Change @dircategory from "GNU programming tools" to "Software development".

[bison.git] / src / state.h

diff --git a/src/state.h b/src/state.h
index 615c7d5cefe160f39304c8f5883e321ba5d6c8c4..36395d1640a25f22d066f4141c4cd9fa987a301c 100644 (file)
--- a/src/state.h
+++ b/src/state.h
@@ -1,5 +1,7 @@
-/* Type definitions for nondeterministic finite state machine for bison,
-   Copyright (C) 1984, 1989, 2000 Free Software Foundation, Inc.
+/* Type definitions for nondeterministic finite state machine for Bison.
+
+   Copyright (C) 1984, 1989, 2000, 2001, 2002, 2003, 2004 Free
+   Software Foundation, Inc.

 
    This file is part of Bison, the GNU Compiler Compiler.
 
 
    This file is part of Bison, the GNU Compiler Compiler.
 


@@ -30,39 +32,35 @@
    state.  These symbols at these items are the allowable inputs that
    can follow now.
 
    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
    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
 
    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 look-ahead 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
+   look-ahead 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
 
    Each reductions structure describes the possible reductions at the
    state whose number is in the number field.  The data is a list of


@@ -72,62 +70,188 @@
    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
    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).
    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_
 
 
 #ifndef STATE_H_
 # define STATE_H_
 

-typedef struct core
+# include <bitset.h>
+
+# include "gram.h"
+# include "symtab.h"
+
+
+/*-------------------.
+| Numbering states.  |
+`-------------------*/
+
+typedef int state_number;
+# define STATE_NUMBER_MAXIMUM INT_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;
+  int 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 SYM.
+   Abort if none found.  */
+struct state *transitions_to (transitions *shifts, symbol_number sym);

 
 
 
 

-typedef struct errs
+/*-------.
+| Errs.  |
+`-------*/
+
+typedef struct

 {
 {

-  short nerrs;
-  short errs[1];
-}
-errs;
+  int 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;
+  int num;
+  bitset *look_ahead_tokens;
+  rule *rules[1];
+} reductions;
+
+
+
+/*---------.
+| states.  |
+`---------*/
+
+struct state
+{
+  state_number number;
+  symbol_number accessing_symbol;
+  transitions *transitions;
+  reductions *reductions;
+  errs *errs;
+
+  /* Nonzero if no look-ahead 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.
+     */
+  size_t 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 look-ahead tokens such that this STATE wants to
+   reduce R.  */
+void state_rule_look_ahead_tokens_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_ */
 #endif /* !STATE_H_ */