--- IO-AIO/README	2005/08/20 00:32:42	1.11
+++ IO-AIO/README	2005/08/23 00:05:00	1.12
@@ -132,6 +132,28 @@
               print "read $_[0] bytes: <$buffer>\n";
            };
 
+    aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback
+        Tries to copy $length bytes from $in_fh to $out_fh. It starts
+        reading at byte offset $in_offset, and starts writing at the current
+        file offset of $out_fh. Because of that, it is not safe to issue
+        more than one "aio_sendfile" per $out_fh, as they will interfere
+        with each other.
+
+        This call tries to make use of a native "sendfile" syscall to
+        provide zero-copy operation. For this to work, $out_fh should refer
+        to a socket, and $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 "aio_sendfile" on any type of filehandle
+        regardless of the limitations of the operating system.
+
+        Please note, however, that "aio_sendfile" can read more bytes from
+        $in_fh than are written, and there is no way to find out how many
+        bytes have been read from "aio_sendfile" alone, as "aio_sendfile"
+        only provides the number of bytes written to $out_fh. Only if the
+        result value equals $length one can assume that $length bytes have
+        been read.
+
     aio_readahead $fh,$offset,$length, $callback
         "aio_readahead" populates the page cache with data from a file so
         that subsequent reads from that file will not block on disk I/O. The