Foreign.C.String

| Haskell Hierarchical Libraries (base package) | Contents | Index
Foreign.C.String |
Portability | portable
Stability | provisional
Maintainer | ffi@haskell.org
Contents
C strings Using a locale-dependent encoding Using 8-bit characters C wide strings
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
type CString = Ptr CChar
type CStringLen = (Ptr CChar, Int)
peekCString :: CString -> IO String
peekCStringLen :: CStringLen -> IO String
newCString :: String -> IO CString
newCStringLen :: String -> IO CStringLen
withCString :: String -> (CString -> IO a) -> IO a
withCStringLen :: String -> (CStringLen -> IO a) -> IO a
charIsRepresentable :: Char -> IO Bool
castCharToCChar :: Char -> CChar
castCCharToChar :: CChar -> Char
peekCAString :: CString -> IO String
peekCAStringLen :: CStringLen -> IO String
newCAString :: String -> IO CString
newCAStringLen :: String -> IO CStringLen
withCAString :: String -> (CString -> IO a) -> IO a
withCAStringLen :: String -> (CStringLen -> IO a) -> IO a
type CWString = Ptr CWchar
type CWStringLen = (Ptr CWchar, Int)
peekCWString :: CWString -> IO String
peekCWStringLen :: CWStringLen -> IO String
newCWString :: String -> IO CWString
newCWStringLen :: String -> IO CWStringLen
withCWString :: String -> (CWString -> IO a) -> IO a
withCWStringLen :: String -> (CWStringLen -> IO a) -> IO a
C strings
type CString = Ptr CChar
A C string is a reference to an array of C characters terminated by NUL.
type CStringLen = (Ptr CChar, Int)
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
Currently these functions are identical to their `CAString` counterparts; eventually they will use an encoding determined by the current locale.
peekCString :: CString -> IO String
Marshal a NUL terminated C string into a Haskell string.
peekCStringLen :: CStringLen -> IO String
Marshal a C string with explicit length into a Haskell string.
newCString :: String -> IO CString
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 -> IO CStringLen
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
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
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.
charIsRepresentable :: Char -> IO Bool
Determines whether a character can be accurately encoded in a `CString`. Unrepresentable characters are converted to `'?'`. Currently only Latin-1 characters are representable.
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 -> CChar
Convert a Haskell character to a C character. This function is only safe on the first 256 characters.
castCCharToChar :: CChar -> Char
Convert a C byte, representing a Latin-1 character, to the corresponding Haskell character.
peekCAString :: CString -> IO String
Marshal a NUL terminated C string into a Haskell string.
peekCAStringLen :: CStringLen -> IO String
Marshal a C string with explicit length into a Haskell string.
newCAString :: String -> IO CString
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 -> IO CStringLen
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
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
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.
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 `__STDC_ISO_10646__`), or UTF-16 (as used on Windows systems).
type CWString = Ptr CWchar
A C wide string is a reference to an array of C wide characters terminated by NUL.
type CWStringLen = (Ptr CWchar, Int)
A wide character string with explicit length information in bytes instead of a terminating NUL (allowing NUL characters in the middle of the string).
peekCWString :: CWString -> IO String
Marshal a NUL terminated C wide string into a Haskell string.
peekCWStringLen :: CWStringLen -> IO String
Marshal a C wide string with explicit length into a Haskell string.
newCWString :: String -> IO CWString
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 -> IO CWStringLen
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
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
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.
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