[Haskell-cafe] data.binary get reading beyond end of input bytestring?

[Conrad Parker]

On 29 July 2010 19:13, Duncan Coutts <duncan.coutts at googlemail.com> wrote:
> On Thu, 2010-07-29 at 19:01 +0900, Conrad Parker wrote:
>> On 29 July 2010 17:46, Duncan Coutts <duncan.coutts at googlemail.com> wrote:
>> > On 29 July 2010 07:53, Conrad Parker <conrad at metadecks.org> wrote:
>> >
>> >>> Something smells fishy here. I have a hard time believing that binary is
>> >>> reading more input than is available? Could you post more code please?
>> >>
>> >> The issue seems to just be the return value for "bytes consumed" from
>> >> getLazyByteString. Here's a small example.
>> >
>> > http://hackage.haskell.org/packages/archive/binary/0.5.0.2/doc/html/Data-Binary-Get.html#v%3AgetLazyByteString
>> >
>> > getLazyByteString :: Int64 -> Get ByteString
>> > An efficient get method for lazy ByteStrings. Does not fail if fewer
>> > than n bytes are left in the input.
>> >
>> >
>> > Because it does it lazily it cannot check if it's gone past the end of
>> > the input. Arguably this is crazy and the function should not exist.
>>
>> cheers Duncan, that confirms my guess about the reason. Would you
>> accept a patch quoting you on that last point to the comment? ;-)
>
> The consensus plan amongst the binary hackers is to eliminate lazy
> lookahead functions and to rebuild binary on top of a continuation style
> using strict chunks (then with lazy decoding built on top).

I'll take that as a no on the patch.

How would that plan differ from having an iteratee version of
data.binary? ie. something that is easily compatible with
WrappedByteString, as the existing Data.Binary is easily compatible
with Data.ByteString.Lazy?

Conrad.