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 |
Data.ByteString.Lazy
Contents
Description
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.
Synopsis
- data ByteString
- empty :: ByteString
- singleton :: Word8 -> ByteString
- pack :: [Word8] -> ByteString
- unpack :: ByteString -> [Word8]
- fromStrict :: ByteString -> ByteString
- toStrict :: ByteString -> ByteString
- fromChunks :: [ByteString] -> ByteString
- toChunks :: ByteString -> [ByteString]
- foldrChunks :: (ByteString -> a -> a) -> a -> ByteString -> a
- foldlChunks :: (a -> ByteString -> a) -> a -> ByteString -> a
- cons :: Word8 -> ByteString -> ByteString
- cons' :: Word8 -> ByteString -> ByteString
- snoc :: ByteString -> Word8 -> ByteString
- append :: ByteString -> ByteString -> ByteString
- head :: ByteString -> Word8
- uncons :: ByteString -> Maybe (Word8, ByteString)
- unsnoc :: ByteString -> Maybe (ByteString, Word8)
- last :: ByteString -> Word8
- tail :: ByteString -> ByteString
- init :: ByteString -> ByteString
- null :: ByteString -> Bool
- length :: ByteString -> Int64
- 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
- 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
- mapAccumL :: (acc -> Word8 -> (acc, Word8)) -> acc -> ByteString -> (acc, ByteString)
- mapAccumR :: (acc -> Word8 -> (acc, Word8)) -> acc -> ByteString -> (acc, ByteString)
- repeat :: Word8 -> ByteString
- replicate :: Int64 -> Word8 -> ByteString
- cycle :: ByteString -> ByteString
- iterate :: (Word8 -> Word8) -> Word8 -> ByteString
- unfoldr :: (a -> Maybe (Word8, a)) -> a -> ByteString
- take :: Int64 -> ByteString -> ByteString
- drop :: Int64 -> ByteString -> ByteString
- splitAt :: Int64 -> ByteString -> (ByteString, ByteString)
- takeWhile :: (Word8 -> Bool) -> ByteString -> ByteString
- dropWhile :: (Word8 -> Bool) -> ByteString -> ByteString
- span :: (Word8 -> Bool) -> ByteString -> (ByteString, ByteString)
- break :: (Word8 -> Bool) -> ByteString -> (ByteString, ByteString)
- group :: ByteString -> [ByteString]
- groupBy :: (Word8 -> Word8 -> Bool) -> ByteString -> [ByteString]
- inits :: ByteString -> [ByteString]
- tails :: ByteString -> [ByteString]
- stripPrefix :: ByteString -> ByteString -> Maybe ByteString
- stripSuffix :: ByteString -> ByteString -> Maybe ByteString
- split :: Word8 -> ByteString -> [ByteString]
- splitWith :: (Word8 -> Bool) -> ByteString -> [ByteString]
- isPrefixOf :: ByteString -> ByteString -> Bool
- isSuffixOf :: ByteString -> ByteString -> Bool
- 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 -> Int64 -> Word8
- elemIndex :: Word8 -> ByteString -> Maybe Int64
- elemIndexEnd :: Word8 -> ByteString -> Maybe Int64
- elemIndices :: Word8 -> ByteString -> [Int64]
- findIndex :: (Word8 -> Bool) -> ByteString -> Maybe Int64
- findIndexEnd :: (Word8 -> Bool) -> ByteString -> Maybe Int64
- findIndices :: (Word8 -> Bool) -> ByteString -> [Int64]
- count :: Word8 -> ByteString -> Int64
- zip :: ByteString -> ByteString -> [(Word8, Word8)]
- zipWith :: (Word8 -> Word8 -> a) -> ByteString -> ByteString -> [a]
- unzip :: [(Word8, Word8)] -> (ByteString, ByteString)
- copy :: ByteString -> 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 ()
The ByteString
type
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.
Instances
Introducing and eliminating ByteString
s
empty :: ByteString Source #
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.
Basic interface
cons :: Word8 -> ByteString -> ByteString infixr 5 Source #
O(1) cons
is analogous to '(Prelude.:)' 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 #
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.
Transforming ByteStrings
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.
Reducing ByteString
s (folds)
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 #
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 ByteString
s.
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
Special folds
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
Building ByteStrings
Scans
scanl :: (Word8 -> Word8 -> Word8) -> Word8 -> ByteString -> ByteString Source #
Accumulating maps
mapAccumL :: (acc -> Word8 -> (acc, Word8)) -> acc -> ByteString -> (acc, ByteString) Source #
mapAccumR :: (acc -> Word8 -> (acc, Word8)) -> acc -> ByteString -> (acc, ByteString) Source #
Infinite ByteStrings
repeat :: Word8 -> ByteString Source #
is an infinite ByteString, with repeat
xx
the value of every
element.
replicate :: Int64 -> Word8 -> ByteString Source #
O(n)
is a ByteString of length replicate
n xn
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 #
returns an infinite ByteString of repeated applications
of iterate
f xf
to x
:
iterate f x == [x, f x, f (f x), ...]
Unfolding ByteStrings
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.
Substrings
Breaking strings
take :: Int64 -> ByteString -> ByteString Source #
drop :: Int64 -> ByteString -> ByteString Source #
splitAt :: Int64 -> ByteString -> (ByteString, ByteString) Source #
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 #
span :: (Word8 -> Bool) -> ByteString -> (ByteString, ByteString) Source #
break :: (Word8 -> Bool) -> ByteString -> (ByteString, ByteString) Source #
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 #
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.
stripPrefix :: ByteString -> ByteString -> Maybe ByteString Source #
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 Source #
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 :: Word8 -> ByteString -> [ByteString] Source #
O(n) Break a ByteString
into pieces separated by the byte
argument, consuming the delimiter. I.e.
split 10 "a\nb\nd\ne" == ["a","b","d","e"] -- fromEnum '\n' == 10 split 97 "aXaXaXa" == ["","X","X","X",""] -- fromEnum 'a' == 97 split 120 "x" == ["",""] -- fromEnum 'x' == 120
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 ByteString
s 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 (==97) "aabbaca" == ["","","bb","c",""] -- fromEnum 'a' == 97 splitWith (==97) [] == []
Predicates
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
Search for arbitrary substrings
Searching ByteStrings
Searching by equality
elem :: Word8 -> ByteString -> Bool Source #
O(n) elem
is the ByteString
membership predicate.
Searching with a predicate
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)
Indexing ByteStrings
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)
Since: bytestring-0.10.6.0
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.
findIndexEnd :: (Word8 -> Bool) -> ByteString -> Maybe Int64 Source #
The findIndexEnd
function takes a predicate and a ByteString
and
returns the index of the last element in the ByteString
satisfying the predicate.
Since: bytestring-0.10.12.0
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.
Zipping and unzipping ByteStrings
zip :: ByteString -> ByteString -> [(Word8, Word8)] Source #
zipWith :: (Word8 -> Word8 -> a) -> ByteString -> ByteString -> [a] Source #
unzip :: [(Word8, Word8)] -> (ByteString, ByteString) Source #
Ordered ByteStrings
Low level conversions
Copying ByteStrings
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.
I/O with ByteString
s
Standard input and output
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.
Files
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.
I/O with Handles
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
. 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 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
.