jamie.love:
Hello all,
I'm wondering if anyone has a reference to any binary IO and data conversion tutorials.
A good place to start looking is Data.Binary, http://hackage.haskell.org/cgi-bin/hackage-scripts/package/binary
I'm playing around with generating a BMP file in haskell, and am a little stuck on the "best" way to go about the simple task of creating the BMP header. The header is
"BM" + 4 bytes for file size + 4 bytes reserved + 4 bytes for offset where data begins.
I have the basis starting off at:
bmpHeader = runPut $ [ 0x42, 0x4D ] ++ [0 , 0, 0, 0] ++ [0 , 0, 0, 0] ++ [14 :: Int32]
bmpHeader = runPut $ do put 'B' put 'M' put (0 :: Int32) put (0 :: Int32) put (14 :: Int32) Yields the lazy bytestring, "BM\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\SO"
(where B is Data.ByteString)
I'm wondering how I can:
1/ convert a 32 bit number (Int32, Char32) to 4 Char8 elements
Data.Binary.put (x :: Int32) etc.
2/ rotate bits/bytes in a 32 bit Char32 (or Int32) so they are explicitly little-endian (I work on a mac powerbook, and it is big-endian)
Use the little endian 'put' primitives, putWord32le (fromIntegral (7 :: Int32))
3/ convert an Integer or Int type to an Int32 type
Any pointers or suggestions would be helpful.
fromIntegral Data.Binary should support all this nicely, I hope. -- Don