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/*++
Module Name:
BufferedAsync.h
Abstract:
Double-buffered asynchronous file I/O
Environment:
User mode service.
This class is NOT thread safe. It's the caller's responsibility to ensure that
at most one thread uses an instance at any time.
--*/
#pragma once
#include "stdafx.h"
#include "Compat.h"
class BufferedAsyncReader
{
public:
bool open(AsyncFile* file, size_t offset, size_t length, size_t bufferSize, bool async = false, void* buffer0 = NULL, void* buffer1 = NULL);
void endOpen();
bool atEnd();
bool read(void* data, size_t bytes);
bool close();
_int64 getWaitTimeInMillis() { return waitTime / 1000000; }
private:
int reading; // 0 or 1
size_t readOffset;
size_t bufferSize;
size_t nextFileOffset;
size_t fileSize;
AsyncFile::Reader* reader[2];
char* buffer[2];
size_t length[2];
bool ownBuffer;
_int64 waitTime; // in nanos
};
class BufferedAsyncWriter
{
public:
bool open(AsyncFile* file, size_t bufferSize, volatile _int64* sharedOffset = NULL);
bool write(void* data, size_t bytes);
void* forWrite(size_t bytes);
bool close();
_int64 getWaitTimeInMillis() { return waitTime / 1000000; }
private:
int writing; // 0 or 1
size_t writeOffset; // within buffer
size_t bufferSize;
volatile _int64 privateFileOffset; // used by default
volatile _int64* nextFileOffset; // for current buffer to write
AsyncFile::Writer* writer[2];
char* buffer[2];
_int64 waitTime; // in nanos
};
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