On Fri, Jan 28, 2005 at 10:58:24AM +0000, Jonathan Wakely wrote:
Looking at the implementation of copy_file() I'm wondering why it isn't done like this (this provides noclobber support too):
std::fstream out; if (noclobber) { out.open(to_file_ph.string().c_str(), std::ios::in); if (out.is_open()) { // file exists boost::throw_exception( filesystem_error( "boost::filesystem::copy_file", from_file_ph, to_file_ph, fs::detail::system_error_code() ) ); } } std::ifstream in(from_file_ph.string().c_str()); out.open(to_file_ph.string().c_str(), std::ios::out); out << in.rdbuf();
Hmm, this has a race-condition, which is a good reason to stick with open(2) and O_CREAT|O_EXCL and read(2)/write(2). 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. jon -- Message terminated with signal 11, SIGFAULT