-/* Type definitions for nondeterministic finite state machine for bison,
- Copyright 1984, 1989, 2000 Free Software Foundation, Inc.
+/* Type definitions for nondeterministic finite state machine for Bison.
+
+ Copyright (C) 1984, 1989, 2000, 2001, 2002 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.
-
- 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.
+ ACCESSING_SYMBOL of the core.
- 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.
+ 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 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.
+ 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.
- 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.
+ Each transition 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.
- 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>
+
+# include "gram.h"
+# include "symtab.h"
+
+
+/*-------------------.
+| Numbering states. |
+`-------------------*/
+
+typedef short state_number;
+# define STATE_NUMBER_MAXIMUM SHRT_MAX
+
+/* Be ready to map a state_number to an int. */
+static inline int
+state_number_as_int (state_number s)
{
- struct core *next;
- struct core *link;
- short number;
- short accessing_symbol;
- short nitems;
- short items[1];
+ return s;
}
-core;
+typedef struct state state;
+
+/*--------------.
+| Transitions. |
+`--------------*/
-typedef struct shifts
+typedef struct
{
- struct shifts *next;
- short number;
- short nshifts;
- short shifts[1];
-}
-shifts;
+ short num;
+ state *states[1];
+} transitions;
+
+
+/* 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 SHIFTS contain a shift/goto to it on S.
+ Abort if none found. */
+struct state *transitions_to (transitions *shifts, symbol_number s);
-typedef struct errs
+/*-------.
+| Errs. |
+`-------*/
+
+typedef struct
{
- short nerrs;
- short errs[1];
-}
-errs;
+ short num;
+ symbol *symbols[1];
+} errs;
+
+errs *errs_new (int num, symbol **tokens);
+/*-------------.
+| Reductions. |
+`-------------*/
-typedef struct reductions
+typedef struct
{
- struct reductions *next;
- short number;
- short nreds;
- short rules[1];
-}
-reductions;
+ short num;
+ bitset *lookaheads;
+ rule *rules[1];
+} reductions;
+
+
+
+/*---------.
+| states. |
+`---------*/
+
+struct state
+{
+ state_number number;
+ symbol_number accessing_symbol;
+ transitions *transitions;
+ reductions *reductions;
+ errs *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 items[1];
+};
+
+extern state_number nstates;
+extern state *final_state;
+
+/* Create a new state with ACCESSING_SYMBOL for those items. */
+state *state_new (symbol_number accessing_symbol,
+ size_t core_size, item_number *core);
+
+/* Set the transitions of STATE. */
+void state_transitions_set (state *s, int num, state **trans);
+
+/* Set the reductions of STATE. */
+void state_reductions_set (state *s, int num, rule **reds);
+
+int state_reduction_find (state *s, rule *r);
+
+/* Set the errs of STATE. */
+void state_errs_set (state *s, int num, symbol **errors);
+
+/* Print on OUT all the lookaheads such that this STATE wants to
+ reduce R. */
+void state_rule_lookaheads_print (state *s, rule *r, 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 *state_hash_lookup (size_t core_size, item_number *core);
+
+/* Insert STATE in the state hash table. */
+void state_hash_insert (state *s);
+
+/* All the states, indexed by the state number. */
+extern state **states;
+/* Free all the states. */
+void states_free (void);
#endif /* !STATE_H_ */
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