FlattenRestore.h

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// Copyright 2019-2020 CERN and copyright holders of ALICE O2.
// See https://alice-o2.web.cern.ch/copyright for details of the copyright holders.
// All rights not expressly granted are reserved.
//
// This software is distributed under the terms of the GNU General Public
// License v3 (GPL Version 3), copied verbatim in the file "COPYING".
//
// In applying this license CERN does not waive the privileges and immunities
// granted to it by virtue of its status as an Intergovernmental Organization
// or submit itself to any jurisdiction.
 
#ifndef FLATTERRESTORE_H
#define FLATTERRESTORE_H
 
 
#include <type_traits>
 
namespace o2::algorithm
{
namespace flatten
{
 
template <typename ValueType, typename... Args>
constexpr size_t value_size(ValueType const& value, Args&&... args)
{
  size_t size = sizeof(typename std::remove_pointer<typename std::remove_reference<ValueType>::type>::type);
  if constexpr (sizeof...(Args) > 0) {
    size += value_size(std::forward<Args>(args)...);
  }
  return size;
}
 
template <typename TargetType, typename ValueType, typename... Args>
static size_t copy_to(TargetType& wrtptr, size_t count, ValueType* array, Args&&... args)
{
  static_assert(std::is_pointer<TargetType>::value == true, "need reference to pointer");
  static_assert(sizeof(typename std::remove_pointer<TargetType>::type) == 1, "need char-like pointer");
 
  size_t copySize = 0;
  if (array != nullptr) {
    copySize = count * value_size(array);
    memcpy(wrtptr, array, copySize);
    wrtptr += copySize;
  } else if (count > 0) {
    throw std::runtime_error("invalid nullptr to array of " + std::to_string(count) + " element(s)");
  }
  if constexpr (sizeof...(Args) > 0) {
    copySize += copy_to(wrtptr, count, std::forward<Args>(args)...);
  }
  return copySize;
}
 
template <typename BufferType, typename ValueType, typename... Args>
static size_t set_from(BufferType& readptr, size_t count, ValueType& array, Args&&... args)
{
  static_assert(std::is_pointer<typename std::remove_reference<ValueType>::type>::value == true, "need reference to pointer");
  array = reinterpret_cast<typename std::remove_reference<ValueType>::type>(readptr);
  size_t readSize = count * value_size(array);
  readptr += readSize;
  if constexpr (sizeof...(Args) > 0) {
    readSize += set_from(readptr, count, std::forward<Args>(args)...);
  }
  return readSize;
}
 
template <typename BufferType, typename... Args>
static size_t calc_size(BufferType const& dummyptr, size_t count, Args&&... args)
{
  return count * value_size(std::forward<Args>(args)...);
}
 
} // namespace flatten
} // namespace o2::algorithm
 
#endif