Build the CFFI lib in a nice way when possible.

.gitignore

@@ -5,6 +5,7 @@
 *.egg-info
 *.pyc
 *.pyo
+*.so
 *.sublime-*
 .coverage
 htmlcov/

relstorage/cache/_cache_ring_build.py

@@ -0,0 +1,36 @@
+# -*- coding: utf-8 -*-
+##############################################################################
+#
+# Copyright (c) 2016 Zope Foundation and Contributors.
+# All Rights Reserved.
+#
+# This software is subject to the provisions of the Zope Public License,
+# Version 2.1 (ZPL).  A copy of the ZPL should accompany this distribution.
+# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
+# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
+# FOR A PARTICULAR PURPOSE.
+#
+##############################################################################
+from __future__ import absolute_import, print_function, division
+
+import os
+from cffi import FFI
+
+this_dir = os.path.dirname(os.path.abspath(__file__))
+
+ffi = FFI()
+with open(os.path.join(this_dir, 'cache_ring.h')) as f:
+    ffi.cdef(f.read())
+
+ffi.set_source('relstorage.cache._cache_ring',
+               '#include "cache_ring.c"',
+               include_dirs=[this_dir])
+
+def verify():
+    return ffi.verify('#include "cache_ring.c"',
+                      include_dirs=[this_dir])
+
+
+if __name__ == '__main__':
+    ffi.compile()

relstorage/cache/cache_ring.py

@@ -19,18 +19,17 @@ Segmented LRU implementations.
 
 """
 
-import os
-from cffi import FFI
-
-this_dir = os.path.dirname(os.path.abspath(__file__))
-
-ffi = FFI()
-with open(os.path.join(this_dir, 'cache_ring.h')) as f:
-    ffi.cdef(f.read())
-
-_FFI_RING = ffi.verify("""
-#include "cache_ring.c"
-""", include_dirs=[this_dir])
+try:
+    from relstorage.cache import _cache_ring
+except ImportError:
+    # Must be on an old pypy version, stuck with an old
+    # CFFI
+    from relstorage.cache import _cache_ring_build
+    _FFI_RING = _cache_ring_build.verify()
+    ffi = _cache_ring_build.ffi
+else:
+    ffi = _cache_ring.ffi
+    _FFI_RING = _cache_ring.lib
 
 _ring_move_to_head = _FFI_RING.rsc_ring_move_to_head
 _ring_del = _FFI_RING.rsc_ring_del

setup.py

@@ -84,6 +84,10 @@ setup(
         'zc.lockfile',
         # ZODB and ZEO are handled as environment-markers in extras.
     ],
+    # If a new-enough CFFI is installed, build the module as part of installation.
+    # Otherwise, we'll build it at import time. The wheels we distribute should have
+    # cffi installed so we distribute the built binaries.
+    cffi_modules = ['relstorage/cache/_cache_ring_build.py:ffi'],
     tests_require=tests_require,
     extras_require={
         # We previously used MySQL-python (C impl) on CPython 2.7,