Data.ByteString.Lazy.Char8

bytestring-0.10.7.0: Fast, compact, strict and lazy byte strings with a list interface

Copyright | (c) Don Stewart 2006-2008 (c) Duncan Coutts 2006-2011
License | BSD-style
Maintainer | dons00@gmail.com, duncan@community.haskell.org
Stability | stable
Portability | portable
Safe Haskell | Trustworthy
Language | Haskell98

Data.ByteString.Lazy.Char8

Contents

- The `ByteString` type
- Introducing and eliminating `ByteString`s
- Basic interface
- Transforming ByteStrings
- Reducing `ByteString`s (folds)
  - Special folds
- Building ByteStrings
  - Scans
  - Accumulating maps
  - Infinite ByteStrings
  - Unfolding ByteStrings
- Substrings
  - Breaking strings
  - Breaking into many substrings
  - Breaking into lines and words
- Predicates
- Searching ByteStrings
  - Searching by equality
  - Searching with a predicate
- Indexing ByteStrings
- Zipping and unzipping ByteStrings
- Ordered ByteStrings
- Low level conversions
  - Copying ByteStrings
- Reading from ByteStrings
- I/O with `ByteString`s
  - Standard input and output
  - Files
  - I/O with Handles

Description

Manipulate lazy `ByteString`s using `Char` operations. All Chars will be truncated to 8 bits. It can be expected that these functions will run at identical speeds to their `Word8` equivalents in Data.ByteString.Lazy.

This module is intended to be imported `qualified`, to avoid name clashes with Prelude functions. eg.

    import qualified Data.ByteString.Lazy.Char8 as C

The Char8 interface to bytestrings provides an instance of IsString for the ByteString type, enabling you to use string literals, and have them implicitly packed to ByteStrings. Use `{-# LANGUAGE OverloadedStrings #-}` to enable this.

Synopsis

- data ByteString
- empty :: ByteString
- singleton :: Char -> ByteString
- pack :: [Char] -> ByteString
- unpack :: ByteString -> [Char]
- fromChunks :: [ByteString] -> ByteString
- toChunks :: ByteString -> [ByteString]
- fromStrict :: ByteString -> ByteString
- toStrict :: ByteString -> ByteString
- cons :: Char -> ByteString -> ByteString
- cons' :: Char -> ByteString -> ByteString
- snoc :: ByteString -> Char -> ByteString
- append :: ByteString -> ByteString -> ByteString
- head :: ByteString -> Char
- uncons :: ByteString -> Maybe (Char, ByteString)
- last :: ByteString -> Char
- tail :: ByteString -> ByteString
- unsnoc :: ByteString -> Maybe (ByteString, Char)
- init :: ByteString -> ByteString
- null :: ByteString -> Bool
- length :: ByteString -> Int64
- map :: (Char -> Char) -> ByteString -> ByteString
- reverse :: ByteString -> ByteString
- intersperse :: Char -> ByteString -> ByteString
- intercalate :: ByteString -> [ByteString] -> ByteString
- transpose :: [ByteString] -> [ByteString]
- foldl :: (a -> Char -> a) -> a -> ByteString -> a
- foldl' :: (a -> Char -> a) -> a -> ByteString -> a
- foldl1 :: (Char -> Char -> Char) -> ByteString -> Char
- foldl1' :: (Char -> Char -> Char) -> ByteString -> Char
- foldr :: (Char -> a -> a) -> a -> ByteString -> a
- foldr1 :: (Char -> Char -> Char) -> ByteString -> Char
- concat :: [ByteString] -> ByteString
- concatMap :: (Char -> ByteString) -> ByteString -> ByteString
- any :: (Char -> Bool) -> ByteString -> Bool
- all :: (Char -> Bool) -> ByteString -> Bool
- maximum :: ByteString -> Char
- minimum :: ByteString -> Char
- scanl :: (Char -> Char -> Char) -> Char -> ByteString -> ByteString
- mapAccumL :: (acc -> Char -> (acc, Char)) -> acc -> ByteString -> (acc, ByteString)
- mapAccumR :: (acc -> Char -> (acc, Char)) -> acc -> ByteString -> (acc, ByteString)
- repeat :: Char -> ByteString
- replicate :: Int64 -> Char -> ByteString
- cycle :: ByteString -> ByteString
- iterate :: (Char -> Char) -> Char -> ByteString
- unfoldr :: (a -> Maybe (Char, a)) -> a -> ByteString
- take :: Int64 -> ByteString -> ByteString
- drop :: Int64 -> ByteString -> ByteString
- splitAt :: Int64 -> ByteString -> (ByteString, ByteString)
- takeWhile :: (Char -> Bool) -> ByteString -> ByteString
- dropWhile :: (Char -> Bool) -> ByteString -> ByteString
- span :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)
- break :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)
- group :: ByteString -> [ByteString]
- groupBy :: (Char -> Char -> Bool) -> ByteString -> [ByteString]
- inits :: ByteString -> [ByteString]
- tails :: ByteString -> [ByteString]
- split :: Char -> ByteString -> [ByteString]
- splitWith :: (Char -> Bool) -> ByteString -> [ByteString]
- lines :: ByteString -> [ByteString]
- words :: ByteString -> [ByteString]
- unlines :: [ByteString] -> ByteString
- unwords :: [ByteString] -> ByteString
- isPrefixOf :: ByteString -> ByteString -> Bool
- isSuffixOf :: ByteString -> ByteString -> Bool
- elem :: Char -> ByteString -> Bool
- notElem :: Char -> ByteString -> Bool
- find :: (Char -> Bool) -> ByteString -> Maybe Char
- filter :: (Char -> Bool) -> ByteString -> ByteString
- index :: ByteString -> Int64 -> Char
- elemIndex :: Char -> ByteString -> Maybe Int64
- elemIndices :: Char -> ByteString -> [Int64]
- findIndex :: (Char -> Bool) -> ByteString -> Maybe Int64
- findIndices :: (Char -> Bool) -> ByteString -> [Int64]
- count :: Char -> ByteString -> Int64
- zip :: ByteString -> ByteString -> [(Char, Char)]
- zipWith :: (Char -> Char -> a) -> ByteString -> ByteString -> [a]
- copy :: ByteString -> ByteString
- readInt :: ByteString -> Maybe (Int, ByteString)
- readInteger :: ByteString -> Maybe (Integer, ByteString)
- getContents :: IO ByteString
- putStr :: ByteString -> IO ()
- putStrLn :: ByteString -> IO ()
- interact :: (ByteString -> ByteString) -> IO ()
- readFile :: FilePath -> IO ByteString
- writeFile :: FilePath -> ByteString -> IO ()
- appendFile :: FilePath -> ByteString -> IO ()
- hGetContents :: Handle -> IO ByteString
- hGet :: Handle -> Int -> IO ByteString
- hGetNonBlocking :: Handle -> Int -> IO ByteString
- hPut :: Handle -> ByteString -> IO ()
- hPutNonBlocking :: Handle -> ByteString -> IO ByteString
- hPutStr :: Handle -> ByteString -> IO ()
- hPutStrLn :: Handle -> ByteString -> IO ()

# The `ByteString` type

data ByteString Source

A space-efficient representation of a `Word8` vector, supporting many efficient operations.

A lazy `ByteString` contains 8-bit bytes, or by using the operations from Data.ByteString.Lazy.Char8 it can be interpreted as containing 8-bit characters.

Instances

Eq ByteString |
Methods (==) :: ByteString -> ByteString -> Bool Source (/=) :: ByteString -> ByteString -> Bool Source
Data ByteString |
Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> ByteString -> c ByteString Source gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c ByteString Source toConstr :: ByteString -> Constr Source dataTypeOf :: ByteString -> DataType Source dataCast1 :: Typeable (TYPE Lifted -> TYPE Lifted) t => (forall d. Data d => c (t d)) -> Maybe (c ByteString) Source dataCast2 :: Typeable (TYPE Lifted -> TYPE Lifted -> TYPE Lifted) t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c ByteString) Source gmapT :: (forall b. Data b => b -> b) -> ByteString -> ByteString Source gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> ByteString -> r Source gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> ByteString -> r Source gmapQ :: (forall d. Data d => d -> u) -> ByteString -> [u] Source gmapQi :: Int -> (forall d. Data d => d -> u) -> ByteString -> u Source gmapM :: Monad m => (forall d. Data d => d -> m d) -> ByteString -> m ByteString Source gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> ByteString -> m ByteString Source gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> ByteString -> m ByteString Source
Ord ByteString |
Methods compare :: ByteString -> ByteString -> Ordering Source (<) :: ByteString -> ByteString -> Bool Source (<=) :: ByteString -> ByteString -> Bool Source (>) :: ByteString -> ByteString -> Bool Source (>=) :: ByteString -> ByteString -> Bool Source max :: ByteString -> ByteString -> ByteString Source min :: ByteString -> ByteString -> ByteString Source
Read ByteString |
Methods readsPrec :: Int -> ReadS ByteString Source readList :: ReadS [ByteString] Source readPrec :: ReadPrec ByteString Source readListPrec :: ReadPrec [ByteString] Source
Show ByteString |
Methods showsPrec :: Int -> ByteString -> ShowS Source show :: ByteString -> String Source showList :: [ByteString] -> ShowS Source
IsString ByteString |
Methods fromString :: String -> ByteString Source
Semigroup ByteString |
Methods (<>) :: ByteString -> ByteString -> ByteString Source sconcat :: NonEmpty ByteString -> ByteString Source stimes :: Integral b => b -> ByteString -> ByteString Source
Monoid ByteString |
Methods mempty :: ByteString Source mappend :: ByteString -> ByteString -> ByteString Source mconcat :: [ByteString] -> ByteString Source
NFData ByteString |
Methods rnf :: ByteString -> () Source

# Introducing and eliminating `ByteString`s

empty :: ByteString Source

O(1) The empty `ByteString`

singleton :: Char -> ByteString Source

O(1) Convert a `Char` into a `ByteString`

pack :: [Char] -> ByteString Source

O(n) Convert a `String` into a `ByteString`.

unpack :: ByteString -> [Char] Source

O(n) Converts a `ByteString` to a `String`.

fromChunks :: [ByteString] -> ByteString Source

O(c) Convert a list of strict `ByteString` into a lazy `ByteString`

toChunks :: ByteString -> [ByteString] Source

O(c) Convert a lazy `ByteString` into a list of strict `ByteString`

fromStrict :: ByteString -> ByteString Source

O(1) Convert a strict `ByteString` into a lazy `ByteString`.

toStrict :: ByteString -> ByteString Source

O(n) Convert a lazy `ByteString` into a strict `ByteString`.

Note that this is an expensive operation that forces the whole lazy ByteString into memory and then copies all the data. If possible, try to avoid converting back and forth between strict and lazy bytestrings.

# Basic interface

cons :: Char -> ByteString -> ByteString infixr 5 Source

O(1) `cons` is analogous to '(:)' for lists.

cons' :: Char -> ByteString -> ByteString infixr 5 Source

O(1) Unlike `cons`, 'cons\'' is strict in the ByteString that we are consing onto. More precisely, it forces the head and the first chunk. It does this because, for space efficiency, it may coalesce the new byte onto the first 'chunk' rather than starting a new 'chunk'.

So that means you can't use a lazy recursive contruction like this:

    let xs = cons\' c xs in xs

You can however use `cons`, as well as `repeat` and `cycle`, to build infinite lazy ByteStrings.

snoc :: ByteString -> Char -> ByteString infixl 5 Source

O(n) Append a Char to the end of a `ByteString`. Similar to `cons`, this function performs a memcpy.

append :: ByteString -> ByteString -> ByteString Source

O(n/c) Append two ByteStrings

head :: ByteString -> Char Source

O(1) Extract the first element of a ByteString, which must be non-empty.

uncons :: ByteString -> Maybe (Char, ByteString) Source

O(1) Extract the head and tail of a ByteString, returning Nothing if it is empty.

last :: ByteString -> Char Source

O(1) Extract the last element of a packed string, which must be non-empty.

tail :: ByteString -> ByteString Source

O(1) Extract the elements after the head of a ByteString, which must be non-empty.

unsnoc :: ByteString -> Maybe (ByteString, Char) Source

O(n/c) Extract the `init` and `last` of a ByteString, returning Nothing if it is empty.

init :: ByteString -> ByteString Source

O(n/c) Return all the elements of a `ByteString` except the last one.

null :: ByteString -> Bool Source

O(1) Test whether a ByteString is empty.

length :: ByteString -> Int64 Source

O(n/c) `length` returns the length of a ByteString as an `Int64`

# Transforming ByteStrings

map :: (Char -> Char) -> ByteString -> ByteString Source

O(n) `map` `f xs` is the ByteString obtained by applying `f` to each element of `xs`

reverse :: ByteString -> ByteString Source

O(n) `reverse` `xs` returns the elements of `xs` in reverse order.

intersperse :: Char -> ByteString -> ByteString Source

O(n) The `intersperse` function takes a Char and a `ByteString` and `intersperses' that Char between the elements of the `ByteString`. It is analogous to the intersperse function on Lists.

intercalate :: ByteString -> [ByteString] -> ByteString Source

O(n) The `intercalate` function takes a `ByteString` and a list of `ByteString`s and concatenates the list after interspersing the first argument between each element of the list.

transpose :: [ByteString] -> [ByteString] Source

The `transpose` function transposes the rows and columns of its `ByteString` argument.

# Reducing `ByteString`s (folds)

foldl :: (a -> Char -> a) -> a -> ByteString -> a Source

`foldl`, applied to a binary operator, a starting value (typically the left-identity of the operator), and a ByteString, reduces the ByteString using the binary operator, from left to right.

foldl' :: (a -> Char -> a) -> a -> ByteString -> a Source

'foldl\'' is like foldl, but strict in the accumulator.

foldl1 :: (Char -> Char -> Char) -> ByteString -> Char Source

`foldl1` is a variant of `foldl` that has no starting value argument, and thus must be applied to non-empty `ByteStrings`.

foldl1' :: (Char -> Char -> Char) -> ByteString -> Char Source

'foldl1\'' is like `foldl1`, but strict in the accumulator.

foldr :: (Char -> a -> a) -> a -> ByteString -> a Source

`foldr`, applied to a binary operator, a starting value (typically the right-identity of the operator), and a packed string, reduces the packed string using the binary operator, from right to left.

foldr1 :: (Char -> Char -> Char) -> ByteString -> Char Source

`foldr1` is a variant of `foldr` that has no starting value argument, and thus must be applied to non-empty `ByteString`s

## Special folds

concat :: [ByteString] -> ByteString Source

O(n) Concatenate a list of ByteStrings.

concatMap :: (Char -> ByteString) -> ByteString -> ByteString Source

Map a function over a `ByteString` and concatenate the results

any :: (Char -> Bool) -> ByteString -> Bool Source

Applied to a predicate and a ByteString, `any` determines if any element of the `ByteString` satisfies the predicate.

all :: (Char -> Bool) -> ByteString -> Bool Source

Applied to a predicate and a `ByteString`, `all` determines if all elements of the `ByteString` satisfy the predicate.

maximum :: ByteString -> Char Source

`maximum` returns the maximum value from a `ByteString`

minimum :: ByteString -> Char Source

`minimum` returns the minimum value from a `ByteString`

# Building ByteStrings

## Scans

scanl :: (Char -> Char -> Char) -> Char -> ByteString -> ByteString Source

`scanl` is similar to `foldl`, but returns a list of successive reduced values from the left. This function will fuse.

    scanl f z [x1, x2, ...] == [z, z `f` x1, (z `f` x1) `f` x2, ...]

Note that

    last (scanl f z xs) == foldl f z xs.

## Accumulating maps

mapAccumL :: (acc -> Char -> (acc, Char)) -> acc -> ByteString -> (acc, ByteString) Source

The `mapAccumL` function behaves like a combination of `map` and `foldl`; it applies a function to each element of a ByteString, passing an accumulating parameter from left to right, and returning a final value of this accumulator together with the new ByteString.

mapAccumR :: (acc -> Char -> (acc, Char)) -> acc -> ByteString -> (acc, ByteString) Source

The `mapAccumR` function behaves like a combination of `map` and `foldr`; it applies a function to each element of a ByteString, passing an accumulating parameter from right to left, and returning a final value of this accumulator together with the new ByteString.

## Infinite ByteStrings

repeat :: Char -> ByteString Source

``repeat` x` is an infinite ByteString, with `x` the value of every element.

replicate :: Int64 -> Char -> ByteString Source

O(n) ``replicate` n x` is a ByteString of length `n` with `x` the value of every element.

cycle :: ByteString -> ByteString Source

`cycle` ties a finite ByteString into a circular one, or equivalently, the infinite repetition of the original ByteString.

iterate :: (Char -> Char) -> Char -> ByteString Source

``iterate` f x` returns an infinite ByteString of repeated applications of `f` to `x`:

    iterate f x == [x, f x, f (f x), ...]

## Unfolding ByteStrings

unfoldr :: (a -> Maybe (Char, a)) -> a -> ByteString Source

O(n) The `unfoldr` function is analogous to the List 'unfoldr'. `unfoldr` builds a ByteString from a seed value. The function takes the element and returns `Nothing` if it is done producing the ByteString or returns `Just` `(a,b)`, in which case, `a` is a prepending to the ByteString and `b` is used as the next element in a recursive call.

# Substrings

## Breaking strings

take :: Int64 -> ByteString -> ByteString Source

O(n/c) `take` `n`, applied to a ByteString `xs`, returns the prefix of `xs` of length `n`, or `xs` itself if `n > `length` xs`.

drop :: Int64 -> ByteString -> ByteString Source

O(n/c) `drop` `n xs` returns the suffix of `xs` after the first `n` elements, or `[]` if `n > `length` xs`.

splitAt :: Int64 -> ByteString -> (ByteString, ByteString) Source

O(n/c) `splitAt` `n xs` is equivalent to `(`take` n xs, `drop` n xs)`.

takeWhile :: (Char -> Bool) -> ByteString -> ByteString Source

`takeWhile`, applied to a predicate `p` and a ByteString `xs`, returns the longest prefix (possibly empty) of `xs` of elements that satisfy `p`.

dropWhile :: (Char -> Bool) -> ByteString -> ByteString Source

`dropWhile` `p xs` returns the suffix remaining after `takeWhile` `p xs`.

span :: (Char -> Bool) -> ByteString -> (ByteString, ByteString) Source

`span` `p xs` breaks the ByteString into two segments. It is equivalent to `(`takeWhile` p xs, `dropWhile` p xs)`

break :: (Char -> Bool) -> ByteString -> (ByteString, ByteString) Source

`break` `p` is equivalent to ``span` (`not` . p)`.

group :: ByteString -> [ByteString] Source

The `group` function takes a ByteString and returns a list of ByteStrings such that the concatenation of the result is equal to the argument. Moreover, each sublist in the result contains only equal elements. For example,

    group "Mississippi" = ["M","i","ss","i","ss","i","pp","i"]

It is a special case of `groupBy`, which allows the programmer to supply their own equality test.

groupBy :: (Char -> Char -> Bool) -> ByteString -> [ByteString] Source

The `groupBy` function is the non-overloaded version of `group`.

inits :: ByteString -> [ByteString] Source

O(n) Return all initial segments of the given `ByteString`, shortest first.

tails :: ByteString -> [ByteString] Source

O(n) Return all final segments of the given `ByteString`, longest first.

## Breaking into many substrings

split :: Char -> ByteString -> [ByteString] Source

O(n) Break a `ByteString` into pieces separated by the byte argument, consuming the delimiter. I.e.

    split '\n' "a\nb\nd\ne" == ["a","b","d","e"]
    split 'a'  "aXaXaXa"    == ["","X","X","X"]
    split 'x'  "x"          == ["",""]

and

    intercalate [c] . split c == id
    split == splitWith . (==)

As for all splitting functions in this library, this function does not copy the substrings, it just constructs new `ByteStrings` that are slices of the original.

splitWith :: (Char -> Bool) -> ByteString -> [ByteString] Source

O(n) Splits a `ByteString` into components delimited by separators, where the predicate returns True for a separator element. The resulting components do not contain the separators. Two adjacent separators result in an empty component in the output. eg.

    splitWith (=='a') "aabbaca" == ["","","bb","c",""]

## Breaking into lines and words

lines :: ByteString -> [ByteString] Source

`lines` breaks a ByteString up into a list of ByteStrings at newline Chars. The resulting strings do not contain newlines.

As of bytestring 0.9.0.3, this function is stricter than its list cousin.

words :: ByteString -> [ByteString] Source

`words` breaks a ByteString up into a list of words, which were delimited by Chars representing white space. And

    tokens isSpace = words

unlines :: [ByteString] -> ByteString Source

`unlines` is an inverse operation to `lines`. It joins lines, after appending a terminating newline to each.

unwords :: [ByteString] -> ByteString Source

The `unwords` function is analogous to the `unlines` function, on words.

# Predicates

isPrefixOf :: ByteString -> ByteString -> Bool Source

O(n) The `isPrefixOf` function takes two ByteStrings and returns `True` iff the first is a prefix of the second.

isSuffixOf :: ByteString -> ByteString -> Bool Source

O(n) The `isSuffixOf` function takes two ByteStrings and returns `True` iff the first is a suffix of the second.

The following holds:

    isSuffixOf x y == reverse x `isPrefixOf` reverse y

# Searching ByteStrings

## Searching by equality

elem :: Char -> ByteString -> Bool Source

O(n) `elem` is the `ByteString` membership predicate. This implementation uses `memchr(3)`.

notElem :: Char -> ByteString -> Bool Source

O(n) `notElem` is the inverse of `elem`

## Searching with a predicate

find :: (Char -> Bool) -> ByteString -> Maybe Char Source

O(n) The `find` function takes a predicate and a ByteString, and returns the first element in matching the predicate, or `Nothing` if there is no such element.

filter :: (Char -> Bool) -> ByteString -> ByteString Source

O(n) `filter`, applied to a predicate and a ByteString, returns a ByteString containing those characters that satisfy the predicate.

# Indexing ByteStrings

index :: ByteString -> Int64 -> Char Source

O(1) `ByteString` index (subscript) operator, starting from 0.

elemIndex :: Char -> ByteString -> Maybe Int64 Source

O(n) The `elemIndex` function returns the index of the first element in the given `ByteString` which is equal (by memchr) to the query element, or `Nothing` if there is no such element.

elemIndices :: Char -> ByteString -> [Int64] Source

O(n) The `elemIndices` function extends `elemIndex`, by returning the indices of all elements equal to the query element, in ascending order.

findIndex :: (Char -> Bool) -> ByteString -> Maybe Int64 Source

The `findIndex` function takes a predicate and a `ByteString` and returns the index of the first element in the ByteString satisfying the predicate.

findIndices :: (Char -> Bool) -> ByteString -> [Int64] Source

The `findIndices` function extends `findIndex`, by returning the indices of all elements satisfying the predicate, in ascending order.

count :: Char -> ByteString -> Int64 Source

count returns the number of times its argument appears in the ByteString

    count      == length . elemIndices
    count '\n' == length . lines

But more efficiently than using length on the intermediate list.

# Zipping and unzipping ByteStrings

zip :: ByteString -> ByteString -> [(Char, Char)] Source

O(n) `zip` takes two ByteStrings and returns a list of corresponding pairs of Chars. If one input ByteString is short, excess elements of the longer ByteString are discarded. This is equivalent to a pair of `unpack` operations, and so space usage may be large for multi-megabyte ByteStrings

zipWith :: (Char -> Char -> a) -> ByteString -> ByteString -> [a] Source

`zipWith` generalises `zip` by zipping with the function given as the first argument, instead of a tupling function. For example, ``zipWith` (+)` is applied to two ByteStrings to produce the list of corresponding sums.

# Ordered ByteStrings

# Low level conversions

## Copying ByteStrings

copy :: ByteString -> ByteString Source

O(n) Make a copy of the `ByteString` with its own storage. This is mainly useful to allow the rest of the data pointed to by the `ByteString` to be garbage collected, for example if a large string has been read in, and only a small part of it is needed in the rest of the program.

# Reading from ByteStrings

readInt :: ByteString -> Maybe (Int, ByteString) Source

readInt reads an Int from the beginning of the ByteString. If there is no integer at the beginning of the string, it returns Nothing, otherwise it just returns the int read, and the rest of the string.

readInteger :: ByteString -> Maybe (Integer, ByteString) Source

readInteger reads an Integer from the beginning of the ByteString. If there is no integer at the beginning of the string, it returns Nothing, otherwise it just returns the int read, and the rest of the string.

# I/O with `ByteString`s

ByteString I/O uses binary mode, without any character decoding or newline conversion. The fact that it does not respect the Handle newline mode is considered a flaw and may be changed in a future version.

## Standard input and output

getContents :: IO ByteString Source

getContents. Equivalent to hGetContents stdin. Will read lazily

putStr :: ByteString -> IO () Source

Write a ByteString to stdout

putStrLn :: ByteString -> IO () Source

Write a ByteString to stdout, appending a newline byte

interact :: (ByteString -> ByteString) -> IO () Source

The interact function takes a function of type `ByteString -> ByteString` as its argument. The entire input from the standard input device is passed to this function as its argument, and the resulting string is output on the standard output device.

## Files

readFile :: FilePath -> IO ByteString Source

Read an entire file lazily into a `ByteString`.

writeFile :: FilePath -> ByteString -> IO () Source

Write a `ByteString` to a file.

appendFile :: FilePath -> ByteString -> IO () Source

Append a `ByteString` to a file.

## I/O with Handles

hGetContents :: Handle -> IO ByteString Source

Read entire handle contents lazily into a `ByteString`. Chunks are read on demand, using the default chunk size.

Once EOF is encountered, the Handle is closed.

Note: the `Handle` should be placed in binary mode with `hSetBinaryMode` for `hGetContents` to work correctly.

hGet :: Handle -> Int -> IO ByteString Source

Read `n` bytes into a `ByteString`, directly from the specified `Handle`.

hGetNonBlocking :: Handle -> Int -> IO ByteString Source

hGetNonBlocking is similar to `hGet`, except that it will never block waiting for data to become available, instead it returns only whatever data is available. If there is no data available to be read, `hGetNonBlocking` returns `empty`.

Note: on Windows and with Haskell implementation other than GHC, this function does not work correctly; it behaves identically to `hGet`.

hPut :: Handle -> ByteString -> IO () Source

Outputs a `ByteString` to the specified `Handle`.

hPutNonBlocking :: Handle -> ByteString -> IO ByteString Source

Similar to `hPut` except that it will never block. Instead it returns any tail that did not get written. This tail may be `empty` in the case that the whole string was written, or the whole original string if nothing was written. Partial writes are also possible.

Note: on Windows and with Haskell implementation other than GHC, this function does not work correctly; it behaves identically to `hPut`.

hPutStr :: Handle -> ByteString -> IO () Source

A synonym for `hPut`, for compatibility

hPutStrLn :: Handle -> ByteString -> IO () Source

Write a ByteString to a handle, appending a newline byte