python: add get_npn_protocols() function

get_npn_protocols() is high level wrapper for
spdylay_npn_get_proto_list() and the returned list can be passed to
ssl.SSLContext.set_npn_protocols().

doc/python.rst

@@ -546,6 +546,15 @@ Session Objects
 Helper Functions
 ----------------
 
+.. py:function:: get_npn_protocols()
+
+    Returns SPDY version strings which can be directly passed to
+    ``ssl.SSLContext.set_npn_protocols()``. Please note that the
+    returned list only includes SPDY version strings this library
+    supports. If the application intends to support other fallback
+    protocols (e.g., ``http/1.1``), the application should add them to
+    the returned list.
+
 .. py:function:: npn_get_version(proto)
 
     Returns SPDY version which spdylay library supports from the given

python/cspdylay.pxd

@@ -323,5 +323,12 @@ cdef extern from 'spdylay/spdylay.h':
                                      int32_t stream_id,
                                      int32_t delta_window_size)
 
+    ctypedef struct spdylay_npn_proto:
+        unsigned char *proto
+        uint8_t len
+        uint16_t version
+
+    spdylay_npn_proto* spdylay_npn_get_proto_list(size_t *len_ptr)
+
     uint16_t spdylay_npn_get_version(unsigned char *proto,
                                      size_t protolen)

python/spdylay.pyx

@@ -982,6 +982,16 @@ cdef class Session:
 cdef _strerror(int error_code):
     return cspdylay.spdylay_strerror(error_code).decode('UTF-8')
 
+cpdef get_npn_protocols():
+    cdef size_t proto_list_len
+    cdef cspdylay.spdylay_npn_proto *proto_list
+    proto_list = cspdylay.spdylay_npn_get_proto_list(&proto_list_len)
+    res = []
+    for i in range(proto_list_len):
+        res.append((<char*>proto_list[i].proto)[:proto_list[i].len]\
+                       .decode('UTF-8'))
+    return res
+
 cpdef int npn_get_version(proto):
     cdef char *cproto
     if proto == None:
@@ -1449,7 +1459,7 @@ try:
             self.ctx.options = ssl.OP_ALL | ssl.OP_NO_SSLv2 | \
                 ssl.OP_NO_COMPRESSION
             self.ctx.load_cert_chain(cert_file, key_file)
-            self.ctx.set_npn_protocols(['spdy/3', 'spdy/2'])
+            self.ctx.set_npn_protocols(get_npn_protocols())
 
             socketserver.TCPServer.__init__(self, server_address,
                                             RequestHandlerCalss)

python/spdylay_tests.py

@@ -338,5 +338,9 @@ class SpdylayTests(unittest.TestCase):
         self.assertEqual(1, frame.stream_id)
         self.assertEqual(4096, frame.delta_window_size)
 
+    def test_get_npn_protocols(self):
+        protos = spdylay.get_npn_protocols()
+        self.assertEqual(['spdy/3', 'spdy/2'], protos)
+
 if __name__ == '__main__':
     unittest.main()