feat: Add lazy isolation mode #111
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`ensure` is a publically exported function, which has some odd behaviour when given a byte length of zero or less. It raises an error when the value is zero, but happily returns a value when the byte length is negative. I've switched these two behaviours around. ``` λ> runGet (ensure (-1)) "0123" Right "0123" λ> runGet (isolate 0 getWord8) "0123" Left "too few bytes\nFrom:\tdemandInput\n\n" ``` ``` λ> runGet (ensure (-1)) "0123" Left "Failed reading: Attempted to ensure negative amount of bytes\nEmpty call stack\n" λ> runGet (ensure 0) "0123" Right "" ```
This adds an internal variant, `ensure'`, which is used to avoid checking for `0` and `<0` more than once in a given code path.
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Taking this out of draft mode, because I've got it integrated with |
414owen
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Mar 20, 2024
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@glguy quick ping, because you're the last committer/merger to the repo. It doesn't look like there have been any major updates to |
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@glguy would you be able to take a look at this please? Or do you know of someone who could? |
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@elliottt any chance of a review, or an opinion on this change? I'd really appreciate it. |
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I'll take a week this weekend 👍 |
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This adds a lazy (incremental) isolation combinator.
The use case I have for it is this:
pinch, which decodes thrift messages usingcerealisolates parsing the apparently astronomically huge message hereBy introducing an incremental isolation primitive, users can make sure the data they're parsing is valid before it all hits main memory.
Implementation notes
I tried to make sure the errors were as close as possible between
isolateandisolateLazy. This is useful for fuzzing the implementation with quickcheck, as well as just good practice. This meant I had to expose more of the failure API. I could have added an internal partial runner, which exposes this information, but that seemed like it would require a lot of changes, so I opted for adding the info to the current partial runner, and added a pattern synonym so that users (shouldn't) notice a difference.These changes are stacked on #110