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diff --git a/bzrlib/_export_c_api.h b/bzrlib/_export_c_api.h
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+/* Copyright (C) 2009 Canonical Ltd
+ * 
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+
+/* This file contains helper functions for exporting a C API for a CPython
+ * extension module.
+ */
+
+#ifndef _EXPORT_C_API_H_
+#define _EXPORT_C_API_H_
+
+static const char *_C_API_NAME = "_C_API";
+
+/**
+ * Add a C function to the modules _C_API
+ * This wraps the function in a PyCObject, and inserts that into a dict.
+ * The key of the dict is the function name, and the description is the
+ * signature of the function.
+ * This is generally called during a modules init_MODULE function.
+ *
+ * @param   module  A Python module (the one being initialized)
+ * @param   funcname The name of the function being exported
+ * @param   func    A pointer to the function
+ * @param   signature The C signature of the function
+ * @return  0 if everything is successful, -1 if there is a problem. An
+ *          exception should also be set
+ */
+static int
+_export_function(PyObject *module, char *funcname, void *func, char *signature)
+{
+    PyObject *d = NULL;
+    PyObject *c_obj = NULL;
+
+    /* (char *) is because python2.4 declares this api as 'char *' rather than
+     * const char* which it really is.
+     */
+    d = PyObject_GetAttrString(module, (char *)_C_API_NAME);
+    if (!d) {
+        PyErr_Clear();
+        d = PyDict_New();
+        if (!d)
+            goto bad;
+        Py_INCREF(d);
+        if (PyModule_AddObject(module, (char *)_C_API_NAME, d) < 0)
+            goto bad;
+    }
+    c_obj = PyCObject_FromVoidPtrAndDesc(func, signature, 0);
+    if (!c_obj)
+        goto bad;
+    if (PyDict_SetItemString(d, funcname, c_obj) < 0)
+        goto bad;
+    Py_DECREF(d);
+    return 0;
+bad:
+    Py_XDECREF(c_obj);
+    Py_XDECREF(d);
+    return -1;
+}
+
+/* Note:
+ *  It feels like more could be done here. Specifically, if you look at
+ *  _static_tuple_c.h you can see some boilerplate where we have:
+ * #ifdef STATIC_TUPLE_MODULE  // are we exporting or importing
+ * static RETVAL FUNCNAME PROTO;
+ * #else
+ * static RETVAL (*FUNCNAME) PROTO;
+ * #endif
+ * 
+ * And then in _static_tuple_c.c we have
+ * int setup_c_api()
+ * {
+ *   _export_function(module, #FUNCNAME, FUNCNAME, #PROTO);
+ * }
+ *
+ * And then in _static_tuple_c.h import_##MODULE
+ * struct function_definition functions[] = {
+ *   {#FUNCNAME, (void **)&FUNCNAME, #RETVAL #PROTO},
+ *   ...
+ *   {NULL}};
+ *
+ * And some similar stuff for types. However, this would mean that we would
+ * need a way for the C preprocessor to build up a list of definitions to be
+ * generated, and then expand that list at the appropriate time.
+ * I would guess there would be a way to do this, but probably not without a
+ * lot of magic, and the end result probably wouldn't be very pretty to
+ * maintain. Perhaps python's dynamic nature has left me jaded about writing
+ * boilerplate....
+ */
+
+#endif // _EXPORT_C_API_H_