#4144: Exception: ToDo: hGetBuf - when using custom handle infrastructure
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Reporter: AntoineLatter | Owner: joeyadams
Type: bug | Status: new
Priority: normal | Milestone:
Component: libraries/base | Version: 7.6.1
Resolution: | Keywords:
Os: Unknown/Multiple | Architecture: Unknown/Multiple
Failure: Runtime crash | Difficulty:
Testcase: | Blockedby:
Blocking: | Related:
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Changes (by joeyadams):
* owner: => joeyadams
Comment:
I plan to fix this by adding the following methods to BufferedIO:
{{{
readBuffered :: dev -> Buffer Word8 -> Ptr Word8 -> Int -> IO (Int,
Buffer Word8)
readBuffered0 :: dev -> Buffer Word8 -> Ptr Word8 -> Int -> IO (Maybe
Int, Buffer Word8)
writeBuffered :: dev
-> Bool -- ^ If 'True', flush after writing.
-> Buffer Word8
-> Ptr Word8
-> Int
-> IO (Buffer Word8)
writeBuffered0 :: dev
-> Bool -> Buffer Word8 -> Ptr Word8 -> Int
-> IO (Int, Buffer Word8)
}}}
The default implementations will use the fill and flush methods of
BufferedIO, but an instance may provide more efficient substitutes.
RawIO-based methods will be provided, which will go directly to the device
when possible and efficient.
This will move a lot of the complexity of the hGetBuf, hPutBuf, etc.
functions out of GHC.IO.Handle.Text and into GHC.IO.BufferedIO (in the
form of default methods and RawIO drop-ins).
I will be changing the behavior of hGetBufSome slightly: if the buffer is
not empty, it will fetch its contents and return immediately, rather than
trying to squeeze more bytes out of the device with non-blocking fills and
reads. See #5843
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4144#comment:5>
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