| bytestring-0.9.1.4: Fast, packed, strict and lazy byte arrays with a list interface | Source code | Contents | Index

Data.ByteString

Portability | portable
Stability | experimental
Maintainer | dons@cse.unsw.edu.au

Contents

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

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, 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.

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 Data.Array.Unboxed.UArray by Simon Marlow. Rewritten to support slices and use `ForeignPtr` by David Roundy. Polished and extended by Don Stewart.

Synopsis

data ByteString
empty :: ByteString
singleton :: Word8 -> ByteString
pack :: [Word8] -> ByteString
unpack :: ByteString -> [Word8]
cons :: Word8 -> ByteString -> ByteString
snoc :: ByteString -> Word8 -> ByteString
append :: ByteString -> ByteString -> ByteString
head :: ByteString -> Word8
uncons :: ByteString -> Maybe (Word8, ByteString)
last :: ByteString -> Word8
tail :: ByteString -> ByteString
init :: 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 :: (Word8 -> Word8 -> Word8) -> ByteString -> Word8
foldl1' :: (Word8 -> Word8 -> Word8) -> ByteString -> Word8
foldr :: (Word8 -> a -> a) -> a -> ByteString -> a
foldr' :: (Word8 -> a -> a) -> a -> ByteString -> a
foldr1 :: (Word8 -> Word8 -> Word8) -> ByteString -> Word8
foldr1' :: (Word8 -> Word8 -> Word8) -> ByteString -> Word8
concat :: [ByteString] -> ByteString
concatMap :: (Word8 -> ByteString) -> ByteString -> ByteString
any :: (Word8 -> Bool) -> ByteString -> Bool
all :: (Word8 -> Bool) -> ByteString -> Bool
maximum :: ByteString -> Word8
minimum :: 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
drop :: Int -> ByteString -> ByteString
splitAt :: Int -> ByteString -> (ByteString, ByteString)
takeWhile :: (Word8 -> Bool) -> ByteString -> ByteString
dropWhile :: (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]
split :: Word8 -> ByteString -> [ByteString]
splitWith :: (Word8 -> Bool) -> ByteString -> [ByteString]
isPrefixOf :: ByteString -> ByteString -> Bool
isSuffixOf :: ByteString -> ByteString -> Bool
isInfixOf :: ByteString -> ByteString -> Bool
breakSubstring :: ByteString -> ByteString -> (ByteString, ByteString)
findSubstring :: ByteString -> ByteString -> Maybe Int
findSubstrings :: ByteString -> ByteString -> [Int]
elem :: 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 :: ByteString -> Int -> 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]
count :: Word8 -> ByteString -> Int
zip :: ByteString -> ByteString -> [(Word8, Word8)]
zipWith :: (Word8 -> Word8 -> a) -> ByteString -> ByteString -> [a]
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 ()
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
hGetNonBlocking :: Handle -> Int -> IO ByteString
hPut :: Handle -> ByteString -> IO ()
hPutStr :: Handle -> ByteString -> IO ()
hPutStrLn :: Handle -> ByteString -> IO ()
breakByte :: Word8 -> ByteString -> (ByteString, ByteString)

The `ByteString` type

data ByteString | Source

A space-efficient representation of a Word8 vector, supporting many efficient operations. A `ByteString` contains 8-bit characters only. Instances of Eq, Ord, Read, Show, Data, Typeable
Instances

Eq ByteString
Data ByteString
Ord ByteString
Read ByteString
Show ByteString
Typeable ByteString
IsString ByteString
Monoid ByteString

Introducing and eliminating `ByteString`s

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 packAddress (GHC only).

unpack :: ByteString -> [Word8] | Source

O(n) Converts a `ByteString` to a '[Word8]'.
Basic interface

cons :: Word8 -> ByteString -> ByteString | Source

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

snoc :: ByteString -> Word8 -> ByteString | 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.

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`.
Transforming ByteStrings

map :: (Word8 -> Word8) -> ByteString -> ByteString | Source

O(n) `map` `f xs` is the ByteString obtained by applying `f` to each element of `xs`. This function is subject to array fusion.

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.
Reducing `ByteString`s (folds)

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. This function is subject to array fusion.

foldl' :: (a -> Word8 -> a) -> a -> ByteString -> a | Source

'foldl\'' is like `foldl`, but strict in the accumulator. However, for ByteStrings, all left folds are 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. This function is subject to array fusion. 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.
Special folds

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.
Building ByteStrings
Scans

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.
Accumulating maps

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.
Generating and unfolding ByteStrings

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`:

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

Substrings
Breaking strings

take :: Int -> ByteString -> ByteString | Source

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

drop :: Int -> ByteString -> ByteString | Source

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

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

O(1) `splitAt` `n xs` is equivalent to `(`take` n xs, `drop` n xs)`.

takeWhile :: (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.
Breaking into many substrings

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') []        == []

Predicates

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))`.
Search for arbitrary substrings

breakSubstring | Source

:: 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)

findSubstring | Source

:: ByteString | String to search for.
-> ByteString | String to seach in.
-> Maybe Int |
Get the first index of a substring in another string, or `Nothing` if the string is not found. `findSubstring p s` is equivalent to `listToMaybe (findSubstrings p s)`.

findSubstrings | Source

:: ByteString | String to search for.
-> ByteString | String to seach in.
-> [Int] |
Find the indexes of all (possibly overlapping) occurances of a substring in a string.

Searching ByteStrings
Searching by equality

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`
Searching with a predicate

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. This function is subject to array fusion.

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)

Indexing ByteStrings

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.

Zipping and unzipping ByteStrings

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.
Ordered ByteStrings

sort :: ByteString -> ByteString | Source

O(n) Sort a ByteString efficiently, using counting sort.
Low level 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 `CString`s 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 `CString`s

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

O(n) construction Use a `ByteString` with a function requiring a null-terminated `CString`. The `CString` will be freed automatically. This is a memcpy(3).

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`.
I/O with `ByteString`s
Standard input and output

getLine :: IO ByteString | Source

Read a line from stdin.

getContents :: IO ByteString | Source

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

putStr :: ByteString -> IO () | Source

Write a ByteString to stdout

putStrLn :: ByteString -> IO () | Source

Write a ByteString to stdout, appending a newline byte

interact :: (ByteString -> ByteString) -> IO () | Source

The interact function takes a function of type `ByteString -> ByteString` as its argument. The entire input from the standard input device is passed to this function as its argument, and the resulting string is output on the standard output device.
Files

readFile :: FilePath -> IO ByteString | Source

Read an entire file strictly into a `ByteString`. This is far more efficient than reading the characters into a `String` and then using `pack`. It also may be more efficient than opening the file and reading it using hGet. Files are read using 'binary mode' on Windows, for 'text mode' use the Char8 version of this function.

writeFile :: FilePath -> ByteString -> IO () | Source

Write a `ByteString` to a file.

appendFile :: FilePath -> ByteString -> IO () | Source

Append a `ByteString` to a file.
I/O with Handles

hGetLine :: Handle -> IO ByteString | Source

Read a line from a handle

hGetContents :: Handle -> IO ByteString | Source

Read entire handle contents strictly into a `ByteString`.

This function reads chunks at a time, doubling the chunksize on each read. The final buffer 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.

As with `hGet`, the string representation in the file is assumed to be ISO-8859-1.

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 EOF.

`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.

hGetNonBlocking :: Handle -> Int -> IO ByteString | Source

hGetNonBlocking is identical to `hGet`, except that it will never block waiting for data to become available, instead it returns only whatever data is available.

hPut :: Handle -> ByteString -> IO () | Source

Outputs a `ByteString` to the specified `Handle`.

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

A synonym for `hPut`, for compatibility

hPutStrLn :: Handle -> ByteString -> IO () | Source

Write a ByteString to a handle, appending a newline byte

breakByte :: Word8 -> ByteString -> (ByteString, ByteString) | Source

`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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