//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.

//  This source code is licensed under both the GPLv2 (found in the

//  COPYING file in the root directory) and Apache 2.0 License

//  (found in the LICENSE.Apache file in the root directory).

#include "utilities/merge_operators/bytesxor.h"

#include <algorithm>

#include <string>

namespace ROCKSDB_NAMESPACE {

std::shared_ptr<MergeOperator> MergeOperators::CreateBytesXOROperator() {

  return std::make_shared<BytesXOROperator>();

}

bool BytesXOROperator::Merge(const Slice& /*key*/, const Slice* existing_value,

                             const Slice& value, std::string* new_value,

                             Logger* /*logger*/) const {

  XOR(existing_value, value, new_value);

  return true;

}

void BytesXOROperator::XOR(const Slice* existing_value, const Slice& value,

                           std::string* new_value) const {

  if (!existing_value) {

    new_value->clear();

    new_value->assign(value.data(), value.size());

    return;

  }

  size_t min_size = std::min(existing_value->size(), value.size());

  size_t max_size = std::max(existing_value->size(), value.size());

  new_value->clear();

  new_value->reserve(max_size);

  const char* existing_value_data = existing_value->data();

  const char* value_data = value.data();

  for (size_t i = 0; i < min_size; i++) {

    new_value->push_back(existing_value_data[i] ^ value_data[i]);

  }

  if (existing_value->size() == max_size) {

    for (size_t i = min_size; i < max_size; i++) {

      new_value->push_back(existing_value_data[i]);

    }

  } else {

    assert(value.size() == max_size);

    for (size_t i = min_size; i < max_size; i++) {

      new_value->push_back(value_data[i]);

    }

  }

}

}  // namespace ROCKSDB_NAMESPACE