Make pv logging compatible with EPICS 3.15 and above

In EPICS 3.15 the interface to caput event hooking was changed.  We need
to detect the correct EPICS version and handle the update accordingly.

Author: Araneidae

softIocApp/PythonSupport.c

@@ -9,6 +9,15 @@
 #include <dbFldTypes.h>
 #include <dbStaticLib.h>
 #include <asTrapWrite.h>
+#include <epicsVersion.h>
+
+
+/* The interface to the caput event callback has changed as of EPICS 3.15, and
+ * we need to compile as appropriate. */
+#define BASE_3_15 (EPICS_VERSION * 100 + EPICS_REVISION >= 315)
+#if BASE_3_15
+#include <dbChannel.h>
+#endif
 
 
 
@@ -169,7 +178,12 @@ static void PrintValue(struct formatted *formatted)
 
 void EpicsPvPutHook(struct asTrapWriteMessage *pmessage, int after)
 {
-    struct dbAddr *dbaddr = pmessage->serverSpecific;
+#if BASE_3_15
+    struct dbChannel *pchan = pmessage->serverSpecific;
+    dbAddr *dbaddr = &pchan->addr;
+#else
+    dbAddr *dbaddr = pmessage->serverSpecific;
+#endif
     struct formatted *value = FormatValue(dbaddr);
 
     if (after)