text- An efficient packed Unicode text type

Maintainerbos@serpentine.com, rtharper@aftereternity.co.uk, duncan@haskell.org




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-16, using the platform's native endianness. This makes copied data suitable for use with native libraries that use a similar representation, such as ICU. To interoperate with native libraries that use different internal representations, such as UTF-8 or UTF-32, consider using the functions in the Data.Text.Encoding module.

Safe conversion functions



:: Ptr Word16

source array

-> Int

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 Word16 -> Int -> IO a) -> IO aSource

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

Unsafe conversion code

lengthWord16 :: Text -> IntSource

O(1) Return the length of a Text in units of Word16. This is useful for sizing a target array appropriately before using unsafeCopyToPtr.

unsafeCopyToPtr :: Text -> Ptr Word16 -> IO ()Source

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