Re: [Boost-users] Re: R: filesystem::copy_file throws -- but why?

From: Beman Dawes (bdawes_at_[hidden])
Date: 2003-12-12 12:21:11

At 09:03 AM 12/12/2003, Peter Dimov wrote:
 >Beman Dawes wrote:
 >> It would have to be:
 >>
 >>     int processFile(const fs::path& fileName)
 >>     {
 >>         fs::path copyFileName(fileName.string() + ".bak", fs::native);
 >>         fs::copy_file(fileName, copyFileName);
 >>     }
 >
 >I don't see why. string() returns a path "formatted according to the 
rules
 >of the generic path string grammar", i.e. '/' separator. Aren't native
 >paths allowed to use a ':' separator with '/' being a legitimate part
 >of the name, for instance?

Yep. My mistake. See below.

 >Why does the original
 >
 >    fs::path copyFileName(fileName.string() + ".bak");
 >
 >throw? I see nothing that could cause fileName.string() + ".bak" to fail
 >validation. Am I missing something, or is this a bug?

(What follows is based on current CVS version)

It throws because the name_check was set to portable_name, and that doesn't 
allow ':' as a character.

Because the function's fileName argument is already a path, it is known to 
have already been check by an appropriate name checker. Furthermore, if 
appending ".bak" to copyFileName invalidates it, that will be detected 
right away by the copy_file call. So not checking at all might be 
appropriate:

   void processFile(const fs::path& fileName)
   {
       fs::path copyFileName(fileName.string() + ".bak", fs::no_check);
       fs::copy_file(fileName, copyFileName);
   }

But Michele Galante's original suggestion is perhaps better:

   int processFile(const fs::path& fileName)
   {
       fs::path copyFileName(fileName.native_file_string() + ".bak",
                             fs::native);
       fs::copy_file(fileName, copyFileName);
   }

--Beman