4 stable releases
1.0.6 | Feb 24, 2023 |
---|---|
1.0.5 | Feb 23, 2023 |
1.0.4 | Sep 20, 2022 |
1.0.2 |
|
0.1.0 |
|
#83 in #hasher
28 downloads per month
78KB
961 lines
Slice-by-8 do not load the standard library (a.k.a #![no_std]
)
Status
Table of contents
Introduction
Slice-by-8 crate provides function that performs CRC hashing using improved variant of intel's Slice-by-8 algorithm.
The crate provides the slice-by-8 algorithm that take the loopup table to use as parameter if you want to use your own.
The crate also provides the CRC32 (Polynomial 0x04c11db7
) available in slice_by_8::crc32
and the CRC32c (Polynomial 0x1EDC6F41
) in slice_by_8::crc32c
.
CRC32c hash can use CRC32c intrinsics if enabled. You can enable intrinsic version on x86_64
target_arch by enabling sse4.2
target_feature or on aarch64
target_arch by enabling crc
target_feature.
Usage
Using Hasher
use slice_by_8::crc32::CRC32BuildHasher;
use std::collections::HashMap;
const KEY: &str = "hash";
const VALUE: &str = "me!";
// Create a HashMap that use CRC32Hasher to hash keys
let mut map = HashMap::with_hasher(CRC32BuildHasher::default());
map.insert(KEY, VALUE);
assert_eq!(map.get(&KEY), Some(&VALUE));
Using slice-by-8 functions
Slice-by-8 provides functions to hash slice of bytes.
use slice_by_8::crc32c;
const HASH_ME: &[u8] = b"abcdefghijklmnopqrstuvwxyz";
assert_eq!(crc32c::slice_by_8(HASH_ME), 0x9EE6EF25);
Note: slice_by_8
is a similar to slice_by_8_with_seed
with seed
equals 0
.
Using your own lookup table
You own lookup table must be [[u32; 256]; 8]
.
use slice_by_8::slice_by_8;
let my_lookup_table: [[u32; 256]; 8] = slice_by_8::generate_table(slice_by_8::crc32::POLYNOMIAL);
const HASH_ME: &[u8] = b"abcdefghijklmnopqrstuvwxyz";
assert_eq!(slice_by_8(HASH_ME, &my_lookup_table), 0x4C2750BD);
Generate Lookup table
The crate provide generate_table
function to generate a lookup table from a polynomial.
use slice_by_8::generate_table;
use slice_by_8::{crc32, crc32c};
assert_eq!(generate_table(crc32::POLYNOMIAL), crc32::LOOKUP_TABLE);
assert_eq!(generate_table(crc32c::POLYNOMIAL), crc32c::LOOKUP_TABLE);
Performance
Improvement are based on :
No runtime deps
~0–280KB