// Copyright (c) 2013, Facebook, Inc. All rights reserved. // This source code is licensed under the BSD-style license found in the // LICENSE file in the root directory of this source tree. An additional grant // of patent rights can be found in the PATENTS file in the same directory. #include <memory> #include "rocksdb/env.h" #include "rocksdb/merge_operator.h" #include "rocksdb/slice.h" #include "util/coding.h" #include "utilities/merge_operators.h" using namespace rocksdb; namespace { // anonymous namespace // A 'model' merge operator with uint64 addition semantics // Implemented as an AssociativeMergeOperator for simplicity and example. class UInt64AddOperator : public AssociativeMergeOperator { public: virtual bool Merge(const Slice& key, const Slice* existing_value, const Slice& value, std::string* new_value, Logger* logger) const override { uint64_t orig_value = 0; if (existing_value){ orig_value = DecodeInteger(*existing_value, logger); } uint64_t operand = DecodeInteger(value, logger); assert(new_value); new_value->clear(); PutFixed64(new_value, orig_value + operand); return true; // Return true always since corruption will be treated as 0 } virtual const char* Name() const override { return "UInt64AddOperator"; } private: // Takes the string and decodes it into a uint64_t // On error, prints a message and returns 0 uint64_t DecodeInteger(const Slice& value, Logger* logger) const { uint64_t result = 0; if (value.size() == sizeof(uint64_t)) { result = DecodeFixed64(value.data()); } else if (logger != nullptr) { // If value is corrupted, treat it as 0 Log(InfoLogLevel::ERROR_LEVEL, logger, "uint64 value corruption, size: %zu > %zu", value.size(), sizeof(uint64_t)); } return result; } }; } namespace rocksdb { std::shared_ptr<MergeOperator> MergeOperators::CreateUInt64AddOperator() { return std::make_shared<UInt64AddOperator>(); } }