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// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
#pragma once
#include "generationhandler.h"
#include <vector>
#include <memory>
namespace vespalib {
class GenerationHeldBase
{
public:
typedef GenerationHandler::generation_t generation_t;
typedef std::unique_ptr<GenerationHeldBase> UP;
typedef std::shared_ptr<GenerationHeldBase> SP;
generation_t _generation;
private:
size_t _byte_size;
public:
GenerationHeldBase(size_t byte_size_in)
: _generation(0u),
_byte_size(byte_size_in)
{ }
virtual ~GenerationHeldBase();
size_t byte_size() const { return _byte_size; }
};
/*
* GenerationHolder is meant to hold large elements until readers can
* no longer access them.
*/
class GenerationHolder
{
private:
typedef GenerationHandler::generation_t generation_t;
typedef GenerationHandler::sgeneration_t sgeneration_t;
typedef std::vector<GenerationHeldBase::UP> HoldList;
HoldList _hold1List;
HoldList _hold2List;
std::atomic<size_t> _heldBytes;
/**
* Transfer holds from hold1 to hold2 lists, assigning generation.
*/
void transferHoldListsSlow(generation_t generation);
/**
* Remove all data elements from this holder where generation < usedGen.
**/
void trimHoldListsSlow(generation_t usedGen);
public:
GenerationHolder();
~GenerationHolder();
/**
* Add the given data pointer to this holder.
**/
void hold(GenerationHeldBase::UP data);
/**
* Transfer holds from hold1 to hold2 lists, assigning generation.
*/
void transferHoldLists(generation_t generation) {
if (!_hold1List.empty()) {
transferHoldListsSlow(generation);
}
}
/**
* Remove all data elements from this holder where generation < usedGen.
**/
void trimHoldLists(generation_t usedGen) {
if (!_hold2List.empty() && static_cast<sgeneration_t>(_hold2List.front()->_generation - usedGen) < 0) {
trimHoldListsSlow(usedGen);
}
}
void clearHoldLists();
size_t getHeldBytes() const { return _heldBytes.load(std::memory_order_relaxed); }
};
}
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