import qualified Data.ByteString as B

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.

type StrictByteString = ByteString Source

Type synonym for the strict flavour of ByteString.

Since: bytestring-0.11.2.0

empty :: ByteString Source

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 unsafePackAddress (GHC only).

unpack :: ByteString -> [Word8] Source

O(n) Converts a ByteString to a [Word8].

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.

fromFilePath :: FilePath -> IO ByteString Source

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 Source

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

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 :: HasCallStack => 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 :: HasCallStack => 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 :: 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.

init :: HasCallStack => 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 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.

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 :: HasCallStack => (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' :: HasCallStack => (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 :: HasCallStack => (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 ByteStrings An exception will be thrown in the case of an empty ByteString.

foldr1' :: HasCallStack => (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 :: HasCallStack => ByteString -> Word8 Source

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 Source

O(n) minimum returns the minimum value from a ByteString An exception will be thrown in the case of an empty ByteString.

scanl 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

head (scanl f z xs) == z
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.

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

scanr Source

scanr is similar to foldr, but returns a list of successive reduced values from the right.

scanr f z [..., x{n-1}, xn] == [..., x{n-1} `f` (xn `f` z), xn `f` z, z]

Note that

head (scanr f z xs) == foldr f z xs
last (scanr f z xs) == z

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 ByteString.

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 implementation 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.

takeEnd :: Int -> ByteString -> ByteString Source

O(1) takeEnd n xs is equivalent to drop (length xs - n) xs. Takes n elements from end of bytestring.

>>> takeEnd 3 "abcdefg"
"efg"
>>> takeEnd 0 "abcdefg"
""
>>> takeEnd 4 "abc"
"abc"

Since: bytestring-0.11.1.0

drop :: Int -> ByteString -> ByteString Source

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

dropEnd :: Int -> ByteString -> ByteString Source

O(1) dropEnd n xs is equivalent to take (length xs - n) xs. Drops n elements from end of bytestring.

>>> dropEnd 3 "abcdefg"
"abcd"
>>> dropEnd 0 "abcdefg"
"abcdefg"
>>> dropEnd 4 "abc"
""

Since: bytestring-0.11.1.0

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

Similar to takeWhile, returns the longest (possibly empty) prefix of elements satisfying the predicate.

takeWhileEnd :: (Word8 -> Bool) -> ByteString -> ByteString Source

Returns the longest (possibly empty) suffix of elements satisfying the predicate.

takeWhileEnd p is equivalent to reverse . takeWhile p . reverse.

Since: bytestring-0.10.12.0

dropWhile :: (Word8 -> Bool) -> ByteString -> ByteString Source

Similar to dropWhile, drops the longest (possibly empty) prefix of elements satisfying the predicate and returns the remainder.

dropWhileEnd :: (Word8 -> Bool) -> ByteString -> ByteString Source

Similar to dropWhileEnd, drops the longest (possibly empty) suffix of elements satisfying the predicate and returns the remainder.

dropWhileEnd p is equivalent to reverse . dropWhile p . reverse.

Since: bytestring-0.10.12.0

span :: (Word8 -> Bool) -> ByteString -> (ByteString, ByteString) Source

Similar to span, returns the longest (possibly empty) prefix of elements satisfying the predicate and the remainder of the string.

span p is equivalent to break (not . p) and to (takeWhile p &&& dropWhile p).

spanEnd :: (Word8 -> Bool) -> ByteString -> (ByteString, ByteString) Source

Returns the longest (possibly empty) suffix of elements satisfying the predicate and the remainder of the string.

spanEnd p is equivalent to breakEnd (not . p) and to (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) Source

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 span (not . p) and to (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) Source

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 spanEnd (not . p) and to (takeWhileEnd (not . p) &&& dropWhileEnd (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 :: (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.

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.

split :: Word8 -> ByteString -> [ByteString] Source

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] 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 (==97) "aabbaca" == ["","","bb","c",""] -- fromEnum 'a' == 97
splitWith undefined ""     == []                  -- and not [""]

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.

isValidUtf8 :: ByteString -> Bool Source

O(n) Check whether a ByteString represents valid UTF-8.

Since: bytestring-0.11.2.0

breakSubstring Source

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 y

To 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.

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 :: HasCallStack => ByteString -> Int -> Word8 Source

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

indexMaybe :: ByteString -> Int -> Maybe Word8 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 Word8 Source

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 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 = case elemIndex c (reverse xs) of
  Nothing -> Nothing
  Just i  -> Just (length xs - 1 - i)

findIndex :: (Word8 -> Bool) -> ByteString -> Maybe Int Source

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] Source

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 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-0.10.12.0

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.

packZipWith :: (Word8 -> Word8 -> Word8) -> 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 :: [(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.

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.

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.

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

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 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.

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

A synonym for hPut, for compatibility