addressed parameters

- generic method to access parameters with just an address
  changed to avoid boilerplate code
- it would really be nice to include the generic methods
  into Module

Change-Id: I898e5eeb282f03d3177a324fa88813976fb15f3c

frappy/addrparam.py

@@ -0,0 +1,75 @@
+# *****************************************************************************
+#
+# 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.,
+# 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+#
+# Module authors:
+#   Markus Zolliker <markus.zolliker@psi.ch>
+#
+# *****************************************************************************
+
+from frappy.core import Parameter, Property
+from frappy.datatypes import ValueType
+
+
+class AddrParam(Parameter):
+    """parameter with an address field
+
+    instead of implementing read_<param> and write_<param>, just implement
+    addressed_read and addressed_write.
+    """
+    addr = Property('address', ValueType())
+
+
+class AddrMixin:
+    """mixin for addressed parameters
+
+    in case a read_<param> and/or write_<param> are not implemented,
+    they are created with a call to addressed_read and/or addressed_write
+    """
+    def __init_subclass__(cls):
+        for aname, aobj in list(cls.__dict__.items()):
+            if isinstance(aobj, AddrParam):
+                methodname = f'read_{aname}'
+
+                if not hasattr(cls, methodname):
+                    def rfunc(self, pname=aname):
+                        return self.addressed_read(self.accessibles[pname])
+
+                    setattr(cls, methodname, rfunc)
+
+                if not aobj.readonly:
+                    methodname = f'write_{aname}'
+                    if not hasattr(cls, methodname):
+                        def wfunc(self, value, pname=aname):
+                            return self.addressed_write(self.accessibles[pname], value)
+
+                        setattr(cls, methodname, wfunc)
+        super().__init_subclass__()
+
+    def addressed_read(self, pobj):
+        """addressed read
+
+        :param pobj: the AddrParam
+        :return: the value read
+        """
+        return getattr(self, pobj.name)
+
+    def addressed_write(self, pobj, value):
+        """addressed write
+
+        :param pobj: the AddrParam
+        :param value: the value to be written
+        :return: the value written or None
+        """