| 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.Lazy.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
- Low level conversions
- Reading from ByteStrings
- I/O with ByteStrings
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
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 :: [Char] -> ByteString
- unpack :: ByteString -> [Char]
- fromChunks :: [ByteString] -> ByteString
- toChunks :: ByteString -> [ByteString]
- fromStrict :: ByteString -> ByteString
- toStrict :: ByteString -> ByteString
- cons :: Char -> ByteString -> ByteString
- cons' :: Char -> ByteString -> ByteString
- snoc :: ByteString -> Char -> ByteString
- append :: ByteString -> ByteString -> ByteString
- head :: ByteString -> Char
- uncons :: ByteString -> Maybe (Char, ByteString)
- last :: ByteString -> Char
- tail :: ByteString -> ByteString
- unsnoc :: ByteString -> Maybe (ByteString, Char)
- init :: ByteString -> ByteString
- null :: ByteString -> Bool
- length :: ByteString -> Int64
- 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
- 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
- mapAccumL :: (acc -> Char -> (acc, Char)) -> acc -> ByteString -> (acc, ByteString)
- mapAccumR :: (acc -> Char -> (acc, Char)) -> acc -> ByteString -> (acc, ByteString)
- repeat :: Char -> ByteString
- replicate :: Int64 -> Char -> ByteString
- cycle :: ByteString -> ByteString
- iterate :: (Char -> Char) -> Char -> ByteString
- unfoldr :: (a -> Maybe (Char, a)) -> a -> ByteString
- take :: Int64 -> ByteString -> ByteString
- drop :: Int64 -> ByteString -> ByteString
- splitAt :: Int64 -> ByteString -> (ByteString, ByteString)
- takeWhile :: (Char -> Bool) -> ByteString -> ByteString
- dropWhile :: (Char -> Bool) -> ByteString -> ByteString
- span :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)
- break :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)
- group :: ByteString -> [ByteString]
- groupBy :: (Char -> Char -> Bool) -> ByteString -> [ByteString]
- inits :: ByteString -> [ByteString]
- tails :: 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
- 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 -> Int64 -> Char
- elemIndex :: Char -> ByteString -> Maybe Int64
- elemIndices :: Char -> ByteString -> [Int64]
- findIndex :: (Char -> Bool) -> ByteString -> Maybe Int64
- findIndices :: (Char -> Bool) -> ByteString -> [Int64]
- count :: Char -> ByteString -> Int64
- zip :: ByteString -> ByteString -> [(Char, Char)]
- zipWith :: (Char -> Char -> a) -> ByteString -> ByteString -> [a]
- copy :: ByteString -> ByteString
- readInt :: ByteString -> Maybe (Int, ByteString)
- readInteger :: ByteString -> Maybe (Integer, 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 ()
- hGetContents :: Handle -> IO ByteString
- hGet :: 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 lazy ByteString contains 8-bit bytes, or by using the operations
 from Data.ByteString.Lazy.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 :: [Char] -> ByteString #
O(n) Convert a String into a ByteString.
unpack :: ByteString -> [Char] #
O(n) Converts a ByteString to a String.
fromChunks :: [ByteString] -> ByteString #
O(c) Convert a list of strict ByteString into a lazy ByteString
toChunks :: ByteString -> [ByteString] #
O(c) Convert a lazy ByteString into a list of strict ByteString
fromStrict :: ByteString -> ByteString #
O(1) Convert a strict ByteString into a lazy ByteString.
toStrict :: ByteString -> ByteString #
O(n) Convert a lazy ByteString into a strict ByteString.
Note that this is an expensive operation that forces the whole lazy ByteString into memory and then copies all the data. If possible, try to avoid converting back and forth between strict and lazy bytestrings.
Basic interface
cons :: Char -> ByteString -> ByteString infixr 5 #
cons' :: Char -> ByteString -> ByteString infixr 5 #
O(1) Unlike cons, cons' is
 strict in the ByteString that we are consing onto. More precisely, it forces
 the head and the first chunk. It does this because, for space efficiency, it
 may coalesce the new byte onto the first 'chunk' rather than starting a
 new 'chunk'.
So that means you can't use a lazy recursive contruction like this:
let xs = cons' c xs in xs
You can however use cons, as well as repeat and cycle, to build
 infinite lazy ByteStrings.
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/c) 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.
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.
unsnoc :: ByteString -> Maybe (ByteString, Char) #
init :: ByteString -> ByteString #
O(n/c) Return all the elements of a ByteString except the last one.
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 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.
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 #
Accumulating maps
mapAccumL :: (acc -> Char -> (acc, Char)) -> acc -> ByteString -> (acc, ByteString) #
mapAccumR :: (acc -> Char -> (acc, Char)) -> acc -> ByteString -> (acc, ByteString) #
Infinite ByteStrings
repeat :: Char -> ByteString #
repeat xx the value of every
 element.
replicate :: Int64 -> Char -> ByteString #
O(n) replicate n xn with x
 the value of every element.
cycle :: ByteString -> ByteString #
cycle ties a finite ByteString into a circular one, or equivalently,
 the infinite repetition of the original ByteString.
iterate :: (Char -> Char) -> Char -> ByteString #
iterate f xf to x:
iterate f x == [x, f x, f (f x), ...]
Unfolding ByteStrings
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.
Substrings
Breaking strings
take :: Int64 -> ByteString -> ByteString #
drop :: Int64 -> ByteString -> ByteString #
splitAt :: Int64 -> 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.
dropWhile :: (Char -> Bool) -> ByteString -> ByteString #
span :: (Char -> Bool) -> ByteString -> (ByteString, ByteString) #
break :: (Char -> Bool) -> ByteString -> (ByteString, ByteString) #
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.
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.
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.
As of bytestring 0.9.0.3, this function is stricter than its list cousin.
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. And
tokens isSpace = words
unlines :: [ByteString] -> ByteString #
unwords :: [ByteString] -> ByteString #
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
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 -> Int64 -> Char #
O(1) ByteString index (subscript) operator, starting from 0.
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.
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.
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.
findIndices :: (Char -> Bool) -> ByteString -> [Int64] #
The findIndices function extends findIndex, by returning the
 indices of all elements satisfying the predicate, in ascending order.
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.
Zipping and unzipping ByteStrings
zip :: ByteString -> ByteString -> [(Char, Char)] #
zipWith :: (Char -> Char -> a) -> ByteString -> ByteString -> [a] #
Ordered ByteStrings
Low level 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.
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.
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
getContents :: IO ByteString #
getContents. Equivalent to hGetContents stdin. Will read lazily
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 lazily into a ByteString.
 The Handle will be held open until EOF is encountered.
writeFile :: FilePath -> ByteString -> IO () #
Write a ByteString to a file.
appendFile :: FilePath -> ByteString -> IO () #
Append a ByteString to a file.
I/O with Handles
hGetContents :: Handle -> IO ByteString #
Read entire handle contents lazily into a ByteString. Chunks
 are read on demand, using the default chunk size.
Once EOF is encountered, the Handle is closed.
Note: the Handle should be placed in binary mode with
 hSetBinaryMode for hGetContents to
 work correctly.
hGet :: Handle -> Int -> IO ByteString #
Read n bytes into a ByteString, directly from the specified Handle.
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. The chunks will be
 written one at a time. Other threads might write to the Handle between the
 writes, and hence hPut alone might not be suitable for concurrent writes.
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