Simplify and encapsulate ReadDecoder implementation
#523
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Before this commit calling `Reader.finish` a 2nd time would return a random, accidental error (`UnexpectedEof`), because of how `StreamingDecoder`'s `state` is set after processing the `IEND` chunk. After this commit, `Reader.finish` will handle this condition explicitly, in a similar same way to how `next_frame` handles being called when we have already consumed all the frames.
After a recent commit, all public APIs of a `Reader` take care of not going beyond the `IEND` chunk and returning `PolledAfterEndOfImage` instead. This means that tracking `at_eof` at the level of `ReadDecoder` is obsolete and leads to unnecessary complexity. This commit refactors away this complexity.
`ReadDecoder::finish_decoding` now reuses `decode_next` instead of duplicating some of its code. Some duplication (e.g. handling of `Decoded::Nothing` remains - this will be taken care of in a subsequent commit).
This commit means that `decode_next` can be a private method of `ReadDecoder` (this is not enforced yet, before a subsequent commit moves `ReadDecoder` into a separate `mod`ule).
Before this commit `fn decode_next` would `loop` to skip `Decoded::Nothing` events. This is unnecessary, because all the callers of `decode_next` already account for `Decoded::Nothing` (explicitly or implicitly via a wildcard).
This commit helps to keep some aspects of `ReadDecoder` private (e.g. its fields, `decode_next` methods, etc.). This commit also means that `mod.rs` no longer directly depends on `Decoded` nor `StreamingDecoder`.
anforowicz
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My appologies for the force push above. I've realized that in the last commit (when moving some of the code into the new file) I didn't preserve the comment tweaks that I've made in the earlier commits after a self-review... |
fintelia
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Oct 18, 2024
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BTW, I've redesigned the same bits in the |
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Hello!
This PR isn't strictly necessary for any major feature requests or bug fixes, but I think that this PR is still desirable - I think the resulting encapsulation helps with readability of the code.
I hope that splitting this PR into smaller, granular commits helps to follow along and review the changes.
PTAL?