| Copyright | (c) Don Stewart 2006-2008 (c) Duncan Coutts 2006-2011 |
|---|---|
| License | BSD-style |
| Maintainer | dons00@gmail.com, duncan@community.haskell.org |
| Stability | stable |
| Portability | portable |
| Safe Haskell | Trustworthy |
| Language | Haskell98 |
Data.ByteString.Char8
Contents
- The
ByteStringtype - Introducing and eliminating
ByteStrings - Basic interface
- Transforming ByteStrings
- Reducing
ByteStrings (folds) - Building ByteStrings
- Substrings
- Predicates
- Searching ByteStrings
- Indexing ByteStrings
- Zipping and unzipping ByteStrings
- Ordered ByteStrings
- Reading from ByteStrings
- Low level CString conversions
- I/O with
ByteStrings
Description
Manipulate 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.
More specifically these byte strings are taken to be in the subset of Unicode covered by code points 0-255. This covers Unicode Basic Latin, Latin-1 Supplement and C0+C1 Controls.
See:
- http://www.unicode.org/charts/
- http://www.unicode.org/charts/PDF/U0000.pdf
- http://www.unicode.org/charts/PDF/U0080.pdf
This module is intended to be imported qualified, to avoid name
clashes with Prelude functions. eg.
import qualified Data.ByteString.Char8 as C
The Char8 interface to bytestrings provides an instance of IsString
for the ByteString type, enabling you to use string literals, and
have them implicitly packed to ByteStrings.
Use {-# LANGUAGE OverloadedStrings #-} to enable this.
Synopsis
- data ByteString
- empty :: ByteString
- singleton :: Char -> ByteString
- pack :: String -> ByteString
- unpack :: ByteString -> [Char]
- cons :: Char -> ByteString -> ByteString
- snoc :: ByteString -> Char -> ByteString
- append :: ByteString -> ByteString -> ByteString
- head :: ByteString -> Char
- uncons :: ByteString -> Maybe (Char, ByteString)
- unsnoc :: ByteString -> Maybe (ByteString, Char)
- last :: ByteString -> Char
- tail :: ByteString -> ByteString
- init :: ByteString -> ByteString
- null :: ByteString -> Bool
- length :: ByteString -> Int
- map :: (Char -> Char) -> ByteString -> ByteString
- reverse :: ByteString -> ByteString
- intersperse :: Char -> ByteString -> ByteString
- intercalate :: ByteString -> [ByteString] -> ByteString
- transpose :: [ByteString] -> [ByteString]
- foldl :: (a -> Char -> a) -> a -> ByteString -> a
- foldl' :: (a -> Char -> a) -> a -> ByteString -> a
- foldl1 :: (Char -> Char -> Char) -> ByteString -> Char
- foldl1' :: (Char -> Char -> Char) -> ByteString -> Char
- foldr :: (Char -> a -> a) -> a -> ByteString -> a
- foldr' :: (Char -> a -> a) -> a -> ByteString -> a
- foldr1 :: (Char -> Char -> Char) -> ByteString -> Char
- foldr1' :: (Char -> Char -> Char) -> ByteString -> Char
- concat :: [ByteString] -> ByteString
- concatMap :: (Char -> ByteString) -> ByteString -> ByteString
- any :: (Char -> Bool) -> ByteString -> Bool
- all :: (Char -> Bool) -> ByteString -> Bool
- maximum :: ByteString -> Char
- minimum :: ByteString -> Char
- scanl :: (Char -> Char -> Char) -> Char -> ByteString -> ByteString
- scanl1 :: (Char -> Char -> Char) -> ByteString -> ByteString
- scanr :: (Char -> Char -> Char) -> Char -> ByteString -> ByteString
- scanr1 :: (Char -> Char -> Char) -> ByteString -> ByteString
- mapAccumL :: (acc -> Char -> (acc, Char)) -> acc -> ByteString -> (acc, ByteString)
- mapAccumR :: (acc -> Char -> (acc, Char)) -> acc -> ByteString -> (acc, ByteString)
- replicate :: Int -> Char -> ByteString
- unfoldr :: (a -> Maybe (Char, a)) -> a -> ByteString
- unfoldrN :: Int -> (a -> Maybe (Char, a)) -> a -> (ByteString, Maybe a)
- take :: Int -> ByteString -> ByteString
- drop :: Int -> ByteString -> ByteString
- splitAt :: Int -> ByteString -> (ByteString, ByteString)
- takeWhile :: (Char -> Bool) -> ByteString -> ByteString
- takeWhileEnd :: (Char -> Bool) -> ByteString -> ByteString
- dropWhile :: (Char -> Bool) -> ByteString -> ByteString
- dropWhileEnd :: (Char -> Bool) -> ByteString -> ByteString
- dropSpace :: ByteString -> ByteString
- span :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)
- spanEnd :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)
- break :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)
- breakEnd :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)
- group :: ByteString -> [ByteString]
- groupBy :: (Char -> Char -> Bool) -> ByteString -> [ByteString]
- inits :: ByteString -> [ByteString]
- tails :: ByteString -> [ByteString]
- strip :: ByteString -> ByteString
- stripPrefix :: ByteString -> ByteString -> Maybe ByteString
- stripSuffix :: ByteString -> ByteString -> Maybe ByteString
- split :: Char -> ByteString -> [ByteString]
- splitWith :: (Char -> Bool) -> ByteString -> [ByteString]
- lines :: ByteString -> [ByteString]
- words :: ByteString -> [ByteString]
- unlines :: [ByteString] -> ByteString
- unwords :: [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 :: Char -> ByteString -> Bool
- notElem :: Char -> ByteString -> Bool
- find :: (Char -> Bool) -> ByteString -> Maybe Char
- filter :: (Char -> Bool) -> ByteString -> ByteString
- partition :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)
- index :: ByteString -> Int -> Char
- elemIndex :: Char -> ByteString -> Maybe Int
- elemIndices :: Char -> ByteString -> [Int]
- elemIndexEnd :: Char -> ByteString -> Maybe Int
- findIndex :: (Char -> Bool) -> ByteString -> Maybe Int
- findIndices :: (Char -> Bool) -> ByteString -> [Int]
- count :: Char -> ByteString -> Int
- zip :: ByteString -> ByteString -> [(Char, Char)]
- zipWith :: (Char -> Char -> a) -> ByteString -> ByteString -> [a]
- unzip :: [(Char, Char)] -> (ByteString, ByteString)
- sort :: ByteString -> ByteString
- readInt :: ByteString -> Maybe (Int, ByteString)
- readInteger :: ByteString -> Maybe (Integer, 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
- hGetSome :: Handle -> Int -> IO ByteString
- hGetNonBlocking :: Handle -> Int -> IO ByteString
- hPut :: Handle -> ByteString -> IO ()
- hPutNonBlocking :: Handle -> ByteString -> IO ByteString
- hPutStr :: Handle -> ByteString -> IO ()
- hPutStrLn :: Handle -> ByteString -> IO ()
The ByteString type
data ByteString #
A space-efficient representation of a Word8 vector, supporting many
efficient operations.
A ByteString contains 8-bit bytes, or by using the operations from
Data.ByteString.Char8 it can be interpreted as containing 8-bit
characters.
Instances
Introducing and eliminating ByteStrings
empty :: ByteString #
O(1) The empty ByteString
singleton :: Char -> ByteString #
O(1) Convert a Char into a ByteString
pack :: String -> ByteString #
O(n) Convert a String into a ByteString
For applications with large numbers of string literals, pack can be a bottleneck.
unpack :: ByteString -> [Char] #
O(n) Converts a ByteString to a String.
Basic interface
cons :: Char -> ByteString -> ByteString infixr 5 #
O(n) cons is analogous to (:) for lists, but of different
complexity, as it requires a memcpy.
snoc :: ByteString -> Char -> ByteString infixl 5 #
O(n) Append a Char to the end of a ByteString. Similar to
cons, this function performs a memcpy.
append :: ByteString -> ByteString -> ByteString #
O(n) Append two ByteStrings
head :: ByteString -> Char #
O(1) Extract the first element of a ByteString, which must be non-empty.
uncons :: ByteString -> Maybe (Char, ByteString) #
O(1) Extract the head and tail of a ByteString, returning Nothing if it is empty.
unsnoc :: ByteString -> Maybe (ByteString, Char) #
last :: ByteString -> Char #
O(1) Extract the last element of a packed string, which must be non-empty.
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.
Transforming ByteStrings
map :: (Char -> Char) -> ByteString -> ByteString #
O(n) map f xs is the ByteString obtained by applying f to each element of xs
reverse :: ByteString -> ByteString #
O(n) reverse xs efficiently returns the elements of xs in reverse order.
intersperse :: Char -> ByteString -> ByteString #
O(n) The intersperse function takes a Char and a ByteString
and `intersperses' that Char between the elements of the
ByteString. It is analogous to the intersperse function on Lists.
intercalate :: ByteString -> [ByteString] -> ByteString #
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] #
The transpose function transposes the rows and columns of its
ByteString argument.
Reducing ByteStrings (folds)
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.
foldl' :: (a -> Char -> a) -> a -> ByteString -> a #
foldl' is like foldl, but strict in the accumulator.
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.
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.
foldr' :: (Char -> a -> a) -> a -> ByteString -> a #
foldr' is a strict variant of foldr
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
Special folds
concat :: [ByteString] -> ByteString #
O(n) Concatenate a list of ByteStrings.
concatMap :: (Char -> ByteString) -> ByteString -> ByteString #
Map a function over a ByteString and concatenate the results
any :: (Char -> Bool) -> ByteString -> Bool #
Applied to a predicate and a ByteString, any determines if
any element of the ByteString satisfies the predicate.
all :: (Char -> Bool) -> ByteString -> Bool #
Applied to a predicate and a ByteString, all determines if
all elements of the ByteString satisfy the predicate.
maximum :: ByteString -> Char #
maximum returns the maximum value from a ByteString
minimum :: ByteString -> Char #
minimum returns the minimum value from a ByteString
Building ByteStrings
Scans
scanl :: (Char -> Char -> Char) -> Char -> ByteString -> ByteString #
scanl1 :: (Char -> Char -> Char) -> ByteString -> ByteString #
scanr :: (Char -> Char -> Char) -> Char -> ByteString -> ByteString #
scanr is the right-to-left dual of scanl.
scanr1 :: (Char -> Char -> Char) -> ByteString -> ByteString #
Accumulating maps
mapAccumL :: (acc -> Char -> (acc, Char)) -> acc -> ByteString -> (acc, ByteString) #
mapAccumR :: (acc -> Char -> (acc, Char)) -> acc -> ByteString -> (acc, ByteString) #
Generating and unfolding ByteStrings
replicate :: Int -> Char -> 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 (Char, 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 character in the string,
and b is the seed value for further production.
Examples:
unfoldr (\x -> if x <= '9' then Just (x, succ x) else Nothing) '0' == "0123456789"
unfoldrN :: Int -> (a -> Maybe (Char, 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 #
drop :: Int -> ByteString -> ByteString #
splitAt :: Int -> ByteString -> (ByteString, ByteString) #
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.
takeWhileEnd :: (Char -> Bool) -> ByteString -> ByteString #
takeWhileEnd, applied to a predicate p and a ByteString xs,
returns the longest suffix (possibly empty) of xs of elements that
satisfy p.
Since: bytestring-0.10.12.0
dropWhile :: (Char -> Bool) -> ByteString -> ByteString #
dropWhileEnd :: (Char -> Bool) -> ByteString -> ByteString #
dropWhile p xs returns the prefix remaining after takeWhileEnd p
xs.
Since: bytestring-0.10.12.0
dropSpace :: ByteString -> ByteString #
dropSpace efficiently returns the ByteString argument with
white space Chars removed from the front. It is more efficient than
calling dropWhile for removing whitespace. I.e.
dropWhile isSpace == dropSpace
Since: bytestring-0.10.12.0
span :: (Char -> Bool) -> ByteString -> (ByteString, ByteString) #
spanEnd :: (Char -> 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 :: (Char -> Bool) -> ByteString -> (ByteString, ByteString) #
breakEnd :: (Char -> 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 :: (Char -> Char -> Bool) -> ByteString -> [ByteString] #
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.
strip :: ByteString -> ByteString #
Remove leading and trailing white space from a ByteString.
Since: bytestring-0.10.12.0
stripPrefix :: ByteString -> ByteString -> Maybe ByteString #
O(n) The stripPrefix function takes two ByteStrings and returns Just
the remainder of the second iff the first is its prefix, and otherwise
Nothing.
Since: bytestring-0.10.8.0
stripSuffix :: ByteString -> ByteString -> Maybe ByteString #
O(n) The stripSuffix function takes two ByteStrings and returns Just
the remainder of the second iff the first is its suffix, and otherwise
Nothing.
Breaking into many substrings
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
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 :: (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",""]
Breaking into lines and words
lines :: ByteString -> [ByteString] #
lines breaks a ByteString up into a list of ByteStrings at
newline Chars ('\n'). The resulting strings do not contain newlines.
Note that it does not regard CR ('\r') as a newline character.
words :: ByteString -> [ByteString] #
words breaks a ByteString up into a list of words, which
were delimited by Chars representing white space.
unlines :: [ByteString] -> ByteString #
unwords :: [ByteString] -> ByteString #
Predicates
isPrefixOf :: ByteString -> ByteString -> Bool #
O(n) The isPrefixOf function takes two ByteStrings and returns True
if 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..
isInfixOf :: ByteString -> ByteString -> Bool #
Check whether one string is a substring of another. isInfixOf
p s is equivalent to not (null (findSubstrings p s)).
Search for arbitrary substrings
Arguments
| :: 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 yTo 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)
Note that calling `breakSubstring x` does some preprocessing work, so you should avoid unnecessarily duplicating breakSubstring calls with the same pattern.
Arguments
| :: ByteString | String to search for. |
| -> ByteString | String to seach in. |
| -> Maybe Int |
Deprecated: findSubstring is deprecated in favour of breakSubstring.
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).
Arguments
| :: ByteString | String to search for. |
| -> ByteString | String to seach in. |
| -> [Int] |
Deprecated: findSubstrings is deprecated in favour of breakSubstring.
Find the indices of all non-overlapping occurences of a substring in a string.
Note, prior to 0.10.6.0 this function returned the indices of all
possibly-overlapping matches.
Searching ByteStrings
Searching by equality
elem :: Char -> ByteString -> Bool #
O(n) elem is the ByteString membership predicate. This
implementation uses memchr(3).
Searching with a predicate
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.
partition :: (Char -> Bool) -> ByteString -> (ByteString, ByteString) #
Since: bytestring-0.10.12.0
Indexing ByteStrings
index :: ByteString -> Int -> Char #
O(1) ByteString index (subscript) operator, starting from 0.
elemIndex :: Char -> ByteString -> Maybe Int #
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.
elemIndices :: Char -> ByteString -> [Int] #
O(n) The elemIndices function extends elemIndex, by returning
the indices of all elements equal to the query element, in ascending order.
elemIndexEnd :: Char -> 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 :: (Char -> 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 :: (Char -> Bool) -> ByteString -> [Int] #
The findIndices function extends findIndex, by returning the
indices of all elements satisfying the predicate, in ascending order.
count :: Char -> ByteString -> Int #
count returns the number of times its argument appears in the ByteString
count = length . elemIndices
Also
count '\n' == length . lines
But more efficiently than using length on the intermediate list.
Zipping and unzipping ByteStrings
zip :: ByteString -> ByteString -> [(Char, Char)] #
zipWith :: (Char -> Char -> a) -> ByteString -> ByteString -> [a] #
unzip :: [(Char, Char)] -> (ByteString, ByteString) #
Ordered ByteStrings
sort :: ByteString -> ByteString #
O(n) Sort a ByteString efficiently, using counting sort.
Reading from ByteStrings
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.
Note: This function will overflow the Int for large integers.
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.
Low level CString conversions
Copying ByteStrings
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.
Packing CStrings and pointers
packCString :: CString -> IO ByteString #
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 #
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 a #
O(n) construction Use a ByteString with a function requiring a
null-terminated CString. The CString is a copy and will be freed
automatically; it must not be stored or used after the
subcomputation finishes.
useAsCStringLen :: ByteString -> (CStringLen -> IO a) -> IO a #
O(n) construction Use a ByteString with a function requiring a CStringLen.
As for useAsCString this function makes a copy of the original ByteString.
It must not be stored or used after the subcomputation finishes.
I/O with ByteStrings
ByteString I/O uses binary mode, without any character decoding or newline conversion. The fact that it does not respect the Handle newline mode is considered a flaw and may be changed in a future version.
Standard input and output
getLine :: IO ByteString #
Read a line from stdin.
getContents :: IO ByteString #
getContents. Read stdin strictly. Equivalent to hGetContents stdin
The Handle is closed after the contents have been read.
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.
Files
readFile :: FilePath -> IO ByteString #
Read an entire file strictly into a ByteString.
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 a handle's entire contents strictly into a ByteString.
This function reads chunks at a time, increasing the chunk size on each
read. The final string is then reallocated to the appropriate size. For
files > half of available memory, this may lead to memory exhaustion.
Consider using readFile in this case.
The Handle is closed once the contents have been read, or if an exception is thrown.
hGet :: Handle -> Int -> IO ByteString #
Read a ByteString directly from the specified Handle. This
is far more efficient than reading the characters into a String
and then using pack. First argument is the Handle to read from,
and the second is the number of bytes to read. It returns the bytes
read, up to n, or empty if EOF has been reached.
hGet is implemented in terms of hGetBuf.
If the handle is a pipe or socket, and the writing end
is closed, hGet will behave as if EOF was reached.
hGetSome :: Handle -> Int -> IO ByteString #
Like hGet, except that a shorter ByteString may be returned
if there are not enough bytes immediately available to satisfy the
whole request. hGetSome only blocks if there is no data
available, and EOF has not yet been reached.
hGetNonBlocking :: Handle -> Int -> IO ByteString #
hGetNonBlocking is similar to hGet, except that it will never block
waiting for data to become available, instead it returns only whatever data
is available. If there is no data available to be read, hGetNonBlocking
returns empty.
Note: on Windows and with Haskell implementation other than GHC, this
function does not work correctly; it behaves identically to hGet.
hPut :: Handle -> ByteString -> IO () #
Outputs a ByteString to the specified Handle.
hPutNonBlocking :: Handle -> ByteString -> IO ByteString #
Similar to hPut except that it will never block. Instead it returns
any tail that did not get written. This tail may be empty in the case that
the whole string was written, or the whole original string if nothing was
written. Partial writes are also possible.
Note: on Windows and with Haskell implementation other than GHC, this
function does not work correctly; it behaves identically to hPut.
hPutStr :: Handle -> ByteString -> IO () #
A synonym for hPut, for compatibility
hPutStrLn :: Handle -> ByteString -> IO () #
Write a ByteString to a handle, appending a newline byte