1// FNV1a - Fowler-Noll-Vo hash function
2//
3// FNV1a is a fast, non-cryptographic hash function with fairly good distribution properties.
4//
5// https://tools.ietf.org/html/draft-eastlake-fnv-14
6
7const std = @import("std");
8const testing = std.testing;
9
10pub const Fnv1a_32 = Fnv1a(u32, 0x01000193, 0x811c9dc5);
11pub const Fnv1a_64 = Fnv1a(u64, 0x100000001b3, 0xcbf29ce484222325);
12pub const Fnv1a_128 = Fnv1a(u128, 0x1000000000000000000013b, 0x6c62272e07bb014262b821756295c58d);
13
14fn Fnv1a(comptime T: type, comptime prime: T, comptime offset: T) type {
15 return struct {
16 const Self = @This();
17
18 value: T,
19
20 pub fn init() Self {
21 return Self{ .value = offset };
22 }
23
24 pub fn update(self: *Self, input: []const u8) void {
25 for (input) |b| {
26 self.value ^= b;
27 self.value *%= prime;
28 }
29 }
30
31 pub fn final(self: *Self) T {
32 return self.value;
33 }
34
35 pub fn hash(input: []const u8) T {
36 var c = Self.init();
37 c.update(input);
38 return c.final();
39 }
40 };
41}
42
43const verify = @import("verify.zig");
44
45test "fnv1a-32" {
46 try testing.expect(Fnv1a_32.hash("") == 0x811c9dc5);
47 try testing.expect(Fnv1a_32.hash("a") == 0xe40c292c);
48 try testing.expect(Fnv1a_32.hash("foobar") == 0xbf9cf968);
49 try verify.iterativeApi(Fnv1a_32);
50}
51
52test "fnv1a-64" {
53 try testing.expect(Fnv1a_64.hash("") == 0xcbf29ce484222325);
54 try testing.expect(Fnv1a_64.hash("a") == 0xaf63dc4c8601ec8c);
55 try testing.expect(Fnv1a_64.hash("foobar") == 0x85944171f73967e8);
56 try verify.iterativeApi(Fnv1a_64);
57}
58
59test "fnv1a-128" {
60 try testing.expect(Fnv1a_128.hash("") == 0x6c62272e07bb014262b821756295c58d);
61 try testing.expect(Fnv1a_128.hash("a") == 0xd228cb696f1a8caf78912b704e4a8964);
62 try verify.iterativeApi(Fnv1a_128);
63}