Fix inflate_fast_help loop bound
#260
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folkertdev
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bjorn3
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Dec 10, 2024
| @@ -77,6 +77,11 @@ impl<'a> BitReader<'a> { | |||
| self.end as usize - self.ptr as usize | |||
| } | |||
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| #[inline(always)] | |||
| pub fn bytes_remaining_including_buffer(&self) -> usize { | |||
| (self.end as usize - self.ptr as usize) + (self.bits_used as usize >> 3) | |||
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Using / 8 instead of >> 3 may be a bit clearer and will optimize to the same assembly.
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we can make a pass over the repo at some point. I think zlib-ng never updated this, and the original zlib that it forked was written at a time when apparently that optimization was not (effectively) guaranteed.
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When you finally spot the thing... 🤦 we are now faster than zlib-ng for all chunk sizes.
It's only a marginal improvement for chunk size 2**4, but quite significant for what are probably the most common chunk sizes (very small chunk sizes likely indicate io-bound operation).
After fixing the bug of exiting the loop too early (first commit), I then made the bound a bit more accurate, and finally refactored the output type of
len_and_friends. The final commit has no performance impact.