Add method to check for decoding errors

[tcerqueira]

Feature for #286

• Add check_encoded method to Engine trait.
• Implement feature for all engines.
• Add tests
• Add benchmarks

The tests decode_invalid_trailing_bytes are failing because the error for decoding does not match with check implementation. I don't know if it's necessarily incorrect but it's definitely less useful error compared to the decode implementation. Either way, I think the check should error the same way as decode, for everyone's sanity.

The msrv build fails because of range pattern syntax.

[tcerqueira]

@marshallpierce do you have any suggestion on the best solution to throw the proper error?

[tcerqueira]

Benchamarks show it's slower than decode_slice 🥀

[apasel422]

What's the status of this? I'm interested in the new functionality myself.

[tcerqueira]

@apasel422 Stale. Use decode_slice and ignore what was written to the buffer.

[apasel422]

@apasel422 Stale. Use decode_slice and ignore what was written to the buffer.

Doesn't that require allocating a slice of sufficient size to avoid hitting an error?

[marshallpierce]

Sorry I haven't gotten to this; real life has been demanding.

You could use DecoderReader to read base64, throwing away the decoded output one byte or chunk at a time. If it succeeds to the end, it's valid, without having to have enough space for the whole thing.