从文本文件或stdin读取

Question

我有一个基本上读取文本文件的程序,并计算每行上每个单词的出现次数.使用ifstream从文本文件中读取时,一切正常,但是,如果未在命令行中输入文件名,我需要从stdin读取.

我目前使用以下内容打开并读取文件:

map<string, map<int,int>,compare> tokens;
ifstream text;
string line;
int count = 1;

if (argc > 1){
    try{
        text.open(argv[1]);
    }
    catch (runtime_error& x){
        cerr << x.what() << '\n';
    }

    // Read file one line at a time, replacing non-desired char's with spaces
    while (getline(text, line)){
        replace_if(line.begin(), line.end(), my_predicate, ' ');

        istringstream iss(line);    
        // Parse line on white space, storing values into tokens map
        while (iss >> line){                
            ++tokens[line][count];
        }
        ++count;
    }
}

else{
while (cin) {
    getline(cin, line);
    replace_if(line.begin(), line.end(), my_predicate, ' ');

    istringstream iss(line);
    // Parse line on white space, storing values into tokens map
    while (iss >> line){
        ++tokens[line][count];
    }
    ++count;
}

有没有办法将cin分配给ifstream,如果argc> 1失败,只需添加一个else语句,之后使用相同的代码而不是像这样重复？我找不到办法做到这一点.

Answer 1

使阅读部分成为自己的功能.通过一个ifstream或cin它.

void readData(std::istream& in)
{
   // Do the necessary work to read the data.
}

int main(int argc, char** argv)
{
   if ( argc > 1 )
   {
      // The input file has been passed in the command line.
      // Read the data from it.
      std::ifstream ifile(argv[1);
      if ( ifile )
      {
         readData(ifile);
      }
      else
      {
         // Deal with error condition
      }
   }
   else
   {
      // No input file has been passed in the command line.
      // Read the data from stdin (std::cin).
      readData(std::cin);
   }

   // Do the needful to process the data.
}