-error_code copy_file(const Twine &from, const Twine &to, copy_option copt) {
- // Get arguments.
- SmallString<128> from_storage;
- SmallString<128> to_storage;
- StringRef f = from.toNullTerminatedStringRef(from_storage);
- StringRef t = to.toNullTerminatedStringRef(to_storage);
-
- const size_t buf_sz = 32768;
- char buffer[buf_sz];
- int from_file = -1, to_file = -1;
-
- // Open from.
- if ((from_file = ::open(f.begin(), O_RDONLY)) < 0)
- return error_code(errno, system_category());
- AutoFD from_fd(from_file);
-
- // Stat from.
- struct stat from_stat;
- if (::stat(f.begin(), &from_stat) != 0)
- return error_code(errno, system_category());
-
- // Setup to flags.
- int to_flags = O_CREAT | O_WRONLY;
- if (copt == copy_option::fail_if_exists)
- to_flags |= O_EXCL;
-
- // Open to.
- if ((to_file = ::open(t.begin(), to_flags, from_stat.st_mode)) < 0)
- return error_code(errno, system_category());
- AutoFD to_fd(to_file);
-
- // Copy!
- ssize_t sz, sz_read = 1, sz_write;
- while (sz_read > 0 &&
- (sz_read = ::read(from_fd, buffer, buf_sz)) > 0) {
- // Allow for partial writes - see Advanced Unix Programming (2nd Ed.),
- // Marc Rochkind, Addison-Wesley, 2004, page 94
- sz_write = 0;
- do {
- if ((sz = ::write(to_fd, buffer + sz_write, sz_read - sz_write)) < 0) {
- sz_read = sz; // cause read loop termination.
- break; // error.
- }
- sz_write += sz;
- } while (sz_write < sz_read);
- }
-
- // After all the file operations above the return value of close actually
- // matters.
- if (::close(from_fd.take()) < 0) sz_read = -1;
- if (::close(to_fd.take()) < 0) sz_read = -1;
-
- // Check for errors.
- if (sz_read < 0)
- return error_code(errno, system_category());
-
- return error_code::success();
-}
-