handle io.BytesIO object with file_wrapper

fix #595

examples/frameworks/flask_sendfile.py

@@ -0,0 +1,14 @@
+import io
+
+from flask import Flask, send_file
+
+app = Flask(__name__)
+
+@app.route('/')
+def index():
+    buf = io.BytesIO()
+    buf.write('hello world')
+    buf.seek(0)
+    return send_file(buf,
+                     attachment_filename="testing.txt",
+                     as_attachment=True)

gunicorn/http/wsgi.py

@@ -10,6 +10,7 @@ import sys
 
 from gunicorn.six import unquote_to_wsgi_str, string_types, binary_type, reraise
 from gunicorn import SERVER_SOFTWARE
+import gunicorn.six as six
 import gunicorn.util as util
 
 try:
@@ -330,11 +331,13 @@ class Response(object):
                 sent += sendfile(sockno, fileno, offset + sent, nbytes - sent)
 
     def write_file(self, respiter):
-        if sendfile is not None and \
-                hasattr(respiter.filelike, 'fileno') and \
-                hasattr(respiter.filelike, 'tell'):
+        if sendfile is not None and util.is_fileobject(respiter.filelike):
+            # sometimes the fileno isn't a callable
+            if six.callable(respiter.filelike.fileno):
+                fileno = respiter.filelike.fileno()
+            else:
+                fileno = respiter.filelike.fileno
 
-            fileno = respiter.filelike.fileno()
             fd_offset = os.lseek(fileno, 0, os.SEEK_CUR)
             fo_offset = respiter.filelike.tell()
             nbytes = max(os.fstat(fileno).st_size - fo_offset, 0)

gunicorn/util.py

@@ -5,6 +5,7 @@
 
 
 import fcntl
+import io
 import os
 import pkg_resources
 import random
@@ -507,3 +508,15 @@ def to_bytestring(value):
         return value
     assert isinstance(value, text_type)
     return value.encode("utf-8")
+
+def is_fileobject(obj):
+    if not hasattr(obj, "tell") or not hasattr(obj, "fileno"):
+        return False
+
+    # check BytesIO case and maybe others
+    try:
+        obj.fileno()
+    except io.UnsupportedOperation:
+        return False
+
+    return True