Re: [boost] Re: boost.filesystem - rationale for copy_file

From: Beman Dawes (bdawes_at_[hidden])
Date: 2005-01-29 20:18:04

At 07:30 AM 1/28/2005, Jonathan Wakely wrote:

 >However, in that case there's a comment about the implementation:
 >
 >      // TODO: Ask POSIX experts if this is the best way to copy a file
 >
 >Now, I'm no POSIX expert, but I believe the loop used:
 >
 >      ssize_t sz;
 >      while ( (sz = ::read( infile, buf.get(), buf_sz )) > 0
 >          && (sz = ::write( outfile, buf.get(), sz )) > 0 ) {}
 >
 >can result in lost data if write(2) only does a partial write, which
 >might happen if the write is interrupted by a signal. I think it should
 >loop on the writes too, until write() has returned sz in total.

Hum... Reading the POSIX spec, it looks like you are right. ::write() will 
also only do a partial write if the process runs out of disk space, for 
example.

Thanks,

--Beman