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/**
* @author Deon Nicholas (dnicholas@fb.com)
* Copyright 2013 Facebook
*/
#include "stringappend2.h"
#include <memory>
#include <assert.h>
#include "rocksdb/slice.h"
#include "rocksdb/merge_operator.h"
#include "utilities/merge_operators.h"
namespace leveldb {
// Constructor: also specify the delimiter character.
StringAppendTESTOperator::StringAppendTESTOperator(char delim_char)
: delim_(delim_char) {
}
// Implementation for the merge operation (concatenates two strings)
bool StringAppendTESTOperator::FullMerge(
const Slice& key,
const Slice* existing_value,
const std::deque<std::string>& operands,
std::string* new_value,
Logger* logger) const {
// Clear the *new_value for writing.
assert(new_value);
new_value->clear();
// Compute the space needed for the final result.
int numBytes = 0;
for(auto it = operands.begin(); it != operands.end(); ++it) {
numBytes += it->size() + 1; // Plus 1 for the delimiter
}
// Only print the delimiter after the first entry has been printed
bool printDelim = false;
// Prepend the *existing_value if one exists.
if (existing_value) {
new_value->reserve(numBytes + existing_value->size());
new_value->append(existing_value->data(), existing_value->size());
printDelim = true;
} else if (numBytes) {
new_value->reserve(numBytes-1); // Minus 1 since we have one less delimiter
}
// Concatenate the sequence of strings (and add a delimiter between each)
for(auto it = operands.begin(); it != operands.end(); ++it) {
if (printDelim) {
new_value->append(1,delim_);
}
new_value->append(*it);
printDelim = true;
}
return true;
}
bool StringAppendTESTOperator::PartialMerge(const Slice& key,
const Slice& left_operand,
const Slice& right_operand,
std::string* new_value,
Logger* logger) const {
return false;
}
// A version of PartialMerge that actually performs "partial merging".
// Use this to simulate the exact behaviour of the StringAppendOperator.
bool StringAppendTESTOperator::_AssocPartialMerge(const Slice& key,
const Slice& left_operand,
const Slice& right_operand,
std::string* new_value,
Logger* logger) const {
// Clear the *new_value for writing.
assert(new_value);
new_value->clear();
// Generic append
// Reserve correct size for *new_value, and apply concatenation.
new_value->reserve(left_operand.size() + 1 + right_operand.size());
new_value->assign(left_operand.data(), left_operand.size());
new_value->append(1,delim_);
new_value->append(right_operand.data(), right_operand.size());
return true;
}
const char* StringAppendTESTOperator::Name() const {
return "StringAppendTESTOperator";
}
std::shared_ptr<MergeOperator>
MergeOperators::CreateStringAppendTESTOperator() {
return std::make_shared<StringAppendTESTOperator>(',');
}
} // namespace leveldb
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