rpcgen: add an XDR protocol abstract syntax tree

This introduces classes needed to form an abstract syntax
tree representing the XDR protocol language.

The syntax requirements are detailed in

  https://www.rfc-editor.org/rfc/rfc4506#section-6.3

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

scripts/rpcgen/rpcgen/ast.py

@@ -0,0 +1,270 @@
+# SPDX-License-Identifier: LGPL-2.1-or-later
+
+import abc
+
+
+class XDRSpecification:
+    def __init__(self):
+        self.definitions = []
+
+    def __repr__(self):
+        return "\n".join([repr(a) for a in self.definitions])
+
+
+class XDRDefinition(abc.ABC):
+    pass
+
+
+class XDRDefinitionConstant(XDRDefinition):
+    def __init__(self, name, value):
+        self.name = name
+        self.value = value
+
+    def __repr__(self):
+        return "const:{name=%s,value=%s}" % (self.name, self.value)
+
+
+class XDRDefinitionTypedef(XDRDefinition):
+    def __init__(self, decl):
+        self.decl = decl
+
+    def __repr__(self):
+        return "typedef:{decl=%s}" % (self.decl)
+
+
+class XDRDefinitionEnum(XDRDefinition):
+    def __init__(self, name, body):
+        self.name = name
+        self.body = body
+
+    def __repr__(self):
+        return "enum:{name=%s,body=%s}" % (self.name, self.body)
+
+
+class XDRDefinitionStruct(XDRDefinition):
+    def __init__(self, name, body):
+        self.name = name
+        self.body = body
+
+    def __repr__(self):
+        return "struct:{name=%s,body=%s}" % (self.name, self.body)
+
+
+class XDRDefinitionUnion(XDRDefinition):
+    def __init__(self, name, body):
+        self.name = name
+        self.body = body
+
+    def __repr__(self):
+        return "union:{name=%s,body=%s}" % (self.name, self.body)
+
+
+class XDRDefinitionCEscape(XDRDefinition):
+    def __init__(self, code):
+        self.code = code
+
+    def __repr__(self):
+        return "c-escape:{code=%s}" % (self.code)
+
+
+class XDRDeclaration(abc.ABC):
+    def __init__(self, typ, identifier):
+        self.typ = typ
+        self.identifier = identifier
+
+
+class XDRDeclarationScalar(XDRDeclaration):
+    def __repr__(self):
+        return "scalar:{type=%s,identifier=%s}" % (self.typ, self.identifier)
+
+
+class XDRDeclarationPointer(XDRDeclaration):
+    def __repr__(self):
+        return "pointer:{type=%s,identifier=%s}" % (self.typ, self.identifier)
+
+
+class XDRDeclarationFixedArray(XDRDeclaration):
+    def __init__(self, typ, identifier, length):
+        super().__init__(typ, identifier)
+        self.length = length
+
+    def __repr__(self):
+        return "fixed-array:{type=%s,identifier=%s,length=%s}" % (
+            self.typ,
+            self.identifier,
+            self.length,
+        )
+
+
+class XDRDeclarationVariableArray(XDRDeclaration):
+    def __init__(self, typ, identifier, maxlength):
+        super().__init__(typ, identifier)
+        self.maxlength = maxlength
+
+    def __repr__(self):
+        return "variable-array:{type=%s,identifier=%s,maxlength=%s}" % (
+            self.typ,
+            self.identifier,
+            self.maxlength,
+        )
+
+
+class XDRType(abc.ABC):
+    def __repr__(self):
+        name = self.__class__.__name__
+        return name[7:].lower()
+
+    def is_scalar(self):
+        return False
+
+
+class XDRTypeScalar(XDRType):
+    def is_scalar(self):
+        return True
+
+
+class XDRTypeVoid(XDRTypeScalar):
+    pass
+
+
+class XDRTypeChar(XDRTypeScalar):
+    pass
+
+
+class XDRTypeUnsignedChar(XDRTypeScalar):
+    pass
+
+
+class XDRTypeShort(XDRTypeScalar):
+    pass
+
+
+class XDRTypeUnsignedShort(XDRTypeScalar):
+    pass
+
+
+class XDRTypeInt(XDRTypeScalar):
+    pass
+
+
+class XDRTypeUnsignedInt(XDRTypeScalar):
+    pass
+
+
+class XDRTypeHyper(XDRTypeScalar):
+    pass
+
+
+class XDRTypeUnsignedHyper(XDRTypeScalar):
+    pass
+
+
+class XDRTypeFloat(XDRTypeScalar):
+    pass
+
+
+class XDRTypeDouble(XDRTypeScalar):
+    pass
+
+
+class XDRTypeBool(XDRTypeScalar):
+    pass
+
+
+class XDRTypeOpaque(XDRType):
+    pass
+
+
+class XDRTypeString(XDRType):
+    pass
+
+
+class XDRTypeCustom(XDRType):
+    def __init__(self, identifier, definition):
+        self.identifier = identifier
+        self.definition = definition
+
+    def is_scalar(self):
+        if type(self.definition) == XDRDefinitionEnum:
+            return True
+        if type(self.definition) == XDRDefinitionTypedef:
+            return self.definition.decl.typ.is_scalar()
+        return False
+
+    def __repr__(self):
+        return "custom{identifier=%s,definition=%s}" % (
+            self.identifier,
+            self.definition,
+        )
+
+
+class XDREnumValue:
+    def __init__(self, name, value):
+        self.name = name
+        self.value = value
+
+    def __repr__(self):
+        return "%s=%s" % (self.name, self.value)
+
+
+class XDREnumBody:
+    def __init__(self, values):
+        self.values = values
+
+    def __repr__(self):
+        return "enum-body{values=[" + ",".join([str(a) for a in self.values]) + "]}"
+
+
+class XDRTypeEnum(XDRTypeScalar):
+    def __init__(self, body):
+        self.body = body
+
+    def __repr__(self):
+        return "enum{%s}" % self.body
+
+
+class XDRStructBody:
+    def __init__(self, fields):
+        self.fields = fields
+
+    def __repr__(self):
+        return "struct-body{fields=[" + ",".join([str(a) for a in self.fields]) + "]}"
+
+
+class XDRTypeStruct(XDRType):
+    def __init__(self, body):
+        self.body = body
+
+    def __repr__(self):
+        return "struct{%s}" % self.body
+
+
+class XDRUnionCase:
+    def __init__(self, value, decl):
+        self.value = value
+        self.decl = decl
+
+    def __repr__(self):
+        return "%s=%s" % (self.value, self.decl)
+
+
+class XDRUnionBody:
+    def __init__(self, discriminator, cases, default):
+        self.discriminator = discriminator
+        self.cases = cases
+        self.default = default
+
+    def __repr__(self):
+        return (
+            "union-body{discriminator=%s,cases=["
+            + ",".join([str(a) for a in self.cases])
+            + "],default=%s}"
+        ) % (self.discriminator, self.default)
+
+
+class XDRTypeUnion(XDRType):
+    def __init__(self, body):
+        self.body = body
+
+    def __repr__(self):
+        return "union{%s}" % self.body