    //

    // SipHash is a moderately fast pseudorandom function, returning a 64-bit or 128-bit tag for an arbitrary long input.

    //

    // Typical use cases include:

    // - protection against DoS attacks for hash tables and bloom filters

    // - authentication of short-lived messages in online protocols

    //

    // https://www.aumasson.jp/siphash/siphash.pdf

    const std = @import("../std.zig");
    const assert = std.debug.assert;
    const testing = std.testing;
    const math = std.math;
    const mem = std.mem;

    /// SipHash function with 64-bit output.
    ///
    /// Recommended parameters are:
    /// - (c_rounds=4, d_rounds=8) for conservative security; regular hash functions such as BLAKE2 or BLAKE3 are usually a better alternative.
    /// - (c_rounds=2, d_rounds=4) standard parameters.
    /// - (c_rounds=1, d_rounds=3) reduced-round function. Faster, no known implications on its practical security level.
    /// - (c_rounds=1, d_rounds=2) fastest option, but the output may be distinguishable from random data with related keys or non-uniform input - not suitable as a PRF.
    ///
    /// SipHash is not a traditional hash function. If the input includes untrusted content, a secret key is absolutely necessary.
    /// And due to its small output size, collisions in SipHash64 can be found with an exhaustive search.
    pub fn SipHash64(comptime c_rounds: usize, comptime d_rounds: usize) type {
        return SipHash(u64, c_rounds, d_rounds);
    }

    /// SipHash function with 128-bit output.
    ///
    /// Recommended parameters are:
    /// - (c_rounds=4, d_rounds=8) for conservative security; regular hash functions such as BLAKE2 or BLAKE3 are usually a better alternative.
    /// - (c_rounds=2, d_rounds=4) standard parameters.
    /// - (c_rounds=1, d_rounds=4) reduced-round function. Recommended to hash very short, similar strings, when a 128-bit PRF output is still required.
    /// - (c_rounds=1, d_rounds=3) reduced-round function. Faster, no known implications on its practical security level.
    /// - (c_rounds=1, d_rounds=2) fastest option, but the output may be distinguishable from random data with related keys or non-uniform input - not suitable as a PRF.
    ///
    /// SipHash is not a traditional hash function. If the input includes untrusted content, a secret key is absolutely necessary.
    pub fn SipHash128(comptime c_rounds: usize, comptime d_rounds: usize) type {
        return SipHash(u128, c_rounds, d_rounds);
    }

    fn SipHashStateless(comptime T: type, comptime c_rounds: usize, comptime d_rounds: usize) type {
        assert(T == u64 or T == u128);
        assert(c_rounds > 0 and d_rounds > 0);

        return struct {
            const Self = @This();
            const block_length = 64;
            const key_length = 16;

            v0: u64,
            v1: u64,
            v2: u64,
            v3: u64,
            msg_len: u8,

            fn init(key: *const [key_length]u8) Self {
                const k0 = mem.readIntLittle(u64, key[0..8]);
                const k1 = mem.readIntLittle(u64, key[8..16]);

                var d = Self{
                    .v0 = k0 ^ 0x736f6d6570736575,
                    .v1 = k1 ^ 0x646f72616e646f6d,
                    .v2 = k0 ^ 0x6c7967656e657261,
                    .v3 = k1 ^ 0x7465646279746573,
                    .msg_len = 0,
                };

                if (T == u128) {
                    d.v1 ^= 0xee;
                }

                return d;
            }

            fn update(self: *Self, b: []const u8) void {
                std.debug.assert(b.len % 8 == 0);

                var off: usize = 0;
                while (off < b.len) : (off += 8) {
                    const blob = b[off..][0..8].*;
                    @call(.always_inline, round, .{ self, blob });
                }

                self.msg_len +%= @as(u8, @truncate(b.len));
            }

            fn final(self: *Self, b: []const u8) T {
                std.debug.assert(b.len < 8);

                self.msg_len +%= @as(u8, @truncate(b.len));

                var buf = [_]u8{0} ** 8;
                @memcpy(buf[0..b.len], b);
                buf[7] = self.msg_len;
                self.round(buf);

                if (T == u128) {
                    self.v2 ^= 0xee;
                } else {
                    self.v2 ^= 0xff;
                }

                comptime var i: usize = 0;
                inline while (i < d_rounds) : (i += 1) {
                    @call(.always_inline, sipRound, .{self});
                }

                const b1 = self.v0 ^ self.v1 ^ self.v2 ^ self.v3;
                if (T == u64) {
                    return b1;
                }

                self.v1 ^= 0xdd;

                comptime var j: usize = 0;
                inline while (j < d_rounds) : (j += 1) {
                    @call(.always_inline, sipRound, .{self});
                }

                const b2 = self.v0 ^ self.v1 ^ self.v2 ^ self.v3;
                return (@as(u128, b2) << 64) | b1;
            }

            fn round(self: *Self, b: [8]u8) void {
                const m = mem.readIntLittle(u64, &b);
                self.v3 ^= m;

                comptime var i: usize = 0;
                inline while (i < c_rounds) : (i += 1) {
                    @call(.always_inline, sipRound, .{self});
                }

                self.v0 ^= m;
            }

            fn sipRound(d: *Self) void {
                d.v0 +%= d.v1;
                d.v1 = math.rotl(u64, d.v1, @as(u64, 13));
                d.v1 ^= d.v0;
                d.v0 = math.rotl(u64, d.v0, @as(u64, 32));
                d.v2 +%= d.v3;
                d.v3 = math.rotl(u64, d.v3, @as(u64, 16));
                d.v3 ^= d.v2;
                d.v0 +%= d.v3;
                d.v3 = math.rotl(u64, d.v3, @as(u64, 21));
                d.v3 ^= d.v0;
                d.v2 +%= d.v1;
                d.v1 = math.rotl(u64, d.v1, @as(u64, 17));
                d.v1 ^= d.v2;
                d.v2 = math.rotl(u64, d.v2, @as(u64, 32));
            }

            fn hash(msg: []const u8, key: *const [key_length]u8) T {
                const aligned_len = msg.len - (msg.len % 8);
                var c = Self.init(key);
                @call(.always_inline, update, .{ &c, msg[0..aligned_len] });
                return @call(.always_inline, final, .{ &c, msg[aligned_len..] });
            }
        };
    }

    fn SipHash(comptime T: type, comptime c_rounds: usize, comptime d_rounds: usize) type {
        assert(T == u64 or T == u128);
        assert(c_rounds > 0 and d_rounds > 0);

        return struct {
            const State = SipHashStateless(T, c_rounds, d_rounds);
            const Self = @This();
            pub const key_length = 16;
            pub const mac_length = @sizeOf(T);
            pub const block_length = 8;

            state: State,
            buf: [8]u8,
            buf_len: usize,

            /// Initialize a state for a SipHash function
            pub fn init(key: *const [key_length]u8) Self {
                return Self{
                    .state = State.init(key),
                    .buf = undefined,
                    .buf_len = 0,
                };
            }

            /// Add data to the state
            pub fn update(self: *Self, b: []const u8) void {
                var off: usize = 0;

                if (self.buf_len != 0 and self.buf_len + b.len >= 8) {
                    off += 8 - self.buf_len;
                    @memcpy(self.buf[self.buf_len..][0..off], 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 % 8);
                self.state.update(b[off .. off + aligned_len]);

                const b_slice = b[off + aligned_len ..];
                @memcpy(self.buf[self.buf_len..][0..b_slice.len], b_slice);
                self.buf_len += @as(u8, @intCast(b_slice.len));
            }

            pub fn peek(self: Self) [mac_length]u8 {
                var copy = self;
                return copy.finalResult();
            }

            /// Return an authentication tag for the current state
            /// Assumes `out` is less than or equal to `mac_length`.
            pub fn final(self: *Self, out: *[mac_length]u8) void {
                mem.writeIntLittle(T, out, self.state.final(self.buf[0..self.buf_len]));
            }

            pub fn finalResult(self: *Self) [mac_length]u8 {
                var result: [mac_length]u8 = undefined;
                self.final(&result);
                return result;
            }

            /// Return an authentication tag for a message and a key
            pub fn create(out: *[mac_length]u8, msg: []const u8, key: *const [key_length]u8) void {
                var ctx = Self.init(key);
                ctx.update(msg);
                ctx.final(out);
            }

            /// Return an authentication tag for the current state, as an integer
            pub fn finalInt(self: *Self) T {
                return self.state.final(self.buf[0..self.buf_len]);
            }

            /// Return an authentication tag for a message and a key, as an integer
            pub fn toInt(msg: []const u8, key: *const [key_length]u8) T {
                return State.hash(msg, key);
            }

            pub const Error = error{};
            pub const Writer = std.io.Writer(*Self, Error, write);

            fn write(self: *Self, bytes: []const u8) Error!usize {
                self.update(bytes);
                return bytes.len;
            }

            pub fn writer(self: *Self) Writer {
                return .{ .context = self };
            }
        };
    }

    // Test vectors from reference implementation.

    // https://github.com/veorq/SipHash/blob/master/vectors.h

    const test_key = "\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f";

    test "siphash64-2-4 sanity" {
        const vectors = [_][8]u8{
            "\x31\x0e\x0e\xdd\x47\xdb\x6f\x72".*, // ""

            "\xfd\x67\xdc\x93\xc5\x39\xf8\x74".*, // "\x00"

            "\x5a\x4f\xa9\xd9\x09\x80\x6c\x0d".*, // "\x00\x01" ... etc

            "\x2d\x7e\xfb\xd7\x96\x66\x67\x85".*,
            "\xb7\x87\x71\x27\xe0\x94\x27\xcf".*,
            "\x8d\xa6\x99\xcd\x64\x55\x76\x18".*,
            "\xce\xe3\xfe\x58\x6e\x46\xc9\xcb".*,
            "\x37\xd1\x01\x8b\xf5\x00\x02\xab".*,
            "\x62\x24\x93\x9a\x79\xf5\xf5\x93".*,
            "\xb0\xe4\xa9\x0b\xdf\x82\x00\x9e".*,
            "\xf3\xb9\xdd\x94\xc5\xbb\x5d\x7a".*,
            "\xa7\xad\x6b\x22\x46\x2f\xb3\xf4".*,
            "\xfb\xe5\x0e\x86\xbc\x8f\x1e\x75".*,
            "\x90\x3d\x84\xc0\x27\x56\xea\x14".*,
            "\xee\xf2\x7a\x8e\x90\xca\x23\xf7".*,
            "\xe5\x45\xbe\x49\x61\xca\x29\xa1".*,
            "\xdb\x9b\xc2\x57\x7f\xcc\x2a\x3f".*,
            "\x94\x47\xbe\x2c\xf5\xe9\x9a\x69".*,
            "\x9c\xd3\x8d\x96\xf0\xb3\xc1\x4b".*,
            "\xbd\x61\x79\xa7\x1d\xc9\x6d\xbb".*,
            "\x98\xee\xa2\x1a\xf2\x5c\xd6\xbe".*,
            "\xc7\x67\x3b\x2e\xb0\xcb\xf2\xd0".*,
            "\x88\x3e\xa3\xe3\x95\x67\x53\x93".*,
            "\xc8\xce\x5c\xcd\x8c\x03\x0c\xa8".*,
            "\x94\xaf\x49\xf6\xc6\x50\xad\xb8".*,
            "\xea\xb8\x85\x8a\xde\x92\xe1\xbc".*,
            "\xf3\x15\xbb\x5b\xb8\x35\xd8\x17".*,
            "\xad\xcf\x6b\x07\x63\x61\x2e\x2f".*,
            "\xa5\xc9\x1d\xa7\xac\xaa\x4d\xde".*,
            "\x71\x65\x95\x87\x66\x50\xa2\xa6".*,
            "\x28\xef\x49\x5c\x53\xa3\x87\xad".*,
            "\x42\xc3\x41\xd8\xfa\x92\xd8\x32".*,
            "\xce\x7c\xf2\x72\x2f\x51\x27\x71".*,
            "\xe3\x78\x59\xf9\x46\x23\xf3\xa7".*,
            "\x38\x12\x05\xbb\x1a\xb0\xe0\x12".*,
            "\xae\x97\xa1\x0f\xd4\x34\xe0\x15".*,
            "\xb4\xa3\x15\x08\xbe\xff\x4d\x31".*,
            "\x81\x39\x62\x29\xf0\x90\x79\x02".*,
            "\x4d\x0c\xf4\x9e\xe5\xd4\xdc\xca".*,
            "\x5c\x73\x33\x6a\x76\xd8\xbf\x9a".*,
            "\xd0\xa7\x04\x53\x6b\xa9\x3e\x0e".*,
            "\x92\x59\x58\xfc\xd6\x42\x0c\xad".*,
            "\xa9\x15\xc2\x9b\xc8\x06\x73\x18".*,
            "\x95\x2b\x79\xf3\xbc\x0a\xa6\xd4".*,
            "\xf2\x1d\xf2\xe4\x1d\x45\x35\xf9".*,
            "\x87\x57\x75\x19\x04\x8f\x53\xa9".*,
            "\x10\xa5\x6c\xf5\xdf\xcd\x9a\xdb".*,
            "\xeb\x75\x09\x5c\xcd\x98\x6c\xd0".*,
            "\x51\xa9\xcb\x9e\xcb\xa3\x12\xe6".*,
            "\x96\xaf\xad\xfc\x2c\xe6\x66\xc7".*,
            "\x72\xfe\x52\x97\x5a\x43\x64\xee".*,
            "\x5a\x16\x45\xb2\x76\xd5\x92\xa1".*,
            "\xb2\x74\xcb\x8e\xbf\x87\x87\x0a".*,
            "\x6f\x9b\xb4\x20\x3d\xe7\xb3\x81".*,
            "\xea\xec\xb2\xa3\x0b\x22\xa8\x7f".*,
            "\x99\x24\xa4\x3c\xc1\x31\x57\x24".*,
            "\xbd\x83\x8d\x3a\xaf\xbf\x8d\xb7".*,
            "\x0b\x1a\x2a\x32\x65\xd5\x1a\xea".*,
            "\x13\x50\x79\xa3\x23\x1c\xe6\x60".*,
            "\x93\x2b\x28\x46\xe4\xd7\x06\x66".*,
            "\xe1\x91\x5f\x5c\xb1\xec\xa4\x6c".*,
            "\xf3\x25\x96\x5c\xa1\x6d\x62\x9f".*,
            "\x57\x5f\xf2\x8e\x60\x38\x1b\xe5".*,
            "\x72\x45\x06\xeb\x4c\x32\x8a\x95".*,
        };

        const siphash = SipHash64(2, 4);

        var buffer: [64]u8 = undefined;
        for (vectors, 0..) |vector, i| {
            buffer[i] = @as(u8, @intCast(i));

            var out: [siphash.mac_length]u8 = undefined;
            siphash.create(&out, buffer[0..i], test_key);
            try testing.expectEqual(out, vector);
        }
    }

    test "siphash128-2-4 sanity" {
        const vectors = [_][16]u8{
            "\xa3\x81\x7f\x04\xba\x25\xa8\xe6\x6d\xf6\x72\x14\xc7\x55\x02\x93".*,
            "\xda\x87\xc1\xd8\x6b\x99\xaf\x44\x34\x76\x59\x11\x9b\x22\xfc\x45".*,
            "\x81\x77\x22\x8d\xa4\xa4\x5d\xc7\xfc\xa3\x8b\xde\xf6\x0a\xff\xe4".*,
            "\x9c\x70\xb6\x0c\x52\x67\xa9\x4e\x5f\x33\xb6\xb0\x29\x85\xed\x51".*,
            "\xf8\x81\x64\xc1\x2d\x9c\x8f\xaf\x7d\x0f\x6e\x7c\x7b\xcd\x55\x79".*,
            "\x13\x68\x87\x59\x80\x77\x6f\x88\x54\x52\x7a\x07\x69\x0e\x96\x27".*,
            "\x14\xee\xca\x33\x8b\x20\x86\x13\x48\x5e\xa0\x30\x8f\xd7\xa1\x5e".*,
            "\xa1\xf1\xeb\xbe\xd8\xdb\xc1\x53\xc0\xb8\x4a\xa6\x1f\xf0\x82\x39".*,
            "\x3b\x62\xa9\xba\x62\x58\xf5\x61\x0f\x83\xe2\x64\xf3\x14\x97\xb4".*,
            "\x26\x44\x99\x06\x0a\xd9\xba\xab\xc4\x7f\x8b\x02\xbb\x6d\x71\xed".*,
            "\x00\x11\x0d\xc3\x78\x14\x69\x56\xc9\x54\x47\xd3\xf3\xd0\xfb\xba".*,
            "\x01\x51\xc5\x68\x38\x6b\x66\x77\xa2\xb4\xdc\x6f\x81\xe5\xdc\x18".*,
            "\xd6\x26\xb2\x66\x90\x5e\xf3\x58\x82\x63\x4d\xf6\x85\x32\xc1\x25".*,
            "\x98\x69\xe2\x47\xe9\xc0\x8b\x10\xd0\x29\x93\x4f\xc4\xb9\x52\xf7".*,
            "\x31\xfc\xef\xac\x66\xd7\xde\x9c\x7e\xc7\x48\x5f\xe4\x49\x49\x02".*,
            "\x54\x93\xe9\x99\x33\xb0\xa8\x11\x7e\x08\xec\x0f\x97\xcf\xc3\xd9".*,
            "\x6e\xe2\xa4\xca\x67\xb0\x54\xbb\xfd\x33\x15\xbf\x85\x23\x05\x77".*,
            "\x47\x3d\x06\xe8\x73\x8d\xb8\x98\x54\xc0\x66\xc4\x7a\xe4\x77\x40".*,
            "\xa4\x26\xe5\xe4\x23\xbf\x48\x85\x29\x4d\xa4\x81\xfe\xae\xf7\x23".*,
            "\x78\x01\x77\x31\xcf\x65\xfa\xb0\x74\xd5\x20\x89\x52\x51\x2e\xb1".*,
            "\x9e\x25\xfc\x83\x3f\x22\x90\x73\x3e\x93\x44\xa5\xe8\x38\x39\xeb".*,
            "\x56\x8e\x49\x5a\xbe\x52\x5a\x21\x8a\x22\x14\xcd\x3e\x07\x1d\x12".*,
            "\x4a\x29\xb5\x45\x52\xd1\x6b\x9a\x46\x9c\x10\x52\x8e\xff\x0a\xae".*,
            "\xc9\xd1\x84\xdd\xd5\xa9\xf5\xe0\xcf\x8c\xe2\x9a\x9a\xbf\x69\x1c".*,
            "\x2d\xb4\x79\xae\x78\xbd\x50\xd8\x88\x2a\x8a\x17\x8a\x61\x32\xad".*,
            "\x8e\xce\x5f\x04\x2d\x5e\x44\x7b\x50\x51\xb9\xea\xcb\x8d\x8f\x6f".*,
            "\x9c\x0b\x53\xb4\xb3\xc3\x07\xe8\x7e\xae\xe0\x86\x78\x14\x1f\x66".*,
            "\xab\xf2\x48\xaf\x69\xa6\xea\xe4\xbf\xd3\xeb\x2f\x12\x9e\xeb\x94".*,
            "\x06\x64\xda\x16\x68\x57\x4b\x88\xb9\x35\xf3\x02\x73\x58\xae\xf4".*,
            "\xaa\x4b\x9d\xc4\xbf\x33\x7d\xe9\x0c\xd4\xfd\x3c\x46\x7c\x6a\xb7".*,
            "\xea\x5c\x7f\x47\x1f\xaf\x6b\xde\x2b\x1a\xd7\xd4\x68\x6d\x22\x87".*,
            "\x29\x39\xb0\x18\x32\x23\xfa\xfc\x17\x23\xde\x4f\x52\xc4\x3d\x35".*,
            "\x7c\x39\x56\xca\x5e\xea\xfc\x3e\x36\x3e\x9d\x55\x65\x46\xeb\x68".*,
            "\x77\xc6\x07\x71\x46\xf0\x1c\x32\xb6\xb6\x9d\x5f\x4e\xa9\xff\xcf".*,
            "\x37\xa6\x98\x6c\xb8\x84\x7e\xdf\x09\x25\xf0\xf1\x30\x9b\x54\xde".*,
            "\xa7\x05\xf0\xe6\x9d\xa9\xa8\xf9\x07\x24\x1a\x2e\x92\x3c\x8c\xc8".*,
            "\x3d\xc4\x7d\x1f\x29\xc4\x48\x46\x1e\x9e\x76\xed\x90\x4f\x67\x11".*,
            "\x0d\x62\xbf\x01\xe6\xfc\x0e\x1a\x0d\x3c\x47\x51\xc5\xd3\x69\x2b".*,
            "\x8c\x03\x46\x8b\xca\x7c\x66\x9e\xe4\xfd\x5e\x08\x4b\xbe\xe7\xb5".*,
            "\x52\x8a\x5b\xb9\x3b\xaf\x2c\x9c\x44\x73\xcc\xe5\xd0\xd2\x2b\xd9".*,
            "\xdf\x6a\x30\x1e\x95\xc9\x5d\xad\x97\xae\x0c\xc8\xc6\x91\x3b\xd8".*,
            "\x80\x11\x89\x90\x2c\x85\x7f\x39\xe7\x35\x91\x28\x5e\x70\xb6\xdb".*,
            "\xe6\x17\x34\x6a\xc9\xc2\x31\xbb\x36\x50\xae\x34\xcc\xca\x0c\x5b".*,
            "\x27\xd9\x34\x37\xef\xb7\x21\xaa\x40\x18\x21\xdc\xec\x5a\xdf\x89".*,
            "\x89\x23\x7d\x9d\xed\x9c\x5e\x78\xd8\xb1\xc9\xb1\x66\xcc\x73\x42".*,
            "\x4a\x6d\x80\x91\xbf\x5e\x7d\x65\x11\x89\xfa\x94\xa2\x50\xb1\x4c".*,
            "\x0e\x33\xf9\x60\x55\xe7\xae\x89\x3f\xfc\x0e\x3d\xcf\x49\x29\x02".*,
            "\xe6\x1c\x43\x2b\x72\x0b\x19\xd1\x8e\xc8\xd8\x4b\xdc\x63\x15\x1b".*,
            "\xf7\xe5\xae\xf5\x49\xf7\x82\xcf\x37\x90\x55\xa6\x08\x26\x9b\x16".*,
            "\x43\x8d\x03\x0f\xd0\xb7\xa5\x4f\xa8\x37\xf2\xad\x20\x1a\x64\x03".*,
            "\xa5\x90\xd3\xee\x4f\xbf\x04\xe3\x24\x7e\x0d\x27\xf2\x86\x42\x3f".*,
            "\x5f\xe2\xc1\xa1\x72\xfe\x93\xc4\xb1\x5c\xd3\x7c\xae\xf9\xf5\x38".*,
            "\x2c\x97\x32\x5c\xbd\x06\xb3\x6e\xb2\x13\x3d\xd0\x8b\x3a\x01\x7c".*,
            "\x92\xc8\x14\x22\x7a\x6b\xca\x94\x9f\xf0\x65\x9f\x00\x2a\xd3\x9e".*,
            "\xdc\xe8\x50\x11\x0b\xd8\x32\x8c\xfb\xd5\x08\x41\xd6\x91\x1d\x87".*,
            "\x67\xf1\x49\x84\xc7\xda\x79\x12\x48\xe3\x2b\xb5\x92\x25\x83\xda".*,
            "\x19\x38\xf2\xcf\x72\xd5\x4e\xe9\x7e\x94\x16\x6f\xa9\x1d\x2a\x36".*,
            "\x74\x48\x1e\x96\x46\xed\x49\xfe\x0f\x62\x24\x30\x16\x04\x69\x8e".*,
            "\x57\xfc\xa5\xde\x98\xa9\xd6\xd8\x00\x64\x38\xd0\x58\x3d\x8a\x1d".*,
            "\x9f\xec\xde\x1c\xef\xdc\x1c\xbe\xd4\x76\x36\x74\xd9\x57\x53\x59".*,
            "\xe3\x04\x0c\x00\xeb\x28\xf1\x53\x66\xca\x73\xcb\xd8\x72\xe7\x40".*,
            "\x76\x97\x00\x9a\x6a\x83\x1d\xfe\xcc\xa9\x1c\x59\x93\x67\x0f\x7a".*,
            "\x58\x53\x54\x23\x21\xf5\x67\xa0\x05\xd5\x47\xa4\xf0\x47\x59\xbd".*,
            "\x51\x50\xd1\x77\x2f\x50\x83\x4a\x50\x3e\x06\x9a\x97\x3f\xbd\x7c".*,
        };

        const siphash = SipHash128(2, 4);

        var buffer: [64]u8 = undefined;
        for (vectors, 0..) |vector, i| {
            buffer[i] = @as(u8, @intCast(i));

            var out: [siphash.mac_length]u8 = undefined;
            siphash.create(&out, buffer[0..i], test_key[0..]);
            try testing.expectEqual(out, vector);
        }
    }

    test "iterative non-divisible update" {
        var buf: [1024]u8 = undefined;
        for (&buf, 0..) |*e, i| {
            e.* = @as(u8, @truncate(i));
        }

        const key = "0x128dad08f12307";
        const Siphash = SipHash64(2, 4);

        var end: usize = 9;
        while (end < buf.len) : (end += 9) {
            const non_iterative_hash = Siphash.toInt(buf[0..end], key[0..]);

            var siphash = Siphash.init(key);
            var i: usize = 0;
            while (i < end) : (i += 7) {
                siphash.update(buf[i..@min(i + 7, end)]);
            }
            const iterative_hash = siphash.finalInt();

            try std.testing.expectEqual(iterative_hash, non_iterative_hash);
        }
    }