qapi-types/visit.py: Inheritance for structs

This introduces a new 'base' key for struct definitions that refers to
another struct type. On the JSON level, the fields of the base type are
included directly into the same namespace as the fields of the defined
type, like with unions. On the C level, a pointer to a struct of the
base type is included.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>

diff --git a/docs/qapi-code-gen.txt b/docs/qapi-code-gen.txt
index 0ce045c0b3a0351605732d9ae8b96406a9d4b937..91f44d01b9522e56e8332516810fd3bf860afc69 100644 (file)
--- a/docs/qapi-code-gen.txt
+++ b/docs/qapi-code-gen.txt
@@ -53,6 +53,23 @@ The use of '*' as a prefix to the name means the member is optional.  Optional
 members should always be added to the end of the dictionary to preserve
 backwards compatibility.
 
+
+A complex type definition can specify another complex type as its base.
+In this case, the fields of the base type are included as top-level fields
+of the new complex type's dictionary in the QMP wire format. An example
+definition is:
+
+ { 'type': 'BlockdevOptionsGenericFormat', 'data': { 'file': 'str' } }
+ { 'type': 'BlockdevOptionsGenericCOWFormat',
+   'base': 'BlockdevOptionsGenericFormat',
+   'data': { '*backing': 'str' } }
+
+An example BlockdevOptionsGenericCOWFormat object on the wire could use
+both fields like this:
+
+ { "file": "/some/place/my-image",
+   "backing": "/some/place/my-backing-file" }
+
 === Enumeration types ===
 
 An enumeration type is a dictionary containing a single key whose value is a

diff --git a/scripts/qapi-types.py b/scripts/qapi-types.py
index 566fe5e4d958fe11b50f4c08832bf41c4d693747..4a1652b56f3c40e25dce0d7da4ebd334ce80322c 100644 (file)
--- a/scripts/qapi-types.py
+++ b/scripts/qapi-types.py
@@ -86,6 +86,7 @@ def generate_struct(expr):
     structname = expr.get('type', "")
     fieldname = expr.get('field', "")
     members = expr['data']
+    base = expr.get('base')
 
     ret = mcgen('''
 struct %(name)s
@@ -93,6 +94,9 @@ struct %(name)s
 ''',
           name=structname)
 
+    if base:
+        ret += generate_struct_fields({'base': base})
+
     ret += generate_struct_fields(members)
 
     if len(fieldname):

diff --git a/scripts/qapi-visit.py b/scripts/qapi-visit.py
index 1e44004a1e0b67d8c234c3f718e418917d307782..c39e6284b8d03e3f055ba68cd0e665717d014191 100644 (file)
--- a/scripts/qapi-visit.py
+++ b/scripts/qapi-visit.py
@@ -17,7 +17,7 @@ import os
 import getopt
 import errno
 
-def generate_visit_struct_fields(name, field_prefix, fn_prefix, members):
+def generate_visit_struct_fields(name, field_prefix, fn_prefix, members, base = None):
     substructs = []
     ret = ''
     full_name = name if not fn_prefix else "%s_%s" % (name, fn_prefix)
@@ -42,6 +42,19 @@ static void visit_type_%(full_name)s_fields(Visitor *m, %(name)s ** obj, Error *
         name=name, full_name=full_name)
     push_indent()
 
+    if base:
+        ret += mcgen('''
+visit_start_implicit_struct(m, obj ? (void**) &(*obj)->%(c_name)s : NULL, sizeof(%(type)s), &err);
+if (!err) {
+    visit_type_%(type)s_fields(m, obj ? &(*obj)->%(c_prefix)s%(c_name)s : NULL, &err);
+    error_propagate(errp, err);
+    err = NULL;
+    visit_end_implicit_struct(m, &err);
+}
+''',
+                     c_prefix=c_var(field_prefix),
+                     type=type_name(base), c_name=c_var('base'))
+
     for argname, argentry, optional, structured in parse_args(members):
         if optional:
             ret += mcgen('''
@@ -124,8 +137,9 @@ def generate_visit_struct(expr):
 
     name = expr['type']
     members = expr['data']
+    base = expr.get('base')
 
-    ret = generate_visit_struct_fields(name, "", "", members)
+    ret = generate_visit_struct_fields(name, "", "", members, base)
 
     ret += mcgen('''