LineReader.h

#pragma once

#include "CharBuffer.h"
#include "ScanFile.h"

#include <optional>    // this is STL, but it does not need exceptions
#include <string_view> // this is STL, but it does not need exceptions

#include <wchar.h> // for size_t


//////////////////////////////////////////////////////////////////////////

// Implementation with 2 buffers and async calls to ReadFile()
class CSyncLineReader
{
public:
    CSyncLineReader();

    bool Open(const wchar_t* const filename);
    void Close();

    // request next matching line; line may contain '\0' and may end with '\n'; return false on error or EOF
    // returned line is never empty (it contains at least one '\n' or any other character).
    std::optional<std::string_view> GetNextLine();

protected:
    CScanFile        _file;
    // Buffer structure: [    rest_of_previousline|data_read_from_file  ]
    //                   [ len = MaxLogLineLength | len = ReadChunkSize ]
    CCharBuffer      _buffer;
    std::string_view _bufferData; // filled part of the buffer
};

//////////////////////////////////////////////////////////////////////////

// Implementation with usual sync calls to ReadFile()
class CAsyncLineReader
{
public:
    CAsyncLineReader();

    bool Open(const wchar_t* const filename);
    void Close();

    // request next matching line; line may contain '\0' and may end with '\n'; return false on error or EOF
    // returned line is never empty (it contains at least one '\n' or any other character).
    std::optional<std::string_view> GetNextLine();

protected:
    CScanFile        _file;
    // Buffer structure: [    rest_of_previousline|data_read_from_file  ]
    //                   [ len = MaxLogLineLength | len = ReadChunkSize ]
    bool             _firstBufferIsActive = true;
    CCharBuffer      _buffer1;
    CCharBuffer      _buffer2;
    std::string_view _bufferData; // filled part of the current buffer
};

//////////////////////////////////////////////////////////////////////////

// Implementation with file mapped to a big single readonly memory block
class CMappingLineReader
{
public:
    bool Open(const wchar_t* const filename);
    void Close();

    // request next matching line; line may contain '\0' and may end with '\n'; return false on error or EOF
    // returned line is never empty (it contains at least one '\n' or any other character).
    std::optional<std::string_view> GetNextLine();

protected:
    CScanFile        _file;
    bool             _mappedToMemory = false;
    std::string_view _bufferData; // filled part of the current buffer
};

//////////////////////////////////////////////////////////////////////////

// Implementation with 2 buffers and separate thread for sync calls to ReadFile(); synchronization is done without Windows EVENTs (manual spin locks)
class CSpinlockLineReader
{
public:
    CSpinlockLineReader();

    bool Open(const wchar_t* const filename);
    void Close();

    // request next matching line; line may contain '\0' and may end with '\n'; return false on error or EOF
    // returned line is never empty (it contains at least one '\n' or any other character).
    std::optional<std::string_view> GetNextLine();

protected:
    CScanFile        _file;
    // Buffer structure: [    rest_of_previousline|data_read_from_file  ]
    //                   [ len = MaxLogLineLength | len = ReadChunkSize ]
    bool             _firstBufferIsActive = true;
    CCharBuffer      _buffer1;
    CCharBuffer      _buffer2;
    std::string_view _bufferData; // filled part of the current buffer
};

//////////////////////////////////////////////////////////////////////////