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authorMateusz Kowalczyk <fuuzetsu@fuuzetsu.co.uk>2014-08-08 01:41:34 +0200
committerMateusz Kowalczyk <fuuzetsu@fuuzetsu.co.uk>2014-08-08 04:58:19 +0200
commitd8f1c1cc4e8825f39ffc87fddfe6ff9c58f9ef8e (patch)
treefee259c5f50174842c5c843ab89a8f88250547f4 /haddock-library/vendor/attoparsec-0.12.1.1/Data/Attoparsec/ByteString.hs
parentd9b224f124edc99f051dfc0dcab922041654c36a (diff)
Update to attoparsec-0.12.1.1
There seems to be memory and speed improvement.
Diffstat (limited to 'haddock-library/vendor/attoparsec-0.12.1.1/Data/Attoparsec/ByteString.hs')
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+-- |
+-- Module : Data.Attoparsec.ByteString
+-- Copyright : Bryan O'Sullivan 2007-2014
+-- License : BSD3
+--
+-- Maintainer : bos@serpentine.com
+-- Stability : experimental
+-- Portability : unknown
+--
+-- Simple, efficient combinator parsing for 'B.ByteString' strings,
+-- loosely based on the Parsec library.
+
+module Data.Attoparsec.ByteString
+ (
+ -- * Differences from Parsec
+ -- $parsec
+
+ -- * Incremental input
+ -- $incremental
+
+ -- * Performance considerations
+ -- $performance
+
+ -- * Parser types
+ I.Parser
+ , Result
+ , T.IResult(..)
+ , I.compareResults
+
+ -- * Running parsers
+ , parse
+ , feed
+ , I.parseOnly
+ , parseWith
+ , parseTest
+
+ -- ** Result conversion
+ , maybeResult
+ , eitherResult
+
+ -- * Parsing individual bytes
+ , I.word8
+ , I.anyWord8
+ , I.notWord8
+ , I.satisfy
+ , I.satisfyWith
+ , I.skip
+
+ -- ** Lookahead
+ , I.peekWord8
+ , I.peekWord8'
+
+ -- ** Byte classes
+ , I.inClass
+ , I.notInClass
+
+ -- * Efficient string handling
+ , I.string
+ , I.skipWhile
+ , I.take
+ , I.scan
+ , I.takeWhile
+ , I.takeWhile1
+ , I.takeTill
+
+ -- ** Consume all remaining input
+ , I.takeByteString
+ , I.takeLazyByteString
+
+ -- * Combinators
+ , try
+ , (<?>)
+ , choice
+ , count
+ , option
+ , many'
+ , many1
+ , many1'
+ , manyTill
+ , manyTill'
+ , sepBy
+ , sepBy'
+ , sepBy1
+ , sepBy1'
+ , skipMany
+ , skipMany1
+ , eitherP
+ , I.match
+ -- * State observation and manipulation functions
+ , I.endOfInput
+ , I.atEnd
+ ) where
+
+import Data.Attoparsec.Combinator
+import qualified Data.Attoparsec.ByteString.Internal as I
+import qualified Data.Attoparsec.Internal as I
+import qualified Data.ByteString as B
+import Data.Attoparsec.ByteString.Internal (Result, parse)
+import qualified Data.Attoparsec.Internal.Types as T
+
+-- $parsec
+--
+-- Compared to Parsec 3, attoparsec makes several tradeoffs. It is
+-- not intended for, or ideal for, all possible uses.
+--
+-- * While attoparsec can consume input incrementally, Parsec cannot.
+-- Incremental input is a huge deal for efficient and secure network
+-- and system programming, since it gives much more control to users
+-- of the library over matters such as resource usage and the I/O
+-- model to use.
+--
+-- * Much of the performance advantage of attoparsec is gained via
+-- high-performance parsers such as 'I.takeWhile' and 'I.string'.
+-- If you use complicated combinators that return lists of bytes or
+-- characters, there is less performance difference between the two
+-- libraries.
+--
+-- * Unlike Parsec 3, attoparsec does not support being used as a
+-- monad transformer.
+--
+-- * attoparsec is specialised to deal only with strict 'B.ByteString'
+-- input. Efficiency concerns rule out both lists and lazy
+-- bytestrings. The usual use for lazy bytestrings would be to
+-- allow consumption of very large input without a large footprint.
+-- For this need, attoparsec's incremental input provides an
+-- excellent substitute, with much more control over when input
+-- takes place. If you must use lazy bytestrings, see the
+-- "Data.Attoparsec.ByteString.Lazy" module, which feeds lazy chunks
+-- to a regular parser.
+--
+-- * Parsec parsers can produce more helpful error messages than
+-- attoparsec parsers. This is a matter of focus: attoparsec avoids
+-- the extra book-keeping in favour of higher performance.
+
+-- $incremental
+--
+-- attoparsec supports incremental input, meaning that you can feed it
+-- a bytestring that represents only part of the expected total amount
+-- of data to parse. If your parser reaches the end of a fragment of
+-- input and could consume more input, it will suspend parsing and
+-- return a 'T.Partial' continuation.
+--
+-- Supplying the 'T.Partial' continuation with a bytestring will
+-- resume parsing at the point where it was suspended, with the
+-- bytestring you supplied used as new input at the end of the
+-- existing input. You must be prepared for the result of the resumed
+-- parse to be another 'T.Partial' continuation.
+--
+-- To indicate that you have no more input, supply the 'T.Partial'
+-- continuation with an empty bytestring.
+--
+-- Remember that some parsing combinators will not return a result
+-- until they reach the end of input. They may thus cause 'T.Partial'
+-- results to be returned.
+--
+-- If you do not need support for incremental input, consider using
+-- the 'I.parseOnly' function to run your parser. It will never
+-- prompt for more input.
+--
+-- /Note/: incremental input does /not/ imply that attoparsec will
+-- release portions of its internal state for garbage collection as it
+-- proceeds. Its internal representation is equivalent to a single
+-- 'ByteString': if you feed incremental input to a parser, it will
+-- require memory proportional to the amount of input you supply.
+-- (This is necessary to support arbitrary backtracking.)
+
+-- $performance
+--
+-- If you write an attoparsec-based parser carefully, it can be
+-- realistic to expect it to perform similarly to a hand-rolled C
+-- parser (measuring megabytes parsed per second).
+--
+-- To actually achieve high performance, there are a few guidelines
+-- that it is useful to follow.
+--
+-- Use the 'B.ByteString'-oriented parsers whenever possible,
+-- e.g. 'I.takeWhile1' instead of 'many1' 'I.anyWord8'. There is
+-- about a factor of 100 difference in performance between the two
+-- kinds of parser.
+--
+-- For very simple byte-testing predicates, write them by hand instead
+-- of using 'I.inClass' or 'I.notInClass'. For instance, both of
+-- these predicates test for an end-of-line byte, but the first is
+-- much faster than the second:
+--
+-- >endOfLine_fast w = w == 13 || w == 10
+-- >endOfLine_slow = inClass "\r\n"
+--
+-- Make active use of benchmarking and profiling tools to measure,
+-- find the problems with, and improve the performance of your parser.
+
+-- | Run a parser and print its result to standard output.
+parseTest :: (Show a) => I.Parser a -> B.ByteString -> IO ()
+parseTest p s = print (parse p s)
+
+-- | Run a parser with an initial input string, and a monadic action
+-- that can supply more input if needed.
+parseWith :: Monad m =>
+ (m B.ByteString)
+ -- ^ An action that will be executed to provide the parser
+ -- with more input, if necessary. The action must return an
+ -- 'B.empty' string when there is no more input available.
+ -> I.Parser a
+ -> B.ByteString
+ -- ^ Initial input for the parser.
+ -> m (Result a)
+parseWith refill p s = step $ parse p s
+ where step (T.Partial k) = (step . k) =<< refill
+ step r = return r
+{-# INLINE parseWith #-}
+
+-- | Convert a 'Result' value to a 'Maybe' value. A 'T.Partial' result
+-- is treated as failure.
+maybeResult :: Result r -> Maybe r
+maybeResult (T.Done _ r) = Just r
+maybeResult _ = Nothing
+
+-- | Convert a 'Result' value to an 'Either' value. A 'T.Partial'
+-- result is treated as failure.
+eitherResult :: Result r -> Either String r
+eitherResult (T.Done _ r) = Right r
+eitherResult (T.Fail _ _ msg) = Left msg
+eitherResult _ = Left "Result: incomplete input"