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#pragma once
#include <forward_list>
#include <IO/WriteBuffer.h>
#include <IO/IReadableWriteBuffer.h>
#include <Common/Allocator.h>
#include <Core/Defines.h>
#include <boost/noncopyable.hpp>
namespace DB
{
/// Stores data in memory chunks, size of chunks are exponentially increasing during write
/// Written data could be reread after write
class MemoryWriteBuffer : public WriteBuffer, public IReadableWriteBuffer, boost::noncopyable, private Allocator<false>
{
public:
/// Special exception to throw when the current WriteBuffer cannot receive data
class CurrentBufferExhausted : public std::exception
{
public:
const char * what() const noexcept override { return "MemoryWriteBuffer limit is exhausted"; }
};
/// Use max_total_size_ = 0 for unlimited storage
explicit 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);
~MemoryWriteBuffer() override;
protected:
void nextImpl() override;
void finalizeImpl() override { /* no op */ }
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;
};
}
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