Ptr Word8 to [Word8]

Question

I'm using the library Network.Pcap, and it has the function toBS

toBS :: (PktHdr, Ptr Word8) -> IO (PktHdr, B.ByteString)
toBS (hdr, ptr) = do
    let len = hdrCaptureLength hdr
    s <- B.create (fromIntegral len) $ \p -> B.memcpy p ptr (fromIntegral len)
    return (hdr, s)

Right now I am unpacking the ByteString which gives me the [Word8] I want. I' m looking for a way to avoid having to unpack the ByteString, and get the [Word8] directly.

(1) Does this function exist? (2) If not, could I get some advice on how to proceed?

In the end, do you want some function `g :: IO (PktHdr, B.ByteString) -> IO (PktHdr, [Word8])`? — chepner, Jan 07 '17 at 21:37

score 1 · Accepted Answer · answered Jan 07 '17 at 21:40

1

I'm not familiar with those libraries, but can't you just do this?

import Foreign.Marshal.Array

toByteList :: PktHdr -> Ptr Word8 -> IO [Word8]
toByteList hdr ptr = peekArray (fromIntegral (hdrCaptureLength hdr)) ptr

answered Jan 07 '17 at 21:40

melpomene

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Ptr Word8 to [Word8]

1 Answers1