C 11/14中的高效文件读取

我目前有2段代码：

bool IOManager::readFileToBuffer(std::string filePath,std::vector<unsigned char>& buffer) {
    std::ifstream file(filePath,std::ios::binary);
    if (file.fail()) {
        perror(filePath.c_str());
        return false;
    }

    //seek to the end
    file.seekg(0,std::ios::end);

    //Get the file size
    int fileSize = file.tellg();
    file.seekg(0,std::ios::beg);

    //Reduce the file size by any header bytes that might be present
    fileSize -= file.tellg();

    buffer.resize(fileSize);
    file.read((char *)&(buffer[0]),fileSize);
    file.close();

    return true;
}

和

bool IOManager::readFileToBuffer(std::string filePath,std::vector<char>& buffer) {

    std::ifstream file(filePath,std::ios::binary);

    if (file.fail()) {
        perror(filePath.c_str());
        return false;
    }

    // copies all data into buffer
    std::vector<char> prov(
        (std::istreambuf_iterator<char>(file)),(std::istreambuf_iterator<char>()));

    buffer = prov;

    file.close();

    return true;
}

哪一个更好？根据C 11/14标准,这是最快速,最有效的方法吗？