#include <Core/Core.h>
#include <Functions4U/Functions4U.h>
#include <sys/mman.h>

using namespace Upp;

class MemoryMapStream : public MemStream {
public:
    void Load(String filename) {
        file.Open(filename);
        map = (char*)mmap(0, file.GetSize(), PROT_READ, MAP_SHARED, file.GetHandle(), 0);
        Create(map, file.GetSize());
    }

    MemoryMapStream(String filename) {
        Load(filename);
    }
    
    ~MemoryMapStream() {
        if(map) {
            munmap(map, file.GetSize());
        }
    }

private:
    FileIn    file;
    char*     map {};
};

CONSOLE_APP_MAIN {
    Vector<int64> positions;
    
    // 1 gigabyte test csv file
    const String fname = "test.csv";
    
    {
        FileIn f(fname);
        
        while(!f.IsEof()) {
            GetCsvLine(f, ',', CHARSET_DEFAULT);
            positions.Add() = f.GetPos();
        }
        
        positions.Drop();
        Shuffle(positions);
    }
    
    Vector<String> lines;
    
    {
        MemoryMapStream mms(fname);
        
        TimeStop tm;
        RTIMESTOP("MemoryMapStream serial performance");
        
        while(!mms.IsEof()) {
            RTIMING("GetCsvLine MemorymapStream");
            lines = GetCsvLine(mms, ',', CHARSET_DEFAULT);
        }
        
        RDUMP(tm.Elapsed());
    }
    
    {
        FileIn f(fname);
        
        TimeStop tm;
        RTIMESTOP("FileIn serial performance");
        
        while(!f.IsEof()) {
            RTIMING("GetCsvLine FileIn");
            lines = GetCsvLine(f, ',', CHARSET_DEFAULT);
        }
        
        RDUMP(tm.Elapsed());
    }
     
    {
        MemoryMapStream mms(fname);
        
        TimeStop tm;
        RTIMESTOP("MemoryMapStream random performance");
        
        for(int i = 0; i < positions.GetCount(); i++) {
            RTIMING("GetCsvLine MemoryMapStream (random seek)");
            
            mms.Seek(positions[i]);
            lines = GetCsvLine(mms, ',', CHARSET_DEFAULT);
        }
        
        RDUMP(tm.Elapsed());
    }
    
    {
        FileIn f(fname);
        
        TimeStop tm;
        RTIMESTOP("FileIn random performance");
        
        for(int i = 0; i < positions.GetCount(); i++) {
			RTIMING("GetCsvLine FileIn (random seek)");
            
            f.Seek(positions[i]);
            lines = GetCsvLine(f, ',', CHARSET_DEFAULT);
        }
        
        RDUMP(tm.Elapsed());
    }
}

tm.Elapsed() = 6755842
MemoryMapStream serial performance 6.755847 s
tm.Elapsed() = 7023237
FileIn serial performance 7.023258 s
tm.Elapsed() = 7768212
MemoryMapStream random performance 7.768234 s
tm.Elapsed() = 16070698
FileIn random performance 16.070718 s
TIMING GetCsvLine FileIn (random seek): 15.70 s  -  2.35 us (15.83 s  / 6674559 ), min:  0.00 ns, max:  1.00 ms, nesting: 0 - 6674559
TIMING GetCsvLine MemoryMapStream (random seek):  7.43 s  -  1.11 us ( 7.55 s  / 6674559 ), min:  0.00 ns, max:  1.00 ms, nesting: 0 - 6674559
TIMING GetCsvLine FileIn:  6.69 s  -  1.00 us ( 6.81 s  / 6674560 ), min:  0.00 ns, max:  1.00 ms, nesting: 0 - 6674560
TIMING GetCsvLine MemorymapStream:  6.39 s  - 956.63 ns ( 6.51 s  / 6674560 ), min:  0.00 ns, max:  1.00 ms, nesting: 0 - 6674560