#9447: Add support for resizing `MutableByteArray#`s -------------------------------------+------------------------------------- Reporter: hvr | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.2 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: | Differential Revisions: Phab:D133 -------------------------------------+------------------------------------- This is motivated by #9281 which changes how memory is allocated, and gives rise to the need to be able to efficiently shrink or grow `MutableByteArray#`s before they're frozen into `ByteArray#` while retaining their original byte content to avoid a major bottle-neck. This ticket is for tracking/documenting all changes related to this new facility. Here's the current road-map: 1. Implement {{{#!hs shrinkMutableByteArray# :: MutableByteArray# s -> Int# -> State# s -> State# s resizeMutableByteArray# :: MutableByteArray# s -> Int# -> State# s -> (# State# s, MutableByteArray# s #) }}} (see Phab:D133) 2. As suggested by Johan, {{{#!hs getSizeofMutableByteArray# :: MutableByteArray# s -> State# s -> (# State# s Int# #) }}} This is similar in spirit to `numCapabilities` and `getNumCapabilities`. Add a deprecate pragma (or equivalent) for `sizeofMutableByteArray#`. Add a note to `sizeofMutableByteArray#` stating that it's unsafe in the presence of calls to resize-operations on the same MBA. 3. Submit patches to upstream libraries replacing calls to `sizeofMutableByteArray#` with `getSizeofMutableByteArray#` 4. Investigate how to provide in-place (zero-copy) growing of MBAs (step 1. only implements in-place shrinking). -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9447 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler