On Sat, Jan 7, 2012 at 8:06 AM, Greg Weber wrote:

I am wondering if you can provide even higher-level APIs for the common case:

hash <- runResourceT $ hashFile "my-file"

and possibly something that runs the ResourceT transformer:

hash <- runHashFile "my-file"

That's dead simple to add, I just wonder which ones should be added (since triplicating the whole API wouldn't be fun). So you're assuming that hashing is the most common case of the library, right? Now, having 'hashFile' inside ResourceT isn't terribly useful and if the user needs it, it's trivial to implement, so I'm thinking of just exporting a single new function: hashFile :: (MonadIO m, Hash ctx d) => FilePath -> m d I'll include it on the next version. =) Cheers, -- Felipe.

On Sat, Jan 7, 2012 at 9:12 AM, Aristid Breitkreuz wrote:

And while we're at it, some code to deal with the cumbersome decoding of those hash objects would be nice!

I'm sorry, but what do you mean by "cumbersome decoding"? Cheers, =) -- Felipe.

On Sat, Jan 7, 2012 at 12:16 PM, Aristid Breitkreuz wrote:

Well, how do you get a ByteString from the hash object?

Just use encode from Data.Serialize. =) Cheers, -- Felipe.

On Sat, Jan 7, 2012 at 8:45 PM, Grant wrote:

So I want to take the sha-1 of the file contents prefixed with a string containing the file size (similar to how git hashes files). Is there a nice way to compose this without having to create two sources against the same file?

Thanks, Grant

I can think of three approaches that should work: 1. Create a Sink which "forks" its input to two other Sinks (similar to &&& for Arrow). It would have a type signature like: Sink a m b -> Sink a m c -> Sink a m (b, c) 2. Create a specialized Sink that will wrap a single sink and add the byte count of the input stream, eg: Sink ByteString m a -> Sink ByteString m (Int, a) 3. Use a Conduit that will simply update some mutable variable. I think (1) is the most generally useful, though (3) would be the easiest to put together. If you want help implementing any of these approaches, let me know. Michael

On Sat, Jan 7, 2012 at 10:04 PM, Grant wrote:

Thanks for getting back to me so fast!  Actually, I need to include a string with the file length plus the file stream itself and THEN hash that whole thing together. The example below works, but the file is processed twice.

Alternatively, I could create a specialised Source that gets the file size from the handle and then processes the file but that looks ugly. Any ideas?

I think we need the following: openFile :: ResourceIO m :: FilePath -> ResourceT m Handle sourceHandle :: ResourceIO m => Handle -> Source m B.ByteString So you would do something like runResourceT $ do handle <- CB.openFile fp fileSize <- liftIO $ hFileSize handle let source = CL.sourceList [encodeFileSize fileSize] `mappend` CB.sourceHandle handle source $$ sinkHash Cheers! -- Felipe.

On Sun, Jan 8, 2012 at 2:39 AM, Felipe Almeida Lessa wrote:

On Sat, Jan 7, 2012 at 10:04 PM, Grant wrote:

...

Thanks for getting back to me so fast!  Actually, I need to include a string with the file length plus the file stream itself and THEN hash that whole thing together. The example below works, but the file is processed twice.

Alternatively, I could create a specialised Source that gets the file size from the handle and then processes the file but that looks ugly. Any ideas?

I think we need the following:

 openFile :: ResourceIO m :: FilePath -> ResourceT m Handle  sourceHandle :: ResourceIO m => Handle -> Source m B.ByteString

So you would do something like

 runResourceT $ do    handle <- CB.openFile fp    fileSize <- liftIO $ hFileSize handle    let source = CL.sourceList [encodeFileSize fileSize]                 `mappend` CB.sourceHandle handle    source $$ sinkHash

Cheers!

-- Felipe.

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I've added openFile, sourceHandle and sinkHandle on Git[1]. Grant: does that give you enough to solve the issues you were facing? Michael [1] https://github.com/snoyberg/conduit/blob/master/conduit/Data/Conduit/Binary....