Re: [Boost-users] [iostreams] Question about correct opened file

From: Jonathan Turkanis (turkanis_at_[hidden])
Date: 2008-02-13 17:02:02

ope wrote:
> Hi,
> 
> I've the following code:
> 
> namespace io = boost::iostreams;
> 
> bool foo::open( const std::string& file )
> {
>      io::filtering_istream is;
> 
>      is.push( my_line_filter() );
>      is.push( io::file_source( file ) );
> 
>      // ??? how to check success
> 
>      do {
>          std::string line;
>          std::getline(is, line);
>          std::cout << line << std::endl;
>      } while (!is.eof());
> 
>      return true;
> }
> 
> Well, how can I check that the file is opened correct/the stream is 
> valid? is_open() and good() seems not supported? Or I'm wrong? Giving a 
> wrong name does nothings.

Use file_source::is_open() (http://tinyurl.com/29o2wm). You can call it 
before adding the filter to the chain:

        file_source src(file);
        if (!is_open(src)) { ... }
        ...
        is.push(src);

or after adding it (http://tinyurl.com/2cmlke):

         is.push(my_line_filter());
        is.push(file_source(file));
        if (!is.component<file_source>(1).is_open())
           ....

Here 1 is the offset of the file_source in the filter chain.

> Thanks,
> Olaf

-- 
Jonathan Turkanis
CodeRage
http://www.coderage.com