Hi,

I'm totally confused with all the fixes related to Zip and PNG. If one 
of you can review/approve
summarise this would help.

Stef


>> Anyway, this is stuff from highly esteemed Squeakers, and it seems to
>> have been tested a bit by other people too. And if we can't trust them
>> then... :)
>
> Trust or not - it ain't working correctly ;-( Turns out that the CRC
> validation is broken since a) #pastEndRead may return nil so that the 
> crc
> update is incorrectly applied to the "same bytes" multiple times and 
> b) some
> internal methods quite deliberately set the #position explicitly. What 
> then
> happens is that perfectly valid PNGs will raise crc errors.
>
> So CRC checking needs to be added at a lower level - namely right at 
> the
> place where the data is decoded. The attached CS (which should go 
> after V7)
> addresses these issues.
>
> "Change Set:  ZipCrcTests
> Date:   29 February 2004
> Author:   Andreas Raab
>
> Integrates CRC validation at the level of InflateStream thereby 
> avoiding
> some of the problems when dealing with it in subclasses. With these 
> changes
> CRC validation is implicit - when we hit the end of a stream (such as 
> upon
> #contents, #upToEnd or similar) the CRC will be validated 
> automatically. If
> a missing or wrong crc is encountered a CRCError will be raised. Some 
> tests
> are provided to show what is expected if a missing/wrong CRC is 
> encountered.
> "