commit plain_hasher to util
This commit is contained in:
debris
parent
e0c2995f78
commit
752dad6829
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@ -548,7 +548,7 @@ dependencies = [
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"bigint 4.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
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"heapsize 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
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"libc 0.2.21 (registry+https://github.com/rust-lang/crates.io-index)",
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"plain_hasher 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
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"plain_hasher 0.1.0",
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"rand 0.3.14 (registry+https://github.com/rust-lang/crates.io-index)",
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"rustc-hex 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
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]
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@ -2201,9 +2201,8 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
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[[package]]
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name = "plain_hasher"
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version = "0.1.0"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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dependencies = [
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"crunchy 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
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"crunchy 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)",
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]
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[[package]]
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@ -3394,7 +3393,6 @@ dependencies = [
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"checksum phf_generator 0.7.14 (registry+https://github.com/rust-lang/crates.io-index)" = "db005608fd99800c8c74106a7c894cf582055b689aa14a79462cefdcb7dc1cc3"
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"checksum phf_shared 0.7.14 (registry+https://github.com/rust-lang/crates.io-index)" = "fee4d039930e4f45123c9b15976cf93a499847b6483dc09c42ea0ec4940f2aa6"
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"checksum pkg-config 0.3.9 (registry+https://github.com/rust-lang/crates.io-index)" = "3a8b4c6b8165cd1a1cd4b9b120978131389f64bdaf456435caa41e630edba903"
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"checksum plain_hasher 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "83ae80873992f511142c07d0ec6c44de5636628fdb7e204abd655932ea79d995"
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"checksum podio 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)" = "e5422a1ee1bc57cc47ae717b0137314258138f38fd5f3cea083f43a9725383a0"
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"checksum pretty_assertions 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)" = "2412f3332a07c7a2a50168988dcc184f32180a9758ad470390e5f55e089f6b6e"
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"checksum primal 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)" = "0e31b86efadeaeb1235452171a66689682783149a6249ff334a2c5d8218d00a4"
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@ -13,7 +13,7 @@ rustc-hex = "1.0"
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rand = "0.3.12"
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libc = "0.2"
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heapsize = { version = "0.4", optional = true }
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plain_hasher = "0.1"
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plain_hasher = { path = "../plain_hasher" }
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[features]
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x64asm_arithmetic=[]
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@ -0,0 +1,12 @@
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[package]
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name = "plain_hasher"
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description = "Hasher for 32-bit keys."
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version = "0.1.0"
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authors = ["Parity Technologies <admin@parity.io>"]
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license = "MIT"
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keywords = ["hash", "hasher"]
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categories = ["no-std"]
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homepage = "https://github.com/paritytech/plain_hasher"
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[dependencies]
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crunchy = "0.1.6"
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@ -0,0 +1,33 @@
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#![feature(test)]
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extern crate test;
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extern crate plain_hasher;
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use std::hash::Hasher;
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use std::collections::hash_map::DefaultHasher;
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use test::{Bencher, black_box};
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use plain_hasher::PlainHasher;
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#[bench]
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fn write_plain_hasher(b: &mut Bencher) {
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b.iter(|| {
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let n: u8 = black_box(100);
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(0..n).fold(PlainHasher::default(), |mut old, new| {
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let bb = black_box([new; 32]);
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old.write(&bb as &[u8]);
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old
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});
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});
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}
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#[bench]
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fn write_default_hasher(b: &mut Bencher) {
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b.iter(|| {
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let n: u8 = black_box(100);
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(0..n).fold(DefaultHasher::default(), |mut old, new| {
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let bb = black_box([new; 32]);
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old.write(&bb as &[u8]);
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old
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});
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});
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}
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@ -0,0 +1,55 @@
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#![no_std]
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#[macro_use]
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extern crate crunchy;
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use core::{hash, mem};
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/// Hasher that just takes 8 bytes of the provided value.
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/// May only be used for keys which are 32 bytes.
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#[derive(Default)]
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pub struct PlainHasher {
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prefix: u64,
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}
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impl hash::Hasher for PlainHasher {
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#[inline]
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fn finish(&self) -> u64 {
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self.prefix
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}
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#[inline]
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#[allow(unused_assignments)]
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fn write(&mut self, bytes: &[u8]) {
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debug_assert!(bytes.len() == 32);
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unsafe {
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let mut bytes_ptr = bytes.as_ptr();
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let prefix_u8: &mut [u8; 8] = mem::transmute(&mut self.prefix);
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let mut prefix_ptr = prefix_u8.as_mut_ptr();
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unroll! {
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for _i in 0..8 {
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*prefix_ptr ^= (*bytes_ptr ^ *bytes_ptr.offset(8)) ^ (*bytes_ptr.offset(16) ^ *bytes_ptr.offset(24));
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bytes_ptr = bytes_ptr.offset(1);
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prefix_ptr = prefix_ptr.offset(1);
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}
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}
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}
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}
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}
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#[cfg(test)]
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mod tests {
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use core::hash::Hasher;
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use super::PlainHasher;
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#[test]
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fn it_works() {
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let mut bytes = [32u8; 32];
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bytes[0] = 15;
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let mut hasher = PlainHasher::default();
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hasher.write(&bytes);
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assert_eq!(hasher.prefix, 47);
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}
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}
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