CODEWITHSUNDEEP
c++stringostringstream
fakeaccount
fakeaccount

Reputation: 943

Output a ostringstream to file

I currently do this to write the contents of an ostringstream to a file:

... // -- Loop 1 Start

std::ostringstream osStr;

... // -- Loop 2 Start

    cv::string s(osStr.str());
    std::istringstream iss(s);
    cv::vector<cv::string> subVec;
    do{
        cv::string sub;
        iss >> sub;
        subVec.push_back(sub);
    } while (iss);

    cv::FileStorage fs("subVec.txt", cv::FileStorage::WRITE);
    fs << "subVec" << subVec;
    fs.release();

... // -- Loop 2 End

... // -- Loop 1 End

but this overwrites what was previously in the file.

So I moved the cv::FileStorage fs("subVec.txt", cv::FileStorage::WRITE); to before the loop, and fs.release to after the loop.

cv::FileStorage fs("subVec.txt", cv::FileStorage::WRITE);

... // -- Loop 1 Start

std::ostringstream osStr;

... // -- Loop 2 Start

    cv::string s(osStr.str());
    std::istringstream iss(s);
    cv::vector<cv::string> subVec;
    do{
        cv::string sub;
        iss >> sub;
        subVec.push_back(sub);
    } while (iss);

    fs << "subVec" << subVec;

... // -- Loop 2 End

... // -- Loop 1 End

fs.release();

This worked in a way as it did continuously write to the .txt, but was unusable due to Duplicated Keys:

%YAML:1.0
subVec:
   - "1"
   - "2"
...
   - "33"
   - "34"
subVec:
   - "1"
   - "3"
...
   - "30"
   - "31"

See how subVec is repeated

I'm looking for a way to save the contents of the ostringstream to a file where it doesn't overwrite the contents each time, but is actually readable.

OpenCV Error: Parsing error (subVec.txt(27): Duplicated key) in cvGetFileNode

Upvotes: 1

Views: 6010

Answers (2)

fakeaccount
fakeaccount

Reputation: 943

As there is little response, I'll have to settle with this fix:

cv::vector<cv::string> subVec; // -- MOVED
cv::FileStorage fs("subVec.txt", cv::FileStorage::WRITE);

... // -- Loop 1 Start

std::ostringstream osStr;

... // -- Loop 2 Start

    cv::string s(osStr.str());
    std::istringstream iss(s);
    do{
        cv::string sub;
        iss >> sub;
        subVec.push_back(sub);
    } while (iss);

... // -- Loop 2 End

... // -- Loop 1 End

fs << "subVec" << subVec; // -- MOVED
fs.release();

Although it does leave me with the issue of cv::vector<cv::string> being able to only hold so much.

A fix for this would be good!

Upvotes: 1

Colin
Colin

Reputation: 454

If it helps, I open a std::ofstream m_OutFile member at class level, open it with m_OutFile.open(file.c_str(), std::ios::out); in a constructor call. I also give it a buffer to save hard drive access:

m_OutFile.rdbuf()->pubsetbuf(m_CharBuffer,BUFFER_SIZE);

and then whenever I want to write to it in a function, I use 

std::ostringstream oStr;
oStr << "some text and things" << std::ends;
m_OutFile << oStr.str() << std::endl;

Works neat for me.

Upvotes: 2

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