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|
(***********************************************************************)
(* *)
(* OCaml *)
(* *)
(* Xavier Leroy, projet Cristal, INRIA Rocquencourt *)
(* *)
(* Copyright 1996 Institut National de Recherche en Informatique et *)
(* en Automatique. All rights reserved. This file is distributed *)
(* under the terms of the GNU Library General Public License, with *)
(* the special exception on linking described in file ../LICENSE. *)
(* *)
(***********************************************************************)
(* $Id$ *)
(* The parsing engine *)
open Lexing
(* Internal interface to the parsing engine *)
type parser_env =
{ mutable s_stack : int array; (* States *)
mutable v_stack : Obj.t array; (* Semantic attributes *)
mutable symb_start_stack : position array; (* Start positions *)
mutable symb_end_stack : position array; (* End positions *)
mutable stacksize : int; (* Size of the stacks *)
mutable stackbase : int; (* Base sp for current parse *)
mutable curr_char : int; (* Last token read *)
mutable lval : Obj.t; (* Its semantic attribute *)
mutable symb_start : position; (* Start pos. of the current symbol*)
mutable symb_end : position; (* End pos. of the current symbol *)
mutable asp : int; (* The stack pointer for attributes *)
mutable rule_len : int; (* Number of rhs items in the rule *)
mutable rule_number : int; (* Rule number to reduce by *)
mutable sp : int; (* Saved sp for parse_engine *)
mutable state : int; (* Saved state for parse_engine *)
mutable errflag : int } (* Saved error flag for parse_engine *)
type parse_tables =
{ actions : (parser_env -> Obj.t) array;
transl_const : int array;
transl_block : int array;
lhs : string;
len : string;
defred : string;
dgoto : string;
sindex : string;
rindex : string;
gindex : string;
tablesize : int;
table : string;
check : string;
error_function : string -> unit;
names_const : string;
names_block : string }
exception YYexit of Obj.t
exception Parse_error
type parser_input =
Start
| Token_read
| Stacks_grown_1
| Stacks_grown_2
| Semantic_action_computed
| Error_detected
type parser_output =
Read_token
| Raise_parse_error
| Grow_stacks_1
| Grow_stacks_2
| Compute_semantic_action
| Call_error_function
external parse_engine :
parse_tables -> parser_env -> parser_input -> Obj.t -> parser_output
= "caml_parse_engine"
external set_trace: bool -> bool
= "caml_set_parser_trace"
let env =
{ s_stack = Array.create 100 0;
v_stack = Array.create 100 (Obj.repr ());
symb_start_stack = Array.create 100 dummy_pos;
symb_end_stack = Array.create 100 dummy_pos;
stacksize = 100;
stackbase = 0;
curr_char = 0;
lval = Obj.repr ();
symb_start = dummy_pos;
symb_end = dummy_pos;
asp = 0;
rule_len = 0;
rule_number = 0;
sp = 0;
state = 0;
errflag = 0 }
let grow_stacks() =
let oldsize = env.stacksize in
let newsize = oldsize * 2 in
let new_s = Array.create newsize 0
and new_v = Array.create newsize (Obj.repr ())
and new_start = Array.create newsize dummy_pos
and new_end = Array.create newsize dummy_pos in
Array.blit env.s_stack 0 new_s 0 oldsize;
env.s_stack <- new_s;
Array.blit env.v_stack 0 new_v 0 oldsize;
env.v_stack <- new_v;
Array.blit env.symb_start_stack 0 new_start 0 oldsize;
env.symb_start_stack <- new_start;
Array.blit env.symb_end_stack 0 new_end 0 oldsize;
env.symb_end_stack <- new_end;
env.stacksize <- newsize
let clear_parser() =
Array.fill env.v_stack 0 env.stacksize (Obj.repr ());
env.lval <- Obj.repr ()
let current_lookahead_fun = ref (fun (x : Obj.t) -> false)
let yyparse tables start lexer lexbuf =
let rec loop cmd arg =
match parse_engine tables env cmd arg with
Read_token ->
let t = Obj.repr(lexer lexbuf) in
env.symb_start <- lexbuf.lex_start_p;
env.symb_end <- lexbuf.lex_curr_p;
loop Token_read t
| Raise_parse_error ->
raise Parse_error
| Compute_semantic_action ->
let (action, value) =
try
(Semantic_action_computed, tables.actions.(env.rule_number) env)
with Parse_error ->
(Error_detected, Obj.repr ()) in
loop action value
| Grow_stacks_1 ->
grow_stacks(); loop Stacks_grown_1 (Obj.repr ())
| Grow_stacks_2 ->
grow_stacks(); loop Stacks_grown_2 (Obj.repr ())
| Call_error_function ->
tables.error_function "syntax error";
loop Error_detected (Obj.repr ()) in
let init_asp = env.asp
and init_sp = env.sp
and init_stackbase = env.stackbase
and init_state = env.state
and init_curr_char = env.curr_char
and init_lval = env.lval
and init_errflag = env.errflag in
env.stackbase <- env.sp + 1;
env.curr_char <- start;
env.symb_end <- lexbuf.lex_curr_p;
try
loop Start (Obj.repr ())
with exn ->
let curr_char = env.curr_char in
env.asp <- init_asp;
env.sp <- init_sp;
env.stackbase <- init_stackbase;
env.state <- init_state;
env.curr_char <- init_curr_char;
env.lval <- init_lval;
env.errflag <- init_errflag;
match exn with
YYexit v ->
Obj.magic v
| _ ->
current_lookahead_fun :=
(fun tok ->
if Obj.is_block tok
then tables.transl_block.(Obj.tag tok) = curr_char
else tables.transl_const.(Obj.magic tok) = curr_char);
raise exn
let peek_val env n =
Obj.magic env.v_stack.(env.asp - n)
let symbol_start_pos () =
let rec loop i =
if i <= 0 then env.symb_end_stack.(env.asp)
else begin
let st = env.symb_start_stack.(env.asp - i + 1) in
let en = env.symb_end_stack.(env.asp - i + 1) in
if st <> en then st else loop (i - 1)
end
in
loop env.rule_len
;;
let symbol_end_pos () = env.symb_end_stack.(env.asp);;
let rhs_start_pos n = env.symb_start_stack.(env.asp - (env.rule_len - n));;
let rhs_end_pos n = env.symb_end_stack.(env.asp - (env.rule_len - n));;
let symbol_start () = (symbol_start_pos ()).pos_cnum;;
let symbol_end () = (symbol_end_pos ()).pos_cnum;;
let rhs_start n = (rhs_start_pos n).pos_cnum;;
let rhs_end n = (rhs_end_pos n).pos_cnum;;
let is_current_lookahead tok =
(!current_lookahead_fun)(Obj.repr tok)
let parse_error (msg : string) = ()
|
