Data.ByteString.Char8

bytestring-0.10.8.2: 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.Char8

Contents

- The `ByteString` type
- Introducing and eliminating `ByteString`s
- Basic interface
- Transformating ByteStrings
- Reducing `ByteString`s (folds)
  - Special folds
- Building ByteStrings
  - Scans
  - Accumulating maps
  - Generating and unfolding ByteStrings
- Substrings
  - Breaking strings
  - Breaking into many substrings
  - Breaking into lines and words
- Predicates
  - Search for arbitrary substrings
- Searching ByteStrings
  - Searching by equality
  - Searching with a predicate
- Indexing ByteStrings
- Zipping and unzipping ByteStrings
- Ordered ByteStrings
- Reading from ByteStrings
- Low level CString conversions
  - Copying ByteStrings
  - Packing CStrings and pointers
  - Using ByteStrings as CStrings
- I/O with `ByteString`s
  - Standard input and output
  - Files
  - I/O with Handles

Description

Manipulate `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.

More specifically these byte strings are taken to be in the subset of Unicode covered by code points 0-255. This covers Unicode Basic Latin, Latin-1 Supplement and C0+C1 Controls.

See:

- http://www.unicode.org/charts/
- http://www.unicode.org/charts/PDF/U0000.pdf
- http://www.unicode.org/charts/PDF/U0080.pdf

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

    import qualified Data.ByteString.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 :: String -> ByteString
- unpack :: ByteString -> [Char]
- cons :: Char -> ByteString -> ByteString
- snoc :: ByteString -> Char -> ByteString
- append :: ByteString -> ByteString -> ByteString
- head :: ByteString -> Char
- uncons :: ByteString -> Maybe (Char, ByteString)
- unsnoc :: ByteString -> Maybe (ByteString, Char)
- last :: ByteString -> Char
- tail :: ByteString -> ByteString
- init :: ByteString -> ByteString
- null :: ByteString -> Bool
- length :: ByteString -> Int
- 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
- foldr' :: (Char -> a -> a) -> a -> ByteString -> a
- foldr1 :: (Char -> Char -> Char) -> ByteString -> Char
- 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
- scanl1 :: (Char -> Char -> Char) -> ByteString -> ByteString
- scanr :: (Char -> Char -> Char) -> Char -> ByteString -> ByteString
- scanr1 :: (Char -> Char -> Char) -> ByteString -> ByteString
- mapAccumL :: (acc -> Char -> (acc, Char)) -> acc -> ByteString -> (acc, ByteString)
- mapAccumR :: (acc -> Char -> (acc, Char)) -> acc -> ByteString -> (acc, ByteString)
- replicate :: Int -> Char -> ByteString
- unfoldr :: (a -> Maybe (Char, a)) -> a -> ByteString
- unfoldrN :: Int -> (a -> Maybe (Char, a)) -> a -> (ByteString, Maybe a)
- take :: Int -> ByteString -> ByteString
- drop :: Int -> ByteString -> ByteString
- splitAt :: Int -> ByteString -> (ByteString, ByteString)
- takeWhile :: (Char -> Bool) -> ByteString -> ByteString
- dropWhile :: (Char -> Bool) -> ByteString -> ByteString
- span :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)
- spanEnd :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)
- break :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)
- breakEnd :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)
- group :: ByteString -> [ByteString]
- groupBy :: (Char -> Char -> Bool) -> ByteString -> [ByteString]
- inits :: ByteString -> [ByteString]
- tails :: ByteString -> [ByteString]
- stripPrefix :: ByteString -> ByteString -> Maybe ByteString
- stripSuffix :: ByteString -> ByteString -> Maybe 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
- isInfixOf :: ByteString -> ByteString -> Bool
- breakSubstring :: ByteString -> ByteString -> (ByteString, ByteString)
- findSubstring :: ByteString -> ByteString -> Maybe Int
- findSubstrings :: ByteString -> ByteString -> [Int]
- elem :: Char -> ByteString -> Bool
- notElem :: Char -> ByteString -> Bool
- find :: (Char -> Bool) -> ByteString -> Maybe Char
- filter :: (Char -> Bool) -> ByteString -> ByteString
- index :: ByteString -> Int -> Char
- elemIndex :: Char -> ByteString -> Maybe Int
- elemIndices :: Char -> ByteString -> [Int]
- elemIndexEnd :: Char -> ByteString -> Maybe Int
- findIndex :: (Char -> Bool) -> ByteString -> Maybe Int
- findIndices :: (Char -> Bool) -> ByteString -> [Int]
- count :: Char -> ByteString -> Int
- zip :: ByteString -> ByteString -> [(Char, Char)]
- zipWith :: (Char -> Char -> a) -> ByteString -> ByteString -> [a]
- unzip :: [(Char, Char)] -> (ByteString, ByteString)
- sort :: ByteString -> ByteString
- readInt :: ByteString -> Maybe (Int, ByteString)
- readInteger :: ByteString -> Maybe (Integer, ByteString)
- copy :: ByteString -> ByteString
- packCString :: CString -> IO ByteString
- packCStringLen :: CStringLen -> IO ByteString
- useAsCString :: ByteString -> (CString -> IO a) -> IO a
- useAsCStringLen :: ByteString -> (CStringLen -> IO a) -> IO a
- getLine :: IO 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 ()
- hGetLine :: Handle -> IO ByteString
- hGetContents :: Handle -> IO ByteString
- hGet :: Handle -> Int -> IO ByteString
- hGetSome :: 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 `ByteString` contains 8-bit bytes, or by using the operations from Data.ByteString.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 (* -> *) t => (forall d. Data d => c (t d)) -> Maybe (c ByteString) Source # dataCast2 :: Typeable (* -> * -> *) 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 :: String -> ByteString Source #

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

For applications with large numbers of string literals, pack can be a bottleneck.

unpack :: ByteString -> [Char] Source #

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

# Basic interface

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

O(n) `cons` is analogous to (:) for lists, but of different complexity, as it requires a memcpy.

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) 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.

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

O(1) Extract the `init` and `last` 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. An exception will be thrown in the case of an empty ByteString.

init :: ByteString -> ByteString Source #

O(1) Return all the elements of a `ByteString` except the last one. An exception will be thrown in the case of an empty ByteString.

null :: ByteString -> Bool Source #

O(1) Test whether a ByteString is empty.

length :: ByteString -> Int Source #

O(1) `length` returns the length of a ByteString as an `Int`.

# Transformating 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` efficiently 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 #

A strict version of `foldl1`

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.

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

'foldr\'' is a strict variant of foldr

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

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

A strict variant of foldr1

## 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:

    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.

scanl1 :: (Char -> Char -> Char) -> ByteString -> ByteString Source #

`scanl1` is a variant of `scanl` that has no starting value argument:

    scanl1 f [x1, x2, ...] == [x1, x1 `f` x2, ...]

scanr :: (Char -> Char -> Char) -> Char -> ByteString -> ByteString Source #

scanr is the right-to-left dual of scanl.

scanr1 :: (Char -> Char -> Char) -> ByteString -> ByteString Source #

`scanr1` is a variant of `scanr` that has no starting value argument.

## 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 list.

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.

## Generating and unfolding ByteStrings

replicate :: Int -> Char -> ByteString Source #

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

    replicate w c = unfoldr w (\u -> Just (u,u)) c

This implemenation uses `memset(3)`

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

O(n), where n is the length of the result. 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 the next character in the string, and `b` is the seed value for further production.

Examples:

    unfoldr (\x -> if x <= '9' then Just (x, succ x) else Nothing) '0' == "0123456789"

unfoldrN :: Int -> (a -> Maybe (Char, a)) -> a -> (ByteString, Maybe a) Source #

O(n) Like `unfoldr`, `unfoldrN` builds a ByteString from a seed value. However, the length of the result is limited by the first argument to `unfoldrN`. This function is more efficient than `unfoldr` when the maximum length of the result is known.

The following equation relates `unfoldrN` and `unfoldr`:

    unfoldrN n f s == take n (unfoldr f s)

# Substrings

## Breaking strings

take :: Int -> ByteString -> ByteString Source #

O(1) `take` `n`, applied to a ByteString `xs`, returns the prefix of `xs` of length `n`, or `xs` itself if `n > `length` xs`.

drop :: Int -> ByteString -> ByteString Source #

O(1) `drop` `n xs` returns the suffix of `xs` after the first `n` elements, or `[]` if `n > `length` xs`.

splitAt :: Int -> ByteString -> (ByteString, ByteString) Source #

O(1) `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)`

spanEnd :: (Char -> Bool) -> ByteString -> (ByteString, ByteString) Source #

`spanEnd` behaves like `span` but from the end of the `ByteString`. We have

    spanEnd (not.isSpace) "x y z" == ("x y ","z")

and

    spanEnd (not . isSpace) ps
       ==
    let (x,y) = span (not.isSpace) (reverse ps) in (reverse y, reverse x)

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

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

breakEnd :: (Char -> Bool) -> ByteString -> (ByteString, ByteString) Source #

`breakEnd` behaves like `break` but from the end of the `ByteString`

breakEnd p == spanEnd (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. It is about 40% faster than groupBy (==)

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.

stripPrefix :: ByteString -> ByteString -> Maybe ByteString Source #

O(n) The `stripPrefix` function takes two ByteStrings and returns `Just` the remainder of the second iff the first is its prefix, and otherwise `Nothing`.

Since: 0.10.8.0

stripSuffix :: ByteString -> ByteString -> Maybe ByteString Source #

O(n) The `stripSuffix` function takes two ByteStrings and returns `Just` the remainder of the second iff the first is its suffix, and otherwise `Nothing`.

## 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.

words :: ByteString -> [ByteString] Source #

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

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` if 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

However, the real implemenation uses memcmp to compare the end of the string only, with no reverse required..

isInfixOf :: ByteString -> ByteString -> Bool Source #

Check whether one string is a substring of another. `isInfixOf p s` is equivalent to `not (null (findSubstrings p s))`.

## Search for arbitrary substrings

breakSubstring Source #

Arguments

:: ByteString | String to search for
-> ByteString | String to search in
-> (ByteString, ByteString) | Head and tail of string broken at substring

Break a string on a substring, returning a pair of the part of the string prior to the match, and the rest of the string.

The following relationships hold:

    break (== c) l == breakSubstring (singleton c) l

and:

    findSubstring s l ==
       if null s then Just 0
                 else case breakSubstring s l of
                          (x,y) | null y    -> Nothing
                                | otherwise -> Just (length x)

For example, to tokenise a string, dropping delimiters:

    tokenise x y = h : if null t then [] else tokenise x (drop (length x) t)
        where (h,t) = breakSubstring x y

To skip to the first occurence of a string:

    snd (breakSubstring x y)

To take the parts of a string before a delimiter:

    fst (breakSubstring x y)

Note that calling `breakSubstring x` does some preprocessing work, so you should avoid unnecessarily duplicating breakSubstring calls with the same pattern.

findSubstring Source #

Arguments

:: ByteString | String to search for.
-> ByteString | String to seach in.
-> Maybe Int |

Deprecated: findSubstring is deprecated in favour of breakSubstring.

Get the first index of a substring in another string, or `Nothing` if the string is not found. `findSubstring p s` is equivalent to `listToMaybe (findSubstrings p s)`.

findSubstrings Source #

Arguments

:: ByteString | String to search for.
-> ByteString | String to seach in.
-> [Int] |

Deprecated: findSubstrings is deprecated in favour of breakSubstring.

Find the indexes of all (possibly overlapping) occurances of a substring in a string.

# 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 -> Int -> Char Source #

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

elemIndex :: Char -> ByteString -> Maybe Int 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 -> [Int] Source #

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

elemIndexEnd :: Char -> ByteString -> Maybe Int Source #

O(n) The `elemIndexEnd` function returns the last index of the element in the given `ByteString` which is equal to the query element, or `Nothing` if there is no such element. The following holds:

    elemIndexEnd c xs ==
    (-) (length xs - 1) `fmap` elemIndex c (reverse xs)

findIndex :: (Char -> Bool) -> ByteString -> Maybe Int 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 -> [Int] Source #

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

count :: Char -> ByteString -> Int Source #

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

    count = length . elemIndices

Also

    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.

unzip :: [(Char, Char)] -> (ByteString, ByteString) Source #

`unzip` transforms a list of pairs of Chars into a pair of ByteStrings. Note that this performs two `pack` operations.

# Ordered ByteStrings

sort :: ByteString -> ByteString Source #

O(n) Sort a ByteString efficiently, using counting sort.

# 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.

# Low level CString 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.

## Packing CStrings and pointers

packCString :: CString -> IO ByteString Source #

O(n). Construct a new `ByteString` from a `CString`. The resulting `ByteString` is an immutable copy of the original `CString`, and is managed on the Haskell heap. The original `CString` must be null terminated.

packCStringLen :: CStringLen -> IO ByteString Source #

O(n). Construct a new `ByteString` from a `CStringLen`. The resulting `ByteString` is an immutable copy of the original `CStringLen`. The `ByteString` is a normal Haskell value and will be managed on the Haskell heap.

## Using ByteStrings as CStrings

useAsCString :: ByteString -> (CString -> IO a) -> IO a Source #

O(n) construction Use a `ByteString` with a function requiring a null-terminated `CString`. The `CString` is a copy and will be freed automatically; it must not be stored or used after the subcomputation finishes.

useAsCStringLen :: ByteString -> (CStringLen -> IO a) -> IO a Source #

O(n) construction Use a `ByteString` with a function requiring a `CStringLen`. As for `useAsCString` this function makes a copy of the original `ByteString`. It must not be stored or used after the subcomputation finishes.

# 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

getLine :: IO ByteString Source #

Read a line from stdin.

getContents :: IO ByteString Source #

getContents. Read stdin strictly. Equivalent to hGetContents stdin The `Handle` is closed after the contents have been read.

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 strictly 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

hGetLine :: Handle -> IO ByteString Source #

Read a line from a handle

hGetContents :: Handle -> IO ByteString Source #

Read a handle's entire contents strictly into a `ByteString`.

This function reads chunks at a time, increasing the chunk size on each read. The final string is then realloced to the appropriate size. For files > half of available memory, this may lead to memory exhaustion. Consider using `readFile` in this case.

The Handle is closed once the contents have been read, or if an exception is thrown.

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

Read a `ByteString` directly from the specified `Handle`. This is far more efficient than reading the characters into a `String` and then using `pack`. First argument is the Handle to read from, and the second is the number of bytes to read. It returns the bytes read, up to n, or `empty` if EOF has been reached.

`hGet` is implemented in terms of `hGetBuf`.

If the handle is a pipe or socket, and the writing end is closed, `hGet` will behave as if EOF was reached.

hGetSome :: Handle -> Int -> IO ByteString Source #

Like `hGet`, except that a shorter `ByteString` may be returned if there are not enough bytes immediately available to satisfy the whole request. `hGetSome` only blocks if there is no data available, and EOF has not yet been reached.

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