unit_value_handle.h

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// Copyright (c) Microsoft Corporation. All rights reserved.
// Licensed under the Apache 2.0 License.
#pragma once
 
#include "ccf/kv/unit.h"
#include "ccf/kv/untyped_map_handle.h"
 
namespace ccf::kv
{
  template <typename Unit>
  class ReadableUnitValueHandle
  {
  protected:
    ccf::kv::untyped::MapHandle& read_handle;
 
  public:
    ReadableUnitValueHandle(ccf::kv::untyped::MapHandle& uh) : read_handle(uh)
    {}
 
    bool has()
    {
      return read_handle.has(Unit::get());
    }
 
    std::optional<Version> get_version_of_previous_write()
    {
      return read_handle.get_version_of_previous_write(Unit::get());
    }
  };
 
  template <typename Unit>
  class WriteableUnitValueHandle
  {
  protected:
    ccf::kv::untyped::MapHandle& write_handle;
 
  public:
    WriteableUnitValueHandle(ccf::kv::untyped::MapHandle& uh) : write_handle(uh)
    {}
 
    void touch()
    {
      write_handle.put(Unit::get(), Unit::get());
    }
 
    void clear()
    {
      write_handle.clear();
    }
  };
 
  template <typename Unit>
  class UnitValueHandle : public AbstractHandle,
                          public ReadableUnitValueHandle<Unit>,
                          public WriteableUnitValueHandle<Unit>
  {
  protected:
    ccf::kv::untyped::MapHandle untyped_handle;
 
    using ReadableBase = ReadableUnitValueHandle<Unit>;
    using WriteableBase = WriteableUnitValueHandle<Unit>;
 
  public:
    UnitValueHandle(
      ccf::kv::untyped::ChangeSet& changes, const std::string& map_name) :
      ReadableBase(untyped_handle),
      WriteableBase(untyped_handle),
      untyped_handle(changes, map_name)
    {}
  };
}