From c3866ef632c3d06c44f77948d02458ac6a9e8d37 Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Thu, 19 May 2022 10:01:15 +1000
Subject: [PATCH] serialise: add a simple binary serialisation framework

---
 CMakeLists.txt          |   4 +
 serialise/converter.hpp |  61 +++++++++++++
 serialise/ops.hpp       |  50 +++++++++++
 serialise/std.hpp       | 193 ++++++++++++++++++++++++++++++++++++++++
 test/serialise.cpp      |  76 ++++++++++++++++
 5 files changed, 384 insertions(+)
 create mode 100644 serialise/converter.hpp
 create mode 100644 serialise/ops.hpp
 create mode 100644 serialise/std.hpp
 create mode 100644 test/serialise.cpp

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 02f94bf9..7c89e2dd 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -550,6 +550,9 @@ list (
     registrar.hpp
     roots/bisection.hpp
     scoped.hpp
+    serialise/converter.hpp
+    serialise/ops.hpp
+    serialise/std.hpp
     set/dset.cpp
     set/dset.hpp
     signal.cpp
@@ -782,6 +785,7 @@ if (TESTS)
         registrar
         roots/bisection
         scoped
+        serialise
         set/dset
         signal
         singleton
diff --git a/serialise/converter.hpp b/serialise/converter.hpp
new file mode 100644
index 00000000..c9060cf7
--- /dev/null
+++ b/serialise/converter.hpp
@@ -0,0 +1,61 @@
+/*
+ * 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 2022, Danny Robson <danny@nerdcruft.net>
+ */
+
+#pragma once
+
+#include <cruft/util/view.hpp>
+
+#include <cstddef>
+
+
+namespace cruft::serialise {
+    template <typename ValueT>
+    struct converter {
+        static
+        cruft::view<std::byte*>
+        to_bytes [[nodiscard]] (
+            cruft::view<std::byte*> dst,
+            ValueT const &src
+        );
+
+        static
+        ValueT
+        from_bytes (cruft::view<std::byte*> &src);
+
+        static std::size_t size (ValueT const&);
+    };
+
+    template <typename ValueT> struct converter<ValueT const> : public converter<ValueT> {};
+    template <typename ValueT> struct converter<ValueT     &> : public converter<ValueT> {};
+
+    template <typename ValueT>
+    requires (std::is_trivial_v<ValueT>)
+    struct converter<ValueT> {
+        static
+        cruft::view<std::byte*>
+        to_bytes [[nodiscard]] (
+            cruft::view<std::byte*> dst,
+            ValueT const &src
+        ) {
+            if (dst.size () < sizeof (ValueT))
+                throw std::bad_alloc ();
+
+            return write (dst, src);
+        }
+
+        static
+        ValueT
+        from_bytes (cruft::view<std::byte*> &src)
+        {
+            return read<ValueT> (src);
+        }
+
+
+        static std::size_t size (ValueT const&) { return sizeof (ValueT); }
+    };
+}
diff --git a/serialise/ops.hpp b/serialise/ops.hpp
new file mode 100644
index 00000000..1449855d
--- /dev/null
+++ b/serialise/ops.hpp
@@ -0,0 +1,50 @@
+/*
+ * 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 2022, Danny Robson <danny@nerdcruft.net>
+ */
+
+#pragma once
+
+#include "./converter.hpp"
+
+#include <cruft/util/view.hpp>
+
+#include <cstddef>
+
+
+namespace cruft::serialise {
+    template <typename ValueT>
+    cruft::view<std::byte*>
+    to_bytes [[nodiscard]] (cruft::view<std::byte*> dst, ValueT const &src)
+    {
+        return converter<ValueT>::to_bytes (dst, src);
+    }
+
+    template <typename HeadT, typename ...TailT>
+    cruft::view<std::byte*>
+    to_bytes [[nodiscard]] (cruft::view<std::byte*> dst, HeadT const &head, TailT&& ...tail)
+    {
+        dst = to_bytes (dst, head);
+        if constexpr (sizeof... (TailT))
+            dst = to_bytes (dst, std::forward<TailT> (tail)...);
+        return dst;
+    }
+
+
+    template <typename ValueT>
+    ValueT
+    from_bytes (cruft::view<std::byte*> &src)
+    {
+        return converter<ValueT>::from_bytes (src);
+    }
+
+
+    template <typename ...ArgsT>
+    std::size_t size (ArgsT &&...args)
+    {
+        return (converter<ArgsT>::size (args) + ... + 0uz);
+    }
+}
diff --git a/serialise/std.hpp b/serialise/std.hpp
new file mode 100644
index 00000000..9e910a45
--- /dev/null
+++ b/serialise/std.hpp
@@ -0,0 +1,193 @@
+/*
+ * 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 2022, Danny Robson <danny@nerdcruft.net>
+ */
+
+#pragma once
+
+#include "./converter.hpp"
+#include "./ops.hpp"
+
+
+///////////////////////////////////////////////////////////////////////////////
+template <typename ElementT>
+struct cruft::serialise::converter<std::vector<ElementT>> {
+    using value_type = std::vector<ElementT>;
+
+    static std::size_t
+    size (value_type const &val)
+    {
+        std::size_t accum = sizeof (typename value_type::size_type);
+        for (auto const &i: val)
+            accum += converter<ElementT>::size (i);
+        return accum;
+    }
+
+    static
+    cruft::view<std::byte*>
+    to_bytes [[nodiscard]] (
+        cruft::view<std::byte*> dst,
+        value_type const &src
+    ) {
+        dst = ::cruft::serialise::to_bytes (dst, src.size ());
+
+        for (auto const &i: src)
+            dst = ::cruft::serialise::to_bytes (dst, i);
+
+        return dst;
+    }
+
+    static
+    value_type
+    from_bytes (cruft::view<std::byte*> &src)
+    {
+        auto const len = ::cruft::serialise::from_bytes<typename std::vector<ElementT>::size_type> (src);
+
+        std::vector<ElementT> res;
+        res.reserve (len);
+
+        for (std::size_t i = 0; i != len; ++i)
+            res.push_back (::cruft::serialise::from_bytes<ElementT> (src));
+
+        return res;
+    }
+};
+
+
+///////////////////////////////////////////////////////////////////////////////
+template <>
+struct cruft::serialise::converter<std::string> {
+    using value_type = std::string;
+
+    static std::size_t
+    size (value_type const &val)
+    {
+        return sizeof (value_type::size_type) + sizeof (value_type::value_type) * val.size ();
+    }
+
+    static
+    cruft::view<std::byte*>
+    to_bytes [[nodiscard]] (
+        cruft::view<std::byte*> dst,
+        value_type const &src
+    ) {
+        dst = ::cruft::serialise::to_bytes (dst, src.size ());
+        for (auto const &i: src)
+            dst = ::cruft::serialise::to_bytes (dst, i);
+        return dst;
+    }
+
+    static
+    value_type
+    from_bytes (cruft::view<std::byte*> &src)
+    {
+        std::string res;
+        res.resize (::cruft::serialise::converter<std::string::size_type>::from_bytes (src));
+        for (auto &i: res)
+            i = ::cruft::serialise::converter<std::string::value_type>::from_bytes (src);
+        return res;
+    }
+};
+
+
+///////////////////////////////////////////////////////////////////////////////
+template <typename A, typename B>
+struct cruft::serialise::converter<std::pair<A, B>> {
+    using value_type = std::pair<A, B>;
+
+    static std::size_t
+    size (value_type const &val)
+    {
+        return converter<A>::size (val.first) + converter<B>::size (val.second);
+    }
+
+    static
+    cruft::view<std::byte*>
+    to_bytes [[nodiscard]] (
+        cruft::view<std::byte*> dst,
+        value_type const &src
+    ) {
+        dst = ::cruft::serialise::to_bytes (dst, src.first);
+        dst = ::cruft::serialise::to_bytes (dst, src.second);
+        return dst;
+    }
+
+    static
+    value_type
+    from_bytes (cruft::view<std::byte*> &src)
+    {
+        return {
+            cruft::serialise::converter<A>::from_bytes (src),
+            cruft::serialise::converter<B>::from_bytes (src),
+        };
+    }
+};
+
+
+///////////////////////////////////////////////////////////////////////////////
+template <typename ...ElementT>
+struct cruft::serialise::converter<std::tuple<ElementT...>> {
+    using value_type = std::tuple<ElementT...>;
+
+    static std::size_t
+    size (value_type const &val)
+    {
+        return size (val, std::make_index_sequence<sizeof ...(ElementT)> {});
+    }
+
+    static
+    cruft::view<std::byte*>
+    to_bytes [[nodiscard]] (
+        cruft::view<std::byte*> dst,
+        value_type const &src
+    ) {
+        return to_bytes (dst, src, std::make_index_sequence<sizeof... (ElementT)> {});
+    }
+
+    static
+    value_type
+    from_bytes (cruft::view<std::byte*> &src)
+    {
+        return from_bytes (src, std::make_index_sequence<sizeof... (ElementT)> {});
+    }
+
+private:
+    template <std::size_t ...Index>
+    static std::size_t
+    size (value_type const &val, std::index_sequence<Index...> const &)
+    {
+        return (
+            converter<
+                std::tuple_element_t<Index, value_type>
+            >::size (
+                std::get<Index> (val)
+            ) + ... + 0uz
+        );
+    }
+
+
+    template <std::size_t ...IndexV>
+    static
+    cruft::view<std::byte*>
+    to_bytes [[nodiscard]] (
+        cruft::view<std::byte*> dst,
+        value_type const &src,
+        std::index_sequence<IndexV...> const&
+    ) {
+        return ::cruft::serialise::to_bytes (dst, std::get<IndexV> (src)...);
+    }
+
+
+    template <std::size_t ...IndexV>
+    static
+    value_type
+    from_bytes (cruft::view<std::byte*> &src, std::index_sequence<IndexV...> const&)
+    {
+        return std::tuple {
+            ::cruft::serialise::from_bytes<ElementT> (src)...,
+        };
+    }
+};
diff --git a/test/serialise.cpp b/test/serialise.cpp
new file mode 100644
index 00000000..5a22102f
--- /dev/null
+++ b/test/serialise.cpp
@@ -0,0 +1,76 @@
+#include <cruft/util/tap.hpp>
+
+#include <cruft/util/serialise/ops.hpp>
+#include <cruft/util/serialise/std.hpp>
+
+
+///////////////////////////////////////////////////////////////////////////////
+static void
+test_scalars (cruft::TAP::logger &tap)
+{
+    std::vector<std::byte> store (sizeof (f32) + sizeof (i16) + sizeof (char));
+
+    {
+        auto remain = cruft::serialise::to_bytes (store, 2.f, i16 (3), char (4));
+        tap.expect (remain.empty (), "scalar serialise: no remainder");
+    }
+
+    {
+        cruft::view remain (store);
+        tap.expect_eq (cruft::serialise::from_bytes<f32>  (remain), 2.f, "scalar extract: f32");
+        tap.expect_eq (cruft::serialise::from_bytes<i16>  (remain),   3, "scalar extract: i16");
+        tap.expect_eq (cruft::serialise::from_bytes<char> (remain),   4, "scalar extract: char");
+        tap.expect (remain.empty (), "scalar extract: empty");
+    }
+}
+
+
+///////////////////////////////////////////////////////////////////////////////
+template <typename ValueT>
+static void
+test_roundtrip (cruft::TAP::logger &tap, char const *label, ValueT const &val)
+{
+    std::vector<std::byte> raw (cruft::serialise::size (val));
+    {
+        cruft::view remain (raw);
+        remain = cruft::serialise::to_bytes (remain, val);
+        tap.expect (remain.empty (), "round_trip {}: serialise", label);
+    }
+
+    {
+        cruft::view remain (raw);
+        auto const extracted = cruft::serialise::from_bytes<ValueT> (remain);
+        tap.expect_eq (extracted, val, "round_trip {}: extract", label);
+    }
+}
+
+
+///////////////////////////////////////////////////////////////////////////////
+static void
+test_stdlib (cruft::TAP::logger &tap)
+{
+    test_roundtrip (tap, "string", std::string ("this is a string"));
+    test_roundtrip (tap, "pair",   std::pair<int, bool> (1, false));
+    test_roundtrip (tap, "vector", std::vector<i16> { 1, 2, 3 });
+    test_roundtrip (
+        tap,
+        "tuple",
+        std::tuple (
+            std::string ("this is a string"),
+            std::pair<int, bool> { 1, false },
+            std::vector<i16> { 1, 2, 3 }
+        )
+    );
+}
+
+
+///////////////////////////////////////////////////////////////////////////////
+int main ()
+{
+    cruft::TAP::logger tap;
+
+    test_scalars (tap);
+    test_stdlib (tap);
+
+    return tap.status ();
+}
\ No newline at end of file