Pick up correct DBF_ enum values

The DBF_ enum values have changed in EPICS 3.16, so it is no longer safe
to leave them baked into the Python code.  This commit fixes the issue by
passing the values from C to Python.

Author: Araneidae

python/softioc/fields.py

@@ -4,30 +4,19 @@
 
 import sys
 from ctypes import *
-from .imports import get_field_offsets
+from .imports import get_field_offsets, get_DBF_values
 import numpy
 
 from cothread.dbr import *
 from cothread.dbr import ca_timestamp, EPICS_epoch
 
 
-# Record field types, as defined in dbFldTypes.h
-DBF_STRING      = 0
-DBF_CHAR        = 1
-DBF_UCHAR       = 2
-DBF_SHORT       = 3
-DBF_USHORT      = 4
-DBF_LONG        = 5
-DBF_ULONG       = 6
-DBF_FLOAT       = 7
-DBF_DOUBLE      = 8
-DBF_ENUM        = 9
-DBF_MENU        = 10
-DBF_DEVICE      = 11
-DBF_INLINK      = 12
-DBF_OUTLINK     = 13
-DBF_FWDLINK     = 14
-DBF_NOACCESS    = 15
+# Pick up the DBF_ definitions from the C helper layer.  This is safer than
+# defining the values here, as unfortunately the values have been known to
+# change between EPICS releases.
+for name, value in get_DBF_values().items():
+    globals()[name] = value
+
 
 # Mapping from record field type to ctypes type.  Type STRING is handled
 # specially, and types ENUM, MENU, DEVICE and FWDLINK aren't supported.

python/softioc/imports.py

@@ -59,7 +59,7 @@ def auto_decode(result, func, args):
 db_put_field.errcheck = expect_success
 
 
-# char * get_EPICS_BASE()
+# const char *get_EPICS_BASE(void)
 #
 # Returns the path to EPICS_BASE
 get_EPICS_BASE = libPythonSupport.get_EPICS_BASE
@@ -68,6 +68,13 @@ def auto_decode(result, func, args):
 get_EPICS_BASE.errcheck = auto_decode
 
 
+# PyObject *get_DBF_values(void)
+#
+# Returns dictionary mapping DBF_ enum names to values
+get_DBF_values = libPythonSupport.get_DBF_values
+get_DBF_values.restype = py_object
+
+
 # void EpicsPvPutHook(struct asTrapWriteMessage *pmessage, int after)
 #
 # Hook for logging EPICS caput events

softIocApp/PythonSupport.c

@@ -1,3 +1,4 @@
+#include <Python.h>
 #include <string.h>
 
 #define db_accessHFORdb_accessC     // Needed to get correct DBF_ values
@@ -9,13 +10,41 @@
 
 
 /* Returns the EPICS_BASE path used to build this IOC. */
-
-char * get_EPICS_BASE(void)
+const char *get_EPICS_BASE(void)
 {
-    return EPICS_BASE;
+    return EPICS_BASE;         // Passed as #define from Makefile
 }
 
 
+/* Helper for function below. */
+#define ADD_ENUM(dict, name) \
+    PyDict_SetItemString(dict, #name, PyInt_FromLong(name))
+
+/* Alas, EPICS has changed the numerical assignments of the DBF_ enums between
+ * versions, so to avoid unpleasant surprises, we compute thes values here in C
+ * and pass them back to the Python layer. */
+PyObject *get_DBF_values(void)
+{
+    PyObject *dict = PyDict_New();
+    ADD_ENUM(dict, DBF_STRING);
+    ADD_ENUM(dict, DBF_CHAR);
+    ADD_ENUM(dict, DBF_UCHAR);
+    ADD_ENUM(dict, DBF_SHORT);
+    ADD_ENUM(dict, DBF_USHORT);
+    ADD_ENUM(dict, DBF_LONG);
+    ADD_ENUM(dict, DBF_ULONG);
+    ADD_ENUM(dict, DBF_FLOAT);
+    ADD_ENUM(dict, DBF_DOUBLE);
+    ADD_ENUM(dict, DBF_ENUM);
+    ADD_ENUM(dict, DBF_MENU);
+    ADD_ENUM(dict, DBF_DEVICE);
+    ADD_ENUM(dict, DBF_INLINK);
+    ADD_ENUM(dict, DBF_OUTLINK);
+    ADD_ENUM(dict, DBF_FWDLINK);
+    ADD_ENUM(dict, DBF_NOACCESS);
+    return dict;
+}
+
 
 /* Given an array of field names, this routine looks up each field name in
  * the EPICS database and returns the corresponding field offset. */