#include "FileStream.h"
#include <sys/stat.h>
#include <fcntl.h>

#ifdef WIN32
#else
#include <unistd.h>
#include <sys/mman.h>
#endif

namespace
{
    const unsigned long long SKIP_UNIT_SIZE = 2147483647;//maxValue of int
}

FileStream::FileStream()
#ifdef WIN32
    : mStream()
#else
    : mPosition(0)
    , mData(nullptr)
    , mFd()
    , mStSize()
#endif
{

}

FileStream::~FileStream()
{

}

bool FileStream::open(const std::string& aFileName)
{
#ifdef WIN32
    mStream.open(aFileName.c_str(), std::ios_base::binary | std::ios::in);
    return true;
#else
    if ((mFd = ::open(aFileName.c_str(), O_RDONLY)) < 0)
    {
        return false;
    }
    struct stat sb;
    if (fstat(mFd, &sb) == -1)
    {
        return false;
    }
    mStSize = sb.st_size;
    mData = (int16_t*)mmap(NULL, mStSize, PROT_READ, MAP_SHARED, mFd, 0);
    return true;
#endif
}

void FileStream::seekg(unsigned long long aSkipSize, StreamPosition aFlag)
{
#ifdef WIN32
    if(aFlag == StreamPosition::cur)
    {
        unsigned long long skipData = aSkipSize % SKIP_UNIT_SIZE;
        int skipLoop = static_cast<int>((aSkipSize - skipData) / SKIP_UNIT_SIZE);
        for(int i = 0;i < skipLoop ; ++i)
        {
            mStream.seekg(SKIP_UNIT_SIZE,std::ios::cur);
        }
        mStream.seekg(static_cast<int>(skipData),std::ios::cur);
    }
    else if(aFlag == StreamPosition::begin)
    {
        mStream.seekg(static_cast<int>(aSkipSize),std::ios::beg);
    }
#else
    if(aFlag == StreamPosition::cur)
    {
        mPosition += aSkipSize;
    }
    else if(aFlag == StreamPosition::begin)
    {
        mPosition = aSkipSize;
    }
#endif
}

void FileStream::read(int16_t& aValue)
{
#ifdef WIN32
    mStream.read((char*)&aValue,sizeof(int16_t));
#else
    aValue = mData[mPosition/2];
    mPosition += 2;
#endif
}

void FileStream::close()
{
#ifdef WIN32
    mStream.close();
#else
    munmap(mData, mStSize);
    ::close(mFd);
#endif
}