C++11 ifstream和ofstream读写二进制文件_std::c++11 读取二进制数据-优快云博客

本文链接：https://blog.youkuaiyun.com/MyArrow/article/details/53117384

本文介绍如何使用C++标准库中的ifstream和ofstream进行二进制文件的读写操作，具体展示了如何保存和读取OpenCV KeyPoint对象及Mat矩阵数据。

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1. C++11 ifstream和ofstream读写二进制文件

std::ofstream Frame::mfKeyOut("/home/ai/work/tum-data/key.bin", std::ios::binary | std::ios::out);
std::ofstream Frame::mfDescOut("/home/ai/work/tum-data/desc.bin", std::ios::binary | std::ios::out);

std::ifstream Frame::mfKeyIn("/home/ai/work/tum-data/key.bin", std::ios::binary | std::ios::in);
std::ifstream Frame::mfDescIn("/home/ai/work/tum-data/desc.bin", std::ios::binary | std::ios::in);

std::vector<cv::KeyPoint> mvKeys, mvKeysRight;
cv::Mat mDescriptors, mDescriptorsRight;  // the address of vecotr is continous (similar to realloc)

void initOut()
{
    std::string  keyFileName("/home/ai/work/tum-data/key.bin");
    std::string  descFileName("/home/ai/work/tum-data/desc.bin");

    if(!mfKeyOut || !mfKeyOut.is_open())
    {
        mfKeyOut.open(keyFileName.c_str(), std::ios::binary | std::ios::out);
    }

    if(!mfDescOut || !mfDescOut .is_open())
    {
        mfDescOut .open(descFileName.c_str(), std::ios::binary | std::ios::out);
    }
}

void initIn()
{
    std::string  keyFileName("/home/ai/work/tum-data/key.bin");
    std::string  descFileName("/home/ai/work/tum-data/desc.bin");

    if(!mfKeyIn || !mfKeyIn.is_open())
    {
        mfKeyIn.open(keyFileName.c_str(), std::ios::binary | std::ios::in);
    }

    if(!mfDescIn || !mfDescIn .is_open())
    {
        mfDescIn .open(descFileName.c_str(), std::ios::binary | std::ios::in);
    }
}

void saveData()
{
    // generate the data for mvKeys and mDescriptors	
    //(*mpORBextractorLeft)(im,cv::Mat(),mvKeys,mDescriptors);

    save the keypoints, it's a vector
    int numKeys = mvKeys.size();
    mfKeyOut.write((char*)&numKeys, sizeof(int));
    mfKeyOut.write((char*)&mvKeys[0], numKeys * sizeof(cv::KeyPoint));

    // save the descriptors, it's a Mat (nkeypoints, 32, CV_8U)
    int matSize[2];
    matSize[0] = mDescriptors.rows;   // nKeyPoints
    matSize[1] = mDescriptors.cols;   // 32
    mfDescOut.write((char*)&matSize[0], 2 * sizeof(int));
    mfDescOut.write((char*)mDescriptors.data, matSize[0]*matSize[1]*sizeof(char));
}

void readData()
{
     int numKeys;
     mfKeyIn.read((char*)&numKeys, sizeof(int));
     mvKeys.resize(numKeys);
     mfKeyIn.read((char*)&mvKeys[0], numKeys * sizeof(cv::KeyPoint));

     int matSize[2];
     mfDescIn.read((char*)&matSize[0], 2 * sizeof(int));

     if( matSize[0] == 0 )
     {
          mDescriptors.release();
     }
     else
     {
         mDescriptors.create(matSize[0], matSize[1], CV_8U);
         mfDescIn.read((char*)mDescriptors.data, matSize[0]*matSize[1]*sizeof(char));
     }
}
void Close()
{
    if(mfKeyOut.is_open())
    {
        mfKeyOut.close();
    }

    if(mfDescOut.is_open())
    {
        mfDescOut.close();
    }

    if(mfKeyIn.is_open())
    {
        mfKeyIn.close();
    }

    if(mfDescIn.is_open())
    {
        mfDescIn.close();
    }
}