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#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 simplicty 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(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>();
}
}
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