Copyright | (c) Don Stewart 2006 (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 |
ByteString
typeByteString
sByteString
s (folds)
ByteString
s
A time and space-efficient implementation of lazy byte vectors using lists of packed Word8
arrays, suitable for high performance use, both in terms of large data quantities, or high speed requirements. Lazy ByteStrings are encoded as lazy lists of strict chunks of bytes.
A key feature of lazy ByteStrings is the means to manipulate large or unbounded streams of data without requiring the entire sequence to be resident in memory. To take advantage of this you have to write your functions in a lazy streaming style, e.g. classic pipeline composition. The default I/O chunk size is 32k, which should be good in most circumstances.
Some operations, such as concat
, append
, reverse
and cons
, have better complexity than their Data.ByteString equivalents, due to optimisations resulting from the list spine structure. For other operations lazy ByteStrings are usually within a few percent of strict ones.
The recomended way to assemble lazy ByteStrings from smaller parts is to use the builder monoid from Data.ByteString.Builder.
This module is intended to be imported qualified
, to avoid name clashes with Prelude functions. eg.
import qualified Data.ByteString.Lazy as B
Original GHC implementation by Bryan O'Sullivan. Rewritten to use UArray
by Simon Marlow. Rewritten to support slices and use ForeignPtr
by David Roundy. Rewritten again and extended by Don Stewart and Duncan Coutts. Lazy variant by Duncan Coutts and Don Stewart.
data ByteString Source
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.
O(1) The empty ByteString
singleton :: Word8 -> ByteString Source
O(1) Convert a Word8
into a ByteString
pack :: [Word8] -> ByteString Source
O(n) Convert a '[Word8]' into a ByteString
.
unpack :: ByteString -> [Word8] Source
O(n) Converts a ByteString
to a '[Word8]'.
fromStrict :: ByteString -> ByteString Source
O(1) Convert a strict ByteString
into a lazy ByteString
.
toStrict :: ByteString -> ByteString Source
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.
fromChunks :: [ByteString] -> ByteString Source
O(c) Convert a list of strict ByteString
into a lazy ByteString
toChunks :: ByteString -> [ByteString] Source
O(c) Convert a lazy ByteString
into a list of strict ByteString
foldrChunks :: (ByteString -> a -> a) -> a -> ByteString -> a Source
Consume the chunks of a lazy ByteString with a natural right fold.
foldlChunks :: (a -> ByteString -> a) -> a -> ByteString -> a Source
Consume the chunks of a lazy ByteString with a strict, tail-recursive, accumulating left fold.
cons :: Word8 -> ByteString -> ByteString infixr 5 Source
O(1) cons
is analogous to '(:)' for lists.
cons' :: Word8 -> ByteString -> ByteString infixr 5 Source
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 -> Word8 -> ByteString infixl 5 Source
O(n/c) Append a byte to the end of a ByteString
append :: ByteString -> ByteString -> ByteString Source
O(n/c) Append two ByteStrings
head :: ByteString -> Word8 Source
O(1) Extract the first element of a ByteString, which must be non-empty.
uncons :: ByteString -> Maybe (Word8, ByteString) Source
O(1) Extract the head and tail of a ByteString, returning Nothing if it is empty.
unsnoc :: ByteString -> Maybe (ByteString, Word8) Source
O(n/c) Extract the init
and last
of a ByteString, returning Nothing if it is empty.
last :: ByteString -> Word8 Source
O(n/c) Extract the last element of a ByteString, which must be finite and non-empty.
tail :: ByteString -> ByteString Source
O(1) Extract the elements after the head of a ByteString, which must be non-empty.
init :: ByteString -> ByteString Source
O(n/c) Return all the elements of a ByteString
except the last one.
null :: ByteString -> Bool Source
O(1) Test whether a ByteString is empty.
length :: ByteString -> Int64 Source
O(n/c) length
returns the length of a ByteString as an Int64
map :: (Word8 -> Word8) -> ByteString -> ByteString Source
O(n) map
f xs
is the ByteString obtained by applying f
to each element of xs
.
reverse :: ByteString -> ByteString Source
O(n) reverse
xs
returns the elements of xs
in reverse order.
intersperse :: Word8 -> ByteString -> ByteString Source
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] -> ByteString Source
O(n) The intercalate
function takes a ByteString
and a list of ByteString
s and concatenates the list after interspersing the first argument between each element of the list.
transpose :: [ByteString] -> [ByteString] Source
The transpose
function transposes the rows and columns of its ByteString
argument.
foldl :: (a -> Word8 -> a) -> a -> ByteString -> a Source
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 -> Word8 -> a) -> a -> ByteString -> a Source
'foldl\'' is like foldl
, but strict in the accumulator.
foldl1 :: (Word8 -> Word8 -> Word8) -> ByteString -> Word8 Source
foldl1
is a variant of foldl
that has no starting value argument, and thus must be applied to non-empty ByteStrings
.
foldl1' :: (Word8 -> Word8 -> Word8) -> ByteString -> Word8 Source
'foldl1\'' is like foldl1
, but strict in the accumulator.
foldr :: (Word8 -> a -> a) -> a -> ByteString -> a Source
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.
foldr1 :: (Word8 -> Word8 -> Word8) -> ByteString -> Word8 Source
foldr1
is a variant of foldr
that has no starting value argument, and thus must be applied to non-empty ByteString
s
concat :: [ByteString] -> ByteString Source
O(n) Concatenate a list of ByteStrings.
concatMap :: (Word8 -> ByteString) -> ByteString -> ByteString Source
Map a function over a ByteString
and concatenate the results
any :: (Word8 -> Bool) -> ByteString -> Bool Source
O(n) Applied to a predicate and a ByteString, any
determines if any element of the ByteString
satisfies the predicate.
all :: (Word8 -> Bool) -> ByteString -> Bool Source
O(n) Applied to a predicate and a ByteString
, all
determines if all elements of the ByteString
satisfy the predicate.
maximum :: ByteString -> Word8 Source
O(n) maximum
returns the maximum value from a ByteString
minimum :: ByteString -> Word8 Source
O(n) minimum
returns the minimum value from a ByteString
scanl :: (Word8 -> Word8 -> Word8) -> Word8 -> ByteString -> ByteString Source
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.
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 ByteString.
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.
repeat :: Word8 -> ByteString Source
repeat x
is an infinite ByteString, with x
the value of every element.
replicate :: Int64 -> Word8 -> ByteString Source
O(n) replicate n x
is a ByteString of length n
with x
the value of every element.
cycle :: ByteString -> ByteString Source
cycle
ties a finite ByteString into a circular one, or equivalently, the infinite repetition of the original ByteString.
iterate :: (Word8 -> Word8) -> Word8 -> ByteString Source
iterate f x
returns an infinite ByteString of repeated applications of f
to x
:
iterate f x == [x, f x, f (f x), ...]
unfoldr :: (a -> Maybe (Word8, a)) -> a -> ByteString Source
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.
take :: Int64 -> ByteString -> ByteString Source
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
.
drop :: Int64 -> ByteString -> ByteString Source
O(n/c) drop
n xs
returns the suffix of xs
after the first n
elements, or []
if n > length xs
.
splitAt :: Int64 -> ByteString -> (ByteString, ByteString) Source
O(n/c) splitAt
n xs
is equivalent to (take n xs, drop n xs)
.
takeWhile :: (Word8 -> Bool) -> ByteString -> ByteString Source
takeWhile
, applied to a predicate p
and a ByteString xs
, returns the longest prefix (possibly empty) of xs
of elements that satisfy p
.
dropWhile :: (Word8 -> Bool) -> ByteString -> ByteString Source
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)
break :: (Word8 -> Bool) -> ByteString -> (ByteString, ByteString) Source
break
p
is equivalent to span (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.
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.
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') [] == []
isPrefixOf :: ByteString -> ByteString -> Bool Source
O(n) The isPrefixOf
function takes two ByteStrings and returns True
iff the first is a prefix of the second.
isSuffixOf :: ByteString -> ByteString -> Bool Source
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
elem :: Word8 -> ByteString -> Bool Source
O(n) elem
is the ByteString
membership predicate.
notElem :: Word8 -> ByteString -> Bool Source
O(n) notElem
is the inverse of elem
find :: (Word8 -> Bool) -> ByteString -> Maybe Word8 Source
O(n) The find
function takes a predicate and a ByteString, and returns the first element in matching the predicate, or Nothing
if there is no such element.
find f p = case findIndex f p of Just n -> Just (p ! n) ; _ -> Nothing
filter :: (Word8 -> Bool) -> ByteString -> ByteString Source
O(n) filter
, applied to a predicate and a ByteString, returns a ByteString containing those characters that satisfy the predicate.
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)
index :: ByteString -> Int64 -> Word8 Source
O(c) ByteString
index (subscript) operator, starting from 0.
elemIndex :: Word8 -> ByteString -> Maybe Int64 Source
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).
elemIndexEnd :: Word8 -> ByteString -> Maybe Int64 Source
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)
elemIndices :: Word8 -> ByteString -> [Int64] 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).
findIndex :: (Word8 -> Bool) -> ByteString -> Maybe Int64 Source
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 -> [Int64] Source
The findIndices
function extends findIndex
, by returning the indices of all elements satisfying the predicate, in ascending order.
count :: Word8 -> ByteString -> Int64 Source
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.
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.
copy :: ByteString -> ByteString Source
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.
getContents :: IO ByteString Source
getContents. Equivalent to hGetContents stdin. Will read lazily
putStr :: ByteString -> IO () Source
Write a ByteString to stdout
putStrLn :: ByteString -> IO () Source
Deprecated: Use Data.ByteString.Lazy.Char8.putStrLn instead. (Functions that rely on ASCII encodings belong in Data.ByteString.Lazy.Char8)
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.
readFile :: FilePath -> IO ByteString Source
Read an entire file lazily into a ByteString
. The Handle will be held open until EOF is encountered.
writeFile :: FilePath -> ByteString -> IO () Source
Write a ByteString
to a file.
appendFile :: FilePath -> ByteString -> IO () Source
Append a ByteString
to a file.
hGetContents :: Handle -> IO ByteString Source
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 Source
Read n
bytes into a ByteString
, directly from the specified Handle
.
hGetNonBlocking :: Handle -> Int -> IO ByteString Source
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 () Source
Outputs a ByteString
to the specified Handle
.
hPutNonBlocking :: Handle -> ByteString -> IO ByteString Source
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 () Source
A synonym for hPut
, for compatibility
© The University of Glasgow and others
Licensed under a BSD-style license (see top of the page).
https://downloads.haskell.org/~ghc/7.10.3/docs/html/libraries/bytestring-0.10.6.0/Data-ByteString-Lazy.html