| Copyright | (c) The University of Glasgow 2001 (c) David Roundy 2003-2005 (c) Simon Marlow 2005 (c) Bjorn Bringert 2006 (c) Don Stewart 2005-2008 (c) Duncan Coutts 2006-2013 |
|---|---|
| License | BSD-style |
| Maintainer | dons00@gmail.com, duncan@community.haskell.org |
| Stability | stable |
| Portability | portable |
| Safe Haskell | Trustworthy |
| Language | Haskell2010 |
Data.ByteString
Contents
Description
A time- and space-efficient implementation of byte vectors using
packed Word8 arrays, suitable for high performance use, both in terms
of large data quantities and high speed requirements. Byte vectors
are encoded as strict Word8 arrays of bytes, held in a ForeignPtr,
and can be passed between C and Haskell with little effort.
The recomended way to assemble ByteStrings from smaller parts is to use the builder monoid from Data.ByteString.Builder.
This module is intended to be imported qualified, to avoid name
clashes with Prelude functions. eg.
import qualified Data.ByteString as B
Original GHC implementation by Bryan O'Sullivan.
Rewritten to use UArray by Simon Marlow.
Rewritten to support slices and use ForeignPtr by David Roundy.
Rewritten again and extended by Don Stewart and Duncan Coutts.
Synopsis
- data ByteString
- type StrictByteString = ByteString
- empty :: ByteString
- singleton :: Word8 -> ByteString
- pack :: [Word8] -> ByteString
- unpack :: ByteString -> [Word8]
- fromStrict :: ByteString -> ByteString
- toStrict :: ByteString -> ByteString
- fromFilePath :: FilePath -> IO ByteString
- toFilePath :: ByteString -> IO FilePath
- cons :: Word8 -> ByteString -> ByteString
- snoc :: ByteString -> Word8 -> ByteString
- append :: ByteString -> ByteString -> ByteString
- head :: HasCallStack => ByteString -> Word8
- uncons :: ByteString -> Maybe (Word8, ByteString)
- unsnoc :: ByteString -> Maybe (ByteString, Word8)
- last :: HasCallStack => ByteString -> Word8
- tail :: HasCallStack => ByteString -> ByteString
- init :: HasCallStack => ByteString -> ByteString
- null :: ByteString -> Bool
- length :: ByteString -> Int
- map :: (Word8 -> Word8) -> ByteString -> ByteString
- reverse :: ByteString -> ByteString
- intersperse :: Word8 -> ByteString -> ByteString
- intercalate :: ByteString -> [ByteString] -> ByteString
- transpose :: [ByteString] -> [ByteString]
- foldl :: (a -> Word8 -> a) -> a -> ByteString -> a
- foldl' :: (a -> Word8 -> a) -> a -> ByteString -> a
- foldl1 :: HasCallStack => (Word8 -> Word8 -> Word8) -> ByteString -> Word8
- foldl1' :: HasCallStack => (Word8 -> Word8 -> Word8) -> ByteString -> Word8
- foldr :: (Word8 -> a -> a) -> a -> ByteString -> a
- foldr' :: (Word8 -> a -> a) -> a -> ByteString -> a
- foldr1 :: HasCallStack => (Word8 -> Word8 -> Word8) -> ByteString -> Word8
- foldr1' :: HasCallStack => (Word8 -> Word8 -> Word8) -> ByteString -> Word8
- concat :: [ByteString] -> ByteString
- concatMap :: (Word8 -> ByteString) -> ByteString -> ByteString
- any :: (Word8 -> Bool) -> ByteString -> Bool
- all :: (Word8 -> Bool) -> ByteString -> Bool
- maximum :: HasCallStack => ByteString -> Word8
- minimum :: HasCallStack => ByteString -> Word8
- scanl :: (Word8 -> Word8 -> Word8) -> Word8 -> ByteString -> ByteString
- scanl1 :: (Word8 -> Word8 -> Word8) -> ByteString -> ByteString
- scanr :: (Word8 -> Word8 -> Word8) -> Word8 -> ByteString -> ByteString
- scanr1 :: (Word8 -> Word8 -> Word8) -> ByteString -> ByteString
- mapAccumL :: (acc -> Word8 -> (acc, Word8)) -> acc -> ByteString -> (acc, ByteString)
- mapAccumR :: (acc -> Word8 -> (acc, Word8)) -> acc -> ByteString -> (acc, ByteString)
- replicate :: Int -> Word8 -> ByteString
- unfoldr :: (a -> Maybe (Word8, a)) -> a -> ByteString
- unfoldrN :: Int -> (a -> Maybe (Word8, 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 :: (Word8 -> Bool) -> ByteString -> ByteString
- takeWhileEnd :: (Word8 -> Bool) -> ByteString -> ByteString
- dropWhile :: (Word8 -> Bool) -> ByteString -> ByteString
- dropWhileEnd :: (Word8 -> Bool) -> ByteString -> ByteString
- span :: (Word8 -> Bool) -> ByteString -> (ByteString, ByteString)
- spanEnd :: (Word8 -> Bool) -> ByteString -> (ByteString, ByteString)
- break :: (Word8 -> Bool) -> ByteString -> (ByteString, ByteString)
- breakEnd :: (Word8 -> Bool) -> ByteString -> (ByteString, ByteString)
- group :: ByteString -> [ByteString]
- groupBy :: (Word8 -> Word8 -> Bool) -> ByteString -> [ByteString]
- inits :: ByteString -> [ByteString]
- tails :: ByteString -> [ByteString]
- initsNE :: ByteString -> NonEmpty ByteString
- tailsNE :: ByteString -> NonEmpty ByteString
- stripPrefix :: ByteString -> ByteString -> Maybe ByteString
- stripSuffix :: ByteString -> ByteString -> Maybe ByteString
- split :: Word8 -> ByteString -> [ByteString]
- splitWith :: (Word8 -> Bool) -> ByteString -> [ByteString]
- isPrefixOf :: ByteString -> ByteString -> Bool
- isSuffixOf :: ByteString -> ByteString -> Bool
- isInfixOf :: ByteString -> ByteString -> Bool
- isValidUtf8 :: ByteString -> Bool
- breakSubstring :: ByteString -> ByteString -> (ByteString, ByteString)
- elem :: Word8 -> ByteString -> Bool
- notElem :: Word8 -> ByteString -> Bool
- find :: (Word8 -> Bool) -> ByteString -> Maybe Word8
- filter :: (Word8 -> Bool) -> ByteString -> ByteString
- partition :: (Word8 -> Bool) -> ByteString -> (ByteString, ByteString)
- index :: HasCallStack => ByteString -> Int -> Word8
- indexMaybe :: ByteString -> Int -> Maybe Word8
- (!?) :: ByteString -> Int -> Maybe Word8
- elemIndex :: Word8 -> ByteString -> Maybe Int
- elemIndices :: Word8 -> ByteString -> [Int]
- elemIndexEnd :: Word8 -> ByteString -> Maybe Int
- findIndex :: (Word8 -> Bool) -> ByteString -> Maybe Int
- findIndices :: (Word8 -> Bool) -> ByteString -> [Int]
- findIndexEnd :: (Word8 -> Bool) -> ByteString -> Maybe Int
- count :: Word8 -> ByteString -> Int
- zip :: ByteString -> ByteString -> [(Word8, Word8)]
- zipWith :: (Word8 -> Word8 -> a) -> ByteString -> ByteString -> [a]
- packZipWith :: (Word8 -> Word8 -> Word8) -> ByteString -> ByteString -> ByteString
- unzip :: [(Word8, Word8)] -> (ByteString, ByteString)
- sort :: ByteString -> 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 ()
- 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 ()
Strict ByteString
data ByteString #
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
type StrictByteString = ByteString #
Type synonym for the strict flavour of ByteString.
Since: bytestring-0.11.2.0
Introducing and eliminating ByteStrings
empty :: ByteString #
O(1) The empty ByteString
singleton :: Word8 -> ByteString #
O(1) Convert a Word8 into a ByteString
pack :: [Word8] -> ByteString #
O(n) Convert a [ into a Word8]ByteString.
For applications with large numbers of string literals, pack can be a
bottleneck. In such cases, consider using unsafePackAddress (GHC only).
unpack :: ByteString -> [Word8] #
O(n) Converts a ByteString to a [.Word8]
fromStrict :: ByteString -> ByteString #
O(1) Convert a strict ByteString into a lazy ByteString.
toStrict :: ByteString -> ByteString #
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.
fromFilePath :: FilePath -> IO ByteString #
Convert a FilePath to a ByteString.
The FilePath type is expected to use the file system encoding
as reported by getFileSystemEncoding. This
encoding allows for round-tripping of arbitrary data on platforms
that allow arbitrary bytes in their paths. This conversion
function does the same thing that openFile would
do when decoding the FilePath.
This function is in IO because the file system encoding can be
changed. If the encoding can be assumed to be constant in your
use case, you may invoke this function via unsafePerformIO.
Since: bytestring-0.11.2.0
toFilePath :: ByteString -> IO FilePath #
Convert a ByteString to a FilePath.
This function uses the file system encoding, and resulting FilePaths
can be safely used with standard IO functions and will reference the
correct path in the presence of arbitrary non-UTF-8 encoded paths.
This function is in IO because the file system encoding can be
changed. If the encoding can be assumed to be constant in your
use case, you may invoke this function via unsafePerformIO.
Since: bytestring-0.11.2.0
Basic interface
cons :: Word8 -> ByteString -> ByteString infixr 5 #
O(n) cons is analogous to (:) for lists, but of different
complexity, as it requires making a copy.
snoc :: ByteString -> Word8 -> ByteString infixl 5 #
O(n) Append a byte to the end of a ByteString
append :: ByteString -> ByteString -> ByteString #
O(n) Append two ByteStrings
head :: HasCallStack => ByteString -> Word8 #
O(1) Extract the first element 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.
uncons :: ByteString -> Maybe (Word8, ByteString) #
unsnoc :: ByteString -> Maybe (ByteString, Word8) #
last :: HasCallStack => ByteString -> Word8 #
O(1) Extract the last element of a ByteString, which must be finite and non-empty. An exception will be thrown in the case of an empty ByteString.
This is a partial function, consider using unsnoc instead.
tail :: HasCallStack => ByteString -> ByteString #
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 #
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 #
O(1) Test whether a ByteString is empty.
Transforming ByteStrings
map :: (Word8 -> Word8) -> ByteString -> ByteString #
O(n) map f xs is the ByteString obtained by applying f to each
element of xs.
reverse :: ByteString -> ByteString #
O(n) reverse xs efficiently returns the elements of xs in reverse order.
intersperse :: Word8 -> ByteString -> ByteString #
O(n) The intersperse function takes a Word8 and a
ByteString and `intersperses' that byte between the elements of
the ByteString. It is analogous to the intersperse function on
Lists.
intercalate :: ByteString -> [ByteString] -> ByteString #
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] #
The transpose function transposes the rows and columns of its
ByteString argument.
Reducing ByteStrings (folds)
foldl :: (a -> Word8 -> a) -> a -> ByteString -> a #
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 -> Word8 -> a) -> a -> ByteString -> a #
foldl1 :: HasCallStack => (Word8 -> Word8 -> Word8) -> ByteString -> Word8 #
foldl1 is a variant of foldl that has no starting value
argument, and thus must be applied to non-empty ByteStrings.
An exception will be thrown in the case of an empty ByteString.
foldl1' :: HasCallStack => (Word8 -> Word8 -> Word8) -> ByteString -> Word8 #
foldr :: (Word8 -> a -> a) -> a -> ByteString -> a #
foldr, applied to a binary operator, a starting value
(typically the right-identity of the operator), and a ByteString,
reduces the ByteString using the binary operator, from right to left.
foldr' :: (Word8 -> a -> a) -> a -> ByteString -> a #
foldr1 :: HasCallStack => (Word8 -> Word8 -> Word8) -> ByteString -> Word8 #
foldr1 is a variant of foldr that has no starting value argument,
and thus must be applied to non-empty ByteStrings
An exception will be thrown in the case of an empty ByteString.
foldr1' :: HasCallStack => (Word8 -> Word8 -> Word8) -> ByteString -> Word8 #
Special folds
concat :: [ByteString] -> ByteString #
O(n) Concatenate a list of ByteStrings.
concatMap :: (Word8 -> ByteString) -> ByteString -> ByteString #
Map a function over a ByteString and concatenate the results
any :: (Word8 -> Bool) -> ByteString -> Bool #
O(n) Applied to a predicate and a ByteString, any determines if
any element of the ByteString satisfies the predicate.
all :: (Word8 -> Bool) -> ByteString -> Bool #
O(n) Applied to a predicate and a ByteString, all determines
if all elements of the ByteString satisfy the predicate.
maximum :: HasCallStack => ByteString -> Word8 #
O(n) maximum returns the maximum value from a ByteString
An exception will be thrown in the case of an empty ByteString.
minimum :: HasCallStack => ByteString -> Word8 #
O(n) minimum returns the minimum value from a ByteString
An exception will be thrown in the case of an empty ByteString.
Building ByteStrings
Scans
Arguments
| :: (Word8 -> Word8 -> Word8) | accumulator -> element -> new accumulator |
| -> Word8 | starting value of accumulator |
| -> ByteString | input of length n |
| -> ByteString | output of length n+1 |
scanl1 :: (Word8 -> Word8 -> Word8) -> ByteString -> ByteString #
Arguments
| :: (Word8 -> Word8 -> Word8) | element -> accumulator -> new accumulator |
| -> Word8 | starting value of accumulator |
| -> ByteString | input of length n |
| -> ByteString | output of length n+1 |
scanr1 :: (Word8 -> Word8 -> Word8) -> ByteString -> ByteString #
Accumulating maps
mapAccumL :: (acc -> Word8 -> (acc, Word8)) -> acc -> ByteString -> (acc, ByteString) #
mapAccumR :: (acc -> Word8 -> (acc, Word8)) -> acc -> ByteString -> (acc, ByteString) #
Generating and unfolding ByteStrings
replicate :: Int -> Word8 -> ByteString #
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 (Word8, a)) -> a -> ByteString #
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 byte in the string,
and b is the seed value for further production.
Examples:
unfoldr (\x -> if x <= 5 then Just (x, x + 1) else Nothing) 0 == pack [0, 1, 2, 3, 4, 5]
unfoldrN :: Int -> (a -> Maybe (Word8, a)) -> a -> (ByteString, Maybe a) #
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:
fst (unfoldrN n f s) == take n (unfoldr f s)
Substrings
Breaking strings
take :: Int -> ByteString -> ByteString #
takeEnd :: Int -> ByteString -> ByteString #
drop :: Int -> ByteString -> ByteString #
dropEnd :: Int -> ByteString -> ByteString #
splitAt :: Int -> ByteString -> (ByteString, ByteString) #
takeWhile :: (Word8 -> Bool) -> ByteString -> ByteString #
Similar to takeWhile,
returns the longest (possibly empty) prefix of elements
satisfying the predicate.
takeWhileEnd :: (Word8 -> Bool) -> ByteString -> ByteString #
Returns the longest (possibly empty) suffix of elements satisfying the predicate.
is equivalent to takeWhileEnd p.reverse . takeWhile p . reverse
Since: bytestring-0.10.12.0
dropWhile :: (Word8 -> Bool) -> ByteString -> ByteString #
Similar to dropWhile,
drops the longest (possibly empty) prefix of elements
satisfying the predicate and returns the remainder.
dropWhileEnd :: (Word8 -> Bool) -> ByteString -> ByteString #
Similar to dropWhileEnd,
drops the longest (possibly empty) suffix of elements
satisfying the predicate and returns the remainder.
is equivalent to dropWhileEnd p.reverse . dropWhile p . reverse
Since: bytestring-0.10.12.0
span :: (Word8 -> Bool) -> ByteString -> (ByteString, ByteString) #
spanEnd :: (Word8 -> Bool) -> ByteString -> (ByteString, ByteString) #
Returns the longest (possibly empty) suffix of elements satisfying the predicate and the remainder of the string.
spanEnd p is equivalent to and to breakEnd (not . p)(.takeWhileEnd p &&& dropWhileEnd p)
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 :: (Word8 -> Bool) -> ByteString -> (ByteString, ByteString) #
Similar to break,
returns the longest (possibly empty) prefix of elements which do not
satisfy the predicate and the remainder of the string.
break p is equivalent to and to span (not . p)(.takeWhile (not . p) &&& dropWhile (not . p))
Under GHC, a rewrite rule will transform break (==) into a call to the specialised breakByte:
break ((==) x) = breakByte x break (==x) = breakByte x
breakEnd :: (Word8 -> Bool) -> ByteString -> (ByteString, ByteString) #
Returns the longest (possibly empty) suffix of elements which do not satisfy the predicate and the remainder of the string.
breakEnd p is equivalent to and to spanEnd (not . p)(.takeWhileEnd (not . p) &&& dropWhileEnd (not . p))
group :: ByteString -> [ByteString] #
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 :: (Word8 -> Word8 -> Bool) -> ByteString -> [ByteString] #
inits :: ByteString -> [ByteString] #
O(n) Returns all initial segments of the given ByteString, shortest first.
tails :: ByteString -> [ByteString] #
O(n) Returns all final segments of the given ByteString, longest first.
initsNE :: ByteString -> NonEmpty ByteString #
O(n) Returns all initial segments of the given ByteString, shortest first.
Since: bytestring-0.11.4.0
tailsNE :: ByteString -> NonEmpty ByteString #
O(n) Returns all final segments of the given ByteString, longest first.
Since: bytestring-0.11.4.0
stripPrefix :: ByteString -> ByteString -> Maybe ByteString #
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 #
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 :: Word8 -> ByteString -> [ByteString] #
O(n) Break a ByteString into pieces separated by the byte
argument, consuming the delimiter. I.e.
split 10 "a\nb\nd\ne" == ["a","b","d","e"] -- fromEnum '\n' == 10 split 97 "aXaXaXa" == ["","X","X","X",""] -- fromEnum 'a' == 97 split 120 "x" == ["",""] -- fromEnum 'x' == 120 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 :: (Word8 -> Bool) -> ByteString -> [ByteString] #
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 (==97) "aabbaca" == ["","","bb","c",""] -- fromEnum 'a' == 97 splitWith undefined "" == [] -- and not [""]
Predicates
isPrefixOf :: ByteString -> ByteString -> Bool #
O(n) The isPrefixOf function takes two ByteStrings and returns True
if the first is a prefix of the second.
isSuffixOf :: ByteString -> ByteString -> Bool #
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 #
Check whether one string is a substring of another.
Encoding validation
isValidUtf8 :: ByteString -> Bool #
O(n) Check whether a ByteString represents valid UTF-8.
Since: bytestring-0.11.2.0
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 :: Word8 -> ByteString -> Bool #
O(n) elem is the ByteString membership predicate.
Searching with a predicate
filter :: (Word8 -> Bool) -> ByteString -> ByteString #
O(n) filter, applied to a predicate and a ByteString,
returns a ByteString containing those characters that satisfy the
predicate.
partition :: (Word8 -> Bool) -> ByteString -> (ByteString, ByteString) #
O(n) The partition function takes a predicate a ByteString and returns
the pair of ByteStrings with elements which do and do not satisfy the
predicate, respectively; i.e.,
partition p bs == (filter p xs, filter (not . p) xs)
Indexing ByteStrings
index :: HasCallStack => ByteString -> Int -> Word8 #
O(1) ByteString index (subscript) operator, starting from 0.
This is a partial function, consider using indexMaybe instead.
indexMaybe :: ByteString -> Int -> Maybe Word8 #
O(1) ByteString index, starting from 0, that returns Just if:
0 <= n < length bs
Since: bytestring-0.11.0.0
(!?) :: ByteString -> Int -> Maybe Word8 #
O(1) ByteString index, starting from 0, that returns Just if:
0 <= n < length bs
Since: bytestring-0.11.0.0
elemIndex :: Word8 -> ByteString -> Maybe Int #
O(n) The elemIndex function returns the index of the first
element in the given ByteString which is equal to the query
element, or Nothing if there is no such element.
This implementation uses memchr(3).
elemIndices :: Word8 -> ByteString -> [Int] #
O(n) The elemIndices function extends elemIndex, by returning
the indices of all elements equal to the query element, in ascending order.
This implementation uses memchr(3).
elemIndexEnd :: Word8 -> ByteString -> Maybe Int #
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 :: (Word8 -> Bool) -> ByteString -> Maybe Int #
O(n) The findIndex function takes a predicate and a ByteString and
returns the index of the first element in the ByteString
satisfying the predicate.
findIndices :: (Word8 -> Bool) -> ByteString -> [Int] #
O(n) The findIndices function extends findIndex, by returning the
indices of all elements satisfying the predicate, in ascending order.
findIndexEnd :: (Word8 -> Bool) -> ByteString -> Maybe Int #
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-0.10.12.0
count :: Word8 -> ByteString -> Int #
count returns the number of times its argument appears in the ByteString
count = length . elemIndices
But more efficiently than using length on the intermediate list.
Zipping and unzipping ByteStrings
zip :: ByteString -> ByteString -> [(Word8, Word8)] #
zipWith :: (Word8 -> Word8 -> a) -> ByteString -> ByteString -> [a] #
packZipWith :: (Word8 -> Word8 -> Word8) -> ByteString -> ByteString -> ByteString #
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 :: [(Word8, Word8)] -> (ByteString, ByteString) #
Ordered ByteStrings
sort :: ByteString -> ByteString #
O(n) Sort a ByteString efficiently, using counting sort.
Low level conversions
Copying ByteStrings
copy :: ByteString -> ByteString #
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 #
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 #
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 #
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 #
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
Standard input and output
getLine :: IO ByteString #
Read a line from stdin.
getContents :: IO ByteString #
getContents. Read stdin strictly. Equivalent to hGetContents stdin
The Handle is closed after the contents have been read.
putStr :: ByteString -> IO () #
Write a ByteString to stdout.
interact :: (ByteString -> ByteString) -> IO () #
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 #
Read an entire file strictly into a ByteString.
writeFile :: FilePath -> ByteString -> IO () #
Write a ByteString to a file.
appendFile :: FilePath -> ByteString -> IO () #
Append a ByteString to a file.
I/O with Handles
hGetLine :: Handle -> IO ByteString #
Read a line from a handle
hGetContents :: Handle -> IO ByteString #
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 #
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 #
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 #
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 () #
Outputs a ByteString to the specified Handle.
hPutNonBlocking :: Handle -> ByteString -> IO ByteString #
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.