Documentation

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(c) Convert a list of strict ByteString into a lazy ByteString

O(n/c) Append two ByteStrings

O(1) Convert a Word8 into a ByteString

O(1) The empty ByteString

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.

Write a ByteString to stdout, appending a newline byte

Write a ByteString to stdout

A synonym for hPut, for compatibility

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.

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.

getContents. Equivalent to hGetContents stdin. Will read lazily

Append a ByteString to a file.

Write a ByteString to a file.

Read an entire file lazily into a ByteString. The Handle will be held open until EOF is encountered.

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.

Read n bytes into a ByteString, directly from the specified Handle.

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.

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.

O(n) Return all final segments of the given ByteString, longest first.

O(n) Return all initial segments of the given ByteString, shortest first.

O(n) unzip transforms a list of pairs of bytes into a pair of ByteStrings. Note that this performs two pack operations.

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.

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.

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.

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

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

O(n) The isPrefixOf function takes two ByteStrings and returns True iff the first is a prefix of the second.

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)

O(n) filter, applied to a predicate and a ByteString, returns a ByteString containing those characters that satisfy the predicate.

O(n) notElem is the inverse of elem

O(n) elem is the ByteString membership predicate.

The findIndices function extends findIndex, by returning the indices of all elements satisfying the predicate, in ascending order.

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

The findIndex function takes a predicate and a ByteString and returns the index of the first element in the ByteString satisfying the predicate.

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.

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).

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

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).

O(c) ByteString index (subscript) operator, starting from 0.

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.

The groupBy function is the non-overloaded version of group.

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.

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') []        == []

span p xs breaks the ByteString into two segments. It is equivalent to (takeWhile p xs, dropWhile p xs)

break p is equivalent to span (not . p).

dropWhile p xs returns the suffix remaining after takeWhile p xs.

takeWhile, applied to a predicate p and a ByteString xs, returns the longest prefix (possibly empty) of xs of elements that satisfy p.

O(n/c) splitAt n xs is equivalent to (take n xs, drop n xs).

O(n/c) drop n xs returns the suffix of xs after the first n elements, or [] if n > length xs.

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.

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.

cycle ties a finite ByteString into a circular one, or equivalently, the infinite repetition of the original ByteString.

O(n) replicate n x is a ByteString of length n with x the value of every element.

repeat x is an infinite ByteString, with x the value of every element.

iterate f x returns an infinite ByteString of repeated applications of f to x:

iterate f x == [x, f x, f (f x), ...]

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.

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.

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.

O(n) minimum returns the minimum value from a ByteString

O(n) maximum returns the maximum value from a ByteString

O(n) Applied to a predicate and a ByteString, all determines if all elements of the ByteString satisfy the predicate.

O(n) Applied to a predicate and a ByteString, any determines if any element of the ByteString satisfies the predicate.

Map a function over a ByteString and concatenate the results

O(n) Concatenate a list of ByteStrings.

foldr1 is a variant of foldr that has no starting value argument, and thus must be applied to non-empty ByteStrings

'foldl1\'' is like foldl1, but strict in the accumulator.

foldl1 is a variant of foldl that has no starting value argument, and thus must be applied to non-empty ByteStrings.

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.

'foldl\'' is like foldl, but strict in the accumulator.

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.

The transpose function transposes the rows and columns of its ByteString argument.

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.

O(n) reverse xs returns the elements of xs in reverse order.

O(n) map f xs is the ByteString obtained by applying f to each element of xs.

O(n/c) Extract the init and last of a ByteString, returning Nothing if it is empty.

• It is no faster than using init and last

O(n/c) Return all the elements of a ByteString except the last one.

O(n/c) Extract the last element of a ByteString, which must be finite and non-empty.

O(1) Extract the elements after the head of a ByteString, which must be non-empty.

O(1) Extract the head and tail of a ByteString, returning Nothing if it is empty.

O(1) Extract the first element of a ByteString, which must be non-empty.

O(n/c) Append a byte to the end of a ByteString

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.

O(1) cons is analogous to '(:)' for lists.

O(n/c) length returns the length of a ByteString as an Int64

O(1) Test whether a ByteString is empty.

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.

O(1) Convert a strict ByteString into a lazy ByteString.

O(c) Convert a lazy ByteString into a list of strict ByteString

O(n) Converts a ByteString to a '[Word8]'.

O(n) Convert a '[Word8]' into a ByteString.

Consume the chunks of a lazy ByteString with a strict, tail-recursive, accumulating left fold.

Consume the chunks of a lazy ByteString with a natural right fold.

breakAfter pattern target splits target behind the first occurrence of pattern. An empty second component means that either the pattern does not occur in the target or the first occurrence of pattern is at the very end of target. If you need to discriminate between those cases, use breakFindAfter. If the pattern is empty, the first component is empty. For a non-empty pattern, the first component is generated lazily, thus the first parts of it can be available before the pattern has been found or determined to be absent.

  uncurry append . breakAfter pattern = id

breakFindAfter does the same as breakAfter but additionally indicates whether the pattern is present in the target.

  fst . breakFindAfter pat = breakAfter pat

breakOn pattern target splits target at the first occurrence of pattern. If the pattern does not occur in the target, the second component of the result is empty, otherwise it starts with pattern. If the pattern is empty, the first component is empty. For a non-empty pattern, the first component is generated lazily, thus the first parts of it can be available before the pattern has been found or determined to be absent.

  uncurry append . breakOn pattern = id

indices finds the starting indices of all possibly overlapping occurrences of the pattern in the target string. If the pattern is empty, the result is [0 .. length target].

nonOverlappingIndices finds the starting indices of all non-overlapping occurrences of the pattern in the target string. It is more efficient than removing indices from the list produced by indices.

replace pat sub text replaces all (non-overlapping) occurrences of pat in text with sub. If occurrences of pat overlap, the first occurrence that does not overlap with a replaced previous occurrence is substituted. Occurrences of pat arising from a substitution will not be substituted. For example:

  replace "ana" "olog" "banana" = "bologna"
  replace "ana" "o" "bananana" = "bono"
  replace "aab" "abaa" "aaabb" = "aabaab"

The result is a lazy ByteString, which is lazily produced, without copying. Equality of pattern and substitution is not checked, but

  replace pat pat text == text

holds (the internal structure is generally different). If the pattern is empty but not the substitution, the result is equivalent to (were they Strings) cycle sub.

For non-empty pat and sub a lazy ByteString,

  concat . intersperse sub . split pat = replace pat sub

and analogous relations hold for other types of sub.

split pattern target splits target at each (non-overlapping) occurrence of pattern, removing pattern. If pattern is empty, the result is an infinite list of empty ByteStrings, if target is empty but not pattern, the result is an empty list, otherwise the following relations hold (where patL is the lazy ByteString corresponding to pat):

  concat . intersperse patL . split pat = id,
  length (split pattern target) ==
              length (nonOverlappingIndices pattern target) + 1,

no fragment in the result contains an occurrence of pattern.

splitKeepEnd pattern target splits target after each (non-overlapping) occurrence of pattern. If pattern is empty, the result is an infinite list of empty ByteStrings, otherwise the following relations hold:

  concat . splitKeepEnd pattern = id,

all fragments in the result except possibly the last end with pattern, no fragment contains more than one occurrence of pattern.

splitKeepFront is like splitKeepEnd, except that target is split before each occurrence of pattern and hence all fragments with the possible exception of the first begin with pattern. No fragment contains more than one non-overlapping occurrence of pattern.

Traverse each Word8 in a strict or lazy ByteString

This Traversal walks each strict ByteString chunk in a tree-like fashion enable zippers to seek to locations more quickly and accelerate many monoidal queries, but up to associativity (and constant factors) it is equivalent to the much slower:

bytes ≡ unpackedBytes . traversed

anyOf bytes (== 0x80) :: ByteString -> Bool

pack (or unpack) a list of bytes into a strict or lazy ByteString.

pack x ≡ x ^. packedBytes
unpack x ≡ x ^. from packedBytes
packedBytes ≡ from unpackedBytes

unpack (or pack) a ByteString into a list of bytes

unpackedBytes ≡ from packedBytes
unpack x ≡ x ^. unpackedBytes
pack x ≡  x ^. from unpackedBytes

unpackedBytes :: Iso' ByteString [Word8]
unpackedBytes :: Iso' ByteString [Word8]