Data.Text.Foreign

Support for using Text data with native code via the Haskell foreign function interface.

Interoperability with native code

The Text type is implemented using arrays that are not guaranteed to have a fixed address in the Haskell heap. All communication with native code must thus occur by copying data back and forth.

The Text type's internal representation is UTF-8. To interoperate with native libraries that use different internal representations, such as UTF-16 or UTF-32, consider using the functions in the Encoding module.

data I8

A type representing a number of UTF-16 code units.

Instances

Bounded I8

Methods

minBound :: I8

maxBound :: I8

Enum I8

Methods

succ :: I8 -> I8

pred :: I8 -> I8

toEnum :: Int -> I8

fromEnum :: I8 -> Int

enumFrom :: I8 -> [I8]

enumFromThen :: I8 -> I8 -> [I8]

enumFromTo :: I8 -> I8 -> [I8]

enumFromThenTo :: I8 -> I8 -> I8 -> [I8]

Eq I8

Methods

(==) :: I8 -> I8 -> Bool

(/=) :: I8 -> I8 -> Bool

Integral I8

Methods

quot :: I8 -> I8 -> I8

rem :: I8 -> I8 -> I8

div :: I8 -> I8 -> I8

mod :: I8 -> I8 -> I8

quotRem :: I8 -> I8 -> (I8, I8)

divMod :: I8 -> I8 -> (I8, I8)

toInteger :: I8 -> Integer

Num I8

Methods

(+) :: I8 -> I8 -> I8

(-) :: I8 -> I8 -> I8

(*) :: I8 -> I8 -> I8

negate :: I8 -> I8

abs :: I8 -> I8

signum :: I8 -> I8

fromInteger :: Integer -> I8

Ord I8

Methods

compare :: I8 -> I8 -> Ordering

(<) :: I8 -> I8 -> Bool

(<=) :: I8 -> I8 -> Bool

(>) :: I8 -> I8 -> Bool

(>=) :: I8 -> I8 -> Bool

max :: I8 -> I8 -> I8

min :: I8 -> I8 -> I8

Read I8

Methods

readsPrec :: Int -> ReadS I8

readList :: ReadS [I8]

readPrec :: ReadPrec I8

readListPrec :: ReadPrec [I8]

Real I8

Methods

toRational :: I8 -> Rational

Show I8

Methods

showsPrec :: Int -> I8 -> ShowS

show :: I8 -> String

showList :: [I8] -> ShowS

Safe conversion functions

fromPtr

Arguments

:: Ptr Word8

source array

-> I8

length of source array (in Word16 units)

-> IO Text

O(n) Create a new Text from a Ptr Word16 by copying the contents of the array.

useAsPtr :: Text -> (Ptr Word8 -> I8 -> IO a) -> IO a

O(n) Perform an action on a temporary, mutable copy of a Text. The copy is freed as soon as the action returns.

asForeignPtr :: Text -> IO (ForeignPtr Word8, I8)

O(n) Make a mutable copy of a Text.

Encoding as UTF-8

peekCStringLen :: CStringLen -> IO Text

O(n) Decode a C string with explicit length, which is assumed to have been encoded as UTF-8. If decoding fails, a UnicodeException is thrown.

Since: 1.0.0.0

withCStringLen :: Text -> (CStringLen -> IO a) -> IO a

Marshal a Text into a C string encoded as UTF-8 in temporary storage, with explicit length information. The encoded string may contain NUL bytes, and is not followed by a trailing NUL byte.

The temporary storage is freed when the subcomputation terminates (either normally or via an exception), so the pointer to the temporary storage must not be used after this function returns.

Since: 1.0.0.0

Unsafe conversion code

lengthWord8 :: Text -> Int

O(1) Return the length of a Text in units of Word8. This is useful for sizing a target array appropriately before using unsafeCopyToPtr.

unsafeCopyToPtr :: Text -> Ptr Word8 -> IO ()

O(n) Copy a Text to an array. The array is assumed to be big enough to hold the contents of the entire Text.

Low-level manipulation

Foreign functions that use UTF-16 internally may return indices in units of Word16 instead of characters. These functions may safely be used with such indices, as they will adjust offsets if necessary to preserve the validity of a Unicode string.

dropWord8 :: I8 -> Text -> Text

O(1) Return the suffix of the Text, with n Word16 units dropped from its beginning.

If n would cause the Text to begin inside a surrogate pair, the beginning of the suffix will be advanced by one additional Word16 unit to maintain its validity.

takeWord8 :: I8 -> Text -> Text

O(1) Return the prefix of the Text of n Word16 units in length.

If n would cause the Text to end inside a surrogate pair, the end of the prefix will be advanced by one additional Word16 unit to maintain its validity.