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Data.ByteString.Char8
Contents
The `ByteString` type Introducing and eliminating `ByteString`s Basic interface Transformating ByteStrings Reducing `ByteString`s (folds) Special folds Building ByteStrings Scans Accumulating maps Generating and unfolding ByteStrings Substrings Breaking strings Breaking into many substrings Breaking into lines and words Joining strings Searching for substrings Searching ByteStrings Searching by equality Searching with a predicate Indexing ByteStrings Zipping and unzipping ByteStrings Ordered ByteStrings Reading from ByteStrings Low level CString conversions Packing CStrings and pointers Using ByteStrings as CStrings Copying ByteStrings I/O with `ByteString`s Standard input and output Files I/O with Handles Low level construction Utilities (needed for array fusion)
Description
Manipulate `ByteString`s using `Char` operations. All Chars will be truncated to 8 bits. It can be expected that these functions will run at identical speeds to their `Word8` equivalents in Data.ByteString. More specifically these byte strings are taken to be in the subset of Unicode covered by code points 0-255. This covers Unicode Basic Latin, Latin-1 Supplement and C0+C1 Controls. See: http://www.unicode.org/charts/ http://www.unicode.org/charts/PDF/U0000.pdf http://www.unicode.org/charts/PDF/U0080.pdf This module is intended to be imported `qualified`, to avoid name clashes with Prelude functions. eg.
     import qualified Data.ByteString.Char8 as B
Synopsis
data ByteString
empty :: ByteString
singleton :: Char -> ByteString
pack :: String -> ByteString
unpack :: ByteString -> [Char]
cons :: Char -> ByteString -> ByteString
snoc :: ByteString -> Char -> ByteString
append :: ByteString -> ByteString -> ByteString
head :: ByteString -> Char
last :: ByteString -> Char
tail :: ByteString -> ByteString
init :: ByteString -> ByteString
null :: ByteString -> Bool
length :: ByteString -> Int
map :: (Char -> Char) -> ByteString -> ByteString
reverse :: ByteString -> ByteString
intersperse :: Char -> ByteString -> ByteString
transpose :: [ByteString] -> [ByteString]
foldl :: (a -> Char -> a) -> a -> ByteString -> a
foldl' :: (a -> Char -> a) -> a -> ByteString -> a
foldl1 :: (Char -> Char -> Char) -> ByteString -> Char
foldl1' :: (Char -> Char -> Char) -> ByteString -> Char
foldr :: (Char -> a -> a) -> a -> ByteString -> a
foldr' :: (Char -> a -> a) -> a -> ByteString -> a
foldr1 :: (Char -> Char -> Char) -> ByteString -> Char
foldr1' :: (Char -> Char -> Char) -> ByteString -> Char
concat :: [ByteString] -> ByteString
concatMap :: (Char -> ByteString) -> ByteString -> ByteString
any :: (Char -> Bool) -> ByteString -> Bool
all :: (Char -> Bool) -> ByteString -> Bool
maximum :: ByteString -> Char
minimum :: ByteString -> Char
scanl :: (Char -> Char -> Char) -> Char -> ByteString -> ByteString
scanl1 :: (Char -> Char -> Char) -> ByteString -> ByteString
scanr :: (Char -> Char -> Char) -> Char -> ByteString -> ByteString
scanr1 :: (Char -> Char -> Char) -> ByteString -> ByteString
mapAccumL :: (acc -> Char -> (acc, Char)) -> acc -> ByteString -> (acc, ByteString)
mapAccumR :: (acc -> Char -> (acc, Char)) -> acc -> ByteString -> (acc, ByteString)
mapIndexed :: (Int -> Char -> Char) -> ByteString -> ByteString
replicate :: Int -> Char -> ByteString
unfoldr :: (a -> Maybe (Char, a)) -> a -> ByteString
unfoldrN :: Int -> (a -> Maybe (Char, a)) -> a -> (ByteString, Maybe a)
take :: Int -> ByteString -> ByteString
drop :: Int -> ByteString -> ByteString
splitAt :: Int -> ByteString -> (ByteString, ByteString)
takeWhile :: (Char -> Bool) -> ByteString -> ByteString
dropWhile :: (Char -> Bool) -> ByteString -> ByteString
span :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)
spanEnd :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)
break :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)
breakEnd :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)
group :: ByteString -> [ByteString]
groupBy :: (Char -> Char -> Bool) -> ByteString -> [ByteString]
inits :: ByteString -> [ByteString]
tails :: ByteString -> [ByteString]
split :: Char -> ByteString -> [ByteString]
splitWith :: (Char -> Bool) -> ByteString -> [ByteString]
lines :: ByteString -> [ByteString]
words :: ByteString -> [ByteString]
unlines :: [ByteString] -> ByteString
unwords :: [ByteString] -> ByteString
join :: ByteString -> [ByteString] -> ByteString
isPrefixOf :: ByteString -> ByteString -> Bool
isSuffixOf :: ByteString -> ByteString -> Bool
isSubstringOf :: ByteString -> ByteString -> Bool
findSubstring :: ByteString -> ByteString -> Maybe Int
findSubstrings :: ByteString -> ByteString -> [Int]
elem :: Char -> ByteString -> Bool
notElem :: Char -> ByteString -> Bool
find :: (Char -> Bool) -> ByteString -> Maybe Char
filter :: (Char -> Bool) -> ByteString -> ByteString
index :: ByteString -> Int -> Char
elemIndex :: Char -> ByteString -> Maybe Int
elemIndices :: Char -> ByteString -> [Int]
elemIndexEnd :: Char -> ByteString -> Maybe Int
findIndex :: (Char -> Bool) -> ByteString -> Maybe Int
findIndices :: (Char -> Bool) -> ByteString -> [Int]
count :: Char -> ByteString -> Int
zip :: ByteString -> ByteString -> [(Char, Char)]
zipWith :: (Char -> Char -> a) -> ByteString -> ByteString -> [a]
unzip :: [(Char, Char)] -> (ByteString, ByteString)
sort :: ByteString -> ByteString
readInt :: ByteString -> Maybe (Int, ByteString)
readInteger :: ByteString -> Maybe (Integer, ByteString)
packCString :: CString -> ByteString
packCStringLen :: CStringLen -> ByteString
packMallocCString :: CString -> ByteString
useAsCString :: ByteString -> (CString -> IO a) -> IO a
useAsCStringLen :: ByteString -> (CStringLen -> IO a) -> IO a
copy :: ByteString -> ByteString
copyCString :: CString -> IO ByteString
copyCStringLen :: CStringLen -> IO ByteString
getLine :: IO 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 ()
hGetLine :: Handle -> IO ByteString
hGetNonBlocking :: Handle -> Int -> IO ByteString
hGetContents :: Handle -> IO ByteString
hGet :: Handle -> Int -> IO ByteString
hPut :: Handle -> ByteString -> IO ()
hPutStr :: Handle -> ByteString -> IO ()
hPutStrLn :: Handle -> ByteString -> IO ()
packAddress :: Addr# -> ByteString
unsafePackAddress :: Int -> Addr# -> ByteString
unpackList :: ByteString -> [Word8]
The `ByteString` type
data ByteString
A space-efficient representation of a Word8 vector, supporting many efficient operations. A `ByteString` contains 8-bit characters only. Instances of Eq, Ord, Read, Show, Data, Typeable
Instances
Data ByteString
Eq ByteString
Monoid ByteString
Ord ByteString
Read ByteString
Show ByteString
Typeable ByteString
Introducing and eliminating `ByteString`s
empty :: ByteString
O(1) The empty `ByteString`
singleton :: Char -> ByteString
O(1) Convert a `Char` into a `ByteString`
pack :: String -> ByteString
O(n) Convert a `String` into a `ByteString` For applications with large numbers of string literals, pack can be a bottleneck. In such cases, consider using packAddress (GHC only).
unpack :: ByteString -> [Char]
O(n) Converts a `ByteString` to a `String`.
Basic interface
cons :: Char -> ByteString -> ByteString
O(n) `cons` is analogous to (:) for lists, but of different complexity, as it requires a memcpy.
snoc :: ByteString -> Char -> ByteString
O(n) Append a Char to the end of a `ByteString`. Similar to `cons`, this function performs a memcpy.
append :: ByteString -> ByteString -> ByteString
O(n) Append two ByteStrings
head :: ByteString -> Char
O(1) Extract the first element of a ByteString, which must be non-empty.
last :: ByteString -> Char
O(1) Extract the last element of a packed string, which must be non-empty.
tail :: ByteString -> ByteString
O(1) Extract the elements after the head of a ByteString, which must be non-empty. An exception will be thrown in the case of an empty ByteString.
init :: ByteString -> ByteString
O(1) Return all the elements of a `ByteString` except the last one. An exception will be thrown in the case of an empty ByteString.
null :: ByteString -> Bool
O(1) Test whether a ByteString is empty.
length :: ByteString -> Int
O(1) `length` returns the length of a ByteString as an `Int`.
Transformating ByteStrings
map :: (Char -> Char) -> ByteString -> ByteString
O(n) `map` `f xs` is the ByteString obtained by applying `f` to each element of `xs`
reverse :: ByteString -> ByteString
O(n) `reverse` `xs` efficiently returns the elements of `xs` in reverse order.
intersperse :: Char -> ByteString -> ByteString
O(n) The `intersperse` function takes a Char and a `ByteString` and `intersperses' that Char between the elements of the `ByteString`. It is analogous to the intersperse function on Lists.
transpose :: [ByteString] -> [ByteString]
The `transpose` function transposes the rows and columns of its `ByteString` argument.
Reducing `ByteString`s (folds)
foldl :: (a -> Char -> a) -> a -> ByteString -> a
`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 -> Char -> a) -> a -> ByteString -> a
`foldl` is like foldl, but strict in the accumulator.
foldl1 :: (Char -> Char -> Char) -> ByteString -> Char
`foldl1` is a variant of `foldl` that has no starting value argument, and thus must be applied to non-empty ByteStrings.
foldl1' :: (Char -> Char -> Char) -> ByteString -> Char
A strict version of `foldl1`
foldr :: (Char -> a -> a) -> a -> ByteString -> a
`foldr`, applied to a binary operator, a starting value (typically the right-identity of the operator), and a packed string, reduces the packed string using the binary operator, from right to left.
foldr' :: (Char -> a -> a) -> a -> ByteString -> a
`foldr` is a strict variant of foldr
foldr1 :: (Char -> Char -> Char) -> ByteString -> Char
`foldr1` is a variant of `foldr` that has no starting value argument, and thus must be applied to non-empty `ByteString`s
foldr1' :: (Char -> Char -> Char) -> ByteString -> Char
A strict variant of foldr1
Special folds
concat :: [ByteString] -> ByteString
O(n) Concatenate a list of ByteStrings.
concatMap :: (Char -> ByteString) -> ByteString -> ByteString
Map a function over a `ByteString` and concatenate the results
any :: (Char -> Bool) -> ByteString -> Bool
Applied to a predicate and a ByteString, `any` determines if any element of the `ByteString` satisfies the predicate.
all :: (Char -> Bool) -> ByteString -> Bool
Applied to a predicate and a `ByteString`, `all` determines if all elements of the `ByteString` satisfy the predicate.
maximum :: ByteString -> Char
`maximum` returns the maximum value from a `ByteString`
minimum :: ByteString -> Char
`minimum` returns the minimum value from a `ByteString`
Building ByteStrings
Scans
scanl :: (Char -> Char -> Char) -> Char -> ByteString -> ByteString
`scanl` is similar to `foldl`, but returns a list of successive reduced values from the left:
     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.
scanl1 :: (Char -> Char -> Char) -> ByteString -> ByteString
`scanl1` is a variant of `scanl` that has no starting value argument:
     scanl1 f [x1, x2, ...] == [x1, x1 `f` x2, ...]
scanr :: (Char -> Char -> Char) -> Char -> ByteString -> ByteString
scanr is the right-to-left dual of scanl.
scanr1 :: (Char -> Char -> Char) -> ByteString -> ByteString
`scanr1` is a variant of `scanr` that has no starting value argument.
Accumulating maps
mapAccumL :: (acc -> Char -> (acc, Char)) -> acc -> ByteString -> (acc, 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 list.
mapAccumR :: (acc -> Char -> (acc, Char)) -> acc -> ByteString -> (acc, ByteString)
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.
mapIndexed :: (Int -> Char -> Char) -> ByteString -> ByteString
O(n) map Char functions, provided with the index at each position
Generating and unfolding ByteStrings
replicate :: Int -> Char -> ByteString
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
This implemenation uses `memset(3)`
unfoldr :: (a -> Maybe (Char, a)) -> a -> ByteString
O(n), where n is the length of the result. 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 the next character in the string, and `b` is the seed value for further production. Examples:
     unfoldr (\x -> if x <= '9' then Just (x, succ x) else Nothing) '0' == "0123456789"
unfoldrN :: Int -> (a -> Maybe (Char, a)) -> a -> (ByteString, Maybe a)
O(n) Like `unfoldr`, `unfoldrN` builds a ByteString 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`:
     unfoldrN n f s == take n (unfoldr f s)
Substrings
Breaking strings
take :: Int -> ByteString -> ByteString
O(1) `take` `n`, applied to a ByteString `xs`, returns the prefix of `xs` of length `n`, or `xs` itself if `n > `length` xs`.
drop :: Int -> ByteString -> ByteString
O(1) `drop` `n xs` returns the suffix of `xs` after the first `n` elements, or `[]` if `n > `length` xs`.
splitAt :: Int -> ByteString -> (ByteString, ByteString)
O(1) `splitAt` `n xs` is equivalent to `(`take` n xs, `drop` n xs)`.
takeWhile :: (Char -> Bool) -> ByteString -> ByteString
`takeWhile`, applied to a predicate `p` and a ByteString `xs`, returns the longest prefix (possibly empty) of `xs` of elements that satisfy `p`.
dropWhile :: (Char -> Bool) -> ByteString -> ByteString
`dropWhile` `p xs` returns the suffix remaining after `takeWhile` `p xs`.
span :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)
`span` `p xs` breaks the ByteString into two segments. It is equivalent to `(`takeWhile` p xs, `dropWhile` p xs)`
spanEnd :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)
`spanEnd` behaves like `span` but from the end of the `ByteString`. 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)
break :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)
`break` `p` is equivalent to ``span` (`not` . p)`.
breakEnd :: (Char -> Bool) -> ByteString -> (ByteString, ByteString)
`breakEnd` behaves like `break` but from the end of the `ByteString` breakEnd p == spanEnd (not.p)
group :: ByteString -> [ByteString]
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. It is about 40% faster than groupBy (==)
groupBy :: (Char -> Char -> Bool) -> ByteString -> [ByteString]
The `groupBy` function is the non-overloaded version of `group`.
inits :: ByteString -> [ByteString]
O(n) Return all initial segments of the given `ByteString`, shortest first.
tails :: ByteString -> [ByteString]
O(n) Return all final segments of the given `ByteString`, longest first.
Breaking into many substrings
split :: Char -> ByteString -> [ByteString]
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
     join [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 :: (Char -> Bool) -> ByteString -> [ByteString]
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",""]
Breaking into lines and words
lines :: ByteString -> [ByteString]
`lines` breaks a ByteString up into a list of ByteStrings at newline Chars. The resulting strings do not contain newlines.
words :: ByteString -> [ByteString]
`words` breaks a ByteString up into a list of words, which were delimited by Chars representing white space. And
     tokens isSpace = words
unlines :: [ByteString] -> ByteString
`unlines` is an inverse operation to `lines`. It joins lines, after appending a terminating newline to each.
unwords :: [ByteString] -> ByteString
The `unwords` function is analogous to the `unlines` function, on words.
Joining strings
join :: ByteString -> [ByteString] -> ByteString
O(n) The `join` 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.
Searching for substrings
isPrefixOf :: ByteString -> ByteString -> Bool
O(n) The `isPrefixOf` function takes two ByteStrings and returns `True` iff the first is a prefix of the second.
isSuffixOf :: ByteString -> ByteString -> Bool
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
However, the real implemenation uses memcmp to compare the end of the string only, with no reverse required..
isSubstringOf
:: ByteString | String to search for.
-> ByteString | String to search in.
-> Bool |
Check whether one string is a substring of another. `isSubstringOf p s` is equivalent to `not (null (findSubstrings p s))`.
findSubstring
:: ByteString | String to search for.
-> ByteString | String to seach in.
-> Maybe Int |
Get the first index of a substring in another string, or `Nothing` if the string is not found. `findSubstring p s` is equivalent to `listToMaybe (findSubstrings p s)`.
findSubstrings
:: ByteString | String to search for.
-> ByteString | String to seach in.
-> [Int] |
Find the indexes of all (possibly overlapping) occurances of a substring in a string. This function uses the Knuth-Morris-Pratt string matching algorithm.
Searching ByteStrings
Searching by equality
elem :: Char -> ByteString -> Bool
O(n) `elem` is the `ByteString` membership predicate. This implementation uses `memchr(3)`.
notElem :: Char -> ByteString -> Bool
O(n) `notElem` is the inverse of `elem`
Searching with a predicate
find :: (Char -> Bool) -> ByteString -> Maybe Char
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.
filter :: (Char -> Bool) -> ByteString -> ByteString
O(n) `filter`, applied to a predicate and a ByteString, returns a ByteString containing those characters that satisfy the predicate.
Indexing ByteStrings
index :: ByteString -> Int -> Char
O(1) `ByteString` index (subscript) operator, starting from 0.
elemIndex :: Char -> ByteString -> Maybe Int
O(n) The `elemIndex` function returns the index of the first element in the given `ByteString` which is equal (by memchr) to the query element, or `Nothing` if there is no such element.
elemIndices :: Char -> ByteString -> [Int]
O(n) The `elemIndices` function extends `elemIndex`, by returning the indices of all elements equal to the query element, in ascending order.
elemIndexEnd :: Char -> ByteString -> Maybe Int
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)
findIndex :: (Char -> Bool) -> ByteString -> Maybe Int
The `findIndex` function takes a predicate and a `ByteString` and returns the index of the first element in the ByteString satisfying the predicate.
findIndices :: (Char -> Bool) -> ByteString -> [Int]
The `findIndices` function extends `findIndex`, by returning the indices of all elements satisfying the predicate, in ascending order.
count :: Char -> ByteString -> Int
count returns the number of times its argument appears in the ByteString
     count = length . elemIndices
Also
     count '\n' == length . lines
But more efficiently than using length on the intermediate list.
Zipping and unzipping ByteStrings
zip :: ByteString -> ByteString -> [(Char, Char)]
O(n) `zip` takes two ByteStrings and returns a list of corresponding pairs of Chars. If one input ByteString is short, excess elements of the longer ByteString are discarded. This is equivalent to a pair of `unpack` operations, and so space usage may be large for multi-megabyte ByteStrings
zipWith :: (Char -> Char -> a) -> ByteString -> ByteString -> [a]
`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 :: [(Char, Char)] -> (ByteString, ByteString)
`unzip` transforms a list of pairs of Chars into a pair of ByteStrings. Note that this performs two `pack` operations.
Ordered ByteStrings
sort :: ByteString -> ByteString
O(n) Sort a ByteString efficiently, using counting sort.
Reading from ByteStrings
readInt :: ByteString -> Maybe (Int, ByteString)
readInt reads an Int from the beginning of the ByteString. If there is no integer at the beginning of the string, it returns Nothing, otherwise it just returns the int read, and the rest of the string.
readInteger :: ByteString -> Maybe (Integer, ByteString)
readInteger reads an Integer from the beginning of the ByteString. If there is no integer at the beginning of the string, it returns Nothing, otherwise it just returns the int read, and the rest of the string.
Low level CString conversions
Packing CStrings and pointers
packCString :: CString -> ByteString
The sortBy function is the non-overloaded version of `sort`. Try some linear sorts: radix, counting Or mergesort. sortBy :: (Word8 -> Word8 -> Ordering) -> ByteString -> ByteString sortBy f ps = undefined O(n) Build a `ByteString` from a `CString`. This value will have no finalizer associated to it. The ByteString length is calculated using strlen(3), and thus the complexity is a O(n).
packCStringLen :: CStringLen -> ByteString
O(1) Build a `ByteString` from a `CStringLen`. This value will have no finalizer associated with it. This operation has O(1) complexity as we already know the final size, so no strlen(3) is required.
packMallocCString :: CString -> ByteString
O(n) Build a `ByteString` from a malloced `CString`. This value will have a `free(3)` finalizer associated to it.
Using ByteStrings as CStrings
useAsCString :: ByteString -> (CString -> IO a) -> IO a
O(n) construction Use a `ByteString` with a function requiring a null-terminated `CString`. The `CString` will be freed automatically. This is a memcpy(3).
useAsCStringLen :: ByteString -> (CStringLen -> IO a) -> IO a
O(1) construction Use a `ByteString` with a function requiring a `CStringLen`.
Copying ByteStrings
copy :: ByteString -> ByteString
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.
copyCString :: CString -> IO ByteString
O(n) Duplicate a CString as a ByteString. Useful if you know the CString is going to be deallocated from C land.
copyCStringLen :: CStringLen -> IO ByteString
O(n) Same as copyCString, but saves a strlen call when the length is known.
I/O with `ByteString`s
Standard input and output
getLine :: IO ByteString
Read a line from stdin.
getContents :: IO ByteString
getContents. Equivalent to hGetContents stdin
putStr :: ByteString -> IO ()
Write a ByteString to stdout
putStrLn :: ByteString -> IO ()
Write a ByteString to stdout, appending a newline byte
interact :: (ByteString -> ByteString) -> IO ()
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. It's great for writing one line programs!
Files
readFile :: FilePath -> IO ByteString
Read an entire file strictly into a `ByteString`. This is far more efficient than reading the characters into a `String` and then using `pack`. It also may be more efficient than opening the file and reading it using hGet.
writeFile :: FilePath -> ByteString -> IO ()
Write a `ByteString` to a file.
appendFile :: FilePath -> ByteString -> IO ()
Append a `ByteString` to a file.
I/O with Handles
hGetLine :: Handle -> IO ByteString
Read a line from a handle
hGetNonBlocking :: Handle -> Int -> IO ByteString
hGetNonBlocking is identical to `hGet`, except that it will never block waiting for data to become available, instead it returns only whatever data is available.
hGetContents :: Handle -> IO ByteString
Read entire handle contents into a `ByteString`. This function reads chunks at a time, doubling the chunksize on each read. The final buffer is then realloced to the appropriate size. For files > half of available memory, this may lead to memory exhaustion. Consider using `readFile` in this case. As with `hGet`, the string representation in the file is assumed to be ISO-8859-1.
hGet :: Handle -> Int -> IO ByteString
Read a `ByteString` directly from the specified `Handle`. This is far more efficient than reading the characters into a `String` and then using `pack`.
hPut :: Handle -> ByteString -> IO ()
Outputs a `ByteString` to the specified `Handle`.
hPutStr :: Handle -> ByteString -> IO ()
A synonym for `hPut`, for compatibility
hPutStrLn :: Handle -> ByteString -> IO ()
Write a ByteString to a handle, appending a newline byte
Low level construction
For constructors from foreign language types see Data.ByteString
packAddress :: Addr# -> ByteString
O(n) Pack a null-terminated sequence of bytes, pointed to by an Addr# (an arbitrary machine address assumed to point outside the garbage-collected heap) into a `ByteString`. A much faster way to create an Addr# is with an unboxed string literal, than to pack a boxed string. A unboxed string literal is compiled to a static `char []` by GHC. Establishing the length of the string requires a call to `strlen(3)`, so the Addr# must point to a null-terminated buffer (as is the case with string# literals in GHC). Use `unsafePackAddress` if you know the length of the string statically. An example:
     literalFS = packAddress "literal"#
unsafePackAddress :: Int -> Addr# -> ByteString
O(1) `unsafePackAddress` provides constant-time construction of ByteStrings -- which is ideal for string literals. It packs a null-terminated sequence of bytes into a `ByteString`, given a raw Addr to the string, and the length of the string. Make sure the length is correct, otherwise use the safer `packAddress` (where the length will be calculated once at runtime).
Utilities (needed for array fusion)
unpackList :: ByteString -> [Word8]
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