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#pragma once
#include <IO/ReadBufferFromFileDecorator.h>
namespace DB
{
/// A buffer which allows to make an underlying buffer as right bounded,
/// e.g. the buffer cannot return data beyond offset specified in `setReadUntilPosition`.
class BoundedReadBuffer : public ReadBufferFromFileDecorator
{
public:
explicit BoundedReadBuffer(std::unique_ptr<SeekableReadBuffer> impl_);
bool supportsRightBoundedReads() const override { return true; }
void setReadUntilPosition(size_t position) override;
void setReadUntilEnd() override;
bool nextImpl() override;
off_t seek(off_t off, int whence) override;
size_t getFileOffsetOfBufferEnd() const override { return file_offset_of_buffer_end; }
/// file_offset_of_buffer_end can differ from impl's file_offset_of_buffer_end
/// because of resizing of the tail. => Need to also override getPosition() as
/// it uses file_offset_of_buffer_end.
off_t getPosition() override;
private:
std::optional<size_t> read_until_position;
/// atomic because can be used in log or exception messages while being updated.
std::atomic<size_t> file_offset_of_buffer_end = 0;
};
}
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