| Copyright | (c) Don Stewart 2006-2008 (c) Duncan Coutts 2006-2012 |
|---|---|
| License | BSD-style |
| Maintainer | dons00@gmail.com, duncan@community.haskell.org |
| Stability | unstable |
| Portability | non-portable |
| Safe Haskell | None |
| Language | Haskell2010 |
Data.ByteString.Internal
Description
A module containing semi-public ByteString internals. This exposes the
ByteString representation and low level construction functions. As such
all the functions in this module are unsafe. The API is also not stable.
Where possible application should instead use the functions from the normal public interface modules, such as Data.ByteString.Unsafe. Packages that extend the ByteString system at a low level will need to use this module.
Synopsis
- data ByteString where
- BS !(ForeignPtr Word8) !Int
- pattern PS :: ForeignPtr Word8 -> Int -> Int -> ByteString
- type StrictByteString = ByteString
- findIndexOrLength :: (Word8 -> Bool) -> ByteString -> Int
- packBytes :: [Word8] -> ByteString
- packUptoLenBytes :: Int -> [Word8] -> (ByteString, [Word8])
- unsafePackLenBytes :: Int -> [Word8] -> ByteString
- packChars :: [Char] -> ByteString
- packUptoLenChars :: Int -> [Char] -> (ByteString, [Char])
- unsafePackLenChars :: Int -> [Char] -> ByteString
- unpackBytes :: ByteString -> [Word8]
- unpackAppendBytesLazy :: ByteString -> [Word8] -> [Word8]
- unpackAppendBytesStrict :: ByteString -> [Word8] -> [Word8]
- unpackChars :: ByteString -> [Char]
- unpackAppendCharsLazy :: ByteString -> [Char] -> [Char]
- unpackAppendCharsStrict :: ByteString -> [Char] -> [Char]
- unsafePackAddress :: Addr# -> IO ByteString
- unsafePackLenAddress :: Int -> Addr# -> IO ByteString
- unsafePackLiteral :: Addr# -> ByteString
- unsafePackLenLiteral :: Int -> Addr# -> ByteString
- empty :: ByteString
- create :: Int -> (Ptr Word8 -> IO ()) -> IO ByteString
- createUptoN :: Int -> (Ptr Word8 -> IO Int) -> IO ByteString
- createUptoN' :: Int -> (Ptr Word8 -> IO (Int, a)) -> IO (ByteString, a)
- createAndTrim :: Int -> (Ptr Word8 -> IO Int) -> IO ByteString
- createAndTrim' :: Int -> (Ptr Word8 -> IO (Int, Int, a)) -> IO (ByteString, a)
- unsafeCreate :: Int -> (Ptr Word8 -> IO ()) -> ByteString
- unsafeCreateUptoN :: Int -> (Ptr Word8 -> IO Int) -> ByteString
- unsafeCreateUptoN' :: Int -> (Ptr Word8 -> IO (Int, a)) -> (ByteString, a)
- mallocByteString :: Int -> IO (ForeignPtr a)
- mkDeferredByteString :: ForeignPtr Word8 -> Int -> IO ByteString
- fromForeignPtr :: ForeignPtr Word8 -> Int -> Int -> ByteString
- toForeignPtr :: ByteString -> (ForeignPtr Word8, Int, Int)
- fromForeignPtr0 :: ForeignPtr Word8 -> Int -> ByteString
- toForeignPtr0 :: ByteString -> (ForeignPtr Word8, Int)
- nullForeignPtr :: ForeignPtr Word8
- deferForeignPtrAvailability :: ForeignPtr a -> IO (ForeignPtr a)
- checkedAdd :: String -> Int -> Int -> Int
- c_strlen :: CString -> IO CSize
- c_free_finalizer :: FunPtr (Ptr Word8 -> IO ())
- memchr :: Ptr Word8 -> Word8 -> CSize -> IO (Ptr Word8)
- memcmp :: Ptr Word8 -> Ptr Word8 -> Int -> IO CInt
- memcpy :: Ptr Word8 -> Ptr Word8 -> Int -> IO ()
- memset :: Ptr Word8 -> Word8 -> CSize -> IO (Ptr Word8)
- c_reverse :: Ptr Word8 -> Ptr Word8 -> CSize -> IO ()
- c_intersperse :: Ptr Word8 -> Ptr Word8 -> CSize -> Word8 -> IO ()
- c_maximum :: Ptr Word8 -> CSize -> IO Word8
- c_minimum :: Ptr Word8 -> CSize -> IO Word8
- c_count :: Ptr Word8 -> CSize -> Word8 -> IO CSize
- c_sort :: Ptr Word8 -> CSize -> IO ()
- w2c :: Word8 -> Char
- c2w :: Char -> Word8
- isSpaceWord8 :: Word8 -> Bool
- isSpaceChar8 :: Char -> Bool
- accursedUnutterablePerformIO :: IO a -> a
- plusForeignPtr :: ForeignPtr a -> Int -> ForeignPtr b
- unsafeWithForeignPtr :: ForeignPtr a -> (Ptr a -> IO b) -> IO b
The ByteString type and representation
data ByteString Source #
A space-efficient representation of a Word8 vector, supporting many
efficient operations.
A ByteString contains 8-bit bytes, or by using the operations from
Data.ByteString.Char8 it can be interpreted as containing 8-bit
characters.
Constructors
| BS !(ForeignPtr Word8) !Int | Since: bytestring-0.11.0.0 |
Bundled Patterns
| pattern PS :: ForeignPtr Word8 -> Int -> Int -> ByteString |
This pattern is used to emulate the legacy Note: Matching with this constructor will always be given a 0 offset,
as the base will be manipulated by |
Instances
type StrictByteString = ByteString Source #
Type synonym for the strict flavour of ByteString.
Since: bytestring-0.11.2.0
Internal indexing
findIndexOrLength :: (Word8 -> Bool) -> ByteString -> Int Source #
findIndexOrLength is a variant of findIndex, that returns the length
of the string if no element is found, rather than Nothing.
Conversion with lists: packing and unpacking
packBytes :: [Word8] -> ByteString Source #
packUptoLenBytes :: Int -> [Word8] -> (ByteString, [Word8]) Source #
unsafePackLenBytes :: Int -> [Word8] -> ByteString Source #
packChars :: [Char] -> ByteString Source #
packUptoLenChars :: Int -> [Char] -> (ByteString, [Char]) Source #
unsafePackLenChars :: Int -> [Char] -> ByteString Source #
unpackBytes :: ByteString -> [Word8] Source #
unpackAppendBytesLazy :: ByteString -> [Word8] -> [Word8] Source #
unpackAppendBytesStrict :: ByteString -> [Word8] -> [Word8] Source #
unpackChars :: ByteString -> [Char] Source #
unpackAppendCharsLazy :: ByteString -> [Char] -> [Char] Source #
unpackAppendCharsStrict :: ByteString -> [Char] -> [Char] Source #
unsafePackAddress :: Addr# -> IO ByteString Source #
O(n) Pack a null-terminated sequence of bytes, pointed to by an
Addr# (an arbitrary machine address assumed to point outside the
garbage-collected heap) into a ByteString. A much faster way to
create an Addr# is with an unboxed string literal, than to pack a
boxed string. A unboxed string literal is compiled to a static char
[] by GHC. Establishing the length of the string requires a call to
strlen(3), so the Addr# must point to a null-terminated buffer (as
is the case with "string"# literals in GHC). Use unsafePackAddressLen
if you know the length of the string statically.
An example:
literalFS = unsafePackAddress "literal"#
This function is unsafe. If you modify the buffer pointed to by the
original Addr# this modification will be reflected in the resulting
ByteString, breaking referential transparency.
Note this also won't work if your Addr# has embedded '\0' characters in
the string, as strlen will return too short a length.
unsafePackLenAddress :: Int -> Addr# -> IO ByteString Source #
See unsafePackAddress. This function is similar,
but takes an additional length argument rather then computing
it with strlen.
Therefore embedding '\0' characters is possible.
Since: bytestring-0.11.2.0
unsafePackLiteral :: Addr# -> ByteString Source #
See unsafePackAddress. This function has similar behavior. Prefer
this function when the address in known to be an Addr# literal. In
that context, there is no need for the sequencing guarantees that IO
provides. On GHC 9.0 and up, this function uses the FinalPtr data
constructor for ForeignPtrContents.
Since: bytestring-0.11.1.0
unsafePackLenLiteral :: Int -> Addr# -> ByteString Source #
See unsafePackLiteral. This function is similar,
but takes an additional length argument rather then computing
it with strlen.
Therefore embedding '\0' characters is possible.
Since: bytestring-0.11.2.0
Low level imperative construction
empty :: ByteString Source #
O(1) The empty ByteString
create :: Int -> (Ptr Word8 -> IO ()) -> IO ByteString Source #
Create ByteString of size l and use action f to fill its contents.
createUptoN :: Int -> (Ptr Word8 -> IO Int) -> IO ByteString Source #
Given a maximum size l and an action f that fills the ByteString
starting at the given Ptr and returns the actual utilized length,
createUptoN' l fByteString.
createUptoN' :: Int -> (Ptr Word8 -> IO (Int, a)) -> IO (ByteString, a) Source #
Like createUptoN, but also returns an additional value created by the
action.
Since: bytestring-0.10.12.0
createAndTrim :: Int -> (Ptr Word8 -> IO Int) -> IO ByteString Source #
Given the maximum size needed and a function to make the contents
of a ByteString, createAndTrim makes the ByteString. The generating
function is required to return the actual final size (<= the maximum
size), and the resulting byte array is reallocated to this size.
createAndTrim is the main mechanism for creating custom, efficient ByteString functions, using Haskell or C functions to fill the space.
unsafeCreate :: Int -> (Ptr Word8 -> IO ()) -> ByteString Source #
A way of creating ByteStrings outside the IO monad. The Int
argument gives the final size of the ByteString.
unsafeCreateUptoN :: Int -> (Ptr Word8 -> IO Int) -> ByteString Source #
Like unsafeCreate but instead of giving the final size of the
ByteString, it is just an upper bound. The inner action returns
the actual size. Unlike createAndTrim the ByteString is not
reallocated if the final size is less than the estimated size.
unsafeCreateUptoN' :: Int -> (Ptr Word8 -> IO (Int, a)) -> (ByteString, a) Source #
Since: bytestring-0.10.12.0
mallocByteString :: Int -> IO (ForeignPtr a) Source #
Wrapper of mallocForeignPtrBytes with faster implementation for GHC
Conversion to and from ForeignPtrs
mkDeferredByteString :: ForeignPtr Word8 -> Int -> IO ByteString Source #
Variant of fromForeignPtr0 that calls deferForeignPtrAvailability
Since: bytestring-0.11.5.0
Arguments
| :: ForeignPtr Word8 | |
| -> Int | Offset |
| -> Int | Length |
| -> ByteString |
O(1) Build a ByteString from a ForeignPtr.
If you do not need the offset parameter then you should be using
unsafePackCStringLen or
unsafePackCStringFinalizer instead.
Arguments
| :: ByteString | |
| -> (ForeignPtr Word8, Int, Int) | (ptr, offset, length) |
O(1) Deconstruct a ForeignPtr from a ByteString
Arguments
| :: ForeignPtr Word8 | |
| -> Int | Length |
| -> ByteString |
Since: bytestring-0.11.0.0
Arguments
| :: ByteString | |
| -> (ForeignPtr Word8, Int) | (ptr, length) |
O(1) Deconstruct a ForeignPtr from a ByteString
Since: bytestring-0.11.0.0
Utilities
nullForeignPtr :: ForeignPtr Word8 Source #
The 0 pointer. Used to indicate the empty Bytestring.
deferForeignPtrAvailability :: ForeignPtr a -> IO (ForeignPtr a) Source #
Most operations on a ByteString need to read from the buffer
given by its ForeignPtr Word8 field. But since most operations
on ByteString are (nominally) pure, their implementations cannot
see the IO state thread that was used to initialize the contents of
that buffer. This means that under some circumstances, these
buffer-reads may be executed before the writes used to initialize
the buffer are executed, with unpredictable results.
deferForeignPtrAvailability exists to help solve this problem.
At runtime, a call deferForeignPtrAvailability xpure $! x, but the former is more opaque to the simplifier, so
that reads from the pointer in its result cannot be executed until
the deferForeignPtrAvailability x
The opaque bits evaporate during CorePrep, so using
deferForeignPtrAvailability incurs no direct overhead.
Since: bytestring-0.11.5.0
checkedAdd :: String -> Int -> Int -> Int Source #
Add two non-negative numbers. Errors out on overflow. ...
Standard C Functions
memcpy :: Ptr Word8 -> Ptr Word8 -> Int -> IO () Source #
Deprecated: Use Foreign.Marshal.Utils.copyBytes instead
deprecated since bytestring-0.11.5.0
memset :: Ptr Word8 -> Word8 -> CSize -> IO (Ptr Word8) Source #
Deprecated: Use Foreign.Marshal.Utils.fillBytes instead
deprecated since bytestring-0.11.5.0
cbits functions
Chars
isSpaceWord8 :: Word8 -> Bool Source #
Selects words corresponding to white-space characters in the Latin-1 range
isSpaceChar8 :: Char -> Bool Source #
Selects white-space characters in the Latin-1 range
Deprecated and unmentionable
accursedUnutterablePerformIO :: IO a -> a Source #
This "function" has a superficial similarity to unsafePerformIO but
it is in fact a malevolent agent of chaos. It unpicks the seams of reality
(and the IO monad) so that the normal rules no longer apply. It lulls you
into thinking it is reasonable, but when you are not looking it stabs you
in the back and aliases all of your mutable buffers. The carcass of many a
seasoned Haskell programmer lie strewn at its feet.
Witness the trail of destruction:
- https://github.com/haskell/bytestring/commit/71c4b438c675aa360c79d79acc9a491e7bbc26e7
- https://github.com/haskell/bytestring/commit/210c656390ae617d9ee3b8bcff5c88dd17cef8da
- https://github.com/haskell/aeson/commit/720b857e2e0acf2edc4f5512f2b217a89449a89d
- https://ghc.haskell.org/trac/ghc/ticket/3486
- https://ghc.haskell.org/trac/ghc/ticket/3487
- https://ghc.haskell.org/trac/ghc/ticket/7270
- https://gitlab.haskell.org/ghc/ghc/-/issues/22204
Do not talk about "safe"! You do not know what is safe!
Yield not to its blasphemous call! Flee traveller! Flee or you will be corrupted and devoured!
Exported compatibility shim
plusForeignPtr :: ForeignPtr a -> Int -> ForeignPtr b Source #
Advances the given address by the given offset in bytes.
The new ForeignPtr shares the finalizer of the original,
equivalent from a finalization standpoint to just creating another
reference to the original. That is, the finalizer will not be
called before the new ForeignPtr is unreachable, nor will it be
called an additional time due to this call, and the finalizer will
be called with the same address that it would have had this call
not happened, *not* the new address.
Since: base-4.10.0.0
unsafeWithForeignPtr :: ForeignPtr a -> (Ptr a -> IO b) -> IO b Source #
This is similar to withForeignPtr but comes with an important caveat:
the user must guarantee that the continuation does not diverge (e.g. loop or
throw an exception). In exchange for this loss of generality, this function
offers the ability of GHC to optimise more aggressively.
Specifically, applications of the form:
unsafeWithForeignPtr fptr (forever something)
See GHC issue #17760 for more information about the unsoundness behavior that this function can result in.