properties.h

// Copyright 2025 The Pigweed Authors
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy of
// the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations under
// the License.
#pragma once
 
#include <cstdint>
#include <type_traits>
 
namespace pw::multibuf::v2 {
 
 
enum class Property : uint8_t {
  kConst = 1 << 0,
 
  kLayerable = 1 << 1,
 
  kObservable = 1 << 2,
};
 
 
template <Property...>
class BasicMultiBuf;
 
namespace internal {
 
class GenericMultiBuf;
 
template <Property>
constexpr bool PropertiesAreInOrderWithoutDuplicates() {
  return true;
}
template <Property kLhs, Property kRhs, Property... kOthers>
constexpr bool PropertiesAreInOrderWithoutDuplicates() {
  return (kLhs < kRhs) &&
         PropertiesAreInOrderWithoutDuplicates<kRhs, kOthers...>();
}
 
template <Property... kProperties>
constexpr bool PropertiesAreValid() {
  if constexpr (sizeof...(kProperties) != 0) {
    static_assert(PropertiesAreInOrderWithoutDuplicates<kProperties...>(),
                  "Properties must be specified in the following order, "
                  "without duplicates: kConst, kLayerable, kObservable");
  }
  return true;
}
 
template <typename>
struct IsBasicMultiBuf : public std::false_type {};
 
template <Property... kProperties>
struct IsBasicMultiBuf<BasicMultiBuf<kProperties...>> : public std::true_type {
};
 
template <typename From, typename To>
using EnableIfConvertible =
    std::enable_if_t<std::is_same_v<To, GenericMultiBuf> ||
                     // Only conversion to other MultiBuf types are supported.
                     (IsBasicMultiBuf<To>::value &&
                      // Read-only data cannot be converted to mutable data.
                      (!From::is_const() || To::is_const()) &&
                      // Flat MultiBufs do not have layer-related methods.
                      (From::is_layerable() || !To::is_layerable()) &&
                      // Untracked MultiBufs do not have observer-related
                      // methods.
                      (From::is_observable() || !To::is_observable()))>;
 
template <typename From, typename To>
static constexpr void AssertIsConvertibleIgnoreConst() {
  if constexpr (!std::is_same_v<To, GenericMultiBuf>) {
    static_assert(IsBasicMultiBuf<To>::value,
                  "Only conversion to other MultiBuf types are supported.");
    static_assert(From::is_layerable() || !To::is_layerable(),
                  "Flat MultiBufs do not have layer-related methods.");
    static_assert(From::is_observable() || !To::is_observable(),
                  "Untracked MultiBufs do not have observer-related methods.");
  }
}
 
template <typename From, typename To>
static constexpr void AssertIsConvertible() {
  if constexpr (!std::is_same_v<To, GenericMultiBuf>) {
    AssertIsConvertibleIgnoreConst<From, To>();
    static_assert(!From::is_const() || To::is_const(),
                  "Read-only data cannot be converted to mutable data.");
  }
}
 
template <typename From, typename To>
static constexpr void AssertIsAssignable() {
  if constexpr (!std::is_same_v<To, GenericMultiBuf>) {
    static_assert(IsBasicMultiBuf<To>::value,
                  "Only assignment to other MultiBuf types are supported.");
    static_assert(!From::is_const() || To::is_const(),
                  "Read-only data cannot be assigned to mutable data.");
    static_assert(!From::is_layerable() || To::is_layerable(),
                  "Layered MultiBufs cannot be assigned to flat MultiBufs.");
    static_assert(
        !From::is_observable() || To::is_observable(),
        "Tracked MultiBufs cannot be assigned to untracked MultiBufs.");
  }
}
 
}  // namespace internal
}  // namespace pw::multibuf::v2