On Fri, Jan 23, 2009 at 08:03:52PM +0000, Duncan Coutts wrote:

On Fri, 2009-01-23 at 15:34 +0100, Henning Thielemann wrote:

...

Is there a way to get the underlying Builder of a 'put' of a Binary instance?

The binary package exposes the Data.Binary.Builder module so you can use the Builder monoid directly. There is no need to go via the Put wrapper.

There is no way to get at the 'current' state of the underlying Builder value. In principle, it could provide the normal writer monad access functions. What is the use case?

I imagine one might want to make a Builder for a composite object, using the Binary instances of some types. And one might want to go the other way too, defining a Binary instance using an existing Builder.

On Thu, Feb 12, 2009 at 07:28:07AM -0800, Don Stewart wrote:

ross:

...

Here's a concrete suggestion: have Data.Binary.Put export the existing function

tell :: Builder -> Put

and also

execPut :: PutM a -> Builder execPut = sndS . unPut

What's the use case?

Quoting a previous message:

I imagine one might want to make a Builder for a composite object, using the Binary instances of some types. And one might want to go the other way too, defining a Binary instance using an existing Builder.

On Thu, Feb 12, 2009 at 07:40:21AM -0800, Don Stewart wrote:

ross:

...

On Thu, Feb 12, 2009 at 07:28:07AM -0800, Don Stewart wrote:

...

ross:

...

Here's a concrete suggestion: have Data.Binary.Put export the existing function

tell :: Builder -> Put

and also

execPut :: PutM a -> Builder execPut = sndS . unPut

What's the use case?

Quoting a previous message:

...

I imagine one might want to make a Builder for a composite object, using the Binary instances of some types. And one might want to go the other way too, defining a Binary instance using an existing Builder.

Sounds good. Do you just want these exposed as is?

Yes, though Antoine's suggestion of exporting tell as putBuilder may be better.

Don Stewart wrote:

OK. I'm preparing the 0.5 release of binary atm, so will expose these.

-- Don

Don: I had proposed (with a patch) to let the caller of runPut give a size hint so the first chunk allocated for the Lazy ByteString would not have to always be the default value (which I remember being about 32 kilo bytes). If the first allocation filled up the subsequent chunks are still the default size. My use case was for the protocol-buffers package where the serialized message sizes are both known in advance and often much much smaller than this. I have no benchmarks, but it feels wrong to have my library constantly over-allocating. Is such a feature going to be accepted into the binary package? If not then I may just copy over and patch the Put monad. (I do not use an external Get monad, the protocol-buffers package includes its own Get monad). Cheers, Chris

ross:

On Thu, Feb 12, 2009 at 07:40:21AM -0800, Don Stewart wrote:

...

ross:

...

On Thu, Feb 12, 2009 at 07:28:07AM -0800, Don Stewart wrote:

...

ross:

...

Here's a concrete suggestion: have Data.Binary.Put export the existing function

tell :: Builder -> Put

and also

execPut :: PutM a -> Builder execPut = sndS . unPut

What's the use case?

Quoting a previous message:

...

I imagine one might want to make a Builder for a composite object, using the Binary instances of some types. And one might want to go the other way too, defining a Binary instance using an existing Builder.

Sounds good. Do you just want these exposed as is?

Yes, though Antoine's suggestion of exporting tell as putBuilder may be better.

Is this what you're looking for? Thu Feb 12 09:47:34 PST 2009 Don Stewart * Expose Builder/Put relationship, courtesy Ross New patches: [Expose Builder/Put relationship, courtesy Ross Don Stewart **20090212174734] { hunk ./src/Data/Binary/Put.hs 22 , PutM(..) , runPut , runPutM + , putBuilder + , execPut -- * Flushing the implicit parse state , flush hunk ./src/Data/Binary/Put.hs 112 tell b = Put $ PairS () b {-# INLINE tell #-} +putBuilder :: Builder -> Put +putBuilder = tell +{-# INLINE putBuilder #-} + +-- | Run the 'Put' monad +execPut :: PutM a -> Builder +execPut = sndS . unPut +{-# INLINE execPut #-} + -- | Run the 'Put' monad with a serialiser runPut :: Put -> L.ByteString runPut = toLazyByteString . sndS . unPut }

On Thu, 12 Feb 2009, Ross Paterson wrote:

Here's a concrete suggestion: have Data.Binary.Put export the existing function

tell :: Builder -> Put

and also

execPut :: PutM a -> Builder execPut = sndS . unPut

This would be nice.