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/**
* @author Deon Nicholas (dnicholas@fb.com)
* Copyright 2013 Facebook
*/
#include "stringappend2.h"
#include <memory>
#include <string>
#include <assert.h>
#include "rocksdb/slice.h"
#include "rocksdb/merge_operator.h"
#include "utilities/merge_operators.h"
namespace ROCKSDB_NAMESPACE {
// Constructor: also specify the delimiter character.
StringAppendTESTOperator::StringAppendTESTOperator(char delim_char)
: delim_(delim_char) {
}
// Implementation for the merge operation (concatenates two strings)
bool StringAppendTESTOperator::FullMergeV2(
const MergeOperationInput& merge_in,
MergeOperationOutput* merge_out) const {
// Clear the *new_value for writing.
merge_out->new_value.clear();
if (merge_in.existing_value == nullptr && merge_in.operand_list.size() == 1) {
// Only one operand
merge_out->existing_operand = merge_in.operand_list.back();
return true;
}
// Compute the space needed for the final result.
size_t numBytes = 0;
for (auto it = merge_in.operand_list.begin();
it != merge_in.operand_list.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 (merge_in.existing_value) {
merge_out->new_value.reserve(numBytes + merge_in.existing_value->size());
merge_out->new_value.append(merge_in.existing_value->data(),
merge_in.existing_value->size());
printDelim = true;
} else if (numBytes) {
merge_out->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 = merge_in.operand_list.begin();
it != merge_in.operand_list.end(); ++it) {
if (printDelim) {
merge_out->new_value.append(1, delim_);
}
merge_out->new_value.append(it->data(), it->size());
printDelim = true;
}
return true;
}
bool StringAppendTESTOperator::PartialMergeMulti(
const Slice& /*key*/, const std::deque<Slice>& /*operand_list*/,
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::_AssocPartialMergeMulti(
const Slice& /*key*/, const std::deque<Slice>& operand_list,
std::string* new_value, Logger* /*logger*/) const {
// Clear the *new_value for writing
assert(new_value);
new_value->clear();
assert(operand_list.size() >= 2);
// Generic append
// Determine and reserve correct size for *new_value.
size_t size = 0;
for (const auto& operand : operand_list) {
size += operand.size();
}
size += operand_list.size() - 1; // Delimiters
new_value->reserve(size);
// Apply concatenation
new_value->assign(operand_list.front().data(), operand_list.front().size());
for (std::deque<Slice>::const_iterator it = operand_list.begin() + 1;
it != operand_list.end(); ++it) {
new_value->append(1, delim_);
new_value->append(it->data(), it->size());
}
return true;
}
const char* StringAppendTESTOperator::Name() const {
return "StringAppendTESTOperator";
}
std::shared_ptr<MergeOperator>
MergeOperators::CreateStringAppendTESTOperator() {
return std::make_shared<StringAppendTESTOperator>(',');
}
} // namespace ROCKSDB_NAMESPACE
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