const std = @import("std");
pub const Wyhash = struct {
const secret = [_]u64{
0xa0761d6478bd642f,
0xe7037ed1a0b428db,
0x8ebc6af09c88c6e3,
0x589965cc75374cc3,
};
a: u64,
b: u64,
state: [3]u64,
total_len: usize,
buf: [48]u8,
buf_len: usize,
pub fn init(seed: u64) Wyhash {
var self = Wyhash{
.a = undefined,
.b = undefined,
.state = undefined,
.total_len = 0,
.buf = undefined,
.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, input: []const u8) void {
self.total_len += input.len;
if (input.len <= 48 - self.buf_len) {
@memcpy(self.buf[self.buf_len..][0..input.len], input);
self.buf_len += input.len;
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;
}
while (i + 48 < input.len) : (i += 48) {
self.round(input[i..][0..48]);
}
const remaining_bytes = input[i..];
if (remaining_bytes.len < 16 and i >= 48) {
const rem = 16 - remaining_bytes.len;
@memcpy(self.buf[self.buf.len - rem ..], input[i - rem .. i]);
}
@memcpy(self.buf[0..remaining_bytes.len], remaining_bytes);
self.buf_len = remaining_bytes.len;
}
pub fn final(self: *Wyhash) u64 {
var input: []const u8 = self.buf[0..self.buf_len];
var newSelf = self.shallowCopy();
if (self.total_len <= 16) {
newSelf.smallKey(input);
} else {
var offset: usize = 0;
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]);
input = &scratch;
offset = rem;
}
newSelf.final0();
newSelf.final1(input, offset);
}
return newSelf.final2();
}
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.* = @as(u64, @truncate(x));
b.* = @as(u64, @truncate(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];
}
inline fn final1(self: *Wyhash, input_lb: []const u8, start_pos: usize) void {
std.debug.assert(input_lb.len >= 16);
std.debug.assert(input_lb.len - start_pos <= 48);
const input = input_lb[start_pos..];
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]);
}
self.a = read(8, input_lb[input_lb.len - 16 ..][0..8]);
self.b = read(8, input_lb[input_lb.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 {
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 verify = @import("verify.zig");
const expectEqual = std.testing.expectEqual;
const TestVector = struct {
expected: u64,
seed: u64,
input: []const u8,
};
const vectors = [_]TestVector{
.{ .seed = 0, .expected = 0x409638ee2bde459, .input = "" },
.{ .seed = 1, .expected = 0xa8412d091b5fe0a9, .input = "a" },
.{ .seed = 2, .expected = 0x32dd92e4b2915153, .input = "abc" },
.{ .seed = 3, .expected = 0x8619124089a3a16b, .input = "message digest" },
.{ .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 at comptime" {
comptime {
inline for (vectors) |e| {
try expectEqual(e.expected, Wyhash.hash(e.seed, e.input));
}
}
}
test "smhasher" {
const Test = struct {
fn do() !void {
try expectEqual(verify.smhasher(Wyhash.hash), 0xBD5E840C);
}
};
try Test.do();
@setEvalBranchQuota(50000);
try comptime Test.do();
}
test "iterative api" {
const Test = struct {
fn do() !void {
try verify.iterativeApi(Wyhash);
}
};
try Test.do();
@setEvalBranchQuota(50000);
try comptime Test.do();
}
test "iterative maintains last sixteen" {
const input = "Z" ** 48 ++ "01234567890abcdefg";
const seed = 0;
for (0..17) |i| {
const payload = input[0 .. input.len - i];
const non_iterative_hash = Wyhash.hash(seed, payload);
var wh = Wyhash.init(seed);
wh.update(payload);
const iterative_hash = wh.final();
try expectEqual(non_iterative_hash, iterative_hash);
}
}