Copyright	© 2022 Julian Ospald
License	MIT
Maintainer	Julian Ospald <[email protected]>
Stability	experimental
Portability	portable
Safe Haskell	None
Language	Haskell2010

The ShortByteString type and representation

newtype ShortByteString Source

A compact representation of a Word8 vector.

It has a lower memory overhead than a ByteString and does not contribute to heap fragmentation. It can be converted to or from a ByteString (at the cost of copying the string data). It supports very few other operations.

Introducing and eliminating ShortByteStrings

empty :: ShortByteString Source

O(1). The empty ShortByteString.

singleton :: Word16 -> ShortByteString Source

O(1) Convert a Word16 into a ShortByteString

pack :: [Word16] -> ShortByteString Source

O(n). Convert a list into a ShortByteString

unpack :: ShortByteString -> [Word16] Source

O(n). Convert a ShortByteString into a list.

fromShort :: ShortByteString -> ByteString Source

O(n). Convert a ShortByteString into a ByteString.

toShort :: ByteString -> ShortByteString Source

O(n). Convert a ByteString into a ShortByteString.

This makes a copy, so does not retain the input string.

Basic interface

snoc :: ShortByteString -> Word16 -> ShortByteString infixl 5 Source

O(n) Append a Word16 to the end of a ShortByteString

Note: copies the entire byte array

cons :: Word16 -> ShortByteString -> ShortByteString infixr 5 Source

O(n) cons is analogous to (:) for lists.

Note: copies the entire byte array

append :: ShortByteString -> ShortByteString -> ShortByteString Source

last :: HasCallStack => ShortByteString -> Word16 Source

O(1) Extract the last element of a ShortByteString, which must be finite and at least one Word16. An exception will be thrown in the case of an empty ShortByteString.

tail :: HasCallStack => ShortByteString -> ShortByteString Source

O(n) Extract the elements after the head of a ShortByteString, which must at least one Word16. An exception will be thrown in the case of an empty ShortByteString.

Note: copies the entire byte array

uncons :: ShortByteString -> Maybe (Word16, ShortByteString) Source

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

uncons2 :: ShortByteString -> Maybe (Word16, Word16, ShortByteString) Source

O(n) Extract first two elements and the rest of a ByteString, returning Nothing if it is shorter than two elements.

head :: HasCallStack => ShortByteString -> Word16 Source

O(1) Extract the first element of a ShortByteString, which must be at least one Word16. An exception will be thrown in the case of an empty ShortByteString.

init :: HasCallStack => ShortByteString -> ShortByteString Source

O(n) Return all the elements of a ShortByteString except the last one. An exception will be thrown in the case of an empty ShortByteString.

Note: copies the entire byte array

unsnoc :: ShortByteString -> Maybe (ShortByteString, Word16) Source

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

null :: ShortByteString -> Bool Source

O(1) Test whether a ShortByteString is empty.

length :: ShortByteString -> Int Source

O(1) The length of a ShortByteString.

numWord16 :: ShortByteString -> Int Source

This is like length, but the number of Word16, not Word8.

Transforming ShortByteStrings

map :: (Word16 -> Word16) -> ShortByteString -> ShortByteString Source

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

reverse :: ShortByteString -> ShortByteString Source

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

intercalate :: ShortByteString -> [ShortByteString] -> ShortByteString Source

O(n) The intercalate function takes a ShortByteString and a list of ShortByteStrings and concatenates the list after interspersing the first argument between each element of the list.

Since: bytestring-0.11.3.0

Reducing ShortByteStrings (folds)

foldl :: (a -> Word16 -> a) -> a -> ShortByteString -> a Source

foldl, applied to a binary operator, a starting value (typically the left-identity of the operator), and a ShortByteString, reduces the ShortByteString using the binary operator, from left to right.

foldl' :: (a -> Word16 -> a) -> a -> ShortByteString -> a Source

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

foldl1 :: HasCallStack => (Word16 -> Word16 -> Word16) -> ShortByteString -> Word16 Source

foldl1 is a variant of foldl that has no starting value argument, and thus must be applied to non-empty ShortByteStrings. An exception will be thrown in the case of an empty ShortByteString.

foldl1' :: HasCallStack => (Word16 -> Word16 -> Word16) -> ShortByteString -> Word16 Source

foldl1' is like foldl1, but strict in the accumulator. An exception will be thrown in the case of an empty ShortByteString.

foldr :: (Word16 -> a -> a) -> a -> ShortByteString -> a Source

foldr, applied to a binary operator, a starting value (typically the right-identity of the operator), and a ShortByteString, reduces the ShortByteString using the binary operator, from right to left.

foldr' :: (Word16 -> a -> a) -> a -> ShortByteString -> a Source

foldr' is like foldr, but strict in the accumulator.

foldr1 :: HasCallStack => (Word16 -> Word16 -> Word16) -> ShortByteString -> Word16 Source

foldr1 is a variant of foldr that has no starting value argument, and thus must be applied to non-empty ShortByteStrings An exception will be thrown in the case of an empty ShortByteString.

foldr1' :: HasCallStack => (Word16 -> Word16 -> Word16) -> ShortByteString -> Word16 Source

foldr1' is a variant of foldr1, but is strict in the accumulator.

Special folds

all :: (Word16 -> Bool) -> ShortByteString -> Bool Source

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

any :: (Word16 -> Bool) -> ShortByteString -> Bool Source

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

concat :: [ShortByteString] -> ShortByteString Source

Generating and unfolding ByteStrings

replicate :: Int -> Word16 -> ShortByteString Source

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

unfoldr :: (a -> Maybe (Word16, a)) -> a -> ShortByteString Source

O(n), where n is the length of the result. The unfoldr function is analogous to the List 'unfoldr'. unfoldr builds a ShortByteString from a seed value. The function takes the element and returns Nothing if it is done producing the ShortByteString or returns Just (a,b), in which case, a is the next byte in the string, and b is the seed value for further production.

This function is not efficient/safe. It will build a list of [Word16] and run the generator until it returns Nothing, otherwise recurse infinitely, then finally create a ShortByteString.

Examples:

   unfoldr (\x -> if x <= 5 then Just (x, x + 1) else Nothing) 0
== pack [0, 1, 2, 3, 4, 5]

unfoldrN Source

O(n) Like unfoldr, unfoldrN builds a ShortByteString 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:

fst (unfoldrN n f s) == take n (unfoldr f s)

Substrings

Breaking strings

take Source

O(n) take n, applied to a ShortByteString xs, returns the prefix of xs of length n, or xs itself if n > length xs.

Note: copies the entire byte array

takeEnd Source

O(1) takeEnd n xs is equivalent to drop (length xs - n) xs. Takes n elements from end of bytestring.

>>> takeEnd 3 "a\NULb\NULc\NULd\NULe\NULf\NULg\NUL"
"e\NULf\NULg\NUL"
>>> takeEnd 0 "a\NULb\NULc\NULd\NULe\NULf\NULg\NUL"
""
>>> takeEnd 4 "a\NULb\NULc\NUL"
"a\NULb\NULc\NUL"

takeWhileEnd :: (Word16 -> Bool) -> ShortByteString -> ShortByteString Source

Returns the longest (possibly empty) suffix of elements satisfying the predicate.

takeWhileEnd p is equivalent to reverse . takeWhile p . reverse.

takeWhile :: (Word16 -> Bool) -> ShortByteString -> ShortByteString Source

Similar to takeWhile, returns the longest (possibly empty) prefix of elements satisfying the predicate.

drop Source

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

Note: copies the entire byte array

dropEnd Source

O(1) dropEnd n xs is equivalent to take (length xs - n) xs. Drops n elements from end of bytestring.

>>> dropEnd 3 "a\NULb\NULc\NULd\NULe\NULf\NULg\NUL"
"a\NULb\NULc\NULd\NUL"
>>> dropEnd 0 "a\NULb\NULc\NULd\NULe\NULf\NULg\NUL"
"a\NULb\NULc\NULd\NULe\NULf\NULg\NUL"
>>> dropEnd 4 "a\NULb\NULc\NUL"
""

dropWhile :: (Word16 -> Bool) -> ShortByteString -> ShortByteString Source

Similar to dropWhile, drops the longest (possibly empty) prefix of elements satisfying the predicate and returns the remainder.

Note: copies the entire byte array

dropWhileEnd :: (Word16 -> Bool) -> ShortByteString -> ShortByteString Source

Similar to dropWhileEnd, drops the longest (possibly empty) suffix of elements satisfying the predicate and returns the remainder.

dropWhileEnd p is equivalent to reverse . dropWhile p . reverse.

Since: os-string-0.10.12.0

breakEnd :: (Word16 -> Bool) -> ShortByteString -> (ShortByteString, ShortByteString) Source

Returns the longest (possibly empty) suffix of elements which do not satisfy the predicate and the remainder of the string.

breakEnd p is equivalent to spanEnd (not . p) and to (takeWhileEnd (not . p) &&& dropWhileEnd (not . p)).

break :: (Word16 -> Bool) -> ShortByteString -> (ShortByteString, ShortByteString) Source

Similar to break, returns the longest (possibly empty) prefix of elements which do not satisfy the predicate and the remainder of the string.

break p is equivalent to span (not . p) and to (takeWhile (not . p) &&& dropWhile (not . p)).

span :: (Word16 -> Bool) -> ShortByteString -> (ShortByteString, ShortByteString) Source

Similar to span, returns the longest (possibly empty) prefix of elements satisfying the predicate and the remainder of the string.

span p is equivalent to break (not . p) and to (takeWhile p &&& dropWhile p).

spanEnd :: (Word16 -> Bool) -> ShortByteString -> (ShortByteString, ShortByteString) Source

Returns the longest (possibly empty) suffix of elements satisfying the predicate and the remainder of the string.

spanEnd p is equivalent to breakEnd (not . p) and to (takeWhileEnd p &&& dropWhileEnd p).

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)

splitAt Source

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

Note: copies the substrings

split :: Word16 -> ShortByteString -> [ShortByteString] Source

O(n) Break a ShortByteString 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
split undefined ""     == []                  -- and not [""]

and

intercalate [c] . split c == id
split == splitWith . (==)

Note: copies the substrings

splitWith :: (Word16 -> Bool) -> ShortByteString -> [ShortByteString] Source

O(n) Splits a ShortByteString 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 undefined ""     == []                  -- and not [""]

stripSuffix :: ShortByteString -> ShortByteString -> Maybe ShortByteString Source

O(n) The stripSuffix function takes two ShortByteStrings and returns Just the remainder of the second iff the first is its suffix, and otherwise Nothing.

Since: bytestring-0.11.3.0

stripPrefix :: ShortByteString -> ShortByteString -> Maybe ShortByteString Source

O(n) The stripPrefix function takes two ShortByteStrings and returns Just the remainder of the second iff the first is its prefix, and otherwise Nothing.

Since: bytestring-0.11.3.0

Predicates

isInfixOf :: ShortByteString -> ShortByteString -> Bool Source

Check whether one string is a substring of another.

isPrefixOf :: ShortByteString -> ShortByteString -> Bool Source

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

Since: bytestring-0.11.3.0

isSuffixOf :: ShortByteString -> ShortByteString -> Bool Source

O(n) The isSuffixOf function takes two ShortByteStrings and returns True iff the first is a suffix of the second.

The following holds:

isSuffixOf x y == reverse x `isPrefixOf` reverse y

Since: bytestring-0.11.3.0

Search for arbitrary substrings

breakSubstring Source

Searching ShortByteStrings

Searching by equality

elem :: Word16 -> ShortByteString -> Bool Source

O(n) elem is the ShortByteString membership predicate.

Searching with a predicate

find :: (Word16 -> Bool) -> ShortByteString -> Maybe Word16 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 :: (Word16 -> Bool) -> ShortByteString -> ShortByteString Source

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

partition :: (Word16 -> Bool) -> ShortByteString -> (ShortByteString, ShortByteString) 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 ShortByteStrings

index Source

O(1) ShortByteString index (subscript) operator, starting from 0.

indexMaybe Source

O(1) ShortByteString index, starting from 0, that returns Just if:

0 <= n < length bs

Since: os-string-0.11.0.0

(!?) Source

O(1) ShortByteString index, starting from 0, that returns Just if:

0 <= n < length bs

Since: os-string-0.11.0.0

elemIndex Source

O(n) The elemIndex function returns the index of the first element in the given ShortByteString which is equal to the query element, or Nothing if there is no such element.

elemIndices :: Word16 -> ShortByteString -> [Int] Source

O(n) The elemIndices function extends elemIndex, by returning the indices of all elements equal to the query element, in ascending order.

count :: Word16 -> ShortByteString -> Int Source

count returns the number of times its argument appears in the ShortByteString

findIndex :: (Word16 -> Bool) -> ShortByteString -> Maybe Int Source

O(n) The findIndex function takes a predicate and a ShortByteString and returns the index of the first element in the ByteString satisfying the predicate.

findIndices :: (Word16 -> Bool) -> ShortByteString -> [Int] Source

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

Encoding validation

Low level conversions

Packing CStrings and pointers

packCWString :: Ptr Word16 -> IO ShortByteString Source

O(n). Construct a new ShortByteString from a CWString. The resulting ShortByteString is an immutable copy of the original CWString, and is managed on the Haskell heap. The original CWString must be null terminated.

Since: os-string-0.10.10.0

packCWStringLen :: (Ptr Word16, Int) -> IO ShortByteString Source

O(n). Construct a new ShortByteString from a CWStringLen. The resulting ShortByteString is an immutable copy of the original CWStringLen. The ShortByteString is a normal Haskell value and will be managed on the Haskell heap.

Since: os-string-0.10.10.0

newCWString :: ShortByteString -> IO (Ptr Word16) Source

O(n) construction. Use a ShortByteString with a function requiring a CWStringLen. As for useAsCWString this function makes a copy of the original ShortByteString. It must not be stored or used after the subcomputation finishes.

Since: os-string-0.10.10.0

Using ShortByteStrings as CStrings

useAsCWString :: ShortByteString -> (Ptr Word16 -> IO a) -> IO a Source

O(n) construction. Use a ShortByteString with a function requiring a null-terminated CWString. The CWString is a copy and will be freed automatically; it must not be stored or used after the subcomputation finishes.

Since: os-string-0.10.10.0

useAsCWStringLen :: ShortByteString -> ((Ptr Word16, Int) -> IO a) -> IO a Source

O(n) construction. Use a ShortByteString with a function requiring a CWStringLen. As for useAsCWString this function makes a copy of the original ShortByteString. It must not be stored or used after the subcomputation finishes.

Since: os-string-0.10.10.0