.

wcfs/internal/_wcfs.pyx

@@ -32,6 +32,7 @@ cdef extern from *:
     ctypedef bint cbool "bool"
 
 from ZODB.utils import p64, u64
+from cpython cimport PyBuffer_FillInfo
 
 # XXX hack, why it is needed? (likely top-level wendelin.* redirector
 #from wcfs.internal._wcfs cimport *
@@ -114,6 +115,21 @@ cdef class PyMapping:
     def __dealloc__(PyMapping pywmmap):
         pywmmap.wmmap = nil # XXX unmap too ?
 
+    property blk_start:
+        def __get__(PyMapping pywmmap):
+            return pywmmap.wmmap.blk_start
+    property blk_stop:
+        def __get__(PyMapping pywmmap):
+            return pywmmap.wmmap.blk_stop()
+
+    def __getbuffer__(PyMapping pywmmap, Py_buffer *view, int flags):
+        # XXX do we need readonly=1 here? or let it hit SIGBUS on write access?
+        PyBuffer_FillInfo(view, pywmmap, pywmmap.wmmap.mem_start,
+            pywmmap.wmmap.mem_stop - pywmmap.wmmap.mem_start, readonly=1, flags=flags)
+    property mem:
+        def __get__(PyMapping pywmmap) -> memoryview:
+            return memoryview(pywmmap)
+
     def unmap(PyMapping pywmmap):
         with nogil:
             wmmap_unmap_pyexc(pywmmap.wmmap)    # XXX +err

wcfs/wcfs_test.py

@@ -1719,7 +1719,7 @@ class tMapping(object):
         assert len(dataok) <= f.blksize
         dataok += b'\0'*(f.blksize - len(dataok))   # trailing zeros
 
-        blkview = memoryview(t.mmap.mem[blk_inmmap*f.blksize:][:f.blksize])
+        blkview = t.mmap.mem[blk_inmmap*f.blksize:][:f.blksize]
         # XXX first access without GIL, so that e.g. if there is timeout on
         # wcfs.py side, _abort_ontimeout could run and kill WCFS.
         # FIXME also test with GIL locked, since wcfs.py pinner must be itself