reimplement wyhash v4.1 (#15969)

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Marc Tiehuis 2023-06-08 14:27:17 +12:00 committed by GitHub
parent cb7040154e
commit 00ff653576
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2 changed files with 203 additions and 172 deletions

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@ -343,7 +343,7 @@ test "testHash optional" {
const b: ?u32 = null; const b: ?u32 = null;
try testing.expectEqual(testHash(a), testHash(@as(u32, 123))); try testing.expectEqual(testHash(a), testHash(@as(u32, 123)));
try testing.expect(testHash(a) != testHash(b)); try testing.expect(testHash(a) != testHash(b));
try testing.expectEqual(testHash(b), 0); try testing.expectEqual(testHash(b), 0x409638ee2bde459); // wyhash empty input hash
} }
test "testHash array" { test "testHash array" {

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@ -1,209 +1,240 @@
const std = @import("std"); const std = @import("std");
const mem = std.mem;
const primes = [_]u64{ pub const Wyhash = struct {
const secret = [_]u64{
0xa0761d6478bd642f, 0xa0761d6478bd642f,
0xe7037ed1a0b428db, 0xe7037ed1a0b428db,
0x8ebc6af09c88c6e3, 0x8ebc6af09c88c6e3,
0x589965cc75374cc3, 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, round, .{ self, b[off..][0..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; a: u64,
return mum(self.seed ^ self.msg_len, primes[4]); b: u64,
} state: [3]u64,
total_len: usize,
pub fn hash(seed: u64, input: []const u8) u64 { buf: [48]u8,
const aligned_len = input.len - (input.len % 32);
var c = WyhashStateless.init(seed);
@call(.always_inline, update, .{ &c, input[0..aligned_len] });
return @call(.always_inline, final, .{ &c, 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, buf_len: usize,
pub fn init(seed: u64) Wyhash { pub fn init(seed: u64) Wyhash {
return Wyhash{ var self = Wyhash{
.state = WyhashStateless.init(seed), .a = undefined,
.b = undefined,
.state = undefined,
.total_len = 0,
.buf = undefined, .buf = undefined,
.buf_len = 0, .buf_len = 0,
}; };
self.state[0] = seed ^ mix(seed ^ secret[0], secret[1]);
self.state[1] = self.state[0];
self.state[2] = self.state[0];
return self;
} }
pub fn update(self: *Wyhash, b: []const u8) void { // This is subtly different from other hash function update calls. Wyhash requires the last
var off: usize = 0; // full 48-byte block to be run through final1 if is exactly aligned to 48-bytes.
pub fn update(self: *Wyhash, input: []const u8) void {
self.total_len += input.len;
if (self.buf_len != 0 and self.buf_len + b.len >= 32) { if (input.len <= 48 - self.buf_len) {
off += 32 - self.buf_len; @memcpy(self.buf[self.buf_len..][0..input.len], input);
@memcpy(self.buf[self.buf_len..][0..off], b[0..off]); self.buf_len += input.len;
self.state.update(self.buf[0..]); return;
}
var i: usize = 0;
if (self.buf_len > 0) {
i = 48 - self.buf_len;
@memcpy(self.buf[self.buf_len..][0..i], input[0..i]);
self.round(&self.buf);
self.buf_len = 0; self.buf_len = 0;
} }
const remain_len = b.len - off; while (i + 48 < input.len) : (i += 48) {
const aligned_len = remain_len - (remain_len % 32); self.round(input[i..][0..48]);
self.state.update(b[off .. off + aligned_len]); }
const src = b[off + aligned_len ..]; const remaining_bytes = input[i..];
@memcpy(self.buf[self.buf_len..][0..src.len], src); @memcpy(self.buf[0..remaining_bytes.len], remaining_bytes);
self.buf_len += @intCast(u8, b[off + aligned_len ..].len); self.buf_len = remaining_bytes.len;
} }
pub fn final(self: *Wyhash) u64 { pub fn final(self: *Wyhash) u64 {
const rem_key = self.buf[0..self.buf_len]; var input = self.buf[0..self.buf_len];
var newSelf = self.shallowCopy(); // ensure idempotency
return self.state.final(rem_key); if (self.total_len <= 16) {
newSelf.smallKey(input);
} else {
if (self.buf_len < 16) {
var scratch: [16]u8 = undefined;
const rem = 16 - self.buf_len;
@memcpy(scratch[0..rem], self.buf[self.buf.len - rem ..][0..rem]);
@memcpy(scratch[rem..][0..self.buf_len], self.buf[0..self.buf_len]);
// Same as input with lookbehind to pad to 16-bytes
input = scratch[rem..];
}
newSelf.final0();
newSelf.final1(input);
}
return newSelf.final2();
}
// Copies the core wyhash state but not any internal buffers.
inline fn shallowCopy(self: *Wyhash) Wyhash {
return .{
.a = self.a,
.b = self.b,
.state = self.state,
.total_len = self.total_len,
.buf = undefined,
.buf_len = undefined,
};
}
inline fn smallKey(self: *Wyhash, input: []const u8) void {
std.debug.assert(input.len <= 16);
if (input.len >= 4) {
const end = input.len - 4;
const quarter = (input.len >> 3) << 2;
self.a = (read(4, input[0..]) << 32) | read(4, input[quarter..]);
self.b = (read(4, input[end..]) << 32) | read(4, input[end - quarter ..]);
} else if (input.len > 0) {
self.a = (@as(u64, input[0]) << 16) | (@as(u64, input[input.len >> 1]) << 8) | input[input.len - 1];
self.b = 0;
} else {
self.a = 0;
self.b = 0;
}
}
inline fn round(self: *Wyhash, input: *const [48]u8) void {
inline for (0..3) |i| {
const a = read(8, input[8 * (2 * i) ..]);
const b = read(8, input[8 * (2 * i + 1) ..]);
self.state[i] = mix(a ^ secret[i + 1], b ^ self.state[i]);
}
}
inline fn read(comptime bytes: usize, data: []const u8) u64 {
std.debug.assert(bytes <= 8);
const T = std.meta.Int(.unsigned, 8 * bytes);
return @as(u64, std.mem.readIntLittle(T, data[0..bytes]));
}
inline fn mum(a: *u64, b: *u64) void {
const x = @as(u128, a.*) *% b.*;
a.* = @truncate(u64, x);
b.* = @truncate(u64, x >> 64);
}
inline fn mix(a_: u64, b_: u64) u64 {
var a = a_;
var b = b_;
mum(&a, &b);
return a ^ b;
}
inline fn final0(self: *Wyhash) void {
self.state[0] ^= self.state[1] ^ self.state[2];
}
// Input must reside in a 16-byte buffer. The input slice passed be offset into it in which
// case this function will index in front of the slice.
inline fn final1(self: *Wyhash, input: []const u8) void {
std.debug.assert(input.len <= 48);
var i: usize = 0;
while (i + 16 < input.len) : (i += 16) {
self.state[0] = mix(read(8, input[i..]) ^ secret[1], read(8, input[i + 8 ..]) ^ self.state[0]);
}
// Possible lookbehind past pointer start.
self.a = read(8, (input.ptr + input.len - 16)[0..8]);
self.b = read(8, (input.ptr + input.len - 8)[0..8]);
}
inline fn final2(self: *Wyhash) u64 {
self.a ^= secret[1];
self.b ^= self.state[0];
mum(&self.a, &self.b);
return mix(self.a ^ secret[0] ^ self.total_len, self.b ^ secret[1]);
} }
pub fn hash(seed: u64, input: []const u8) u64 { pub fn hash(seed: u64, input: []const u8) u64 {
return WyhashStateless.hash(seed, input); var self = Wyhash.init(seed);
if (input.len <= 16) {
self.smallKey(input);
} else {
var i: usize = 0;
if (input.len >= 48) {
while (i + 48 < input.len) : (i += 48) {
self.round(input[i..][0..48]);
}
self.final0();
}
self.final1(input[i..]);
}
self.total_len = input.len;
return self.final2();
} }
}; };
const expectEqual = std.testing.expectEqual; const expectEqual = std.testing.expectEqual;
test "test vectors" { const TestVector = struct {
const hash = Wyhash.hash; expected: u64,
seed: u64,
input: []const u8,
};
try expectEqual(hash(0, ""), 0x0); // Run https://github.com/wangyi-fudan/wyhash/blob/77e50f267fbc7b8e2d09f2d455219adb70ad4749/test_vector.cpp directly.
try expectEqual(hash(1, "a"), 0xbed235177f41d328); const vectors = [_]TestVector{
try expectEqual(hash(2, "abc"), 0xbe348debe59b27c3); .{ .seed = 0, .expected = 0x409638ee2bde459, .input = "" },
try expectEqual(hash(3, "message digest"), 0x37320f657213a290); .{ .seed = 1, .expected = 0xa8412d091b5fe0a9, .input = "a" },
try expectEqual(hash(4, "abcdefghijklmnopqrstuvwxyz"), 0xd0b270e1d8a7019c); .{ .seed = 2, .expected = 0x32dd92e4b2915153, .input = "abc" },
try expectEqual(hash(5, "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"), 0x602a1894d3bbfe7f); .{ .seed = 3, .expected = 0x8619124089a3a16b, .input = "message digest" },
try expectEqual(hash(6, "12345678901234567890123456789012345678901234567890123456789012345678901234567890"), 0x829e9c148b75970e); .{ .seed = 4, .expected = 0x7a43afb61d7f5f40, .input = "abcdefghijklmnopqrstuvwxyz" },
.{ .seed = 5, .expected = 0xff42329b90e50d58, .input = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789" },
.{ .seed = 6, .expected = 0xc39cab13b115aad3, .input = "12345678901234567890123456789012345678901234567890123456789012345678901234567890" },
};
test "test vectors" {
for (vectors) |e| {
try expectEqual(e.expected, Wyhash.hash(e.seed, e.input));
}
} }
test "test vectors streaming" { test "test vectors streaming" {
var wh = Wyhash.init(5); const step = 5;
for ("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789") |e| {
wh.update(mem.asBytes(&e));
}
try expectEqual(wh.final(), 0x602a1894d3bbfe7f);
const pattern = "1234567890"; for (vectors) |e| {
const count = 8; var wh = Wyhash.init(e.seed);
const result = 0x829e9c148b75970e; var i: usize = 0;
try expectEqual(Wyhash.hash(6, pattern ** 8), result); while (i < e.input.len) : (i += step) {
const len = if (i + step > e.input.len) e.input.len - i else step;
wh = Wyhash.init(6); wh.update(e.input[i..][0..len]);
var i: u32 = 0; }
while (i < count) : (i += 1) { try expectEqual(e.expected, wh.final());
wh.update(pattern); }
}
test "test ensure idempotent final call" {
const e: TestVector = .{ .seed = 6, .expected = 0xc39cab13b115aad3, .input = "12345678901234567890123456789012345678901234567890123456789012345678901234567890" };
var wh = Wyhash.init(e.seed);
wh.update(e.input);
for (0..10) |_| {
try expectEqual(e.expected, wh.final());
} }
try expectEqual(wh.final(), result);
} }
test "iterative non-divisible update" { test "iterative non-divisible update" {