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Fast path for lexing UTF-8 #264

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Merged
rossberg merged 1 commit into from
Mar 22, 2019
Merged

Fast path for lexing UTF-8 #264

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17 changes: 7 additions & 10 deletions src/lexer.mll
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Original file line number Diff line number Diff line change
Expand Up @@ -23,18 +23,15 @@ let error_nest start lexbuf msg =
error lexbuf msg


let utf8 lexbuf s i =
let len =
if s.[!i] < '\x80' then 0 else
if s.[!i] < '\xe0' then 1 else
if s.[!i] < '\xf0' then 2 else 3
in
let utf8 s i =
let len = if s.[!i] < '\xe0' then 1 else if s.[!i] < '\xf0' then 2 else 3 in
i := !i + len;
List.hd (Utf8.decode (String.sub s (!i - len) (1 + len)))

let unicode lexbuf s i =
let codepoint lexbuf s i =
let u =
if s.[!i] <> '\\' then utf8 lexbuf s i else
if s.[!i] >= '\x80' then utf8 s i else
if s.[!i] <> '\\' then Char.code s.[!i] else
match (incr i; s.[!i]) with
| 'n' -> Char.code '\n'
| 'r' -> Char.code '\r'
Expand All @@ -55,13 +52,13 @@ let unicode lexbuf s i =
in incr i; u

let char lexbuf s =
unicode lexbuf s (ref 1)
codepoint lexbuf s (ref 1)

let text lexbuf s =
let b = Buffer.create (String.length s) in
let i = ref 1 in
while !i < String.length s - 1 do
let bs = Utf8.encode [unicode lexbuf s i] in
let bs = Utf8.encode [codepoint lexbuf s i] in
Buffer.add_substring b bs 0 (String.length bs)
done;
Buffer.contents b
Expand Down