--- IO-AIO/AIO.pm	2005/08/18 16:32:10	1.34
+++ IO-AIO/AIO.pm	2005/08/22 23:20:37	1.35
@@ -164,6 +164,29 @@
       print "read $_[0] bytes: <$buffer>\n";
    };
 
+=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback
+
+Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
+reading at byte offset C<$in_offset>, and starts writing at the current
+file offset of C<$out_fh>. Because of that, it is not safe to issue more
+than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
+other.
+
+This call tries to make use of a native C<sendfile> syscall to provide
+zero-copy operation. For this to work, C<$out_fh> should refer to a
+socket, and C<$in_fh> should refer to mmap'able file.
+
+If the native sendfile call fails or is not implemented, it will be
+emulated, so you can call C<aio_sendfile> on any filehandles regardless of
+the limitations of the OS.
+
+Please note, however, that C<aio_sendfile> can read more bytes from
+C<$in_fh> than are written, and there is no way to find out how many
+bytes have been read form C<aio_sendfile> alone, as C<aio_sendfile> only
+provides the number of bytes written to C<$out_fh>. Only if the return
+value (the value provided to the callback) equals C<$length> one can
+assume that C<$length> bytes have been read.
+
 =item aio_readahead $fh,$offset,$length, $callback
 
 C<aio_readahead> populates the page cache with data from a file so that