100 lines
6.1 KiB
Zig
100 lines
6.1 KiB
Zig
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const std = @import("std");
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const mem = std.mem;
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const primes = [_]u64{
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0xa0761d6478bd642f,
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0xe7037ed1a0b428db,
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0x8ebc6af09c88c6e3,
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0x589965cc75374cc3,
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0x1d8e4e27c47d124f,
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};
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fn read_bytes(comptime bytes: u8, data: []const u8) u64 {
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return mem.readVarInt(u64, data[0..bytes], @import("builtin").endian);
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}
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fn read_8bytes_swapped(data: []const u8) u64 {
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return (read_bytes(4, data) << 32 | read_bytes(4, data[4..]));
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}
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fn mum(a: u64, b: u64) u64 {
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var r: u128 = @intCast(u128, a) * @intCast(u128, b);
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r = (r >> 64) ^ r;
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return @truncate(u64, r);
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}
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fn mix0(a: u64, b: u64, seed: u64) u64 {
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return mum(a ^ seed ^ primes[0], b ^ seed ^ primes[1]);
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}
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fn mix1(a: u64, b: u64, seed: u64) u64 {
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return mum(a ^ seed ^ primes[2], b ^ seed ^ primes[3]);
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}
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pub fn hash(key: []const u8, initial_seed: u64) u64 {
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var seed = initial_seed;
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var i: usize = 0;
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while (i + 32 <= key.len) : (i += 32) {
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seed = mix0(
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read_bytes(8, key[i..]),
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read_bytes(8, key[i + 8 ..]),
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seed,
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) ^ mix1(
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read_bytes(8, key[i + 16 ..]),
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read_bytes(8, key[i + 24 ..]),
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seed,
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);
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}
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const rem_len = @truncate(u5, key.len);
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const rem_key = key[i..];
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seed = switch (rem_len) {
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0 => seed,
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1 => mix0(read_bytes(1, rem_key), primes[4], seed),
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2 => mix0(read_bytes(2, rem_key), primes[4], seed),
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3 => mix0((read_bytes(2, rem_key) << 8) | read_bytes(1, rem_key[2..]), primes[4], seed),
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4 => mix0(read_bytes(4, rem_key), primes[4], seed),
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5 => mix0((read_bytes(4, rem_key) << 8) | read_bytes(1, rem_key[4..]), primes[4], seed),
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6 => mix0((read_bytes(4, rem_key) << 16) | read_bytes(2, rem_key[4..]), primes[4], seed),
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7 => mix0((read_bytes(4, rem_key) << 24) | (read_bytes(2, rem_key[4..]) << 8) | read_bytes(1, rem_key[6..]), primes[4], seed),
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8 => mix0(read_8bytes_swapped(rem_key), primes[4], seed),
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9 => mix0(read_8bytes_swapped(rem_key), read_bytes(1, rem_key[8..]), seed),
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10 => mix0(read_8bytes_swapped(rem_key), read_bytes(2, rem_key[8..]), seed),
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11 => mix0(read_8bytes_swapped(rem_key), (read_bytes(2, rem_key[8..]) << 8) | read_bytes(1, rem_key[10..]), seed),
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12 => mix0(read_8bytes_swapped(rem_key), read_bytes(4, rem_key[8..]), seed),
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13 => mix0(read_8bytes_swapped(rem_key), (read_bytes(4, rem_key[8..]) << 8) | read_bytes(1, rem_key[12..]), seed),
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14 => mix0(read_8bytes_swapped(rem_key), (read_bytes(4, rem_key[8..]) << 16) | read_bytes(2, rem_key[12..]), seed),
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15 => mix0(read_8bytes_swapped(rem_key), (read_bytes(4, rem_key[8..]) << 24) | (read_bytes(2, rem_key[12..]) << 8) | read_bytes(1, rem_key[14..]), seed),
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16 => mix0(read_8bytes_swapped(rem_key), read_8bytes_swapped(rem_key[8..]), seed),
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17 => mix0(read_8bytes_swapped(rem_key), read_8bytes_swapped(rem_key[8..]), seed) ^ mix1(read_bytes(1, rem_key[16..]), primes[4], seed),
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18 => mix0(read_8bytes_swapped(rem_key), read_8bytes_swapped(rem_key[8..]), seed) ^ mix1(read_bytes(2, rem_key[16..]), primes[4], seed),
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19 => mix0(read_8bytes_swapped(rem_key), read_8bytes_swapped(rem_key[8..]), seed) ^ mix1((read_bytes(2, rem_key[16..]) << 8) | read_bytes(1, rem_key[18..]), primes[4], seed),
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20 => mix0(read_8bytes_swapped(rem_key), read_8bytes_swapped(rem_key[8..]), seed) ^ mix1(read_bytes(4, rem_key[16..]), primes[4], seed),
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21 => mix0(read_8bytes_swapped(rem_key), read_8bytes_swapped(rem_key[8..]), seed) ^ mix1((read_bytes(4, rem_key[16..]) << 8) | read_bytes(1, rem_key[20..]), primes[4], seed),
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22 => mix0(read_8bytes_swapped(rem_key), read_8bytes_swapped(rem_key[8..]), seed) ^ mix1((read_bytes(4, rem_key[16..]) << 16) | read_bytes(2, rem_key[20..]), primes[4], seed),
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23 => mix0(read_8bytes_swapped(rem_key), read_8bytes_swapped(rem_key[8..]), seed) ^ mix1((read_bytes(4, rem_key[16..]) << 24) | (read_bytes(2, rem_key[20..]) << 8) | read_bytes(1, rem_key[22..]), primes[4], seed),
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24 => mix0(read_8bytes_swapped(rem_key), read_8bytes_swapped(rem_key[8..]), seed) ^ mix1(read_8bytes_swapped(rem_key[16..]), primes[4], seed),
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25 => mix0(read_8bytes_swapped(rem_key), read_8bytes_swapped(rem_key[8..]), seed) ^ mix1(read_8bytes_swapped(rem_key[16..]), read_bytes(1, rem_key[24..]), seed),
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26 => mix0(read_8bytes_swapped(rem_key), read_8bytes_swapped(rem_key[8..]), seed) ^ mix1(read_8bytes_swapped(rem_key[16..]), read_bytes(2, rem_key[24..]), seed),
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27 => mix0(read_8bytes_swapped(rem_key), read_8bytes_swapped(rem_key[8..]), seed) ^ mix1(read_8bytes_swapped(rem_key[16..]), (read_bytes(2, rem_key[24..]) << 8) | read_bytes(1, rem_key[26..]), seed),
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28 => mix0(read_8bytes_swapped(rem_key), read_8bytes_swapped(rem_key[8..]), seed) ^ mix1(read_8bytes_swapped(rem_key[16..]), read_bytes(4, rem_key[24..]), seed),
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29 => mix0(read_8bytes_swapped(rem_key), read_8bytes_swapped(rem_key[8..]), seed) ^ mix1(read_8bytes_swapped(rem_key[16..]), (read_bytes(4, rem_key[24..]) << 8) | read_bytes(1, rem_key[28..]), seed),
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30 => mix0(read_8bytes_swapped(rem_key), read_8bytes_swapped(rem_key[8..]), seed) ^ mix1(read_8bytes_swapped(rem_key[16..]), (read_bytes(4, rem_key[24..]) << 16) | read_bytes(2, rem_key[28..]), seed),
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31 => mix0(read_8bytes_swapped(rem_key), read_8bytes_swapped(rem_key[8..]), seed) ^ mix1(read_8bytes_swapped(rem_key[16..]), (read_bytes(4, rem_key[24..]) << 24) | (read_bytes(2, rem_key[28..]) << 8) | read_bytes(1, rem_key[30..]), seed),
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};
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return mum(seed ^ key.len, primes[4]);
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}
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test "test vectors" {
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const expectEqual = std.testing.expectEqual;
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expectEqual(hash("", 0), 0x0);
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expectEqual(hash("a", 1), 0xbed235177f41d328);
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expectEqual(hash("abc", 2), 0xbe348debe59b27c3);
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expectEqual(hash("message digest", 3), 0x37320f657213a290);
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expectEqual(hash("abcdefghijklmnopqrstuvwxyz", 4), 0xd0b270e1d8a7019c);
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expectEqual(hash("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789", 5), 0x602a1894d3bbfe7f);
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expectEqual(hash("12345678901234567890123456789012345678901234567890123456789012345678901234567890", 6), 0x829e9c148b75970e);
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}
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