test for seekable method and use it

2 files changed, 7 insertions, 3 deletions

diff --git a/waitress/buffers.py b/waitress/buffers.py
index cacc094..aa11b70 100644
--- a/waitress/buffers.py
+++ b/waitress/buffers.py
@@ -129,6 +129,11 @@ class BytesIOBasedBuffer(FileBasedBuffer):
     def newfile(self):
         return BytesIO()
 
+def _is_seekable(fp):
+    if hasattr(fp, 'seekable'):
+        return fp.seekable()
+    return hasattr(fp, 'seek') and hasattr(fp, 'tell')
+
 class ReadOnlyFileBasedBuffer(FileBasedBuffer):
     # used as wsgi.file_wrapper
 
@@ -137,7 +142,7 @@ class ReadOnlyFileBasedBuffer(FileBasedBuffer):
         self.block_size = block_size # for __iter__
 
     def prepare(self, size=None):
-        if hasattr(self.file, 'seek') and hasattr(self.file, 'tell'):
+        if _is_seekable(self.file):
             start_pos = self.file.tell()
             self.file.seek(0, 2)
             end_pos = self.file.tell()
diff --git a/waitress/tests/fixtureapps/filewrapper.py b/waitress/tests/fixtureapps/filewrapper.py
index f38c606..d4e9a51 100644
--- a/waitress/tests/fixtureapps/filewrapper.py
+++ b/waitress/tests/fixtureapps/filewrapper.py
@@ -58,8 +58,7 @@ def app(environ, start_response): # pragma: no cover
                 ('Content-Type', 'image/jpeg'),
             ]
     else:
-        with open(fn, 'rb') as fp:
-            data = fp.read()
+        data = open(fn, 'rb').read()
         cl = len(data)
         f = KindaFilelike(data)
         if path_info == '/notfilelike':