perf: Refactor underlying buffers for branchless access #229
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compact_str/src/repr2/mod.rs
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| // SAFTEY: Our needed_capacity is >= our length, which is <= than MAX_SIZE | ||
| let inline = unsafe { InlineBuffer::new(self.as_str()) }; | ||
| // SAFETY: `InlineBuffer` and `Repr` are the same size | ||
| *self = unsafe { mem::transmute(inline) }; |
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How about implementing impl From<InlineBuffer> for Repr and impl From<HeapBuffer> for Repr so that we don't need these unsafe transmute blocks everywhere?
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For now I'm going to stick with this pattern because I believe it'll be more performant. Otherwise we'll need to call through fn from(...) which would incur a performance penalty
compact_str/src/repr2/mod.rs
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| } | ||
| } else { | ||
| let pointer = &self as *const _ as *const u8; | ||
| let length = core::cmp::min((last_byte.wrapping_sub(LENGTH_MASK)) as usize, MAX_SIZE); |
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I've seen this a couple of time, maybe it can be extracted as a separate function?
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Not a bad idea, I'll do this in a follow up PR
compact_str/src/repr2/mod.rs
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| #[repr(C)] | ||
| pub struct Repr( | ||
| // We have a pointer in the repesentation to properly carry provenance | ||
| *const (), |
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I think it's possible to use ptr::NonNull<u8> here if we modify push_str, extend and etc to ignore null bytes inserted into the string.
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Good thought! For now I'll just keep it *const () but we could change this in the future
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Thanks for the review @NobodyXu! I'll update the PR soon with the feedback :) |
ParkMyCar
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This PR refactors the underlying
InlineStringandBoxStringstructs in a major way to allow for branch-less string accesses. It also renames these structs toInlineBufferandHeapBuffer, treating these types strictly as "buffers". We also move string operations intoRepr(e.g. pushing and popping), which de-dupes code.