/* Type definitions for nondeterministic finite state machine for bison, Copyright 1984, 1989, 2000, 2001 Free Software Foundation, Inc. This file is part of Bison, the GNU Compiler Compiler. Bison is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2, or (at your option) any later version. Bison is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with Bison; see the file COPYING. If not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ /* These type definitions are used to represent a nondeterministic finite state machine that parses the specified grammar. This information is generated by the function generate_states in the file LR0. Each state of the machine is described by a set of items -- particular positions in particular rules -- that are the possible places where parsing could continue when the machine is in this 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 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). 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. 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 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 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. Each reductions structure describes the possible reductions at the state whose number is in the number field. The data is a list of nreds rules, represented by their rule numbers. first_reduction points to the list of these structures. 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. There is at least one shift 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. */ #ifndef STATE_H_ # define STATE_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) /*---------. | Shifts. | `---------*/ typedef struct shifts { struct shifts *next; short number; short nshifts; short shifts[1]; } shifts; #define SHIFTS_ALLOC(Nshifts) \ (shifts *) xcalloc ((unsigned) (sizeof (shifts) \ + (Nshifts - 1) * sizeof (short)), 1) shifts * shifts_new PARAMS ((int n)); /* 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. */ #define SHIFT_SYMBOL(Shifts, Shift) \ (state_table[Shifts->shifts[Shift]].accessing_symbol) /* Is the SHIFTS->shifts[Shift] a real shift? (as opposed to gotos.) */ #define SHIFT_IS_SHIFT(Shifts, Shift) \ (ISTOKEN (SHIFT_SYMBOL (Shifts, Shift))) /* Is the SHIFTS->shifts[Shift] a goto?. */ #define SHIFT_IS_GOTO(Shifts, Shift) \ (!SHIFT_IS_SHIFT (Shifts, Shift)) /* Is the SHIFTS->shifts[Shift] then handling of the error token?. */ #define SHIFT_IS_ERROR(Shifts, Shift) \ (SHIFT_SYMBOL (Shifts, Shift) == error_token_number) /* When resolving a SR conflicts, if the reduction wins, the shift is disabled. */ #define SHIFT_DISABLE(Shifts, Shift) \ (Shifts->shifts[Shift] = 0) #define SHIFT_IS_DISABLED(Shifts, Shift) \ (Shifts->shifts[Shift] == 0) /*-------. | Errs. | `-------*/ typedef struct errs { short nerrs; short errs[1]; } errs; #define ERRS_ALLOC(Nerrs) \ (errs *) xcalloc ((unsigned) (sizeof (errs) \ + (Nerrs - 1) * sizeof (short)), 1) /*-------------. | Reductions. | `-------------*/ typedef struct reductions { struct reductions *next; short number; short nreds; short rules[1]; } reductions; #define REDUCTIONS_ALLOC(Nreductions) \ (reductions *) xcalloc ((unsigned) (sizeof (reductions) \ + (Nreductions - 1) * sizeof (short)), 1) #endif /* !STATE_H_ */