.

bigfile/_bigfile.c

@@ -920,20 +920,24 @@ pyfileh_open(PyObject *pyfile0, PyObject *args)
     RAM *ram = ram_get_default(NULL);   // TODO get ram from args
     int err;
 
-
-    if (!PyArg_ParseTuple(args, ""))	// XXX parse mmap_overlay=None (True/False)
+    int mmap_overlay = -1; /* -1 means None; https://bugs.python.org/issue14705 */
+    if (!PyArg_ParseTuple(args, "|i", &mmap_overlay))
         return NULL;
 
-    // XXX verify if pyfile has .mmapper()
-    // if mmap_overlay or (mmap_overlay==None and has(pyfile.mmapper)):
-    //	  mmaper = pyfile.mmapper()
+    if (mmap_overlay == -1)
+        mmap_overlay = (pyfile->blkmmap_ops != NULL ? 1 : 0);
+    if (mmap_overlay && pyfile->blkmmap_ops == NULL) {
+        PyErr_SetString(PyExc_TypeError, "BigFile subtype does not provide blkmmapper");
+        return NULL;
+    }
 
     pyfileh = PyType_New(PyBigFileH, &PyBigFileH_Type, NULL);
     if (!pyfileh)
         return NULL;
 
     Py_INCREF(pyfile);
-    err = fileh_open(&pyfileh->fileh, &pyfile->file, ram, DONT_MMAP_OVERLAY);  // XXX -> MMAP_OVERLAY if requested
+    err = fileh_open(&pyfileh->fileh, &pyfile->file, ram,
+                        mmap_overlay ? MMAP_OVERLAY : DONT_MMAP_OVERLAY);
     if (err) {
         XPyErr_SetFromErrno();
         Py_DECREF(pyfile);

bigfile/_bigfile.h

@@ -110,6 +110,11 @@ struct PyBigFile {
      * automatically adds support for weakrefs for in-python defined children   */
 
     BigFile file;
+
+    /* PyCapsule object with blkmmapper if BigFile subclass has it | NULL */
+    PyObject     *blkmmapper_pycapsule;     // XXX traverse for GC?
+    /* bigfile_ops extract from ^^^ capsule | NULL */
+    bigfile_ops  *blkmmap_ops;
 };
 typedef struct PyBigFile PyBigFile;
 

bigfile/_file_zodb.pyx

@@ -24,6 +24,8 @@
 
 """XXX"""
 
+from __future__ import print_function, absolute_import
+
 cdef extern from "wcfs/internal/wcfs.h":
     pass