问C++打开文件并写入任意位置的文件

EN

BOOST_AUTO_TEST_CASE(FileWriteTest_W_PLUS_B) {
    auto started = chrono::high_resolution_clock::now();

    FILE *filePointer = nullptr;
    auto tmpFilename = string("C:\\temp\\") + boost::uuids::to_string(boost::uuids::random_generator()());
    auto bufferSize = 1024 * 1024;

    unique_ptr<unsigned char[]> buffer(new unsigned char[bufferSize]);
    RAND_bytes(buffer.get(), bufferSize);

    for (long long i = 0; i < 5; i++) {
        //Open file
        int openError = fopen_s(&filePointer, tmpFilename.c_str(), "w+b");  
        if (openError != 0)
            BOOST_FAIL(string("Failed to open file ") + tmpFilename);

        auto CurrentPosition = 1024LL * 1024LL * 1024LL * i;

        //Set position to 0/1/2/3/4 GB 
        fsetpos(filePointer, &CurrentPosition);

        //Write 1 GB of data at current position
        for (int n = 0; n < 1024; n++) {
            int written = fwrite(buffer.get(), sizeof(unsigned char), bufferSize, filePointer);
            if (written != bufferSize) {
                BOOST_FAIL(string("Unable to write ") + to_string(bufferSize) + string(" to file ") + tmpFilename + string(" at position ") + to_string(CurrentPosition));
            }
        }

        //Close file
        fclose(filePointer);
    }

    auto ended = chrono::high_resolution_clock::now();
    cout << "Time :" << duration_cast<duration<double>>(ended - started).count() << " seconds";
}