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| Data.ByteString.Lazy.Char8 |
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| Description |
Manipulate lazy ByteStrings using Char operations. All Chars will
be truncated to 8 bits. It can be expected that these functions will
run at identical speeds to their Word8 equivalents in
Data.ByteString.Lazy.
This module is intended to be imported qualified, to avoid name
clashes with Prelude functions. eg.
import qualified Data.ByteString.Lazy.Char8 as C
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| Synopsis |
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| The ByteString type
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| type ByteString = LazyByteString |
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| Introducing and eliminating ByteStrings
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| empty :: ByteString |
| O(1) The empty ByteString
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| singleton :: Char -> ByteString |
| O(1) Convert a Char into a ByteString
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| pack :: [Char] -> ByteString |
| O(n) Convert a String into a ByteString.
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| unpack :: ByteString -> [Char] |
| O(n) Converts a ByteString to a String.
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| fromChunks :: [ByteString] -> ByteString |
| O(c) Convert a list of strict ByteString into a lazy ByteString
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| toChunks :: ByteString -> [ByteString] |
| O(n) Convert a lazy ByteString into a list of strict ByteString
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| Basic interface
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| cons :: Char -> ByteString -> ByteString |
| O(n) cons is analogous to (:) for lists, but of different
complexity, as it requires a memcpy.
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| snoc :: ByteString -> Char -> ByteString |
| O(n) Append a Char to the end of a ByteString. Similar to
cons, this function performs a memcpy.
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| append :: ByteString -> ByteString -> ByteString |
| O(n) Append two ByteStrings
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| head :: ByteString -> Char |
| O(1) Extract the first element of a ByteString, which must be non-empty.
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| last :: ByteString -> Char |
| O(1) Extract the last element of a packed string, which must be non-empty.
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| tail :: ByteString -> ByteString |
| O(1) Extract the elements after the head of a ByteString, which must be non-empty.
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| init :: ByteString -> ByteString |
| O(n/c) Return all the elements of a ByteString except the last one.
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| null :: ByteString -> Bool |
| O(1) Test whether a ByteString is empty.
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| length :: ByteString -> Int64 |
| O(n/c) length returns the length of a ByteString as an Int64
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| Transformating ByteStrings
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| map :: (Char -> Char) -> ByteString -> ByteString |
| O(n) map f xs is the ByteString obtained by applying f to each element of xs
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| reverse :: ByteString -> ByteString |
| O(n) reverse xs efficiently returns the elements of xs in reverse order.
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| transpose :: [ByteString] -> [ByteString] |
| The transpose function transposes the rows and columns of its
ByteString argument.
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| Reducing ByteStrings (folds)
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| foldl :: (a -> Char -> 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.
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| foldl' :: (a -> Char -> a) -> a -> ByteString -> a |
| foldl is like foldl, but strict in the accumulator.
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| foldl1 :: (Char -> Char -> Char) -> ByteString -> Char |
| foldl1 is a variant of foldl that has no starting value
argument, and thus must be applied to non-empty ByteStrings.
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| foldl1' :: (Char -> Char -> Char) -> ByteString -> Char |
| foldl1 is like foldl1, but strict in the accumulator.
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| foldr :: (Char -> a -> a) -> a -> ByteString -> a |
| foldr, applied to a binary operator, a starting value
(typically the right-identity of the operator), and a packed string,
reduces the packed string using the binary operator, from right to left.
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| foldr1 :: (Char -> Char -> Char) -> ByteString -> Char |
| foldr1 is a variant of foldr that has no starting value argument,
and thus must be applied to non-empty ByteStrings
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| Special folds
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| concat :: [ByteString] -> ByteString |
| O(n) Concatenate a list of ByteStrings.
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| concatMap :: (Char -> ByteString) -> ByteString -> ByteString |
| Map a function over a ByteString and concatenate the results
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| any :: (Char -> Bool) -> ByteString -> Bool |
| Applied to a predicate and a ByteString, any determines if
any element of the ByteString satisfies the predicate.
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| all :: (Char -> Bool) -> ByteString -> Bool |
| Applied to a predicate and a ByteString, all determines if
all elements of the ByteString satisfy the predicate.
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| maximum :: ByteString -> Char |
| maximum returns the maximum value from a ByteString
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| minimum :: ByteString -> Char |
| minimum returns the minimum value from a ByteString
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| Building ByteStrings
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| Scans
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| scanl :: (Char -> Char -> Char) -> Char -> 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.
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| Accumulating maps
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| mapAccumL :: (acc -> Char -> (acc, Char)) -> 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 ByteString.
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| mapIndexed :: (Int -> Char -> Char) -> ByteString -> ByteString |
| O(n) map Char functions, provided with the index at each position
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| Infinite ByteStrings
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| repeat :: Char -> ByteString |
| repeat x is an infinite ByteString, with x the value of every
element.
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| replicate :: Int64 -> Char -> ByteString |
| O(n) replicate n x is a ByteString of length n with x
the value of every element.
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| cycle :: [a] -> [a] |
| cycle ties a finite list into a circular one, or equivalently,
the infinite repetition of the original list. It is the identity
on infinite lists.
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| iterate :: (Char -> Char) -> Char -> ByteString |
iterate f x returns an infinite ByteString of repeated applications
of f to x:
iterate f x == [x, f x, f (f x), ...]
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| Unfolding
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| unfoldr :: (a -> Maybe (Char, a)) -> a -> ByteString |
| O(n) 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 a
prepending to the ByteString and b is used as the next element in a
recursive call.
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| Substrings
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| Breaking strings
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| take :: Int64 -> ByteString -> ByteString |
| O(n/c) take n, applied to a ByteString xs, returns the prefix
of xs of length n, or xs itself if n > length xs.
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| drop :: Int64 -> ByteString -> ByteString |
| O(n/c) drop n xs returns the suffix of xs after the first n
elements, or [] if n > length xs.
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| splitAt :: Int64 -> ByteString -> (ByteString, ByteString) |
| O(n/c) splitAt n xs is equivalent to (take n xs, drop n xs).
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| takeWhile :: (Char -> 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.
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| dropWhile :: (Char -> Bool) -> ByteString -> ByteString |
| dropWhile p xs returns the suffix remaining after takeWhile p xs.
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| span :: (Char -> Bool) -> ByteString -> (ByteString, ByteString) |
| span p xs breaks the ByteString into two segments. It is
equivalent to (takeWhile p xs, dropWhile p xs)
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| break :: (Char -> Bool) -> ByteString -> (ByteString, ByteString) |
| break p is equivalent to span (not . p).
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| 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.
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| groupBy :: (Char -> Char -> Bool) -> ByteString -> [ByteString] |
| The groupBy function is the non-overloaded version of group.
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| inits :: ByteString -> [ByteString] |
O(n) unzip transforms a list of pairs of bytes into a pair of
ByteStrings. Note that this performs two pack operations.
O(n) Return all initial segments of the given ByteString, shortest first.
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| tails :: ByteString -> [ByteString] |
| O(n) Return all final segments of the given ByteString, longest first.
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| Breaking into many substrings
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| split :: Char -> 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.
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| splitWith :: (Char -> 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",""]
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| Breaking into lines and words
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| lines :: ByteString -> [ByteString] |
| lines breaks a ByteString up into a list of ByteStrings at
newline Chars. The resulting strings do not contain newlines.
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| words :: ByteString -> [ByteString] |
words breaks a ByteString up into a list of words, which
were delimited by Chars representing white space. And
tokens isSpace = words
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| unlines :: [ByteString] -> ByteString |
| unlines is an inverse operation to lines. It joins lines,
after appending a terminating newline to each.
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| unwords :: [ByteString] -> ByteString |
| The unwords function is analogous to the unlines function, on words.
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| Joining strings
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| join :: ByteString -> [ByteString] -> ByteString |
| O(n) The join function takes a ByteString and a list of
ByteStrings and concatenates the list after interspersing the first
argument between each element of the list.
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| Predicates
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| isPrefixOf :: ByteString -> ByteString -> Bool |
| O(n) The isPrefixOf function takes two ByteStrings and returns True
iff the first is a prefix of the second.
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| Searching ByteStrings
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| Searching by equality
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| elem :: Char -> ByteString -> Bool |
| O(n) elem is the ByteString membership predicate. This
implementation uses memchr(3).
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| notElem :: Char -> ByteString -> Bool |
| O(n) notElem is the inverse of elem
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| Searching with a predicate
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| find :: (Char -> Bool) -> ByteString -> Maybe Char |
| 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.
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| filter :: (Char -> Bool) -> ByteString -> ByteString |
| O(n) filter, applied to a predicate and a ByteString,
returns a ByteString containing those characters that satisfy the
predicate.
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| Indexing ByteStrings
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| index :: ByteString -> Int64 -> Char |
| O(1) ByteString index (subscript) operator, starting from 0.
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| elemIndex :: Char -> ByteString -> Maybe Int64 |
| O(n) The elemIndex function returns the index of the first
element in the given ByteString which is equal (by memchr) to the
query element, or Nothing if there is no such element.
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| elemIndices :: Char -> ByteString -> [Int64] |
| O(n) The elemIndices function extends elemIndex, by returning
the indices of all elements equal to the query element, in ascending order.
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| findIndex :: (Char -> Bool) -> ByteString -> Maybe Int64 |
| The findIndex function takes a predicate and a ByteString and
returns the index of the first element in the ByteString satisfying the predicate.
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| findIndices :: (Char -> Bool) -> ByteString -> [Int64] |
| The findIndices function extends findIndex, by returning the
indices of all elements satisfying the predicate, in ascending order.
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| count :: Char -> ByteString -> Int64 |
count returns the number of times its argument appears in the ByteString
count == length . elemIndices
count '\n' == length . lines
But more efficiently than using length on the intermediate list.
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| Zipping and unzipping ByteStrings
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| zip :: ByteString -> ByteString -> [(Char, Char)] |
| O(n) zip takes two ByteStrings and returns a list of
corresponding pairs of Chars. If one input ByteString is short,
excess elements of the longer ByteString are discarded. This is
equivalent to a pair of unpack operations, and so space
usage may be large for multi-megabyte ByteStrings
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| zipWith :: (Char -> Char -> 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.
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| Ordered ByteStrings
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| 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.
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| Reading from ByteStrings
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| readInt :: ByteString -> Maybe (Int, ByteString) |
| readInt reads an Int from the beginning of the ByteString. If
there is no integer at the beginning of the string, it returns
Nothing, otherwise it just returns the int read, and the rest of the
string.
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| readInteger :: ByteString -> Maybe (Integer, ByteString) |
| readInteger reads an Integer from the beginning of the ByteString. If
there is no integer at the beginning of the string, it returns Nothing,
otherwise it just returns the int read, and the rest of the string.
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| I/O with ByteStrings
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| Standard input and output
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| getContents :: IO ByteString |
| getContents. Equivalent to hGetContents stdin. Will read lazily
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| putStr :: ByteString -> IO () |
| Write a ByteString to stdout
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| putStrLn :: ByteString -> IO () |
| Write a ByteString to stdout, appending a newline byte
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| 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!
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| Files
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| readFile :: FilePath -> IO ByteString |
| Read an entire file lazily into a ByteString. Use 'text mode'
on Windows to interpret newlines
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| writeFile :: FilePath -> ByteString -> IO () |
| Write a ByteString to a file.
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| appendFile :: FilePath -> ByteString -> IO () |
| Append a ByteString to a file.
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| I/O with Handles
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| hGetContents :: Handle -> IO ByteString |
| Read entire handle contents lazily into a ByteString. Chunks
are read on demand, using the default chunk size.
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| hGet :: Handle -> Int -> IO ByteString |
| Read n bytes into a ByteString, directly from the specified Handle.
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| hPut :: Handle -> ByteString -> IO () |
| Outputs a ByteString to the specified Handle.
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| hGetNonBlocking :: Handle -> Int -> IO ByteString |
| 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.
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| Produced by Haddock version 0.8 |
