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#pragma once
#include "align.h"
#include "file.h"
#include <util/generic/buffer.h>
// Supports Linux Direct-IO:
// - Simple buffering logic.
// - Default buffer size of 128KB matches VM page writeback granularity, to maximize IO throughput.
// - Supports writing odd sized files by turning off direct IO for the last chunk.
class TDirectIOBufferedFile {
public:
TDirectIOBufferedFile(const TString& path, EOpenMode oMode, size_t buflen = 1 << 17);
~TDirectIOBufferedFile();
void FlushData();
void Finish();
size_t Read(void* buffer, size_t byteCount);
void Write(const void* buffer, size_t byteCount);
size_t Pread(void* buffer, size_t byteCount, ui64 offset);
void Pwrite(const void* buffer, size_t byteCount, ui64 offset);
inline bool IsOpen() const {
return true;
}
inline ui64 GetWritePosition() const {
return WritePosition;
}
inline ui64 GetLength() const {
return FlushedBytes + DataLen;
}
inline FHANDLE GetHandle() {
return File.GetHandle();
}
inline void FallocateNoResize(ui64 length) {
File.FallocateNoResize(length);
}
inline void ShrinkToFit() {
File.ShrinkToFit();
}
private:
inline bool IsAligned(i64 value) {
return Alignment ? value == AlignDown<i64>(value, Alignment) : true;
}
inline bool IsAligned(const void* value) {
return Alignment ? value == AlignDown(value, Alignment) : true;
}
size_t PreadSafe(void* buffer, size_t byteCount, ui64 offset);
size_t ReadFromFile(void* buffer, size_t byteCount, ui64 offset);
void WriteToFile(const void* buf, size_t len, ui64 position);
void WriteToBuffer(const void* buf, size_t len, ui64 position);
void SetDirectIO(bool value);
private:
TFile File;
size_t Alignment;
size_t BufLen;
size_t DataLen;
void* Buffer;
TBuffer BufferStorage;
ui64 ReadPosition;
ui64 WritePosition;
ui64 FlushedBytes;
ui64 FlushedToDisk;
bool DirectIO;
};
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