, which holds the token numbers.
- There is at least one shift transition present in state zero. It
+ There is at least one goto transition present in state zero. It
leads to a next-to-final state whose accessing_symbol is the
grammar's start symbol. The next-to-final state has one shift to
the final state, whose accessing_symbol is zero (end of input).
- The final state has one shift, which goes to the termination state
- (whose number is nstates-1). The reason for the extra state at the
- end is to placate the parser's strategy of making all decisions one
- token ahead of its actions. */
+ The final state has one shift, which goes to the termination state.
+ The reason for the extra state at the end is to placate the
+ parser's strategy of making all decisions one token ahead of its
+ actions. */
#ifndef STATE_H_
# define STATE_H_
+# include "bitset.h"
-/*-------.
-| Core. |
-`-------*/
-typedef struct core
-{
- struct core *next;
- struct core *link;
- short number;
- short accessing_symbol;
- short nitems;
- short items[1];
-} core;
-
-#define CORE_ALLOC(Nitems) \
- (core *) xcalloc ((unsigned) (sizeof (core) \
- + (Nitems - 1) * sizeof (short)), 1)
+/*-------------------.
+| Numbering states. |
+`-------------------*/
-/*---------.
-| Shifts. |
-`---------*/
+typedef short state_number_t;
+# define STATE_NUMBER_MAX ((state_number_t) SHRT_MAX)
-typedef struct shifts
-{
- struct shifts *next;
- short number;
- short nshifts;
- short shifts[1];
-} shifts;
+/* Be ready to map a state_number_t to an int. */
+# define state_number_as_int(Tok) ((int) (Tok))
-#define SHIFTS_ALLOC(Nshifts) \
- (shifts *) xcalloc ((unsigned) (sizeof (shifts) \
- + (Nshifts - 1) * sizeof (short)), 1)
+typedef struct state_s state_t;
-shifts * shifts_new PARAMS ((int n));
+/*--------------.
+| Transitions. |
+`--------------*/
+
+typedef struct transtion_s
+{
+ short num;
+ state_t *states[1];
+} transitions_t;
-/* What is the symbol which is shifted by SHIFTS->shifts[Shift]? Can
- be a token (amongst which the error token), or non terminals in
- case of gotos. */
+/* What is the symbol labelling the transition to
+ TRANSITIONS->states[Num]? Can be a token (amongst which the error
+ token), or non terminals in case of gotos. */
-#define SHIFT_SYMBOL(Shifts, Shift) \
- (state_table[Shifts->shifts[Shift]].accessing_symbol)
+#define TRANSITION_SYMBOL(Transitions, Num) \
+ (Transitions->states[Num]->accessing_symbol)
-/* Is the SHIFTS->shifts[Shift] a real shift? (as opposed to gotos.) */
+/* Is the TRANSITIONS->states[Num] a shift? (as opposed to gotos). */
-#define SHIFT_IS_SHIFT(Shifts, Shift) \
- (ISTOKEN (SHIFT_SYMBOL (Shifts, Shift)))
+#define TRANSITION_IS_SHIFT(Transitions, Num) \
+ (ISTOKEN (TRANSITION_SYMBOL (Transitions, Num)))
-/* Is the SHIFTS->shifts[Shift] a goto?. */
+/* Is the TRANSITIONS->states[Num] a goto?. */
-#define SHIFT_IS_GOTO(Shifts, Shift) \
- (!SHIFT_IS_SHIFT (Shifts, Shift))
+#define TRANSITION_IS_GOTO(Transitions, Num) \
+ (!TRANSITION_IS_SHIFT (Transitions, Num))
-/* Is the SHIFTS->shifts[Shift] then handling of the error token?. */
+/* Is the TRANSITIONS->states[Num] labelled by the error token? */
-#define SHIFT_IS_ERROR(Shifts, Shift) \
- (SHIFT_SYMBOL (Shifts, Shift) == error_token_number)
+#define TRANSITION_IS_ERROR(Transitions, Num) \
+ (TRANSITION_SYMBOL (Transitions, Num) == errtoken->number)
/* When resolving a SR conflicts, if the reduction wins, the shift is
disabled. */
-#define SHIFT_DISABLE(Shifts, Shift) \
- (Shifts->shifts[Shift] = 0)
+#define TRANSITION_DISABLE(Transitions, Num) \
+ (Transitions->states[Num] = NULL)
-#define SHIFT_IS_DISABLED(Shifts, Shift) \
- (Shifts->shifts[Shift] == 0)
+#define TRANSITION_IS_DISABLED(Transitions, Num) \
+ (Transitions->states[Num] == NULL)
+
+
+/* Iterate over each transition over a token (shifts). */
+#define FOR_EACH_SHIFT(Transitions, Iter) \
+ for (Iter = 0; \
+ Iter < Transitions->num \
+ && (TRANSITION_IS_DISABLED (Transitions, Iter) \
+ || TRANSITION_IS_SHIFT (Transitions, Iter)); \
+ ++Iter) \
+ if (!TRANSITION_IS_DISABLED (Transitions, Iter))
+
+
+/* Return the state such these TRANSITIONS contain a shift/goto to it on
+ SYMBOL. Aborts if none found. */
+struct state_s;
+struct state_s *transitions_to (transitions_t *state, symbol_number_t s);
/*-------.
| Errs. |
`-------*/
-typedef struct errs
+typedef struct errs_s
{
- short nerrs;
- short errs[1];
-} errs;
+ short num;
+ symbol_t *symbols[1];
+} errs_t;
-#define ERRS_ALLOC(Nerrs) \
- (errs *) xcalloc ((unsigned) (sizeof (errs) \
- + (Nerrs - 1) * sizeof (short)), 1)
+errs_t *errs_new (int num, symbol_t **tokens);
/*-------------.
| Reductions. |
`-------------*/
-typedef struct reductions
+typedef struct reductions_s
{
- struct reductions *next;
- short number;
- short nreds;
- short rules[1];
-} reductions;
+ short num;
+ bitset *lookaheads;
+ rule_t *rules[1];
+} reductions_t;
+
+
+
+/*---------.
+| States. |
+`---------*/
+
+struct state_s
+{
+ state_number_t number;
+ symbol_number_t accessing_symbol;
+ transitions_t *transitions;
+ reductions_t *reductions;
+ errs_t *errs;
+
+ /* Nonzero if no lookahead is needed to decide what to do in state S. */
+ char consistent;
+
+ /* If some conflicts were solved thanks to precedence/associativity,
+ a human readable description of the resolution. */
+ const char *solved_conflicts;
+
+ /* Its items. Must be last, since ITEMS can be arbitrarily large.
+ */
+ unsigned short nitems;
+ item_number_t items[1];
+};
+
+extern state_number_t nstates;
+extern state_t *final_state;
+
+/* Create a new state with ACCESSING_SYMBOL for those items. */
+state_t *state_new (symbol_number_t accessing_symbol,
+ size_t core_size, item_number_t *core);
+
+/* Set the transitions of STATE. */
+void state_transitions_set (state_t *state, int num, state_t **transitions);
+
+/* Set the reductions of STATE. */
+void state_reductions_set (state_t *state, int num, rule_t **reductions);
+
+int state_reduction_find (state_t *state, rule_t *rule);
+
+/* Set the errs of STATE. */
+void state_errs_set (state_t *state, int num, symbol_t **errs);
+
+/* Print on OUT all the lookaheads such that this STATE wants to
+ reduce this RULE. */
+void state_rule_lookaheads_print (state_t *state, rule_t *rule, FILE *out);
+
+/* Create/destroy the states hash table. */
+void state_hash_new (void);
+void state_hash_free (void);
+
+/* Find the state associated to the CORE, and return it. If it does
+ not exist yet, return NULL. */
+state_t *state_hash_lookup (size_t core_size, item_number_t *core);
+
+/* Insert STATE in the state hash table. */
+void state_hash_insert (state_t *state);
-#define REDUCTIONS_ALLOC(Nreductions) \
- (reductions *) xcalloc ((unsigned) (sizeof (reductions) \
- + (Nreductions - 1) * sizeof (short)), 1)
+/* All the states, indexed by the state number. */
+extern state_t **states;
+/* Free all the states. */
+void states_free (void);
#endif /* !STATE_H_ */
projects / bison.git / blobdiff