RE: RE: RE: Re: Problem using copyfile and movefile

[John W. Eaton]

On  1-Mar-2007, address@hidden wrote:

| > This more elaborated version also implements recursive copy of
| > directories. What's not handled yet is cyclic copy detection.
| 
| I took a more conservative and OO-oriented approach to
| implement copy mechanism: now it's a 2-steps process, avoiding
| cyclic problems. See code in attachment (starting from my previous
| patch, this code can be copy'n'paste into file-ops.cc in place of
| the actual code from the patch).
|  
| What do you think?
|  
| Note that this does not support symlinks: it's harder for me to
| implement and test as there's no symlinks under Win32.

I haven't tested it, but since copying a symbolic link copies the file
that the link points to, not the link itself, I think your copy
function would work for them.

The core of your function is

          for (;;)
            {
              nr = ::read (fd_src, buf, BUFFER_SIZE);
              if (nr == 0)
                {
                  status = 0;
                  break;
                }
              else if (nr < 0)
                break;
              else
                {
                  nw = ::write (fd_dest, buf, nr);
                  if (nw != nr)
                    break;
                }
            }

I think you may need to handle the possibility of errno == EINTR after
the read and write, and also loop around the write (it is not an error
for write to return a value less than the total number of bytes that
it is requested to write).

All these little details are precisely what I wanted to avoid by using
the gnulib code, which has already considered them and presumably has
all the bugs worked out.  Also, I don't want to be the maintainer of
this code when there is already a project that implements the
functionality and is maintained by people who probably know better
than we do how to get the details right.

jwe