From 8f5604dde6489f48f1c79c14699552507b7e1302 Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Tue, 3 Nov 2020 11:43:35 +1000
Subject: [PATCH] hash: add halfsipmix

---
 CMakeLists.txt           |   3 +
 hash/halfsipmix.cpp      |   1 +
 hash/halfsipmix.hpp      | 147 +++++++++++++++++++++++++++++++++++++++
 test/hash/halfsipmix.cpp |  98 ++++++++++++++++++++++++++
 4 files changed, 249 insertions(+)
 create mode 100644 hash/halfsipmix.cpp
 create mode 100644 hash/halfsipmix.hpp
 create mode 100644 test/hash/halfsipmix.cpp

diff --git a/CMakeLists.txt b/CMakeLists.txt
index e1e94e8c..488821f3 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -383,6 +383,8 @@ list (
     hash/fletcher.hpp
     hash/fnv1a.cpp
     hash/fnv1a.hpp
+    hash/halfsipmix.cpp
+    hash/halfsipmix.hpp
     hash/murmur/common.cpp
     hash/murmur/common.hpp
     hash/murmur.hpp
@@ -698,6 +700,7 @@ if (TESTS)
         hash/crc
         hash/fasthash
         hash/fnv1a
+        hash/halfsipmix
         hash/murmur
         hash/siphash
         hash/table
diff --git a/hash/halfsipmix.cpp b/hash/halfsipmix.cpp
new file mode 100644
index 00000000..e5082aa0
--- /dev/null
+++ b/hash/halfsipmix.cpp
@@ -0,0 +1 @@
+#include "./halfsipmix.hpp"
\ No newline at end of file
diff --git a/hash/halfsipmix.hpp b/hash/halfsipmix.hpp
new file mode 100644
index 00000000..c2cf8f91
--- /dev/null
+++ b/hash/halfsipmix.hpp
@@ -0,0 +1,147 @@
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ *
+ * Copyright 2020, Danny Robson <danny@nerdcruft.net>
+ *
+ * Derived from the CC0 reference implementation by:
+ *  Jean-Philippe Aumasson <jeanphilippe.aumasson@gmail.com>
+ */
+
+#pragma once
+
+#include "../std.hpp"
+
+#include <type_traits>
+#include <span>
+
+
+namespace cruft::hash {
+    template <
+        typename ResultT,
+        int CRoundsV,
+        int DRoundsV,
+        typename = std::enable_if_t<std::is_same_v<ResultT, u32> || std::is_same_v<ResultT, u64>>
+    >
+    struct halfsiphash {
+        u32 rotl (u32 x, u32 b)
+        {
+            return ((x) << (b)) | ((x) >> (32 - (b)));
+        }
+
+        u32 v0, v1, v2, v3;
+
+        constexpr halfsiphash (u32 k0, u32 k1)
+        {
+            v0 =          0 ^ k0;
+            v1 =          0 ^ k1;
+            v2 = 0x6c796765 ^ k0;
+            v3 = 0x74656462 ^ k1;
+
+            if constexpr (std::is_same_v<ResultT, u64>)
+                v1 ^= 0xee;
+        }
+
+        constexpr void round (void)
+        {
+            v0 += v1;
+            v1 = rotl (v1, 5);
+            v1 ^= v0;
+            v0 = rotl (v0, 16);
+            v2 += v3;
+            v3 = rotl (v3, 8);
+            v3 ^= v2;
+            v0 += v3;
+            v3 = rotl (v3, 7);
+            v3 ^= v0;
+            v2 += v1;
+            v1 = rotl (v1, 13);
+            v1 ^= v2;
+            v2 = rotl (v2, 16);
+        }
+
+        constexpr void put (u32 word)
+        {
+            v3 ^= word;
+            for (int i = 0; i < CRoundsV; ++i)
+                round ();
+            v0 ^= word;
+        }
+
+        constexpr ResultT
+        operator() (
+            std::span<u32 const> in
+        ) {
+            for (auto const &m: in)
+                put (m);
+
+            return finish (u32 (in.size ()));
+        }
+
+        template <typename ...ArgsT>
+        requires (std::is_same_v<std::remove_cvref_t<ArgsT>, u32> && ...)
+        constexpr ResultT
+        operator() (ArgsT &&...vals)
+        {
+            (put (vals), ...);
+            return finish (sizeof ...(vals));
+        }
+
+        constexpr ResultT
+        finish (u32 count)
+        {
+            u32 const b = u32(count * sizeof (u32)) << 24;
+
+            v3 ^= b;
+
+            for (int i = 0; i < CRoundsV; ++i)
+                round ();
+
+            v0 ^= b;
+
+            if (std::is_same_v<ResultT,u64>)
+                v2 ^= 0xee;
+            else
+                v2 ^= 0xff;
+
+            for (int i = 0; i < DRoundsV; ++i)
+                round ();
+
+            ResultT res = v1 ^ v3;
+
+            if constexpr (std::is_same_v<ResultT, u32>)
+                return res;
+
+            v1 ^= 0xdd;
+
+            for (int i = 0; i < DRoundsV; ++i)
+                round ();
+
+            res |= u64(v1 ^ v3) << 32;
+
+            return res;
+        }
+    };
+
+
+    template <
+        int CRoundsV,
+        int DRoundsV,
+        typename ...ValuesT
+    >
+    requires (std::is_same_v<std::remove_cvref_t<ValuesT>, u32> && ...)
+    inline constexpr
+    u32 halfsipmix (u32 key0, u32 key1, ValuesT &&...vals)
+    {
+        return halfsiphash<u32, 2,4> (key0, key1) (vals...);
+    }
+
+
+    template <typename ...ValueT>
+    decltype(auto)
+    halfsipmix24 (ValueT &&...vals)
+    {
+        return halfsipmix<2, 4> (vals...);
+    }
+};
diff --git a/test/hash/halfsipmix.cpp b/test/hash/halfsipmix.cpp
new file mode 100644
index 00000000..31a560e5
--- /dev/null
+++ b/test/hash/halfsipmix.cpp
@@ -0,0 +1,98 @@
+#include "hash/halfsipmix.hpp"
+#include "tap.hpp"
+
+#include <cstdio>
+
+
+static constexpr u32
+vectors_hsip32[64] = {
+    0x5b9f35a9,
+    0x89466e2a,
+    0x8f84b8d0,
+    0x2f87f057,
+    0x84acb5d9,
+    0x45104de3,
+    0x630c4027,
+    0x004064b0,
+    0x1221e7fe,
+    0xecc65ce7,
+    0x4018bcb6,
+    0x48d50577,
+    0xe32ce169,
+    0xd4f3853b,
+    0x40b9c5a5,
+    0x736ce7d4,
+};
+
+
+static constexpr u64
+vectors_hsip64[64] = {
+    0xc83cb8b9591f8d21,
+    0xa12ee55b178ae7d5,
+    0x8c85e4bc20e8feed,
+    0x99c7f5ae9f1fc77b,
+    0xb5f37b5fd2aa3673,
+    0xdba7ee6f0a2bf51b,
+    0xf1a63fae45107470,
+    0xb516001efb5f922d,
+    0x6c6211d8469d7028,
+    0xdc7642ec407ad686,
+    0x4caec8671cc8385b,
+    0x5ab1dc27adf3301e,
+    0x3e3ea94bc0a8eaa9,
+    0xe150f598795a4402,
+    0x1d5ff142f992a4a1,
+    0x60e426bf902876d6,
+};
+
+
+static constexpr
+u32 SRC[64] {
+    0x03020100,
+    0x07060504,
+    0x0b0a0908,
+    0x0f0e0d0c,
+    0x13121110,
+    0x17161514,
+    0x1b1a1918,
+    0x1f1e1d1c,
+    0x23222120,
+    0x27262524,
+    0x2b2a2928,
+    0x2f2e2d2c,
+    0x33323130,
+    0x37363534,
+    0x3b3a3938,
+    0x3f3e3d3c,
+};
+
+
+template <typename ValueT>
+int siphash_test (ValueT const *v) {
+    bool any_failed = false;
+    int fails = 0;
+
+    u32 const k0 = 0x03020100;
+    u32 const k1 = 0x07060504;
+
+    for (int i = 0; i < 16; ++i) {
+        ValueT res = cruft::hash::halfsiphash<ValueT, 2, 4>{k0, k1} (std::span (SRC, SRC + i));
+
+        if (v[i] != res) {
+            fails++;
+            any_failed = true;
+        }
+    }
+
+    return any_failed;
+}
+
+
+int main ()
+{
+    cruft::TAP::logger tap;
+    tap.expect_eq  (siphash_test<u32> (vectors_hsip32), 0, "siphash-2-4: u32");
+    tap.expect_eq  (siphash_test<u64> (vectors_hsip64), 0, "siphash-2-4: u64");
+
+    return tap.status ();
+}
\ No newline at end of file