aeson-0.7.0.6: Data/Aeson/Parser/Internal.hs
{-# LANGUAGE CPP, BangPatterns, OverloadedStrings #-}
-- |
-- Module: Data.Aeson.Parser.Internal
-- Copyright: (c) 2011, 2012 Bryan O'Sullivan
-- (c) 2011 MailRank, Inc.
-- License: Apache
-- Maintainer: Bryan O'Sullivan <bos@serpentine.com>
-- Stability: experimental
-- Portability: portable
--
-- Efficiently and correctly parse a JSON string. The string must be
-- encoded as UTF-8.
module Data.Aeson.Parser.Internal
(
-- * Lazy parsers
json, jsonEOF
, value
, jstring
-- * Strict parsers
, json', jsonEOF'
, value'
-- * Helpers
, decodeWith
, decodeStrictWith
, eitherDecodeWith
, eitherDecodeStrictWith
) where
#if defined(USE_BLAZE_BUILDER)
import Blaze.ByteString.Builder (Builder, fromByteString, toByteString)
import Blaze.ByteString.Builder.Char.Utf8 (fromChar)
import Blaze.ByteString.Builder.Word (fromWord8)
#else
#if MIN_VERSION_bytestring(0,10,2)
import Data.ByteString.Builder
#else
import Data.ByteString.Lazy.Builder
#endif
(Builder, byteString, toLazyByteString, charUtf8, word8)
#endif
import Control.Applicative ((*>), (<$>), (<*), liftA2, pure)
import Data.Aeson.Types (Result(..), Value(..))
import Data.Attoparsec.Char8 (Parser, char, endOfInput, scientific,
skipSpace, string)
import Data.Bits ((.|.), shiftL)
import Data.ByteString (ByteString)
import Data.Char (chr)
import Data.Monoid (mappend, mempty)
import Data.Text (Text)
import Data.Text.Encoding (decodeUtf8')
import Data.Vector as Vector (Vector, fromList)
import Data.Word (Word8)
import qualified Data.Attoparsec as A
import qualified Data.Attoparsec.Lazy as L
import qualified Data.Attoparsec.Zepto as Z
import qualified Data.ByteString as B
import qualified Data.ByteString.Lazy as L
import qualified Data.ByteString.Unsafe as B
import qualified Data.HashMap.Strict as H
#define BACKSLASH 92
#define CLOSE_CURLY 125
#define CLOSE_SQUARE 93
#define COMMA 44
#define DOUBLE_QUOTE 34
#define OPEN_CURLY 123
#define OPEN_SQUARE 91
#define C_0 48
#define C_9 57
#define C_A 65
#define C_F 70
#define C_a 97
#define C_f 102
#define C_n 110
#define C_t 116
-- | Parse a top-level JSON value. This must be either an object or
-- an array, per RFC 4627.
--
-- The conversion of a parsed value to a Haskell value is deferred
-- until the Haskell value is needed. This may improve performance if
-- only a subset of the results of conversions are needed, but at a
-- cost in thunk allocation.
json :: Parser Value
json = json_ object_ array_
-- | Parse a top-level JSON value. This must be either an object or
-- an array, per RFC 4627.
--
-- This is a strict version of 'json' which avoids building up thunks
-- during parsing; it performs all conversions immediately. Prefer
-- this version if most of the JSON data needs to be accessed.
json' :: Parser Value
json' = json_ object_' array_'
json_ :: Parser Value -> Parser Value -> Parser Value
json_ obj ary = do
w <- skipSpace *> A.satisfy (\w -> w == OPEN_CURLY || w == OPEN_SQUARE)
if w == OPEN_CURLY
then obj
else ary
{-# INLINE json_ #-}
object_ :: Parser Value
object_ = {-# SCC "object_" #-} Object <$> objectValues jstring value
object_' :: Parser Value
object_' = {-# SCC "object_'" #-} do
!vals <- objectValues jstring' value'
return (Object vals)
where
jstring' = do
!s <- jstring
return s
objectValues :: Parser Text -> Parser Value -> Parser (H.HashMap Text Value)
objectValues str val = do
skipSpace
let pair = liftA2 (,) (str <* skipSpace) (char ':' *> skipSpace *> val)
H.fromList <$> commaSeparated pair CLOSE_CURLY
{-# INLINE objectValues #-}
array_ :: Parser Value
array_ = {-# SCC "array_" #-} Array <$> arrayValues value
array_' :: Parser Value
array_' = {-# SCC "array_'" #-} do
!vals <- arrayValues value'
return (Array vals)
commaSeparated :: Parser a -> Word8 -> Parser [a]
commaSeparated item endByte = do
w <- peekWord8'
if w == endByte
then A.anyWord8 >> return []
else loop
where
loop = do
v <- item <* skipSpace
ch <- A.satisfy $ \w -> w == COMMA || w == endByte
if ch == COMMA
then skipSpace >> (v:) <$> loop
else return [v]
{-# INLINE commaSeparated #-}
arrayValues :: Parser Value -> Parser (Vector Value)
arrayValues val = do
skipSpace
Vector.fromList <$> commaSeparated val CLOSE_SQUARE
{-# INLINE arrayValues #-}
-- | Parse any JSON value. You should usually 'json' in preference to
-- this function, as this function relaxes the object-or-array
-- requirement of RFC 4627.
--
-- In particular, be careful in using this function if you think your
-- code might interoperate with Javascript. A naïve Javascript
-- library that parses JSON data using @eval@ is vulnerable to attack
-- unless the encoded data represents an object or an array. JSON
-- implementations in other languages conform to that same restriction
-- to preserve interoperability and security.
value :: Parser Value
value = do
w <- peekWord8'
case w of
DOUBLE_QUOTE -> A.anyWord8 *> (String <$> jstring_)
OPEN_CURLY -> A.anyWord8 *> object_
OPEN_SQUARE -> A.anyWord8 *> array_
C_f -> string "false" *> pure (Bool False)
C_t -> string "true" *> pure (Bool True)
C_n -> string "null" *> pure Null
_ | w >= 48 && w <= 57 || w == 45
-> Number <$> scientific
| otherwise -> fail "not a valid json value"
-- | Strict version of 'value'. See also 'json''.
value' :: Parser Value
value' = do
w <- peekWord8'
case w of
DOUBLE_QUOTE -> do
!s <- A.anyWord8 *> jstring_
return (String s)
OPEN_CURLY -> A.anyWord8 *> object_'
OPEN_SQUARE -> A.anyWord8 *> array_'
C_f -> string "false" *> pure (Bool False)
C_t -> string "true" *> pure (Bool True)
C_n -> string "null" *> pure Null
_ | w >= 48 && w <= 57 || w == 45
-> do
!n <- scientific
return (Number n)
| otherwise -> fail "not a valid json value"
-- | Parse a quoted JSON string.
jstring :: Parser Text
jstring = A.word8 DOUBLE_QUOTE *> jstring_
-- | Parse a string without a leading quote.
jstring_ :: Parser Text
jstring_ = {-# SCC "jstring_" #-} do
s <- A.scan False $ \s c -> if s then Just False
else if c == DOUBLE_QUOTE
then Nothing
else Just (c == BACKSLASH)
_ <- A.word8 DOUBLE_QUOTE
s1 <- if BACKSLASH `B.elem` s
then case Z.parse unescape s of
Right r -> return r
Left err -> fail err
else return s
case decodeUtf8' s1 of
Right r -> return r
Left err -> fail $ show err
{-# INLINE jstring_ #-}
unescape :: Z.Parser ByteString
unescape = toByteString <$> go mempty where
go acc = do
h <- Z.takeWhile (/=BACKSLASH)
let rest = do
start <- Z.take 2
let !slash = B.unsafeHead start
!t = B.unsafeIndex start 1
escape = case B.findIndex (==t) "\"\\/ntbrfu" of
Just i -> i
_ -> 255
if slash /= BACKSLASH || escape == 255
then fail "invalid JSON escape sequence"
else do
let cont m = go (acc `mappend` byteString h `mappend` m)
{-# INLINE cont #-}
if t /= 117 -- 'u'
then cont (word8 (B.unsafeIndex mapping escape))
else do
a <- hexQuad
if a < 0xd800 || a > 0xdfff
then cont (charUtf8 (chr a))
else do
b <- Z.string "\\u" *> hexQuad
if a <= 0xdbff && b >= 0xdc00 && b <= 0xdfff
then let !c = ((a - 0xd800) `shiftL` 10) +
(b - 0xdc00) + 0x10000
in cont (charUtf8 (chr c))
else fail "invalid UTF-16 surrogates"
done <- Z.atEnd
if done
then return (acc `mappend` byteString h)
else rest
mapping = "\"\\/\n\t\b\r\f"
hexQuad :: Z.Parser Int
hexQuad = do
s <- Z.take 4
let hex n | w >= C_0 && w <= C_9 = w - C_0
| w >= C_a && w <= C_f = w - 87
| w >= C_A && w <= C_F = w - 55
| otherwise = 255
where w = fromIntegral $ B.unsafeIndex s n
a = hex 0; b = hex 1; c = hex 2; d = hex 3
if (a .|. b .|. c .|. d) /= 255
then return $! d .|. (c `shiftL` 4) .|. (b `shiftL` 8) .|. (a `shiftL` 12)
else fail "invalid hex escape"
decodeWith :: Parser Value -> (Value -> Result a) -> L.ByteString -> Maybe a
decodeWith p to s =
case L.parse p s of
L.Done _ v -> case to v of
Success a -> Just a
_ -> Nothing
_ -> Nothing
{-# INLINE decodeWith #-}
decodeStrictWith :: Parser Value -> (Value -> Result a) -> B.ByteString
-> Maybe a
decodeStrictWith p to s =
case either Error to (A.parseOnly p s) of
Success a -> Just a
Error _ -> Nothing
{-# INLINE decodeStrictWith #-}
eitherDecodeWith :: Parser Value -> (Value -> Result a) -> L.ByteString
-> Either String a
eitherDecodeWith p to s =
case L.parse p s of
L.Done _ v -> case to v of
Success a -> Right a
Error msg -> Left msg
L.Fail _ _ msg -> Left msg
{-# INLINE eitherDecodeWith #-}
eitherDecodeStrictWith :: Parser Value -> (Value -> Result a) -> B.ByteString
-> Either String a
eitherDecodeStrictWith p to s =
case either Error to (A.parseOnly p s) of
Success a -> Right a
Error msg -> Left msg
{-# INLINE eitherDecodeStrictWith #-}
-- $lazy
--
-- The 'json' and 'value' parsers decouple identification from
-- conversion. Identification occurs immediately (so that an invalid
-- JSON document can be rejected as early as possible), but conversion
-- to a Haskell value is deferred until that value is needed.
--
-- This decoupling can be time-efficient if only a smallish subset of
-- elements in a JSON value need to be inspected, since the cost of
-- conversion is zero for uninspected elements. The trade off is an
-- increase in memory usage, due to allocation of thunks for values
-- that have not yet been converted.
-- $strict
--
-- The 'json'' and 'value'' parsers combine identification with
-- conversion. They consume more CPU cycles up front, but have a
-- smaller memory footprint.
-- | Parse a top-level JSON value followed by optional whitespace and
-- end-of-input. See also: 'json'.
jsonEOF :: Parser Value
jsonEOF = json <* skipSpace <* endOfInput
-- | Parse a top-level JSON value followed by optional whitespace and
-- end-of-input. See also: 'json''.
jsonEOF' :: Parser Value
jsonEOF' = json' <* skipSpace <* endOfInput
#if defined(USE_BLAZE_BUILDER)
byteString :: ByteString -> Builder
byteString = fromByteString
{-# INLINE byteString #-}
charUtf8 :: Char -> Builder
charUtf8 = fromChar
{-# INLINE charUtf8 #-}
word8 :: Word8 -> Builder
word8 = fromWord8
{-# INLINE word8 #-}
#else
toByteString :: Builder -> ByteString
toByteString = L.toStrict . toLazyByteString
{-# INLINE toByteString #-}
#endif
peekWord8' :: A.Parser Word8
#if MIN_VERSION_attoparsec(0,11,1)
peekWord8' = A.peekWord8'
#else
peekWord8' = maybe (fail "not enough bytes") return =<< A.peekWord8
#endif