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

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#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;
};
}