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 | Haskell98 |
ByteString
typeByteString
sByteString
s (folds)
ByteString
s
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, or 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.
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.
O(1) The empty ByteString
singleton :: Word8 -> ByteString Source
O(1) Convert a Word8
into a ByteString
pack :: [Word8] -> ByteString Source
O(n) Convert a '[Word8]' into a ByteString
.
For applications with large numbers of string literals, pack can be a bottleneck. In such cases, consider using packAddress (GHC only).
unpack :: ByteString -> [Word8] Source
O(n) Converts a ByteString
to a '[Word8]'.
cons :: Word8 -> ByteString -> ByteString infixr 5 Source
O(n) cons
is analogous to (:) for lists, but of different complexity, as it requires making a copy.
snoc :: ByteString -> Word8 -> ByteString infixl 5 Source
O(n) Append a byte to the end of a ByteString
append :: ByteString -> ByteString -> ByteString Source
O(n) Append two ByteStrings
head :: ByteString -> Word8 Source
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.
uncons :: ByteString -> Maybe (Word8, ByteString) Source
O(1) Extract the head and tail of a ByteString, returning Nothing if it is empty.
unsnoc :: ByteString -> Maybe (ByteString, Word8) Source
O(1) Extract the init
and last
of a ByteString, returning Nothing if it is empty.
last :: ByteString -> Word8 Source
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.
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
.
map :: (Word8 -> Word8) -> 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 :: Word8 -> ByteString -> ByteString Source
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 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.
foldl :: (a -> Word8 -> 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 -> Word8 -> a) -> a -> ByteString -> a Source
foldl'
is like foldl
, but strict in the accumulator.
foldl1 :: (Word8 -> Word8 -> Word8) -> ByteString -> Word8 Source
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' :: (Word8 -> Word8 -> Word8) -> ByteString -> Word8 Source
'foldl1\'' is like foldl1
, but strict in the accumulator. An exception will be thrown in the case of an empty ByteString.
foldr :: (Word8 -> a -> a) -> a -> ByteString -> a Source
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 Source
foldr'
is like foldr
, but strict in the accumulator.
foldr1 :: (Word8 -> Word8 -> Word8) -> ByteString -> Word8 Source
foldr1
is a variant of foldr
that has no starting value argument, and thus must be applied to non-empty ByteString
s An exception will be thrown in the case of an empty ByteString.
foldr1' :: (Word8 -> Word8 -> Word8) -> ByteString -> Word8 Source
'foldr1\'' is a variant of foldr1
, but is strict in the accumulator.
concat :: [ByteString] -> ByteString Source
O(n) Concatenate a list of ByteStrings.
concatMap :: (Word8 -> ByteString) -> ByteString -> ByteString Source
Map a function over a ByteString
and concatenate the results
any :: (Word8 -> Bool) -> ByteString -> Bool Source
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 Source
O(n) Applied to a predicate and a ByteString
, all
determines if all elements of the ByteString
satisfy the predicate.
maximum :: ByteString -> Word8 Source
O(n) maximum
returns the maximum value from a ByteString
This function will fuse. An exception will be thrown in the case of an empty ByteString.
minimum :: ByteString -> Word8 Source
O(n) minimum
returns the minimum value from a ByteString
This function will fuse. An exception will be thrown in the case of an empty ByteString.
scanl :: (Word8 -> Word8 -> Word8) -> Word8 -> ByteString -> ByteString Source
scanl
is similar to foldl
, but returns a list of successive reduced values from the left. This function will fuse.
scanl f z [x1, x2, ...] == [z, z `f` x1, (z `f` x1) `f` x2, ...]
Note that
last (scanl f z xs) == foldl f z xs.
scanl1 :: (Word8 -> Word8 -> Word8) -> ByteString -> ByteString Source
scanl1
is a variant of scanl
that has no starting value argument. This function will fuse.
scanl1 f [x1, x2, ...] == [x1, x1 `f` x2, ...]
scanr :: (Word8 -> Word8 -> Word8) -> Word8 -> ByteString -> ByteString Source
scanr is the right-to-left dual of scanl.
scanr1 :: (Word8 -> Word8 -> Word8) -> ByteString -> ByteString Source
scanr1
is a variant of scanr
that has no starting value argument.
mapAccumL :: (acc -> Word8 -> (acc, Word8)) -> 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 -> Word8 -> (acc, Word8)) -> 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.
replicate :: Int -> Word8 -> 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 (Word8, 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 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) 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
:
fst (unfoldrN n f s) == take n (unfoldr f s)
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 :: (Word8 -> 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 :: (Word8 -> Bool) -> ByteString -> ByteString Source
dropWhile
p xs
returns the suffix remaining after takeWhile
p xs
.
span :: (Word8 -> 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 :: (Word8 -> 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 :: (Word8 -> Bool) -> ByteString -> (ByteString, ByteString) Source
break
p
is equivalent to span (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) 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 :: (Word8 -> Word8 -> 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.
split :: Word8 -> 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 :: (Word8 -> 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 (=='a') [] == []
isPrefixOf :: ByteString -> ByteString -> Bool Source
O(n) The isPrefixOf
function takes two ByteStrings and returns True
iff the first is a prefix of the second.
isSuffixOf :: ByteString -> ByteString -> Bool Source
O(n) The isSuffixOf
function takes two ByteStrings and returns True
iff the first is a suffix of the second.
The following holds:
isSuffixOf x y == reverse x `isPrefixOf` reverse y
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))
.
:: 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)
:: 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)
.
:: 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.
elem :: Word8 -> ByteString -> Bool Source
O(n) elem
is the ByteString
membership predicate.
notElem :: Word8 -> ByteString -> Bool Source
O(n) notElem
is the inverse of elem
find :: (Word8 -> Bool) -> ByteString -> Maybe Word8 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.
find f p = case findIndex f p of Just n -> Just (p ! n) ; _ -> Nothing
filter :: (Word8 -> 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 :: (Word8 -> Bool) -> ByteString -> (ByteString, ByteString) Source
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)
index :: ByteString -> Int -> Word8 Source
O(1) ByteString
index (subscript) operator, starting from 0.
elemIndex :: Word8 -> ByteString -> Maybe Int Source
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] Source
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 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 :: (Word8 -> 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 :: (Word8 -> Bool) -> ByteString -> [Int] Source
The findIndices
function extends findIndex
, by returning the indices of all elements satisfying the predicate, in ascending order.
count :: Word8 -> ByteString -> Int Source
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.
zip :: ByteString -> ByteString -> [(Word8, Word8)] Source
O(n) zip
takes two ByteStrings and returns a list of corresponding pairs of bytes. If one input ByteString is short, excess elements of the longer ByteString are discarded. This is equivalent to a pair of unpack
operations.
zipWith :: (Word8 -> Word8 -> 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 :: [(Word8, Word8)] -> (ByteString, ByteString) Source
O(n) unzip
transforms a list of pairs of bytes into a pair of ByteStrings. Note that this performs two pack
operations.
sort :: ByteString -> ByteString Source
O(n) Sort a ByteString efficiently, using counting sort.
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.
CString
s and pointerspackCString :: 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.
CString
suseAsCString :: 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.
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
.
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
Deprecated: Use Data.ByteString.Char8.putStrLn instead. (Functions that rely on ASCII encodings belong in Data.ByteString.Char8)
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.
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.
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
Deprecated: Use Data.ByteString.Char8.hPutStrLn instead. (Functions that rely on ASCII encodings belong in Data.ByteString.Char8)
Write a ByteString to a handle, appending a newline byte
breakByte :: Word8 -> ByteString -> (ByteString, ByteString) Source
Deprecated: It is an internal function and should never have been exported. Use 'break (== x)' instead. (There are rewrite rules that handle this special case of break
.)
breakByte
breaks its ByteString argument at the first occurence of the specified byte. It is more efficient than break
as it is implemented with memchr(3)
. I.e.
break (=='c') "abcd" == breakByte 'c' "abcd"
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Licensed under a BSD-style license (see top of the page).
https://downloads.haskell.org/~ghc/7.10.3/docs/html/libraries/bytestring-0.10.6.0/Data-ByteString.html