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Data.ByteString

Contents

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

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 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
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
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)
mapIndexed :: (Int -> Word8 -> Word8) -> ByteString -> 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]
join :: ByteString -> [ByteString] -> ByteString
isPrefixOf :: ByteString -> ByteString -> Bool
isSuffixOf :: ByteString -> ByteString -> Bool
isSubstringOf :: ByteString -> ByteString -> Bool
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
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
packCString :: CString -> ByteString
packCStringLen :: CStringLen -> ByteString
packMallocCString :: CString -> ByteString
useAsCString :: ByteString -> (CString -> IO a) -> IO a
useAsCStringLen :: ByteString -> (CStringLen -> IO a) -> IO a
copy :: ByteString -> ByteString
copyCString :: CString -> IO ByteString
copyCStringLen :: CStringLen -> IO ByteString
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 ()
unpackList :: ByteString -> [Word8]
lengthU :: ByteString -> Int
maximumU :: ByteString -> Word8
minimumU :: ByteString -> Word8

The `ByteString` type
data ByteString

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

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

Introducing and eliminating `ByteString`s
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 '[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]
O(n) Converts a `ByteString` to a '[Word8]'.
Basic interface
cons :: Word8 -> ByteString -> ByteString
O(n) `cons` is analogous to (:) for lists, but of different complexity, as it requires a memcpy.
snoc :: ByteString -> Word8 -> ByteString
O(n) Append a byte to the end of a `ByteString`
append :: ByteString -> ByteString -> ByteString
O(n) Append two ByteStrings
head :: 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.
last :: 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.
tail :: 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.
init :: ByteString -> ByteString
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
O(1) Test whether a ByteString is empty.
length :: ByteString -> Int
O(1) `length` returns the length of a ByteString as an `Int`.
Transformating ByteStrings
map :: (Word8 -> Word8) -> ByteString -> ByteString
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
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.
transpose :: [ByteString] -> [ByteString]
The `transpose` function transposes the rows and columns of its `ByteString` argument.
Reducing `ByteString`s (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. This function is subject to array fusion.
foldl' :: (a -> Word8 -> a) -> a -> ByteString -> a
`foldl` is like `foldl`, but strict in the accumulator. Though actually foldl is also strict in the accumulator.
foldl1 :: (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. 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
`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
`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
`foldr` is like `foldr`, but strict in the accumulator.
foldr1 :: (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 `ByteString`s An exception will be thrown in the case of an empty ByteString.
foldr1' :: (Word8 -> Word8 -> Word8) -> ByteString -> Word8
`foldr1` is a variant of `foldr1`, but is strict in the accumulator.
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 :: ByteString -> Word8
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
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
`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
`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
scanr is the right-to-left dual of scanl.
scanr1 :: (Word8 -> Word8 -> Word8) -> ByteString -> ByteString
`scanr1` is a variant of `scanr` that has no starting value argument.
Accumulating maps
mapAccumL :: (acc -> Word8 -> (acc, Word8)) -> acc -> ByteString -> (acc, ByteString)
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)
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.
mapIndexed :: (Int -> Word8 -> Word8) -> ByteString -> ByteString
O(n) map Word8 functions, provided with the index at each position
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 implemenation 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`:
     unfoldrN n f s == take n (unfoldr f s)
Substrings
Breaking strings
take :: Int -> ByteString -> ByteString
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
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)
O(1) `splitAt` `n xs` is equivalent to `(`take` n xs, `drop` n xs)`.
takeWhile :: (Word8 -> Bool) -> ByteString -> ByteString
`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
`dropWhile` `p xs` returns the suffix remaining after `takeWhile` `p xs`.
span :: (Word8 -> Bool) -> ByteString -> (ByteString, ByteString)
`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)
`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)
`break` `p` is equivalent to ``span` (`not` . p)`.
breakEnd :: (Word8 -> Bool) -> ByteString -> (ByteString, ByteString)
`breakEnd` behaves like `break` but from the end of the `ByteString` breakEnd p == spanEnd (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 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]
The `groupBy` function is the non-overloaded version of `group`.
inits :: ByteString -> [ByteString]
O(n) Return all initial segments of the given `ByteString`, shortest first.
tails :: ByteString -> [ByteString]
O(n) Return all final segments of the given `ByteString`, longest first.
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 '\n' "a\nb\nd\ne" == ["a","b","d","e"]
     split 'a'  "aXaXaXa"    == ["","X","X","X"]
     split 'x'  "x"          == ["",""]
and
     join [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 (=='a') "aabbaca" == ["","","bb","c",""]
     splitWith (=='a') []        == []
Joining strings
join :: ByteString -> [ByteString] -> ByteString
O(n) The `join` 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.
Predicates
isPrefixOf :: ByteString -> ByteString -> Bool
O(n) The `isPrefixOf` function takes two ByteStrings and returns `True` iff 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 implemenation uses memcmp to compare the end of the string only, with no reverse required..
Search for arbitrary substrings
isSubstringOf

:: ByteString | String to search for.
-> ByteString | String to search in.
-> Bool |
Check whether one string is a substring of another. `isSubstringOf p s` is equivalent to `not (null (findSubstrings p s))`.

findSubstring

:: 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

:: 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. This function uses the Knuth-Morris-Pratt string matching algorithm.

Searching ByteStrings
Searching by equality
These functions use memchr(3) to efficiently search the ByteString
elem :: Word8 -> ByteString -> Bool
O(n) `elem` is the `ByteString` membership predicate.
notElem :: Word8 -> ByteString -> Bool
O(n) `notElem` is the inverse of `elem`
Searching with a predicate
find :: (Word8 -> Bool) -> ByteString -> Maybe Word8
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
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.
Indexing ByteStrings
index :: ByteString -> Int -> Word8
O(1) `ByteString` index (subscript) operator, starting from 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 ==
     (-) (length xs - 1) `fmap` elemIndex c (reverse xs)
findIndex :: (Word8 -> Bool) -> ByteString -> Maybe Int
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]
The `findIndices` function extends `findIndex`, by returning the indices of all elements satisfying the predicate, in ascending order.
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)]
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]
`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)
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
O(n) Sort a ByteString efficiently, using counting sort.
Low level CString conversions
Packing CStrings and pointers
packCString :: CString -> ByteString
The sortBy function is the non-overloaded version of `sort`. Try some linear sorts: radix, counting Or mergesort. sortBy :: (Word8 -> Word8 -> Ordering) -> ByteString -> ByteString sortBy f ps = undefined O(n) Build a `ByteString` from a `CString`. This value will have no finalizer associated to it. The ByteString length is calculated using strlen(3), and thus the complexity is a O(n).
packCStringLen :: CStringLen -> ByteString
O(1) Build a `ByteString` from a `CStringLen`. This value will have no finalizer associated with it. This operation has O(1) complexity as we already know the final size, so no strlen(3) is required.
packMallocCString :: CString -> ByteString
O(n) Build a `ByteString` from a malloced `CString`. This value will have a `free(3)` finalizer associated to it.
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` will be freed automatically. This is a memcpy(3).
useAsCStringLen :: ByteString -> (CStringLen -> IO a) -> IO a
O(1) construction Use a `ByteString` with a function requiring a `CStringLen`.
Copying ByteStrings
These functions perform memcpy(3) operations
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.
copyCString :: CString -> IO ByteString
O(n) Duplicate a CString as a ByteString. Useful if you know the CString is going to be deallocated from C land.
copyCStringLen :: CStringLen -> IO ByteString
O(n) Same as copyCString, but saves a strlen call when the length is known.
I/O with `ByteString`s
Standard input and output
getLine :: IO ByteString
Read a line from stdin.
getContents :: IO ByteString
getContents. Equivalent to hGetContents stdin
putStr :: ByteString -> IO ()
Write a ByteString to stdout
putStrLn :: ByteString -> IO ()
Write a ByteString to stdout, appending a newline byte
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. It's great for writing one line programs!
Files
readFile :: FilePath -> IO ByteString
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 ()
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 entire handle contents 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.

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`.
hGetNonBlocking :: Handle -> Int -> IO ByteString
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 ()
Outputs a `ByteString` to the specified `Handle`.
hPutStr :: Handle -> ByteString -> IO ()
A synonym for `hPut`, for compatibility
hPutStrLn :: Handle -> ByteString -> IO ()
Write a ByteString to a handle, appending a newline byte
Fusion utilities
unpackList :: ByteString -> [Word8]
lengthU :: ByteString -> Int
maximumU :: ByteString -> Word8
minimumU :: ByteString -> Word8
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