Data.Text.Foreign

text-2.0: An efficient packed Unicode text type.

Copyright | (c) 2009 2010 Bryan O'Sullivan
License | BSD-style
Maintainer | bos@serpentine.com
Portability | GHC
Safe Haskell | Safe-Inferred
Language | Haskell2010

Data.Text.Foreign

Contents

- Interoperability with native code
- Safe conversion functions
  - Encoding as UTF-8
- Unsafe conversion code
- Low-level manipulation

Description

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

Synopsis

- data I8
- fromPtr :: Ptr Word8 -> I8 -> IO Text
- fromPtr0 :: Ptr Word8 -> IO Text
- useAsPtr :: Text -> (Ptr Word8 -> I8 -> IO a) -> IO a
- asForeignPtr :: Text -> IO (ForeignPtr Word8, I8)
- peekCStringLen :: CStringLen -> IO Text
- withCStringLen :: Text -> (CStringLen -> IO a) -> IO a
- lengthWord8 :: Text -> Int
- unsafeCopyToPtr :: Text -> Ptr Word8 -> IO ()
- dropWord8 :: I8 -> Text -> Text
- takeWord8 :: I8 -> Text -> Text

# 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 Source #

A type representing a number of UTF-8 code units.

Since: text-2.0

#### Instances

Instances details

Bounded I8 Source # |
Instance details Defined in Data.Text.Foreign Methods minBound :: I8 Source # maxBound :: I8 Source #
Enum I8 Source # |
Instance details Defined in Data.Text.Foreign Methods succ :: I8 -> I8 Source # pred :: I8 -> I8 Source # toEnum :: Int -> I8 Source # fromEnum :: I8 -> Int Source # enumFrom :: I8 -> [I8] Source # enumFromThen :: I8 -> I8 -> [I8] Source # enumFromTo :: I8 -> I8 -> [I8] Source # enumFromThenTo :: I8 -> I8 -> I8 -> [I8] Source #
Num I8 Source # |
Instance details Defined in Data.Text.Foreign Methods (+) :: I8 -> I8 -> I8 Source # (-) :: I8 -> I8 -> I8 Source # (*) :: I8 -> I8 -> I8 Source # negate :: I8 -> I8 Source # abs :: I8 -> I8 Source # signum :: I8 -> I8 Source # fromInteger :: Integer -> I8 Source #
Read I8 Source # |
Instance details Defined in Data.Text.Foreign Methods readsPrec :: Int -> ReadS I8 Source # readList :: ReadS [I8] Source # readPrec :: ReadPrec I8 Source # readListPrec :: ReadPrec [I8] Source #
Integral I8 Source # |
Instance details Defined in Data.Text.Foreign Methods quot :: I8 -> I8 -> I8 Source # rem :: I8 -> I8 -> I8 Source # div :: I8 -> I8 -> I8 Source # mod :: I8 -> I8 -> I8 Source # quotRem :: I8 -> I8 -> (I8, I8) Source # divMod :: I8 -> I8 -> (I8, I8) Source # toInteger :: I8 -> Integer Source #
Real I8 Source # |
Instance details Defined in Data.Text.Foreign Methods toRational :: I8 -> Rational Source #
Show I8 Source # |
Instance details Defined in Data.Text.Foreign Methods showsPrec :: Int -> I8 -> ShowS Source # show :: I8 -> String Source # showList :: [I8] -> ShowS Source #
Eq I8 Source # |
Instance details Defined in Data.Text.Foreign Methods (==) :: I8 -> I8 -> Bool Source # (/=) :: I8 -> I8 -> Bool Source #
Ord I8 Source # |
Instance details Defined in Data.Text.Foreign Methods compare :: I8 -> I8 -> Ordering Source # (<) :: I8 -> I8 -> Bool Source # (<=) :: I8 -> I8 -> Bool Source # (>) :: I8 -> I8 -> Bool Source # (>=) :: I8 -> I8 -> Bool Source # max :: I8 -> I8 -> I8 Source # min :: I8 -> I8 -> I8 Source #

# Safe conversion functions

fromPtr Source #

Arguments

:: Ptr Word8 | source array
-> I8 | length of source array (in `Word8` units)
-> IO Text |

O(n) Create a new `Text` from a `Ptr` `Word8` by copying the contents of the array.

fromPtr0 Source #

Arguments

:: Ptr Word8 | source array
-> IO Text |

O(n) Create a new `Text` from a `Ptr` `Word8` by copying the contents of the NUL-terminated array.

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

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) Source #

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

## Encoding as UTF-8

peekCStringLen :: CStringLen -> IO Text Source #

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: text-1.0.0.0

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

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: text-1.0.0.0

# Unsafe conversion code

lengthWord8 :: Text -> Int Source #

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

Since: text-2.0

unsafeCopyToPtr :: Text -> Ptr Word8 -> 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`.

# Low-level manipulation

Foreign functions that use UTF-8 internally may return indices in units of `Word8` 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 Source #

O(1) Return the suffix of the `Text`, with `n` `Word8` units dropped from its beginning.

If `n` would cause the `Text` to begin inside a code point, the beginning of the suffix will be advanced by several additional `Word8` unit to maintain its validity.

Since: text-2.0

takeWord8 :: I8 -> Text -> Text Source #

O(1) Return the prefix of the `Text` of `n` `Word8` units in length.

If `n` would cause the `Text` to end inside a code point, the end of the prefix will be advanced by several additional `Word8` units to maintain its validity.

Since: text-2.0