Z-Data-0.1.3.1: Array, vector and text
Copyright(c) Dong Han 2017-2018
LicenseBSD
Maintainerwinterland1989@gmail.com
Stabilityexperimental
Portabilitynon-portable
Safe HaskellNone
LanguageHaskell2010

Z.Data.CBytes

Contents

Description

This module provide CBytes with some useful instances / functions, A CBytes is a wrapper for immutable null-terminated string. The main design target of this type is to ease the bridging of C FFI APIs, since most of the unix APIs use null-terminated string. On windows you're encouraged to use a compatibility layer like 'WideCharToMultiByte/MultiByteToWideChar' and keep the same interface, e.g. libuv do this when deal with file paths.

We neither guarantee to store length info, nor support O(1) slice for CBytes: This will defeat the purpose of null-terminated string which is to save memory, We do save the length if it's created on GHC heap though. If you need advance editing, convert a CBytes to Bytes with toBytes and use vector combinators. Use fromBytes to convert it back.

It can be used with OverloadedString, literal encoding is UTF-8 with some modifications: NUL char is encoded to 'C0 80', and 'xD800' ~ 'xDFFF' is encoded as a three bytes normal utf-8 codepoint. This is also how ghc compile string literal into binaries, thus we can use rewrite-rules to construct CBytes value in O(1) without wasting runtime heap.

Note most of the unix API is not unicode awared though, you may find a scandir call return a filename which is not proper encoded in any unicode encoding at all. But still, UTF-8 is recommanded to be used everywhere, and we use UTF-8 assumption in various places, such as displaying CBytes and literals encoding above.

Synopsis

Documentation

data CBytes Source #

A efficient wrapper for immutable null-terminated string which can be automatically freed by ghc garbage collector.

Instances

Instances details
Eq CBytes Source # 
Instance details

Defined in Z.Data.CBytes

Methods

(==) :: CBytes -> CBytes -> Bool #

(/=) :: CBytes -> CBytes -> Bool #

Ord CBytes Source # 
Instance details

Defined in Z.Data.CBytes

Read CBytes Source # 
Instance details

Defined in Z.Data.CBytes

Show CBytes Source # 
Instance details

Defined in Z.Data.CBytes

IsString CBytes Source # 
Instance details

Defined in Z.Data.CBytes

Methods

fromString :: String -> CBytes #

Semigroup CBytes Source # 
Instance details

Defined in Z.Data.CBytes

Monoid CBytes Source # 
Instance details

Defined in Z.Data.CBytes

NFData CBytes Source # 
Instance details

Defined in Z.Data.CBytes

Methods

rnf :: CBytes -> () #

Hashable CBytes Source # 
Instance details

Defined in Z.Data.CBytes

Methods

hashWithSalt :: Int -> CBytes -> Int

hash :: CBytes -> Int

create Source #

Arguments

:: HasCallStack 
=> Int

capacity n, including the NUL terminator

-> (CString -> IO Int)

initialize function write the pointer, return the length (<= n-1)

-> IO CBytes 

Create a CBytes with IO action.

User only have to do content initialization and return the content length, create takes the responsibility to add the NUL ternimator. If the initialize function write NUL terminator(most FFI functions for example), you should use allocCBytes.

If (<=0) capacity is provided, a nullPtr is passed to initialize function and empty will be returned. other than that, if length returned is larger than (capacity-1), a NULLTerminatorNotFound will be thrown.

pack :: String -> CBytes Source #

Pack a String into null-terminated CBytes.

NUL is encoded as two bytes C0 80 , 'xD800' ~ 'xDFFF' is encoded as a three bytes normal UTF-8 codepoint.

empty :: CBytes Source #

empty CBytes

Passing empty to C FFI is equivalent to passing a NULL pointer.

intercalate :: CBytes -> [CBytes] -> CBytes Source #

O(n) The intercalate function takes a CBytes and a list of CBytes s and concatenates the list after interspersing the first argument between each element of the list.

Note: intercalate will force the entire CBytes list.

intercalateElem :: Word8 -> [CBytes] -> CBytes Source #

O(n) An efficient way to join CByte s with a byte.

toBytes :: CBytes -> Bytes Source #

O(1), (O(n) in case of literal), convert to Bytes, which can be processed by vector combinators.

NOTE: the NUL ternimator is not included.

fromBytes :: Bytes -> CBytes Source #

O(n), convert from Bytes, allocate pinned memory and add the NUL ternimator

toText :: CBytes -> Text Source #

O(n), convert to Text using UTF8 encoding assumption.

Throw InvalidUTF8Exception in case of invalid codepoint.

toTextMaybe :: CBytes -> Maybe Text Source #

O(n), convert to Text using UTF8 encoding assumption.

Return Nothing in case of invalid codepoint.

fromText :: Text -> CBytes Source #

O(n), convert from Text, allocate pinned memory and add the NUL ternimator

fromCString :: CString -> IO CBytes Source #

Copy a CString type into a CBytes, return empty if the pointer is NULL.

After copying you're free to free the CString 's memory.

fromCString' :: HasCallStack => CString -> IO (Maybe CBytes) Source #

Same with fromCString, but throw NullPointerException when meet a null pointer.

fromCStringN :: CString -> Int -> IO CBytes Source #

Same with fromCString, but only take N bytes (and append a null byte as terminator).

withCBytes :: CBytes -> (CString -> IO a) -> IO a Source #

Pass CBytes to foreign function as a const char*.

Don't pass a forever loop to this function, see #14346.

allocCBytes Source #

Arguments

:: HasCallStack 
=> Int

capacity n, including the NUL terminator

-> (CString -> IO a)

initialization function,

-> IO (CBytes, a) 

Create a CBytes with IO action.

If (<=0) capacity is provided, a nullPtr is passed to initialize function and empty will be returned. Other than that, User have to make sure a NUL ternimated string will be written, otherwise a NULLTerminatorNotFound will be thrown.

w2c :: Word8 -> Char Source #

Conversion between Word8 and Char. Should compile to a no-op.

c2w :: Char -> Word8 Source #

Unsafe conversion between Char and Word8. This is a no-op and silently truncates to 8 bits Chars > '255'. It is provided as convenience for PrimVector construction.

exception

type CString = Ptr CChar #

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