/* Type definitions for nondeterministic finite state machine for bison,
- Copyright 1984, 1989, 2000 Free Software Foundation, Inc.
+ Copyright 1984, 1989, 2000, 2001 Free Software Foundation, Inc.
This file is part of Bison, the GNU Compiler Compiler.
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_
-typedef struct core
+# include "bitset.h"
+
+
+/*-------------------.
+| Numbering states. |
+`-------------------*/
+
+typedef short state_number_t;
+# define STATE_NUMBER_MAX ((state_number_t) SHRT_MAX)
+
+/* Be ready to map a state_number_t to an int. */
+# define state_number_as_int(Tok) ((int) (Tok))
+
+
+typedef struct state_s state_t;
+
+/*--------------.
+| Transitions. |
+`--------------*/
+
+typedef struct transtion_s
{
- 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)
-
-typedef struct shifts
+ short num;
+ state_t *states[1];
+} transitions_t;
+
+
+/* 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 TRANSITION_SYMBOL(Transitions, Num) \
+ (Transitions->states[Num]->accessing_symbol)
+
+/* Is the TRANSITIONS->states[Num] a shift? (as opposed to gotos). */
+
+#define TRANSITION_IS_SHIFT(Transitions, Num) \
+ (ISTOKEN (TRANSITION_SYMBOL (Transitions, Num)))
+
+/* Is the TRANSITIONS->states[Num] a goto?. */
+
+#define TRANSITION_IS_GOTO(Transitions, Num) \
+ (!TRANSITION_IS_SHIFT (Transitions, Num))
+
+/* Is the TRANSITIONS->states[Num] labelled by the error token? */
+
+#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 TRANSITION_DISABLE(Transitions, Num) \
+ (Transitions->states[Num] = NULL)
+
+#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 PARAMS ((transitions_t *state,
+ symbol_number_t s));
+
+
+/*-------.
+| Errs. |
+`-------*/
+
+typedef struct errs_s
{
- struct shifts *next;
- short number;
- short nshifts;
- short shifts[1];
-}
-shifts;
+ short num;
+ symbol_t *symbols[1];
+} errs_t;
+
+errs_t *errs_new PARAMS ((int num, symbol_t **tokens));
-#define SHIFTS_ALLOC(Nshifts) \
- (shifts *) xcalloc ((unsigned) (sizeof (shifts) \
- + (Nshifts - 1) * sizeof (short)), 1)
+/*-------------.
+| Reductions. |
+`-------------*/
-typedef struct errs
+typedef struct reductions_s
{
- short nerrs;
- short errs[1];
-}
-errs;
+ short num;
+ bitset *lookaheads;
+ rule_t *rules[1];
+} reductions_t;
-#define ERRS_ALLOC(Nerrs) \
- (errs *) xcalloc ((unsigned) (sizeof (errs) \
- + (Nerrs - 1) * sizeof (short)), 1)
+/*---------.
+| States. |
+`---------*/
-typedef struct reductions
+struct state_s
{
- struct reductions *next;
- short number;
- short nreds;
- short rules[1];
-}
-reductions;
+ 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 PARAMS ((symbol_number_t accessing_symbol,
+ size_t core_size, item_number_t *core));
+
+/* Set the transitions of STATE. */
+void state_transitions_set PARAMS ((state_t *state,
+ int num, state_t **transitions));
+
+/* Set the reductions of STATE. */
+void state_reductions_set PARAMS ((state_t *state,
+ int num, rule_t **reductions));
+
+int state_reduction_find PARAMS ((state_t *state, rule_t *rule));
+
+/* Set the errs of STATE. */
+void state_errs_set PARAMS ((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 PARAMS ((state_t *state, rule_t *rule,
+ FILE *out));
+
+/* Create/destroy the states hash table. */
+void state_hash_new PARAMS ((void));
+void state_hash_free PARAMS ((void));
+
+/* Find the state associated to the CORE, and return it. If it does
+ not exist yet, return NULL. */
+state_t *state_hash_lookup PARAMS ((size_t core_size, item_number_t *core));
+
+/* Insert STATE in the state hash table. */
+void state_hash_insert PARAMS ((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 PARAMS ((void));
#endif /* !STATE_H_ */
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