Support size 0 boxes

[eric]

I was trying to decode some of the sample videos from Apple and found that they rely on the box size of 0 to indicate reading through to the end of the file. Is this something that would be hard to implement?

[tobbee]

I have never seen that used in practice, but it is an old QuickTime heritage, so I suppose there may be some old samples lying around. I'd rather not support it, since there are many other things that have higher priority.

[tobbee]

Regarding the implementation complexity, I think it will hit quite hard to support zero size everywhere.

[tobbee]

@eric I think there can be very strange error cases if we allow box size zero, since it means that all remaining bytes until the end of the file will be "swallowed" by that box. Just allowing a specific box to have size zero is more feasible, but requires a very early test when the header is parsed for all boxes. If there is a super-duper good reason to have a zero-size box, please reopen this or open a new issue for that particular case, and we can discuss if it is worth the effort.