    // FNV1a - Fowler-Noll-Vo hash function

    //

    // FNV1a is a fast, non-cryptographic hash function with fairly good distribution properties.

    //

    // https://tools.ietf.org/html/draft-eastlake-fnv-14

    const std = @import("../std.zig");
    const testing = std.testing;

    pub const Fnv1a_32 = Fnv1a(u32, 0x01000193, 0x811c9dc5);
    pub const Fnv1a_64 = Fnv1a(u64, 0x100000001b3, 0xcbf29ce484222325);
    pub const Fnv1a_128 = Fnv1a(u128, 0x1000000000000000000013b, 0x6c62272e07bb014262b821756295c58d);

    fn Fnv1a(comptime T: type, comptime prime: T, comptime offset: T) type {
        return struct {
            const Self = @This();

            value: T,

            pub fn init() Self {
                return Self{ .value = offset };
            }

            pub fn update(self: *Self, input: []const u8) void {
                for (input) |b| {
                    self.value ^= b;
                    self.value *%= prime;
                }
            }

            pub fn final(self: *Self) T {
                return self.value;
            }

            pub fn hash(input: []const u8) T {
                var c = Self.init();
                c.update(input);
                return c.final();
            }
        };
    }

    test "fnv1a-32" {
        try testing.expect(Fnv1a_32.hash("") == 0x811c9dc5);
        try testing.expect(Fnv1a_32.hash("a") == 0xe40c292c);
        try testing.expect(Fnv1a_32.hash("foobar") == 0xbf9cf968);
    }

    test "fnv1a-64" {
        try testing.expect(Fnv1a_64.hash("") == 0xcbf29ce484222325);
        try testing.expect(Fnv1a_64.hash("a") == 0xaf63dc4c8601ec8c);
        try testing.expect(Fnv1a_64.hash("foobar") == 0x85944171f73967e8);
    }

    test "fnv1a-128" {
        try testing.expect(Fnv1a_128.hash("") == 0x6c62272e07bb014262b821756295c58d);
        try testing.expect(Fnv1a_128.hash("a") == 0xd228cb696f1a8caf78912b704e4a8964);
    }