base-4.17.2.1: Basic libraries
Copyright(c) The FFI task force 2001
LicenseBSD-style (see the file libraries/base/LICENSE)
Maintainerffi@haskell.org
Stabilityprovisional
Portabilityportable
Safe HaskellTrustworthy
LanguageHaskell2010

Foreign.C.String

Description

Utilities for primitive marshalling of C strings.

The marshalling converts each Haskell character, representing a Unicode code point, to one or more bytes in a manner that, by default, is determined by the current locale. As a consequence, no guarantees can be made about the relative length of a Haskell string and its corresponding C string, and therefore all the marshalling routines include memory allocation. The translation between Unicode and the encoding of the current locale may be lossy.

Synopsis

C strings

typeCString = PtrCCharSource#

A C string is a reference to an array of C characters terminated by NUL.

typeCStringLen = (PtrCChar, Int) Source#

A string with explicit length information in bytes instead of a terminating NUL (allowing NUL characters in the middle of the string).

Using a locale-dependent encoding

These functions are different from their CAString counterparts in that they will use an encoding determined by the current locale, rather than always assuming ASCII.

peekCString :: CString -> IOStringSource#

Marshal a NUL terminated C string into a Haskell string.

peekCStringLen :: CStringLen -> IOStringSource#

Marshal a C string with explicit length into a Haskell string.

newCString :: String -> IOCStringSource#

Marshal a Haskell string into a NUL terminated C string.

  • the Haskell string may not contain any NUL characters
  • new storage is allocated for the C string and must be explicitly freed using free or finalizerFree.

newCStringLen :: String -> IOCStringLenSource#

Marshal a Haskell string into a C string (ie, character array) with explicit length information.

  • new storage is allocated for the C string and must be explicitly freed using free or finalizerFree.

withCString :: String -> (CString -> IO a) -> IO a Source#

Marshal a Haskell string into a NUL terminated C string using temporary storage.

  • the Haskell string may not contain any NUL characters
  • the memory 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.

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

Marshal a Haskell string into a C string (ie, character array) in temporary storage, with explicit length information.

  • the memory 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.

charIsRepresentable :: Char -> IOBoolSource#

Using 8-bit characters

These variants of the above functions are for use with C libraries that are ignorant of Unicode. These functions should be used with care, as a loss of information can occur.

castCharToCChar :: Char -> CCharSource#

Convert a Haskell character to a C character. This function is only safe on the first 256 characters.

castCCharToChar :: CChar -> CharSource#

Convert a C byte, representing a Latin-1 character, to the corresponding Haskell character.

castCharToCUChar :: Char -> CUCharSource#

Convert a Haskell character to a C unsigned char. This function is only safe on the first 256 characters.

castCUCharToChar :: CUChar -> CharSource#

Convert a C unsigned char, representing a Latin-1 character, to the corresponding Haskell character.

castCharToCSChar :: Char -> CSCharSource#

Convert a Haskell character to a C signed char. This function is only safe on the first 256 characters.

castCSCharToChar :: CSChar -> CharSource#

Convert a C signed char, representing a Latin-1 character, to the corresponding Haskell character.

peekCAString :: CString -> IOStringSource#

Marshal a NUL terminated C string into a Haskell string.

peekCAStringLen :: CStringLen -> IOStringSource#

Marshal a C string with explicit length into a Haskell string.

newCAString :: String -> IOCStringSource#

Marshal a Haskell string into a NUL terminated C string.

  • the Haskell string may not contain any NUL characters
  • new storage is allocated for the C string and must be explicitly freed using free or finalizerFree.

newCAStringLen :: String -> IOCStringLenSource#

Marshal a Haskell string into a C string (ie, character array) with explicit length information.

  • new storage is allocated for the C string and must be explicitly freed using free or finalizerFree.

withCAString :: String -> (CString -> IO a) -> IO a Source#

Marshal a Haskell string into a NUL terminated C string using temporary storage.

  • the Haskell string may not contain any NUL characters
  • the memory 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.

withCAStringLen :: String -> (CStringLen -> IO a) -> IO a Source#

Marshal a Haskell string into a C string (ie, character array) in temporary storage, with explicit length information.

  • the memory 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.

C wide strings

These variants of the above functions are for use with C libraries that encode Unicode using the C wchar_t type in a system-dependent way. The only encodings supported are

  • UTF-32 (the C compiler defines 201706L), or
  • UTF-16 (as used on Windows systems).

typeCWString = PtrCWcharSource#

A C wide string is a reference to an array of C wide characters terminated by NUL.

typeCWStringLen = (PtrCWchar, Int) Source#

A wide character string with explicit length information in CWchars instead of a terminating NUL (allowing NUL characters in the middle of the string).

peekCWString :: CWString -> IOStringSource#

Marshal a NUL terminated C wide string into a Haskell string.

peekCWStringLen :: CWStringLen -> IOStringSource#

Marshal a C wide string with explicit length into a Haskell string.

newCWString :: String -> IOCWStringSource#

Marshal a Haskell string into a NUL terminated C wide string.

  • the Haskell string may not contain any NUL characters
  • new storage is allocated for the C wide string and must be explicitly freed using free or finalizerFree.

newCWStringLen :: String -> IOCWStringLenSource#

Marshal a Haskell string into a C wide string (ie, wide character array) with explicit length information.

  • new storage is allocated for the C wide string and must be explicitly freed using free or finalizerFree.

withCWString :: String -> (CWString -> IO a) -> IO a Source#

Marshal a Haskell string into a NUL terminated C wide string using temporary storage.

  • the Haskell string may not contain any NUL characters
  • the memory 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.

withCWStringLen :: String -> (CWStringLen -> IO a) -> IO a Source#

Marshal a Haskell string into a C wide string (i.e. wide character array) in temporary storage, with explicit length information.

  • the memory 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.
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