import qualified Data.ByteString       as B
import qualified Data.ByteString.Short as B
         (ShortByteString, toShort, fromShort)

import qualified Data.ByteString.Short as B.Short

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.

With GHC, the memory overheads are as follows, expressed in words and in bytes (words are 4 and 8 bytes on 32 or 64bit machines respectively).

• ByteString unshared: 8 words; 32 or 64 bytes.
• ByteString shared substring: 4 words; 16 or 32 bytes.
• ShortByteString: 4 words; 16 or 32 bytes.

For the string data itself, both ShortByteString and ByteString use one byte per element, rounded up to the nearest word. For example, including the overheads, a length 10 ShortByteString would take 16 + 12 = 28 bytes on a 32bit platform and 32 + 16 = 48 bytes on a 64bit platform.

These overheads can all be reduced by 1 word (4 or 8 bytes) when the ShortByteString or ByteString is unpacked into another constructor.

For example:

data ThingId = ThingId {-# UNPACK #-} !Int
                       {-# UNPACK #-} !ShortByteString

This will take 1 + 1 + 3 words (the ThingId constructor + unpacked Int + unpacked ShortByteString), plus the words for the string data.

With GHC, the ByteString representation uses pinned memory, meaning it cannot be moved by the GC. This is usually the right thing to do for larger strings, but for small strings using pinned memory can lead to heap fragmentation which wastes space. The ShortByteString type (and the Text type from the text package) use unpinned memory so they do not contribute to heap fragmentation. In addition, with GHC, small unpinned strings are allocated in the same way as normal heap allocations, rather than in a separate pinned area.

empty :: ShortByteString Source

O(1). The empty ShortByteString.

singleton :: Word8 -> ShortByteString Source

O(1) Convert a Word8 into a ShortByteString

Since: bytestring-0.11.3.0

pack :: [Word8] -> ShortByteString Source

O(n). Convert a list into a ShortByteString

unpack :: ShortByteString -> [Word8] 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.

snoc :: ShortByteString -> Word8 -> ShortByteString infixl 5 Source

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

Note: copies the entire byte array

Since: bytestring-0.11.3.0

cons :: Word8 -> ShortByteString -> ShortByteString infixr 5 Source

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

Note: copies the entire byte array

Since: bytestring-0.11.3.0

append :: ShortByteString -> ShortByteString -> ShortByteString Source

last :: HasCallStack => ShortByteString -> Word8 Source

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

This is a partial function, consider using unsnoc instead.

Since: bytestring-0.11.3.0

tail :: HasCallStack => ShortByteString -> ShortByteString Source

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

This is a partial function, consider using uncons instead.

Note: copies the entire byte array

Since: bytestring-0.11.3.0

uncons :: ShortByteString -> Maybe (Word8, ShortByteString) Source

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

Since: bytestring-0.11.3.0

head :: HasCallStack => ShortByteString -> Word8 Source

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

This is a partial function, consider using uncons instead.

Since: bytestring-0.11.3.0

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.

This is a partial function, consider using unsnoc instead.

Note: copies the entire byte array

Since: bytestring-0.11.3.0

unsnoc :: ShortByteString -> Maybe (ShortByteString, Word8) Source

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

Since: bytestring-0.11.3.0

null :: ShortByteString -> Bool Source

O(1) Test whether a ShortByteString is empty.

length :: ShortByteString -> Int Source

O(1) The length of a ShortByteString.

isValidUtf8 :: ShortByteString -> Bool Source

O(n) Check whether a ShortByteString represents valid UTF-8.

Since: bytestring-0.11.3.0

map :: (Word8 -> Word8) -> ShortByteString -> ShortByteString Source

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

Since: bytestring-0.11.3.0

reverse :: ShortByteString -> ShortByteString Source

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

Since: bytestring-0.11.3.0

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

foldl :: (a -> Word8 -> 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.

Since: bytestring-0.11.3.0

foldl' :: (a -> Word8 -> a) -> a -> ShortByteString -> a Source

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

Since: bytestring-0.11.3.0

foldl1 :: HasCallStack => (Word8 -> Word8 -> Word8) -> ShortByteString -> Word8 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.

Since: bytestring-0.11.3.0

foldl1' :: HasCallStack => (Word8 -> Word8 -> Word8) -> ShortByteString -> Word8 Source

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

Since: bytestring-0.11.3.0

foldr :: (Word8 -> 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.

Since: bytestring-0.11.3.0

foldr' :: (Word8 -> a -> a) -> a -> ShortByteString -> a Source

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

Since: bytestring-0.11.3.0

foldr1 :: HasCallStack => (Word8 -> Word8 -> Word8) -> ShortByteString -> Word8 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.

Since: bytestring-0.11.3.0

foldr1' :: HasCallStack => (Word8 -> Word8 -> Word8) -> ShortByteString -> Word8 Source

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

Since: bytestring-0.11.3.0

all :: (Word8 -> Bool) -> ShortByteString -> Bool Source

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

Since: bytestring-0.11.3.0

any :: (Word8 -> Bool) -> ShortByteString -> Bool Source

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

Since: bytestring-0.11.3.0

concat :: [ShortByteString] -> ShortByteString Source

replicate :: Int -> Word8 -> ShortByteString Source

O(n) replicate n x is a ShortByteString of length n with x the value of every element. The following holds:

replicate w c = unfoldr w (\u -> Just (u,u)) c

Since: bytestring-0.11.3.0

unfoldr :: (a -> Maybe (Word8, 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 [Word8] and run the generator until it returns Nothing, otherwise recurse infinitely, then finally create a ShortByteString.

If you know the maximum length, consider using unfoldrN.

Examples:

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

Since: bytestring-0.11.3.0

unfoldrN :: Int -> (a -> Maybe (Word8, a)) -> a -> (ShortByteString, Maybe a) 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)

Since: bytestring-0.11.3.0

take :: Int -> ShortByteString -> ShortByteString 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

Since: bytestring-0.11.3.0

takeEnd :: Int -> ShortByteString -> ShortByteString Source

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

>>> takeEnd 3 "abcdefg"
"efg"
>>> takeEnd 0 "abcdefg"
""
>>> takeEnd 4 "abc"
"abc"

Since: bytestring-0.11.3.0

takeWhileEnd :: (Word8 -> Bool) -> ShortByteString -> ShortByteString Source

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

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

Since: bytestring-0.11.3.0

takeWhile :: (Word8 -> Bool) -> ShortByteString -> ShortByteString Source

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

Since: bytestring-0.11.3.0

drop :: Int -> ShortByteString -> ShortByteString Source

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

Note: copies the entire byte array

Since: bytestring-0.11.3.0

dropEnd :: Int -> ShortByteString -> ShortByteString Source

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

>>> dropEnd 3 "abcdefg"
"abcd"
>>> dropEnd 0 "abcdefg"
"abcdefg"
>>> dropEnd 4 "abc"
""

Since: bytestring-0.11.3.0

dropWhile :: (Word8 -> 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

Since: bytestring-0.11.3.0

dropWhileEnd :: (Word8 -> 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: bytestring-0.11.3.0

breakEnd :: (Word8 -> 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)).

Since: bytestring-0.11.3.0

break :: (Word8 -> 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)).

Since: bytestring-0.11.3.0

span :: (Word8 -> 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).

Since: bytestring-0.11.3.0

spanEnd :: (Word8 -> 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) sbs
   ==
let (x, y) = span (not . isSpace) (reverse sbs) in (reverse y, reverse x)

Since: bytestring-0.11.3.0

splitAt :: Int -> ShortByteString -> (ShortByteString, ShortByteString) Source

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

Note: copies the substrings

Since: bytestring-0.11.3.0

split :: Word8 -> 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

Since: bytestring-0.11.3.0

splitWith :: (Word8 -> 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 [""]

Since: bytestring-0.11.3.0

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

isInfixOf :: ShortByteString -> ShortByteString -> Bool Source

Check whether one string is a substring of another.

Since: bytestring-0.11.3.0

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

breakSubstring Source

Break a string on a substring, returning a pair of the part of the string prior to the match, and the rest of the string.

The following relationships hold:

break (== c) l == breakSubstring (singleton c) l

For example, to tokenise a string, dropping delimiters:

tokenise x y = h : if null t then [] else tokenise x (drop (length x) t)
    where (h,t) = breakSubstring x y

To skip to the first occurrence of a string:

snd (breakSubstring x y)

To take the parts of a string before a delimiter:

fst (breakSubstring x y)

Note that calling `breakSubstring x` does some preprocessing work, so you should avoid unnecessarily duplicating breakSubstring calls with the same pattern.

Since: bytestring-0.11.3.0

elem :: Word8 -> ShortByteString -> Bool Source

O(n) elem is the ShortByteString membership predicate.

Since: bytestring-0.11.3.0

find :: (Word8 -> Bool) -> ShortByteString -> Maybe Word8 Source

O(n) The find function takes a predicate and a ShortByteString, 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

Since: bytestring-0.11.3.0

filter :: (Word8 -> Bool) -> ShortByteString -> ShortByteString Source

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

Since: bytestring-0.11.3.0

partition :: (Word8 -> Bool) -> ShortByteString -> (ShortByteString, ShortByteString) Source

O(n) The partition function takes a predicate a ShortByteString and returns the pair of ShortByteStrings with elements which do and do not satisfy the predicate, respectively; i.e.,

partition p bs == (filter p sbs, filter (not . p) sbs)

Since: bytestring-0.11.3.0

index :: HasCallStack => ShortByteString -> Int -> Word8 Source

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

This is a partial function, consider using indexMaybe instead.

indexMaybe :: ShortByteString -> Int -> Maybe Word8 Source

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

0 <= n < length bs

Since: bytestring-0.11.0.0

(!?) :: ShortByteString -> Int -> Maybe Word8 Source

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

0 <= n < length bs

Since: bytestring-0.11.0.0

elemIndex :: Word8 -> ShortByteString -> Maybe Int 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.

Since: bytestring-0.11.3.0

elemIndices :: Word8 -> 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.

Since: bytestring-0.11.3.0

count :: Word8 -> ShortByteString -> Int Source

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

Since: bytestring-0.11.3.0

findIndex :: (Word8 -> 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 ShortByteString satisfying the predicate.

Since: bytestring-0.11.3.0

findIndices :: (Word8 -> Bool) -> ShortByteString -> [Int] Source

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

Since: bytestring-0.11.3.0

Packing CStrings and pointers

packCString :: CString -> IO ShortByteString Source

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

Since: bytestring-0.10.10.0

packCStringLen :: CStringLen -> IO ShortByteString Source

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

Since: bytestring-0.10.10.0

Using ShortByteStrings as CStrings

useAsCString :: ShortByteString -> (CString -> IO a) -> IO a Source

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

Since: bytestring-0.10.10.0

useAsCStringLen :: ShortByteString -> (CStringLen -> IO a) -> IO a Source

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

Beware that this function does not add a terminating NUL byte at the end of CStringLen. If you need to construct a pointer to a null-terminated sequence, use useAsCString (and measure length independently if desired).

Since: bytestring-0.10.10.0