ClickHouse/dbms/include/DB/IO/WriteBufferAIO.h
2015-03-10 20:14:07 +03:00

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#pragma once
#include <DB/IO/IBufferAIO.h>
#include <DB/IO/WriteBuffer.h>
#include <DB/IO/BufferWithOwnMemory.h>
#include <statdaemons/AIO.h>
#include <unistd.h>
#include <fcntl.h>
namespace DB
{
/** Класс для асинхронной записи данных.
* Все размеры и смещения должны быть кратны 512 байтам.
*/
class WriteBufferAIO : public IBufferAIO, public BufferWithOwnMemory<WriteBuffer>
{
public:
WriteBufferAIO(const std::string & filename_, size_t buffer_size_ = DBMS_DEFAULT_BUFFER_SIZE, int flags_ = -1, mode_t mode_ = 0666,
char * existing_memory_ = nullptr);
~WriteBufferAIO() override;
WriteBufferAIO(const WriteBufferAIO &) = delete;
WriteBufferAIO & operator=(const WriteBufferAIO &) = delete;
off_t seek(off_t off, int whence = SEEK_SET);
void truncate(off_t length = 0);
void sync();
std::string getFileName() const noexcept override { return filename; }
int getFD() const noexcept override { return fd; }
private:
void nextImpl() override;
void waitForCompletion() override;
void swapBuffers() noexcept override;
private:
/// Буфер для асинхронных операций записи данных.
BufferWithOwnMemory<WriteBuffer> flush_buffer;
const std::string filename;
AIOContext aio_context;
iocb cb;
std::vector<iocb *> request_ptrs;
std::vector<io_event> events;
int fd = -1;
size_t total_bytes_written = 0;
/// Асинхронная операция записи ещё не завершилась.
bool is_pending_write = false;
/// Было получено исключение.
bool got_exception = false;
};
}