| 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 | Haskell2010 | 
Data.ByteString.Char8
Contents
- The ByteStringtype
- Introducing and eliminating ByteStrings
- Basic interface
- Transforming ByteStrings
- Reducing ByteStrings (folds)
- Building ByteStrings
- Substrings
- Predicates
- Searching ByteStrings
- Indexing ByteStrings
- Zipping and unzipping ByteStrings
- Ordered ByteStrings
- Reading from ByteStrings
- Low level CString conversions
- I/O with ByteStrings
Description
Manipulate ByteStrings 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]
- fromStrict :: ByteString -> ByteString
- toStrict :: ByteString -> ByteString
- 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 :: HasCallStack => ByteString -> ByteString
- init :: HasCallStack => 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
- takeEnd :: Int -> ByteString -> ByteString
- drop :: Int -> ByteString -> ByteString
- dropEnd :: Int -> ByteString -> ByteString
- splitAt :: Int -> ByteString -> (ByteString, ByteString)
- takeWhile :: (Char -> Bool) -> ByteString -> ByteString
- takeWhileEnd :: (Char -> Bool) -> ByteString -> ByteString
- dropWhile :: (Char -> Bool) -> ByteString -> ByteString
- dropWhileEnd :: (Char -> Bool) -> ByteString -> ByteString
- dropSpace :: 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]
- initsNE :: ByteString -> NonEmpty ByteString
- tailsNE :: ByteString -> NonEmpty ByteString
- strip :: 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)
- elem :: Char -> ByteString -> Bool
- notElem :: Char -> ByteString -> Bool
- find :: (Char -> Bool) -> ByteString -> Maybe Char
- filter :: (Char -> Bool) -> ByteString -> ByteString
- partition :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)
- index :: ByteString -> Int -> Char
- indexMaybe :: ByteString -> Int -> Maybe Char
- (!?) :: ByteString -> Int -> Maybe 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]
- findIndexEnd :: (Char -> Bool) -> ByteString -> Maybe Int
- count :: Char -> ByteString -> Int
- zip :: ByteString -> ByteString -> [(Char, Char)]
- zipWith :: (Char -> Char -> a) -> ByteString -> ByteString -> [a]
- packZipWith :: (Char -> Char -> Char) -> ByteString -> ByteString -> ByteString
- 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
Introducing and eliminating ByteStrings
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.
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(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 #
last :: ByteString -> Char Source #
O(1) Extract the last element of a packed string, which must be non-empty.
tail :: HasCallStack => 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.
This is a partial function, consider using uncons instead.
init :: HasCallStack => ByteString -> ByteString Source #
O(1) Returns all the elements of a ByteString except the last one.
 An exception will be thrown in the case of an empty ByteString.
This is a partial function, consider using unsnoc instead.
null :: ByteString -> Bool Source #
O(1) Test whether a ByteString is empty.
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 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
 ByteStrings 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 ByteStrings (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.
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 ByteStrings
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 #
scanl1 :: (Char -> Char -> Char) -> ByteString -> ByteString Source #
scanr :: (Char -> Char -> Char) -> Char -> ByteString -> ByteString Source #
scanr is the right-to-left dual of scanl.
scanr1 :: (Char -> Char -> Char) -> ByteString -> ByteString Source #
Accumulating maps
mapAccumL :: (acc -> Char -> (acc, Char)) -> acc -> ByteString -> (acc, ByteString) Source #
mapAccumR :: (acc -> Char -> (acc, Char)) -> acc -> ByteString -> (acc, ByteString) Source #
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 implementation 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 #
takeEnd :: Int -> ByteString -> ByteString Source #
drop :: Int -> ByteString -> ByteString Source #
dropEnd :: Int -> ByteString -> ByteString Source #
splitAt :: Int -> ByteString -> (ByteString, ByteString) Source #
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.
takeWhileEnd :: (Char -> Bool) -> ByteString -> ByteString Source #
takeWhileEnd, applied to a predicate p and a ByteString xs,
 returns the longest suffix (possibly empty) of xs of elements that
 satisfy p.
Since: bytestring-0.10.12.0
dropWhile :: (Char -> Bool) -> ByteString -> ByteString Source #
dropWhileEnd :: (Char -> Bool) -> ByteString -> ByteString Source #
dropWhileEnd p xs returns the prefix remaining after takeWhileEnd p
 xs.
Since: bytestring-0.10.12.0
dropSpace :: ByteString -> ByteString Source #
dropSpace efficiently returns the ByteString argument with
 white space Chars removed from the front. It is more efficient than
 calling dropWhile for removing whitespace. I.e.
dropWhile isSpace == dropSpace
Since: bytestring-0.10.12.0
span :: (Char -> Bool) -> ByteString -> (ByteString, ByteString) Source #
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 #
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 string 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 #
inits :: ByteString -> [ByteString] Source #
O(n) Returns all initial segments of the given ByteString, shortest first.
tails :: ByteString -> [ByteString] Source #
O(n) Returns all final segments of the given ByteString, longest first.
initsNE :: ByteString -> NonEmpty ByteString Source #
O(n) Returns all initial segments of the given ByteString, shortest first.
Since: bytestring-0.11.4.0
tailsNE :: ByteString -> NonEmpty ByteString Source #
O(n) Returns all final segments of the given ByteString, longest first.
Since: bytestring-0.11.4.0
strip :: ByteString -> ByteString Source #
Remove leading and trailing white space from a ByteString.
Since: bytestring-0.10.12.0
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: bytestring-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" == ["",""] split undefined "" == [] -- and not [""]
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",""] splitWith undefined "" == [] -- and not [""]
Breaking into lines and words
lines :: ByteString -> [ByteString] Source #
lines breaks a ByteString up into a list of ByteStrings at
 newline Chars ('\n'). The resulting strings do not contain newlines.
Note that it does not regard CR ('\r') as a newline character.
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 #
unwords :: [ByteString] -> ByteString Source #
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 implementation 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.
Search for arbitrary substrings
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
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 yTo skip to the first occurrence 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.
Searching ByteStrings
Searching by equality
elem :: Char -> ByteString -> Bool Source #
O(n) elem is the ByteString membership predicate. This
 implementation uses memchr(3).
Searching with a predicate
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.
partition :: (Char -> Bool) -> ByteString -> (ByteString, ByteString) Source #
Since: bytestring-0.10.12.0
Indexing ByteStrings
index :: ByteString -> Int -> Char Source #
O(1) ByteString index (subscript) operator, starting from 0.
indexMaybe :: ByteString -> Int -> Maybe Char Source #
O(1) ByteString index, starting from 0, that returns Just if:
0 <= n < length bs
Since: bytestring-0.11.0.0
(!?) :: ByteString -> Int -> Maybe Char Source #
O(1) ByteString index, starting from 0, that returns Just if:
0 <= n < length bs
Since: bytestring-0.11.0.0
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 = case elemIndex c (reverse xs) of Nothing -> Nothing Just i -> Just (length xs - 1 - i)
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.
findIndexEnd :: (Char -> Bool) -> ByteString -> Maybe Int Source #
O(n) The findIndexEnd function takes a predicate and a ByteString and
 returns the index of the last element in the ByteString
 satisfying the predicate.
Since: bytestring-0.11.1.0
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 #
zipWith :: (Char -> Char -> a) -> ByteString -> ByteString -> [a] Source #
packZipWith :: (Char -> Char -> Char) -> ByteString -> ByteString -> ByteString Source #
A specialised version of zipWith for the common case of a
 simultaneous map over two ByteStrings, to build a 3rd.
Since: bytestring-0.11.1.0
unzip :: [(Char, Char)] -> (ByteString, ByteString) Source #
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.
Note: This function will overflow the Int for large integers.
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 ByteStrings
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.
putStrLn :: ByteString -> IO () Source #
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
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 reallocated 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.