ClickHouse/dbms/include/DB/IO/MemoryReadWriteBuffer.h

#pragma once
#include <forward_list>

#include <DB/IO/WriteBuffer.h>
#include <DB/IO/IReadableWriteBuffer.h>
#include <DB/Common/Allocator.h>
#include <DB/Core/Defines.h>

namespace DB
{

/// Stores data in memory chunks, size of cunks are exponentially increasing during write
/// Written data could be reread after write
class MemoryWriteBuffer : public WriteBuffer, public IReadableWriteBuffer, boost::noncopyable, private Allocator<false>
{
public:

	/// Use max_total_size_ = 0 for unlimited storage
	MemoryWriteBuffer(
		size_t max_total_size_ = 0,
		size_t initial_chunk_size_ = DBMS_DEFAULT_BUFFER_SIZE,
		double growth_rate_ = 2.0,
		size_t max_chunk_size_ = 128 * DBMS_DEFAULT_BUFFER_SIZE);

	void nextImpl() override;

	~MemoryWriteBuffer() override;

protected:

	std::shared_ptr<ReadBuffer> getReadBufferImpl() override;

	const size_t max_total_size;
	const size_t initial_chunk_size;
	const size_t max_chunk_size;
	const double growth_rate;

	using Container = std::forward_list<BufferBase::Buffer>;

	Container chunk_list;
	Container::iterator chunk_tail;
	size_t total_chunks_size = 0;

	void addChunk();

	friend class ReadBufferFromMemoryWriteBuffer;
};


}