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const std = @import("std");
const mem = std.mem;
const primes = [_]u64{
0xa0761d6478bd642f,
0xe7037ed1a0b428db,
0x8ebc6af09c88c6e3,
0x589965cc75374cc3,
0x1d8e4e27c47d124f,
};
fn read_bytes(comptime bytes: u8, data: []const u8) u64 {
const T = std.meta.Int(.unsigned, 8 * bytes);
return mem.readIntLittle(T, data[0..bytes]);
}
fn read_8bytes_swapped(data: []const u8) u64 {
return (read_bytes(4, data) << 32 | read_bytes(4, data[4..]));
}
fn mum(a: u64, b: u64) u64 {
var r = std.math.mulWide(u64, a, b);
r = (r >> 64) ^ r;
return @truncate(u64, r);
}
fn mix0(a: u64, b: u64, seed: u64) u64 {
return mum(a ^ seed ^ primes[0], b ^ seed ^ primes[1]);
}
fn mix1(a: u64, b: u64, seed: u64) u64 {
return mum(a ^ seed ^ primes[2], b ^ seed ^ primes[3]);
}
// Wyhash version which does not store internal state for handling partial buffers.
// This is needed so that we can maximize the speed for the short key case, which will
// use the non-iterative api which the public Wyhash exposes.
const WyhashStateless = struct {
seed: u64,
msg_len: usize,
pub fn init(seed: u64) WyhashStateless {
return WyhashStateless{
.seed = seed,
.msg_len = 0,
};
}
fn round(self: *WyhashStateless, b: []const u8) void {
std.debug.assert(b.len == 32);
self.seed = mix0(
read_bytes(8, b[0..]),
read_bytes(8, b[8..]),
self.seed,
) ^ mix1(
read_bytes(8, b[16..]),
read_bytes(8, b[24..]),
self.seed,
);
}
pub fn update(self: *WyhashStateless, b: []const u8) void {
std.debug.assert(b.len % 32 == 0);
var off: usize = 0;
while (off < b.len) : (off += 32) {
@call(.always_inline, self.round, .{b[off .. off + 32]});
}
self.msg_len += b.len;
}
pub fn final(self: *WyhashStateless, b: []const u8) u64 {
std.debug.assert(b.len < 32);
const seed = self.seed;
const rem_len = @intCast(u5, b.len);
const rem_key = b[0..rem_len];
self.seed = switch (rem_len) {
0 => seed,
1 => mix0(read_bytes(1, rem_key), primes[4], seed),
2 => mix0(read_bytes(2, rem_key), primes[4], seed),
3 => mix0((read_bytes(2, rem_key) << 8) | read_bytes(1, rem_key[2..]), primes[4], seed),
4 => mix0(read_bytes(4, rem_key), primes[4], seed),
5 => mix0((read_bytes(4, rem_key) << 8) | read_bytes(1, rem_key[4..]), primes[4], seed),
6 => mix0((read_bytes(4, rem_key) << 16) | read_bytes(2, rem_key[4..]), primes[4], seed),
7 => mix0((read_bytes(4, rem_key) << 24) | (read_bytes(2, rem_key[4..]) << 8) | read_bytes(1, rem_key[6..]), primes[4], seed),
8 => mix0(read_8bytes_swapped(rem_key), primes[4], seed),
9 => mix0(read_8bytes_swapped(rem_key), read_bytes(1, rem_key[8..]), seed),
10 => mix0(read_8bytes_swapped(rem_key), read_bytes(2, rem_key[8..]), seed),
11 => mix0(read_8bytes_swapped(rem_key), (read_bytes(2, rem_key[8..]) << 8) | read_bytes(1, rem_key[10..]), seed),
12 => mix0(read_8bytes_swapped(rem_key), read_bytes(4, rem_key[8..]), seed),
13 => mix0(read_8bytes_swapped(rem_key), (read_bytes(4, rem_key[8..]) << 8) | read_bytes(1, rem_key[12..]), seed),
14 => mix0(read_8bytes_swapped(rem_key), (read_bytes(4, rem_key[8..]) << 16) | read_bytes(2, rem_key[12..]), seed),
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),
16 => mix0(read_8bytes_swapped(rem_key), read_8bytes_swapped(rem_key[8..]), seed),
17 => mix0(read_8bytes_swapped(rem_key), read_8bytes_swapped(rem_key[8..]), seed) ^ mix1(read_bytes(1, rem_key[16..]), primes[4], seed),
18 => mix0(read_8bytes_swapped(rem_key), read_8bytes_swapped(rem_key[8..]), seed) ^ mix1(read_bytes(2, rem_key[16..]), primes[4], seed),
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),
20 => mix0(read_8bytes_swapped(rem_key), read_8bytes_swapped(rem_key[8..]), seed) ^ mix1(read_bytes(4, rem_key[16..]), primes[4], seed),
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),
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),
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),
24 => mix0(read_8bytes_swapped(rem_key), read_8bytes_swapped(rem_key[8..]), seed) ^ mix1(read_8bytes_swapped(rem_key[16..]), primes[4], seed),
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),
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),
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),
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),
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),
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),
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),
};
self.msg_len += b.len;
return mum(self.seed ^ self.msg_len, primes[4]);
}
pub fn hash(seed: u64, input: []const u8) u64 {
const aligned_len = input.len - (input.len % 32);
var c = WyhashStateless.init(seed);
@call(.always_inline, c.update, .{input[0..aligned_len]});
return @call(.always_inline, c.final, .{input[aligned_len..]});
}
};
/// Fast non-cryptographic 64bit hash function.
/// See https://github.com/wangyi-fudan/wyhash
pub const Wyhash = struct {
state: WyhashStateless,
buf: [32]u8,
buf_len: usize,
pub fn init(seed: u64) Wyhash {
return Wyhash{
.state = WyhashStateless.init(seed),
.buf = undefined,
.buf_len = 0,
};
}
pub fn update(self: *Wyhash, b: []const u8) void {
var off: usize = 0;
if (self.buf_len != 0 and self.buf_len + b.len >= 32) {
off += 32 - self.buf_len;
mem.copy(u8, self.buf[self.buf_len..], b[0..off]);
self.state.update(self.buf[0..]);
self.buf_len = 0;
}
const remain_len = b.len - off;
const aligned_len = remain_len - (remain_len % 32);
self.state.update(b[off .. off + aligned_len]);
mem.copy(u8, self.buf[self.buf_len..], b[off + aligned_len ..]);
self.buf_len += @intCast(u8, b[off + aligned_len ..].len);
}
pub fn final(self: *Wyhash) u64 {
const rem_key = self.buf[0..self.buf_len];
return self.state.final(rem_key);
}
pub fn hash(seed: u64, input: []const u8) u64 {
return WyhashStateless.hash(seed, input);
}
};
const expectEqual = std.testing.expectEqual;
test "test vectors" {
const hash = Wyhash.hash;
try expectEqual(hash(0, ""), 0x0);
try expectEqual(hash(1, "a"), 0xbed235177f41d328);
try expectEqual(hash(2, "abc"), 0xbe348debe59b27c3);
try expectEqual(hash(3, "message digest"), 0x37320f657213a290);
try expectEqual(hash(4, "abcdefghijklmnopqrstuvwxyz"), 0xd0b270e1d8a7019c);
try expectEqual(hash(5, "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"), 0x602a1894d3bbfe7f);
try expectEqual(hash(6, "12345678901234567890123456789012345678901234567890123456789012345678901234567890"), 0x829e9c148b75970e);
}
test "test vectors streaming" {
var wh = Wyhash.init(5);
for ("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789") |e| {
wh.update(mem.asBytes(&e));
}
try expectEqual(wh.final(), 0x602a1894d3bbfe7f);
const pattern = "1234567890";
const count = 8;
const result = 0x829e9c148b75970e;
try expectEqual(Wyhash.hash(6, pattern ** 8), result);
wh = Wyhash.init(6);
var i: u32 = 0;
while (i < count) : (i += 1) {
wh.update(pattern);
}
try expectEqual(wh.final(), result);
}
test "iterative non-divisible update" {
var buf: [8192]u8 = undefined;
for (&buf, 0..) |*e, i| {
e.* = @truncate(u8, i);
}
const seed = 0x128dad08f;
var end: usize = 32;
while (end < buf.len) : (end += 32) {
const non_iterative_hash = Wyhash.hash(seed, buf[0..end]);
var wy = Wyhash.init(seed);
var i: usize = 0;
while (i < end) : (i += 33) {
wy.update(buf[i..std.math.min(i + 33, end)]);
}
const iterative_hash = wy.final();
try std.testing.expectEqual(iterative_hash, non_iterative_hash);
}
}
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