ClickHouse/dbms/include/DB/IO/WriteBufferFromFileDescriptor.h
2016-10-25 09:49:24 +03:00

54 lines
958 B
C++

#pragma once
#include <DB/IO/WriteBufferFromFileBase.h>
namespace DB
{
/** Use ready file descriptor. Does not open or close a file.
*/
class WriteBufferFromFileDescriptor : public WriteBufferFromFileBase
{
protected:
int fd;
void nextImpl() override;
/// Name or some description of file.
std::string getFileName() const override;
public:
WriteBufferFromFileDescriptor(
int fd_ = -1,
size_t buf_size = DBMS_DEFAULT_BUFFER_SIZE,
char * existing_memory = nullptr,
size_t alignment = 0);
/** Could be used before initialization if needed 'fd' was not passed to constructor.
* It's not possible to change 'fd' during work.
*/
void setFD(int fd_)
{
fd = fd_;
}
~WriteBufferFromFileDescriptor() override;
int getFD() const override
{
return fd;
}
off_t getPositionInFile() override;
void sync() override;
private:
off_t doSeek(off_t offset, int whence) override;
void doTruncate(off_t length) override;
};
}