diff options
| author | Nicholas Nethercote <nnethercote@mozilla.com> | 2020-02-07 11:53:07 +1100 |
|---|---|---|
| committer | Nicholas Nethercote <nnethercote@mozilla.com> | 2020-02-21 10:11:35 +1100 |
| commit | 100ff5a25666a1903113ecff0dc63ad84e5bdff7 (patch) | |
| tree | 74c89ca9eef234c4270bcace1c06b18c2134d8d8 /src/libcore/hash | |
| parent | 5e7af4669f80e5f682141f050193ab679afdb4b1 (diff) | |
| download | rust-100ff5a25666a1903113ecff0dc63ad84e5bdff7.tar.gz rust-100ff5a25666a1903113ecff0dc63ad84e5bdff7.zip | |
Revert `u8to64_le` changes from #68914.
`SipHasher128`'s `u8to64_le` function was simplified in #68914. Unfortunately, the new version is slower, because it introduces `memcpy` calls with non-statically-known lengths. This commit reverts the change, and adds an explanatory comment (which is also added to `libcore/hash/sip.rs`). This barely affects `SipHasher128`'s speed because it doesn't use `u8to64_le` much, but it does result in `SipHasher128` once again being consistent with `libcore/hash/sip.rs`.
Diffstat (limited to 'src/libcore/hash')
| -rw-r--r-- | src/libcore/hash/sip.rs | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/src/libcore/hash/sip.rs b/src/libcore/hash/sip.rs index 7ebe01e26dc..c4fbd9dbada 100644 --- a/src/libcore/hash/sip.rs +++ b/src/libcore/hash/sip.rs @@ -121,7 +121,9 @@ macro_rules! load_int_le { }}; } -/// Loads an u64 using up to 7 bytes of a byte slice. +/// Loads a u64 using up to 7 bytes of a byte slice. It looks clumsy but the +/// `copy_nonoverlapping` calls that occur (via `load_int_le!`) all have fixed +/// sizes and avoid calling `memcpy`, which is good for speed. /// /// Unsafe because: unchecked indexing at start..start+len #[inline] |