Avoid extraneous call to remaining in get_u8/i8 #490
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I have a chained datastructure that can dereference into a slice quite fast, but remaining requires walking the chain, which is relatively slow. I would hazard a guess that this is the more common perf characteristic of non-contiguous impls of Buf. Separately, this brings these impls in line with all the other get_ impls, which have a fast path with [u8].get(...), which does the same bounds check that I do in this patch I think clippy will say to use non_empty, here, I think in this case this is more clear, but I will do whatever is preferred.
seanmonstar
reviewed
Mar 5, 2021
| @@ -285,7 +286,7 @@ pub trait Buf { | |||
| /// | |||
| /// This function panics if there is no more remaining data in `self`. | |||
| fn get_u8(&mut self) -> u8 { | |||
| assert!(self.remaining() >= 1); | |||
| assert!(self.chunk().len() >= 1); | |||
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I mean, the index bounds check happens just after this, I must assume these asserts are mostly to give a better panic message. Perhaps we could just make them debug_asserts?
@carllerche you added these asserts originally, I think?
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I have a chained datastructure that can dereference into a slice quite fast, but remaining requires walking the chain, which is relatively slow.
I would hazard a guess that this is the more common perf characteristic of non-contiguous impls of Buf.
Separately, this brings these impls in line with all the other get_ impls, which have a fast path with [u8].get(...), which does the same bounds check that I do in this patch
I think clippy will say to use non_empty, here, I think in this case this is more clear, but I will do whatever is preferred.