Fix #3 - add in-memory API's.

[finnbear]

Fixes #3, along with the (roughly) minimum cleanup and documentation needed.

I might clean up some other things in a separate PR.

[alvinometric]

Hello,
Thanks for the PR! Any chance you could revert this 1a9d017 ?

I'm not sure how it's related?

[finnbear]

I believe it is essential, because otherwise there is no way to create that struct when writing IPTC metadata from scratch.

I guess, strictly speaking, this is an orthogonal concern to memory vs. filesystem, so I could move it to a separate PR.

[alvinometric]

OK cool, are you sure you need [u8] ? In #3 you're mentioning that you want to read the buffer as Vec<u8>?

[finnbear]

As a matter of idiomatic Rust, the public API should be &[u8] even if I personally have a Vec<u8> because, e.g., someone might have borrowed bytes from a zero-copy deserializer. Passing &mut Vec<_> is fine but &Vec<_> is an anti-pattern. I then had to change it in other places to make the library compile.

[alvinometric]

Great, can you update the issue ? Then we're good

[finnbear]

I'm not entirely sure what you mean, as &[u8] is a standard way of read-only access to data stored in a Vec<u8>, but I edited the issue description to mention &[u8] :)

[alvinometric]

@finnbear Now available in v0.3.0