# bytestring-streaming
This package depends on the [`streaming` library](https://github.com/michaelt/streaming)
copy 200M file divide it on lines,
adding '!' to each
lazy 0m0.813s 0m8.597s
streaming 0m0.783s 0m9.664s
pipes 0m0.771s 0m49.176s
conduit 0m1.068s 2m25.437s
This library is modeled as far as possible on the internal structure of
`Data.ByteString.Lazy`. There are two changes: a chunk may be delayed
by a monadic step, and the sucession of steps has a 'return' value:
data ByteString m r =
Empty r
| Chunk {-#UNPACK #-} !S.ByteString (ByteString m r)
| Go (m (ByteString m r ))
unlike
data ByteString =
Empty
| Chunk {-#UNPACK #-} !S.ByteString ByteString
That's it.
-----
Another module is planned that would correspond more closely to
`Pipes.Bytestring` than to `Data.ByteString.Lazy`.
`Producer ByteString m r` as it is treated in `pipes-bytestring` as
the `ByteString m r` type is here. The result is much faster, at least
with preliminary tests. The modules integrating `attoparsec` and `aeson`
are simple replicas of k0001's `pipes-attoparsec` and `pipes-aeson`.
Also included is a replica of `pipes-http`.
It is possible that `streaming-bytestring` is conceptually clearer than
`pipes-bytestring` as well - and clearer than the approach taken by
`conduit` and `io-streams`. All of these are forced to integrate the
conception of *an amorphous succession of bytes that may be chunked anywhere* -
the direct result of, say, `fromHandle`, `sourceFile` and
the like - and a succession of 'semantically' distinct bytestrings
of interest under a single concept.
----
Strange as it may seem, it is arguable that the general `Producer`,
`Source`, and `InputStream` concepts from these libraries ought not
to hold `ByteString`s *except* as conceptually separate units, e.g.
the lines of a document taken as strict bytestrings, where that is
legitimate. An `InputStream ByteString` is like an `InputStream Int`;
a `Conduit.Source m ByteString` has the same type as a `Source m Int`;
a `Pipes.Producer ByteString m r` has the same type as a `Producer Int m r`.
These types are suited to the general stream transformations these
libraries make possible.
We can see the strangeness in the `io-streams` `lines`
lines :: InputStream ByteString -> IO (InputStream ByteString)
and the `conduit` `linesUnboundedAscii`
linesUnboundedAscii :: (Monad m) => Conduit ByteString m ByteString
(specializing slightly). In either case, what enters on the left will
be a succession of anyhow-chunked bytes; what exits on the right will
be a succession of significant individual things of type `ByteString`.
What we find in `IOStreams.lines` and
`linesUnlimitedAscii` are comparable to what we would have if `bytestring`
defined
lines :: L.ByteString -> [S.ByteString]
or more absurdly
lines :: L.ByteString -> L.ByteString
and exposed methods for inspecting the hitherto secret chunks contained
in lazy bytestrings.
The model employed by the present package is a little different. First,
the primitive `lines` concept is just
lines :: ByteString m r -> Stream (ByteString m) m r
as in `pipes-bytestring`; this corresponds precisely to
lines :: ByteString -> [ByteString]
as it appears in `Data.ByteString.Lazy` -- the elements of the list (stream) are
themselves lazy bytestrings.
But `pipes-bytestring` attempts to *mean* by `Producer ByteString m r`
what we express by `ByteString m r` - the undifferentiated byte stream.
But (we are provisionally suggesting) that isn't what `Producer ByteString m r`
means, and this is part of the reason why `pipes-bytestring` is difficult
for people to grasp. The user frequently proposes to inspect and work
with individual lines with Pipes themselves and thus needs
produceLines :: Producer ByteString m r -> Producer ByteString m r
produceLines = folds B.concat B.empty id . view Pipes.ByteString.lines
Here we would instead write a
produceLines :: ByteString m r -> Stream (Of ByteString) m r
which is transparently related to the type of lines itself
lines :: ByteString m r -> Stream (ByteString m) m r
The distinctive type of `produceLines` clearly express the transition
from the world of amorphously chunked bytestreams to the world of
significant individual values, in this case individual strict bytestrings.