Write interface for new serialization system

1 files changed, 195 insertions, 0 deletions

diff --git a/contrib/epee/include/serialization/wire/traits.h b/contrib/epee/include/serialization/wire/traits.h
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+++ b/contrib/epee/include/serialization/wire/traits.h
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+// Copyright (c) 2021, The Monero Project
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without modification, are
+// permitted provided that the following conditions are met:
+//
+// 1. Redistributions of source code must retain the above copyright notice, this list of
+//    conditions and the following disclaimer.
+//
+// 2. Redistributions in binary form must reproduce the above copyright notice, this list
+//    of conditions and the following disclaimer in the documentation and/or other
+//    materials provided with the distribution.
+//
+// 3. Neither the name of the copyright holder nor the names of its contributors may be
+//    used to endorse or promote products derived from this software without specific
+//    prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
+// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#pragma once
+
+#include <cstdint>
+#include <type_traits>
+
+#define WIRE_DECLARE_BLOB_NS(type) \
+  template<>                       \
+  struct is_blob<type>             \
+    : std::true_type               \
+  {}
+
+#define WIRE_DECLARE_BLOB(type)                  \
+  namespace wire { WIRE_DECLARE_BLOB_NS(type); }
+
+#define WIRE_DECLARE_OPTIONAL_ROOT(type) \
+  template<>                             \
+  struct is_optional_root<type>          \
+    : std::true_type                     \
+  {}
+
+namespace wire
+{
+  template<typename T>
+  struct unwrap_reference
+  {
+    using type = std::remove_cv_t<std::remove_reference_t<T>>;
+  };
+
+  template<typename T>
+  struct unwrap_reference<std::reference_wrapper<T>>
+    : std::remove_cv<T>
+  {};
+
+  template<typename T>
+  using unwrap_reference_t = typename unwrap_reference<T>::type;
+
+
+  /*! Mark `T` as an array for writing, and reading when
+    `default_min_element_size<T::value_type>::value != 0`. See `array_` in
+    `wrapper/array.h`. */
+  template<typename T>
+  struct is_array : std::false_type
+  {};
+
+  /*! Mark `T` as fixed binary data for reading+writing. Concept requirements
+      for reading:
+        * `T` must be compatible with `epee::as_mut_byte_span` (`std::is_pod<T>`
+          and no padding).
+      Concept requirements for writing:
+        * `T` must be compatible with `epee::as_byte_span` (std::is_pod<T>` and
+          no padding). */
+  template<typename T>
+  struct is_blob : std::false_type
+  {};
+
+  /*! Forces field to be optional when empty. Concept requirements for `T` when
+    `is_optional_on_empty<T>::value == true`:
+      * must have an `empty()` method that toggles whether the associated
+        `wire::field_<...>` is omitted by the `wire::writer`.
+      * must have a `clear()` method where `empty() == true` upon completion,
+        used by the `wire::reader` when the `wire::field_<...>` is omitted. */
+  template<typename T>
+  struct is_optional_on_empty
+    : is_array<T> // all array types in old output engine were optional when empty
+  {};
+
+  //! When `T` is being read as root object, allow an empty read buffer.
+  template<typename T>
+  struct is_optional_root
+    : std::is_empty<T>
+  {};
+
+  //! A constraint for `wire_read::array` where a max of `N` elements can be read.
+  template<std::size_t N>
+  struct max_element_count
+    : std::integral_constant<std::size_t, N>
+  {
+    // The threshold is low - min_element_size is a better constraint metric
+    static constexpr std::size_t max_bytes() noexcept { return 512 * 1024; } // 512 KiB
+
+    //! \return True if `N` C++ objects of type `T` are below `max_bytes()` threshold.
+    template<typename T>
+    static constexpr bool check() noexcept
+    {
+      return N <= (max_bytes() / sizeof(T));
+    }
+  };
+
+  //! A constraint for `wire_read::array` where each element must use at least `N` bytes on the wire.
+  template<std::size_t N>
+  struct min_element_size
+    : std::integral_constant<std::size_t, N>
+  {
+    static constexpr std::size_t max_ratio() noexcept { return 4; }
+
+    //! \return True if C++ object of type `T` with minimum wire size `N` is below `max_ratio()`.
+    template<typename T>
+    static constexpr bool check() noexcept
+    {
+      return N != 0 ? ((sizeof(T) / N) <= max_ratio()) : false;
+    }
+  };
+
+  /*! Trait used in `wire/read.h` for default `min_element_size` behavior based
+    on an array of `T` objects and `R` reader type. This trait can be used
+    instead of the `wire::array(...)` (and associated macros) functionality, as
+    it sets a global value. The last argument is for `enable_if`. */
+  template<typename R, typename T, typename = void>
+  struct default_min_element_size
+    : std::integral_constant<std::size_t, 0>
+  {};
+
+  //! If `T` is a blob, a safe default for all formats is the size of the blob
+  template<typename R, typename T>
+  struct default_min_element_size<R, T, std::enable_if_t<is_blob<T>::value>>
+    : std::integral_constant<std::size_t, sizeof(T)>
+  {};
+
+  // example usage : `wire::sum(std::size_t(wire::available(fields))...)`
+
+  inline constexpr int sum() noexcept
+  {
+    return 0;
+  }
+  template<typename T, typename... U>
+  inline constexpr T sum(const T head, const U... tail) noexcept
+  {
+    return head + sum(tail...);
+  }
+
+  template<typename... T>
+  using min_element_sizeof = min_element_size<sum(sizeof(T)...)>;
+
+  //! If container has no `reserve(0)` function, this function is used
+  template<typename... T>
+  inline void reserve(const T&...) noexcept
+  {}
+
+  //! Container has `reserve(std::size_t)` function, use it
+  template<typename T>
+  inline auto reserve(T& container, const std::size_t count) -> decltype(container.reserve(count))
+  { return container.reserve(count); }
+
+  //! If `T` has no `empty()` function, this function is used
+  template<typename... T>
+  inline constexpr bool empty(const T&...) noexcept
+  {
+    static_assert(sum(is_optional_on_empty<T>::value...) == 0, "type needs empty method");
+    return false;
+  }
+
+  //! `T` has `empty()` function, use it
+  template<typename T>
+  inline auto empty(const T& container) -> decltype(container.empty())
+  { return container.empty(); }
+
+  //! If `T` has no `clear()` function, this function is used
+  template<typename... T>
+  inline void clear(const T&...) noexcept
+  {
+    static_assert(sum(is_optional_on_empty<T>::value...) == 0, "type needs clear method");
+  }
+
+  //! `T` has `clear()` function, use it
+  template<typename T>
+  inline auto clear(T& container) -> decltype(container.clear())
+  { return container.clear(); }
+} // wire