Re: Can LPeg parse PNG?

["Soni L." <fakedme@...>]

On 10/12/16 12:12 AM, KHMan wrote:
> On 12/10/2016 9:46 AM, Duncan Cross wrote:
> > On Sat, Dec 10, 2016 at 12:10 AM, Soni L. wrote:
> > > I was told PNG is a regular language, in the sense that you can 
> > > validate any
> > > PNG chunk with a VERY VERY VERY LONG regex.
> >
> > Including the 32-bit CRC at the end of the chunk? That's got to be a
> > hell of a regex.
>
> I'm really curious about the "I was told PNG is a regular language" 
> though. It directs the blame for the idea on an anonymous someone else.
>
> Perhaps he has VERY VERY VERY LARGE amounts of free time this weekend, 
> or perhaps he wants to trap some unsuspecting folks trying it. I think 
> both.

Each PNG chunk is a finite sequence of bytes. Thus, a long enough regex 
can parse a stream of PNG chunks.

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