bytestring-0.9.1.6: Fast, packed, strict and lazy byte arrays with a list interfaceSource codeContentsIndex
Data.ByteString
Portabilityportable
Stabilityexperimental
Maintainerdons@cse.unsw.edu.au
Contents
The ByteString type
Introducing and eliminating ByteStrings
Basic interface
Transforming ByteStrings
Reducing ByteStrings (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 CStrings and pointers
Using ByteStrings as CStrings
I/O with ByteStrings
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

show/hide Instances
Introducing and eliminating ByteStrings
empty :: ByteStringSource
O(1) The empty ByteString
singleton :: Word8 -> ByteStringSource
O(1) Convert a Word8 into a ByteString
pack :: [Word8] -> ByteStringSource

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 -> ByteStringSource
O(n) cons is analogous to (:) for lists, but of different complexity, as it requires a memcpy.
snoc :: ByteString -> Word8 -> ByteStringSource
O(n) Append a byte to the end of a ByteString
append :: ByteString -> ByteString -> ByteStringSource
O(n) Append two ByteStrings
head :: ByteString -> Word8Source
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 -> Word8Source
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 -> ByteStringSource
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 -> ByteStringSource
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 -> BoolSource
O(1) Test whether a ByteString is empty.
length :: ByteString -> IntSource
O(1) length returns the length of a ByteString as an Int.
Transforming ByteStrings
map :: (Word8 -> Word8) -> ByteString -> ByteStringSource
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 -> ByteStringSource
O(n) reverse xs efficiently returns the elements of xs in reverse order.
intersperse :: Word8 -> ByteString -> ByteStringSource
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] -> ByteStringSource
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.
Reducing ByteStrings (folds)
foldl :: (a -> Word8 -> a) -> a -> ByteString -> aSource

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 -> aSource
'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 -> Word8Source
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 -> Word8Source
'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 -> aSource
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 -> aSource
'foldr\'' is like foldr, but strict in the accumulator.
foldr1 :: (Word8 -> Word8 -> Word8) -> ByteString -> Word8Source
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' :: (Word8 -> Word8 -> Word8) -> ByteString -> Word8Source
'foldr1\'' is a variant of foldr1, but is strict in the accumulator.
Special folds
concat :: [ByteString] -> ByteStringSource
O(n) Concatenate a list of ByteStrings.
concatMap :: (Word8 -> ByteString) -> ByteString -> ByteStringSource
Map a function over a ByteString and concatenate the results
any :: (Word8 -> Bool) -> ByteString -> BoolSource
O(n) Applied to a predicate and a ByteString, any determines if any element of the ByteString satisfies the predicate.
all :: (Word8 -> Bool) -> ByteString -> BoolSource
O(n) Applied to a predicate and a ByteString, all determines if all elements of the ByteString satisfy the predicate.
maximum :: ByteString -> Word8Source
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 -> Word8Source
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 -> ByteStringSource

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 -> ByteStringSource

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 -> ByteStringSource
scanr is the right-to-left dual of scanl.
scanr1 :: (Word8 -> Word8 -> Word8) -> ByteString -> ByteStringSource
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 -> ByteStringSource

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 -> ByteStringSource

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 -> ByteStringSource
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 -> ByteStringSource
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 -> ByteStringSource
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 -> ByteStringSource
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 -> BoolSource
O(n) The isPrefixOf function takes two ByteStrings and returns True iff the first is a prefix of the second.
isSuffixOf :: ByteString -> ByteString -> BoolSource

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 -> BoolSource
Check whether one string is a substring of another. isInfixOf p s is equivalent to not (null (findSubstrings p s)).
Search for arbitrary substrings
breakSubstringSource
:: ByteStringString to search for
-> ByteStringString 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) 
findSubstringSource
:: ByteStringString to search for.
-> ByteStringString 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).
findSubstringsSource
:: ByteStringString to search for.
-> ByteStringString 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 -> BoolSource
O(n) elem is the ByteString membership predicate.
notElem :: Word8 -> ByteString -> BoolSource
O(n) notElem is the inverse of elem
Searching with a predicate
find :: (Word8 -> Bool) -> ByteString -> Maybe Word8Source

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 -> ByteStringSource
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 -> Word8Source
O(1) ByteString index (subscript) operator, starting from 0.
elemIndex :: Word8 -> ByteString -> Maybe IntSource
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 IntSource

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 IntSource
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 -> IntSource

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 -> ByteStringSource
O(n) Sort a ByteString efficiently, using counting sort.
Low level conversions
Copying ByteStrings
copy :: ByteString -> ByteStringSource
O(n) Make a copy of the ByteString with its own storage. This is mainly useful to allow the rest of the data pointed to by the ByteString to be garbage collected, for example if a large string has been read in, and only a small part of it is needed in the rest of the program.
Packing CStrings and pointers
packCString :: CString -> IO ByteStringSource
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 ByteStringSource
O(n). Construct a new ByteString from a CStringLen. The resulting ByteString is an immutable copy of the original CStringLen. The ByteString is a normal Haskell value and will be managed on the Haskell heap.
Using ByteStrings as CStrings
useAsCString :: ByteString -> (CString -> IO a) -> IO aSource
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 aSource
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 ByteStrings
Standard input and output
getLine :: IO ByteStringSource
Read a line from stdin.
getContents :: IO ByteStringSource
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 ByteStringSource
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 ByteStringSource
Read a line from a handle
hGetContents :: Handle -> IO ByteStringSource

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 ByteStringSource

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 null if EOF has been reached.

If there is any data to read, then hGet will not block, instead it will return whatever data is available without blocking. It only blocks if there is no data available to read.

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 ByteStringSource
hGetNonBlocking is identical to hGet, except that it will never block waiting for data to become available. If there is no data available to be read, hGetNonBlocking returns null.
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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