ocaml/lex/lexer.mll

160 lines
4.2 KiB
OCaml

(* The lexical analyzer for lexer definitions. Bootstrapped! *)
{
open Syntax
open Parser
(* Auxiliaries for the lexical analyzer *)
let brace_depth = ref 0
and comment_depth = ref 0
exception Lexical_error of string
let initial_string_buffer = String.create 256
let string_buff = ref initial_string_buffer
let string_index = ref 0
let reset_string_buffer () =
string_buff := initial_string_buffer;
string_index := 0
let store_string_char c =
(if !string_index >= String.length (!string_buff) then
let new_buff = String.create (String.length (!string_buff) * 2) in
String.blit new_buff 0 (!string_buff) 0 (String.length (!string_buff));
string_buff := new_buff;
());
!string_buff.[!string_index] <- c;
incr string_index
let get_stored_string () =
let s = String.sub (!string_buff) 0 (!string_index) in
string_buff := initial_string_buffer;
s
let char_for_backslash = function
'n' -> '\010' (* '\n' when bootstrapped *)
| 't' -> '\009' (* '\t' *)
| 'b' -> '\008' (* '\b' *)
| 'r' -> '\013' (* '\r' *)
| c -> c
let char_for_decimal_code lexbuf i =
Char.chr(100 * (Char.code(Lexing.lexeme_char lexbuf i) - 48) +
10 * (Char.code(Lexing.lexeme_char lexbuf (i+1)) - 48) +
(Char.code(Lexing.lexeme_char lexbuf (i+2)) - 48))
}
rule main = parse
[' ' '\010' '\013' '\009' ] +
{ main lexbuf }
| "(*"
{ comment_depth := 1;
comment lexbuf;
main lexbuf }
| ['A'-'Z' 'a'-'z'] ['A'-'Z' 'a'-'z' '\'' '_' '0'-'9'] *
{ match Lexing.lexeme lexbuf with
"rule" -> Trule
| "parse" -> Tparse
| "and" -> Tand
| "eof" -> Teof
| s -> Tident s }
| '"'
{ reset_string_buffer();
string lexbuf;
Tstring(get_stored_string()) }
| "`" [^ '\\'] "`"
{ Tchar(Lexing.lexeme_char lexbuf 1) }
| "`" '\\' ['\\' '`' 'n' 't' 'b' 'r'] "`"
{ Tchar(char_for_backslash (Lexing.lexeme_char lexbuf 2)) }
| "`" '\\' ['0'-'9'] ['0'-'9'] ['0'-'9'] "`"
{ Tchar(char_for_decimal_code lexbuf 2) }
| "'" [^ '\\'] "'"
{ Tchar(Lexing.lexeme_char lexbuf 1) }
| "'" '\\' ['\\' '\'' 'n' 't' 'b' 'r'] "'"
{ Tchar(char_for_backslash (Lexing.lexeme_char lexbuf 2)) }
| "'" '\\' ['0'-'9'] ['0'-'9'] ['0'-'9'] "'"
{ Tchar(char_for_decimal_code lexbuf 2) }
| '{'
{ let n1 = Lexing.lexeme_end lexbuf in
brace_depth := 1;
let n2 = action lexbuf in
Taction(Location(n1, n2)) }
| '=' { Tequal }
| '|' { Tor }
| '_' { Tunderscore }
| "eof" { Teof }
| '[' { Tlbracket }
| ']' { Trbracket }
| '*' { Tstar }
| '?' { Tmaybe }
| '+' { Tplus }
| '(' { Tlparen }
| ')' { Trparen }
| '^' { Tcaret }
| '-' { Tdash }
| eof { Tend }
| _
{ raise(Lexical_error
("illegal character " ^ String.escaped(Lexing.lexeme lexbuf))) }
and action = parse
'{'
{ incr brace_depth;
action lexbuf }
| '}'
{ decr brace_depth;
if !brace_depth == 0 then Lexing.lexeme_start lexbuf else action lexbuf }
| '"'
{ reset_string_buffer();
string lexbuf;
reset_string_buffer();
action lexbuf }
| "'{'"
{ action lexbuf }
| "'{'"
{ action lexbuf }
| "(*"
{ comment_depth := 1;
comment lexbuf;
action lexbuf }
| eof
{ raise (Lexical_error "unterminated action") }
| _
{ action lexbuf }
and string = parse
'"'
{ () }
| '\\' [' ' '\010' '\013' '\009' '\026' '\012'] +
{ string lexbuf }
| '\\' ['\\' '"' 'n' 't' 'b' 'r']
{ store_string_char(char_for_backslash(Lexing.lexeme_char lexbuf 1));
string lexbuf }
| '\\' ['0'-'9'] ['0'-'9'] ['0'-'9']
{ store_string_char(char_for_decimal_code lexbuf 1);
string lexbuf }
| eof
{ raise(Lexical_error "unterminated string") }
| _
{ store_string_char(Lexing.lexeme_char lexbuf 0);
string lexbuf }
and comment = parse
"(*"
{ incr comment_depth; comment lexbuf }
| "*)"
{ decr comment_depth;
if !comment_depth == 0 then () else comment lexbuf }
| '"'
{ reset_string_buffer();
string lexbuf;
reset_string_buffer();
comment lexbuf }
| eof
{ raise(Lexical_error "unterminated comment") }
| _
{ comment lexbuf }