1 | #pragma once |
2 | |
3 | #include <IO/WriteBufferFromFileBase.h> |
4 | |
5 | |
6 | namespace DB |
7 | { |
8 | |
9 | /** Use ready file descriptor. Does not open or close a file. |
10 | */ |
11 | class WriteBufferFromFileDescriptor : public WriteBufferFromFileBase |
12 | { |
13 | protected: |
14 | int fd; |
15 | |
16 | void nextImpl() override; |
17 | |
18 | /// Name or some description of file. |
19 | std::string getFileName() const override; |
20 | |
21 | public: |
22 | WriteBufferFromFileDescriptor( |
23 | int fd_ = -1, |
24 | size_t buf_size = DBMS_DEFAULT_BUFFER_SIZE, |
25 | char * existing_memory = nullptr, |
26 | size_t alignment = 0); |
27 | |
28 | /** Could be used before initialization if needed 'fd' was not passed to constructor. |
29 | * It's not possible to change 'fd' during work. |
30 | */ |
31 | void setFD(int fd_) |
32 | { |
33 | fd = fd_; |
34 | } |
35 | |
36 | ~WriteBufferFromFileDescriptor() override; |
37 | |
38 | int getFD() const override |
39 | { |
40 | return fd; |
41 | } |
42 | |
43 | off_t getPositionInFile() override; |
44 | |
45 | void sync() override; |
46 | |
47 | private: |
48 | off_t doSeek(off_t offset, int whence) override; |
49 | |
50 | void doTruncate(off_t length) override; |
51 | }; |
52 | |
53 | } |
54 | |