Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Remove sip::Hasher::short_write. #69471

Merged
merged 1 commit into from
Mar 15, 2020
Merged

Remove sip::Hasher::short_write. #69471

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
53 changes: 7 additions & 46 deletions src/libcore/hash/sip.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -220,37 +220,6 @@ impl<S: Sip> Hasher<S> {
self.state.v3 = self.k1 ^ 0x7465646279746573;
self.ntail = 0;
}

// Specialized write function that is only valid for buffers with len <= 8.
// It's used to force inlining of write_u8 and write_usize, those would normally be inlined
// except for composite types (that includes slices and str hashing because of delimiter).
// Without this extra push the compiler is very reluctant to inline delimiter writes,
// degrading performance substantially for the most common use cases.
#[inline]
fn short_write(&mut self, msg: &[u8]) {
debug_assert!(msg.len() <= 8);
let length = msg.len();
self.length += length;

let needed = 8 - self.ntail;
let fill = cmp::min(length, needed);
if fill == 8 {
self.tail = unsafe { load_int_le!(msg, 0, u64) };
} else {
self.tail |= unsafe { u8to64_le(msg, 0, fill) } << (8 * self.ntail);
if length < needed {
self.ntail += length;
return;
}
}
self.state.v3 ^= self.tail;
S::c_rounds(&mut self.state);
self.state.v0 ^= self.tail;

// Buffered tail is now flushed, process new input.
self.ntail = length - needed;
self.tail = unsafe { u8to64_le(msg, needed, self.ntail) };
}
}

#[stable(feature = "rust1", since = "1.0.0")]
Expand Down Expand Up @@ -280,21 +249,13 @@ impl super::Hasher for SipHasher13 {
}

impl<S: Sip> super::Hasher for Hasher<S> {
// see short_write comment for explanation
#[inline]
fn write_usize(&mut self, i: usize) {
let bytes = unsafe {
crate::slice::from_raw_parts(&i as *const usize as *const u8, mem::size_of::<usize>())
};
self.short_write(bytes);
}

// see short_write comment for explanation
#[inline]
fn write_u8(&mut self, i: u8) {
self.short_write(&[i]);
}

// Note: no integer hashing methods (`write_u*`, `write_i*`) are defined
// for this type. We could add them, copy the `short_write` implementation
// in librustc_data_structures/sip128.rs, and add `write_u*`/`write_i*`
// methods to `SipHasher`, `SipHasher13`, and `DefaultHasher`. This would
// greatly speed up integer hashing by those hashers, at the cost of
// slightly slowing down compile speeds on some benchmarks. See #69152 for
// details.
#[inline]
fn write(&mut self, msg: &[u8]) {
let length = msg.len();
Expand Down