rpcgen: define a visitor API for XDR protocol specs

The visitor API defines an interface for visiting each element
in the XDR protocol spec abstract syntax tree.

Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

scripts/rpcgen/rpcgen/visitor.py

@@ -0,0 +1,156 @@
+# SPDX-License-Identifier: LGPL-2.1-or-later
+
+import abc
+
+from .ast import (
+    XDRSpecification,
+    XDRDefinition,
+    XDRDeclaration,
+    XDRType,
+    XDREnumValue,
+    XDREnumBody,
+    XDRStructBody,
+    XDRUnionCase,
+    XDRUnionBody,
+)
+
+
+class XDRVisitor(abc.ABC):
+    def __init__(self, spec):
+        self.spec = spec
+
+    def visit(self, indent="", context=""):
+        return self.visit_object(self.spec, indent="", context=context)
+
+    def visit_object(self, obj, indent="", context=""):
+        if isinstance(obj, XDRSpecification):
+            funcname = "visit_specification"
+        elif isinstance(obj, XDRDefinition):
+            funcname = "visit_definition_" + type(obj).__name__[13:].lower()
+        elif isinstance(obj, XDRDeclaration):
+            funcname = "visit_declaration_" + type(obj).__name__[14:].lower()
+        elif isinstance(obj, XDRType):
+            funcname = "visit_type_" + type(obj).__name__[7:].lower()
+        elif isinstance(obj, XDREnumValue):
+            funcname = "visit_enum_value"
+        elif isinstance(obj, XDREnumBody):
+            funcname = "visit_enum_body"
+        elif isinstance(obj, XDRStructBody):
+            funcname = "visit_struct_body"
+        elif isinstance(obj, XDRUnionCase):
+            funcname = "visit_union_case"
+        elif isinstance(obj, XDRUnionBody):
+            funcname = "visit_union_body"
+        else:
+            raise Exception("Unhandled %s" % obj.__class__.__name__)
+
+        func = getattr(self, funcname)
+        assert func is not None
+        return func(obj, indent, context)
+
+    def visit_specification(self, obj, indent, context):
+        code = []
+        for definition in self.spec.definitions:
+            defcode = self.visit_object(definition, indent, context)
+            if defcode is not None:
+                code.append(defcode)
+        return "\n".join(code)
+
+    def visit_definition_cescape(self, obj, indent, context):
+        pass
+
+    def visit_definition_constant(self, obj, indent, context):
+        pass
+
+    def visit_definition_enum(self, obj, indent, context):
+        pass
+
+    def visit_definition_struct(self, obj, indent, context):
+        pass
+
+    def visit_definition_union(self, obj, indent, context):
+        pass
+
+    def visit_definition_typedef(self, obj, indent, context):
+        pass
+
+    def visit_declaration_scalar(self, obj, indent, context):
+        pass
+
+    def visit_declaration_pointer(self, obj, indent, context):
+        pass
+
+    def visit_declaration_fixedarray(self, obj, indent, context):
+        pass
+
+    def visit_declaration_variablearray(self, obj, indent, context):
+        pass
+
+    def visit_type_custom(self, obj, indent, context):
+        pass
+
+    def visit_type_opaque(self, obj, indent, context):
+        pass
+
+    def visit_type_string(self, obj, indent, context):
+        pass
+
+    def visit_type_void(self, obj, indent, context):
+        pass
+
+    def visit_type_char(self, obj, indent, context):
+        pass
+
+    def visit_type_unsignedchar(self, obj, indent, context):
+        pass
+
+    def visit_type_short(self, obj, indent, context):
+        pass
+
+    def visit_type_unsignedshort(self, obj, indent, context):
+        pass
+
+    def visit_type_int(self, obj, indent, context):
+        pass
+
+    def visit_type_unsignedint(self, obj, indent, context):
+        pass
+
+    def visit_type_hyper(self, obj, indent, context):
+        pass
+
+    def visit_type_unsignedhyper(self, obj, indent, context):
+        pass
+
+    def visit_type_bool(self, obj, indent, context):
+        pass
+
+    def visit_type_float(self, obj, indent, context):
+        pass
+
+    def visit_type_double(self, obj, indent, context):
+        pass
+
+    def visit_type_enum(self, obj, indent, context):
+        pass
+
+    def visit_type_struct(self, obj, indent, context):
+        pass
+
+    def visit_type_union(self, obj, indent, context):
+        pass
+
+    def visit_enum_value(self, obj, indent, context):
+        pass
+
+    def visit_enum_body(self, obj, indent, context):
+        pass
+
+    def visit_struct_body(self, obj, indent, context):
+        pass
+
+    def visit_union_case(self, obj, indent, context):
+        pass
+
+    def visit_union_body(self, obj, indent, context):
+        pass