value.h

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// Copyright (c) Microsoft Corporation. All rights reserved.
// Licensed under the Apache 2.0 License.
#pragma once
 
#include "ccf/kv/get_name.h"
#include "ccf/kv/hooks.h"
#include "ccf/kv/serialisers/blit_serialiser.h"
#include "ccf/kv/serialisers/json_serialiser.h"
#include "ccf/kv/untyped.h"
#include "ccf/kv/value_handle.h"
 
namespace ccf::kv
{
  template <
    typename V,
    typename VSerialiser,
    typename Unit = ccf::kv::serialisers::ZeroBlitUnitCreator>
  class TypedValue : public GetName
  {
  public:
    using ReadOnlyHandle = ccf::kv::ReadableValueHandle<V, VSerialiser, Unit>;
    using WriteOnlyHandle = ccf::kv::WriteableValueHandle<V, VSerialiser, Unit>;
    using Handle = ccf::kv::ValueHandle<V, VSerialiser, Unit>;
 
    using Write = std::optional<V>;
    using MapHook = MapHook<Write>;
    using CommitHook = CommitHook<Write>;
 
    using Value = V;
    using ValueSerialiser = VSerialiser;
 
    using GetName::GetName;
 
    static ccf::kv::serialisers::SerialisedEntry create_unit()
    {
      return Unit::get();
    }
 
  private:
    static Write deserialise_write(const ccf::kv::untyped::Write& w)
    {
      assert(w.size() == 1); // Value contains only one element
      const auto& value = w.begin()->second;
      if (!value.has_value())
      {
        return std::nullopt;
      }
      return VSerialiser::from_serialised(value.value());
    }
 
  public:
    static ccf::kv::untyped::CommitHook wrap_commit_hook(const CommitHook& hook)
    {
      return [hook](Version v, const ccf::kv::untyped::Write& w) {
        hook(v, deserialise_write(w));
      };
    }
 
    static ccf::kv::untyped::MapHook wrap_map_hook(const MapHook& hook)
    {
      return [hook](Version v, const ccf::kv::untyped::Write& w) {
        return hook(v, deserialise_write(w));
      };
    }
  };
 
  template <
    typename V,
    template <typename>
    typename VSerialiser,
    typename Unit = ccf::kv::serialisers::ZeroBlitUnitCreator>
  using ValueSerialisedWith = TypedValue<V, VSerialiser<V>, Unit>;
 
  template <typename V>
  using JsonSerialisedValue =
    ValueSerialisedWith<V, ccf::kv::serialisers::JsonSerialiser>;
 
  template <typename V>
  using RawCopySerialisedValue =
    TypedValue<V, ccf::kv::serialisers::BlitSerialiser<V>>;
 
  template <typename V>
  using Value = JsonSerialisedValue<V>;
}