Data.ByteString.Internal

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.

PS foreignPtr offset length represents a ByteString with data backed by a given foreignPtr, starting at a given offset in bytes and of a specified length.

This pattern is used to emulate the legacy ByteString data constructor, so that pre-existing code generally doesn't need to change to benefit from the simplified BS constructor and can continue to function unchanged.

Note: Matching with this constructor will always be given a 0 offset, as the base will be manipulated by plusForeignPtr instead.

Type synonym for the strict flavour of ByteString.

findIndexOrLength is a variant of findIndex, that returns the length of the string if no element is found, rather than Nothing.

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.

See unsafePackAddress. This function is similar, but takes an additional length argument rather then computing it with strlen. Therefore embedding '\0' characters is possible.

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.

See unsafePackLiteral. This function is similar, but takes an additional length argument rather then computing it with strlen. Therefore embedding '\0' characters is possible.

O(1) The empty ByteString

Create ByteString of size l and use action f to fill its contents.

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 f returns the filled ByteString.

Like createUptoN, but also returns an additional value created by the action.

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.

A way of creating ByteStrings outside the IO monad. The Int argument gives the final size of the ByteString.

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.

Wrapper of mallocForeignPtrBytes with faster implementation for GHC

Variant of fromForeignPtr0 that calls deferForeignPtrAvailability

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.

O(1) Deconstruct a ForeignPtr from a ByteString

O(1) Deconstruct a ForeignPtr from a ByteString

The 0 pointer. Used to indicate the empty Bytestring.

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 x is equivalent to pure $! 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 call is complete.

The opaque bits evaporate during CorePrep, so using deferForeignPtrAvailability incurs no direct overhead.

The type of exception raised by overflowError and on failure by overflow-checked arithmetic operations.

Raises a SizeOverflowException, with a message using the given function name.

Add two non-negative numbers. Calls overflowError on overflow.

Multiplies two non-negative numbers. Calls overflowError on overflow.

deprecated since bytestring-0.11.5.0

deprecated since bytestring-0.11.5.0

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

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 ByteString construction.

Selects words corresponding to white-space characters in the Latin-1 range

Selects white-space characters in the Latin-1 range

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!

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.

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.