add examples/geventsendfile.py

examples/geventsendfile.py

+"""An example how to use sendfile[1] with gevent.
+
+[1] See http://pypi.python.org/pypi/py-sendfile/
+"""
+from errno import EAGAIN
+from sendfile import sendfile as original_sendfile
+from gevent.socket import wait_write
+
+
+def gevent_sendfile(out_fd, in_fd, offset, count):
+    total_sent = 0
+    while total_sent < count:
+        try:
+            _offset, sent = original_sendfile(out_fd, in_fd, offset + total_sent, count - total_sent)
+            #print '%s: sent %s [%d%%]' % (out_fd, sent, 100*total_sent/count)
+            total_sent += sent
+        except OSError, ex:
+            if ex[0] == EAGAIN:
+                wait_write(out_fd)
+            else:
+                raise
+    return offset + total_sent, total_sent
+
+
+def patch_sendfile():
+    import sendfile
+    sendfile.sendfile = gevent_sendfile