Better API

[bovee]

Rather than the callback-style we have now, it would be nice to write something like:

let processor = NeedletailFile::new("test.fasta");
assert_eq!(processor.file_type, NeedletailTypes::FASTA);
assert_eq!(processor.compression_type, NeedletailCompressionTypes::None);

while let record = processor.next()? {
   ...
}

The major issues with this are keeping the state of the iterator and the underlying buffer synced up (Rust's streaming iterator problem; this is also why we can't use for record in ...) and more importantly, the polymorphic nature of record (is it a FASTA? FASTQ? maybe we can do something clever with Into here to allow the processor to spit out a SeqRecord?). I've never been a huge fan of the callbacks and with the big v0.2.0 rewrite I think we're closer to having a decent solution here, but there's still a bit of type-fu necessary to make it work.

[boydgreenfield]

@bovee It'd also be nice to have a function for evaluating a NeedletailFile as a stream of bytes and records (or maybe just the former and a method for conversion). Then you could trivially do a few nice things like compute rolling md5/sha256 checksums, etc. Thoughts?

[bovee]

Yeah, that's a really good idea. It's a bit more complicated, but we should split the compression stuff off into it's own transparent Read + Seek -> Read handler and then you could write a "middleware" to do rolling checksums on either the input or output from that.