ceph/src/rocksdb/utilities/merge_operators/bytesxor.cc

   1 //  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
   2 //  This source code is licensed under both the GPLv2 (found in the
   3 //  COPYING file in the root directory) and Apache 2.0 License
   4 //  (found in the LICENSE.Apache file in the root directory).
   5
   6 #include <algorithm>
   7 #include <string>
   8
   9 #include "utilities/merge_operators/bytesxor.h"
  10
  11 namespace ROCKSDB_NAMESPACE {
  12
  13 std::shared_ptr<MergeOperator> MergeOperators::CreateBytesXOROperator() {
  14   return std::make_shared<BytesXOROperator>();
  15 }
  16
  17 bool BytesXOROperator::Merge(const Slice& /*key*/,
  18                             const Slice* existing_value,
  19                             const Slice& value,
  20                             std::string* new_value,
  21                             Logger* /*logger*/) const {
  22   XOR(existing_value, value, new_value);
  23   return true;
  24 }
  25
  26 void BytesXOROperator::XOR(const Slice* existing_value,
  27           const Slice& value, std::string* new_value) const {
  28   if (!existing_value) {
  29     new_value->clear();
  30     new_value->assign(value.data(), value.size());
  31     return;
  32   }
  33
  34   size_t min_size = std::min(existing_value->size(), value.size());
  35   size_t max_size = std::max(existing_value->size(), value.size());
  36
  37   new_value->clear();
  38   new_value->reserve(max_size);
  39
  40   const char* existing_value_data = existing_value->data();
  41   const char* value_data = value.data();
  42
  43   for (size_t i = 0; i < min_size; i++) {
  44     new_value->push_back(existing_value_data[i] ^ value_data[i]);
  45   }
  46
  47   if (existing_value->size() == max_size) {
  48     for (size_t i = min_size; i < max_size; i++) {
  49       new_value->push_back(existing_value_data[i]);
  50     }
  51   } else {
  52           assert(value.size() == max_size);
  53     for (size_t i = min_size; i < max_size; i++) {
  54       new_value->push_back(value_data[i]);
  55     }
  56   }
  57 }
  58
  59 }  // namespace ROCKSDB_NAMESPACE