Hi.
I'm pleased to announce the availability of my random-stream package.
The cabalized package is available at:
http://haskell.mperillo.ath.cx/random-stream-0.0.1.tar.gz
Note that I have not uploaded it on Hackage, and I do not plan to upload
it in the near future, at least until I will repute the package mature
enough.
From package description:
Portable interface for the operating system source of pseudo
random data.
Supported sources are Unix /dev/urandom, Win32 CryptGenRandom and
OpenSSL pseudo random numbers generator.
This package is based on idea from os.urandom implementation, in
CPython.
The idea is to view the system pseudo random generator as a stream of
infinite random bytes.
So, I have used a lazy bytestring, and
unsafePerformIO/unsafeInterleaveIO.
The underlying data is:
newtype Stream = Stream L.ByteString
and the constructor *is exposed*.
The package configuration *must* be done using a flag to specify the
"source" to use.
As an example:
runghc Setup.hs configure -O2 -fHAVE_URANDOM
runghc Setup.hs configure -O2 -fHAVE_SSL
runghc Setup.hs configure -O2 -fHAVE_WIN32_CRYPT
If the flag is not specified, the compilation will fail.
Note that Windows it not yet supported.
The stream generator implements tha RandomGen interface.
Some notes:
1) The system *pseudo* random generator is used.
As an example, on Linux, /dev/random produces "true" random numbers,
but it may block if there is not enough entropy in the system.
More details on
http://en.wikipedia.org/wiki//dev/random
2) When reading data, the lazy bytestring chunk size is used.
The default chunk size, however, is fine when reading from a regular
file, but may not be the best choice when reading pseudo random
numbers.
For SSL (and Windows) support, the chunk size can be easily changed;
but for Unix support this seems to not be possible, unless I
reimplement hGetContents.
The Data.ByteString.Lazy module have an hGetContentsN function.
Unfortunately it is not exposed.
I find this annoying; is it possible to export the *N functions
from Data.ByteString.Lazy.Internal?
3) I have tested the package on Debian Linux Etch, using GHC 6.8.2.
Feedback will be appreciate.
I not sure about some details.
Usage example:
module Main where
import System.Random
import System.Random.Stream
gen = mkStream
l :: [Int]
l = randoms gen :: [Int]
main = do
print l
Manlio Perillo
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