[Qemu-devel] [RFC PATCH 06/11] qapi: Flat unions with arbitrary discriminator

[Kevin Wolf <kwolf@redhat.com>]

Instead of the rather verbose syntax that distinguishes base and
subclass fields...

  { "type": "file",
    "read-only": true,
    "data": {
        "filename": "test"
    } }

...we can now have both in the same namespace, allowing a more direct
mapping of the command line, and moving fields between the common base
and subclasses without breaking the API:

  { "driver": "file",
    "read-only": true,
    "filename": "test" }

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 scripts/qapi-types.py | 10 +++---
 scripts/qapi-visit.py | 91 ++++++++++++++++++++++++++++++++++++---------------
 2 files changed, 70 insertions(+), 31 deletions(-)

diff --git a/scripts/qapi-types.py b/scripts/qapi-types.py
index 960065b..db2f533 100644
--- a/scripts/qapi-types.py
+++ b/scripts/qapi-types.py
@@ -162,10 +162,8 @@ def generate_union(expr):
     name = expr['union']
     typeinfo = expr['data']
 
-    if expr.has_key('base'):
-        base = expr['base']
-    else:
-        base = None
+    base = expr.get('base')
+    discriminator = expr.get('discriminator')
 
     ret = mcgen('''
 struct %(name)s
@@ -189,7 +187,11 @@ struct %(name)s
 
     if base:
         struct = find_struct(base)
+        if discriminator:
+            del struct['data'][discriminator]
         ret += generate_struct_fields(struct['data'])
+    else:
+        assert not discriminator
 
     ret += mcgen('''
 };
diff --git a/scripts/qapi-visit.py b/scripts/qapi-visit.py
index 3b2e693..bff284f 100644
--- a/scripts/qapi-visit.py
+++ b/scripts/qapi-visit.py
@@ -17,8 +17,26 @@ import os
 import getopt
 import errno
 
-def generate_visit_struct_fields(field_prefix, members):
+def generate_visit_struct_fields(name, field_prefix, members):
+    substructs = []
     ret = ''
+    full_name = name if not field_prefix else "%s_%s" % (name, field_prefix)
+
+    for argname, argentry, optional, structured in parse_args(members):
+        if structured:
+            ret += generate_visit_struct_fields(name, field_prefix + argname, argentry)
+
+    ret += mcgen('''
+
+static void visit_type_%(full_name)s_fields(Visitor *m, %(name)s ** obj, Error **errp)
+{
+    Error *err = NULL;
+''',
+        name=name, full_name=full_name)
+    push_indent()
+
+    if len(field_prefix):
+        field_prefix = field_prefix + "."
 
     for argname, argentry, optional, structured in parse_args(members):
         if optional:
@@ -31,7 +49,7 @@ if (obj && (*obj)->%(prefix)shas_%(c_name)s) {
             push_indent()
 
         if structured:
-            ret += generate_visit_struct_body(field_prefix + argname, argname, argentry)
+            ret += generate_visit_struct_body(full_name, argname, argentry)
         else:
             ret += mcgen('''
 visit_type_%(type)s(m, obj ? &(*obj)->%(c_prefix)s%(c_name)s : NULL, "%(name)s", &err);
@@ -47,6 +65,12 @@ visit_type_%(type)s(m, obj ? &(*obj)->%(c_prefix)s%(c_name)s : NULL, "%(name)s",
 visit_end_optional(m, &err);
 ''')
 
+    pop_indent()
+    ret += mcgen('''
+
+    error_propagate(errp, err);
+}
+''')
     return ret
 
 
@@ -56,8 +80,9 @@ if (!error_is_set(errp)) {
 ''')
     push_indent()
 
+    full_name = name if not field_prefix else "%s_%s" % (field_prefix, name)
+
     if len(field_prefix):
-        field_prefix = field_prefix + "."
         ret += mcgen('''
 Error **errp = &err; /* from outer scope */
 Error *err = NULL;
@@ -74,20 +99,14 @@ visit_start_struct(m, (void **)obj, "%(name)s", name, sizeof(%(name)s), &err);
     ret += mcgen('''
 if (!err) {
     if (!obj || *obj) {
-''')
-    push_indent()
-    push_indent()
-
-    ret += generate_visit_struct_fields(field_prefix, members)
-    pop_indent()
-    ret += mcgen('''
-    error_propagate(errp, err);
-    err = NULL;
-}
-''')
+        visit_type_%(name)s_fields(m, obj, &err);
+        error_propagate(errp, err);
+        err = NULL;
+    }
+''',
+        name=full_name)
 
     pop_indent()
-    pop_indent()
     ret += mcgen('''
         /* Always call end_struct if start_struct succeeded.  */
         visit_end_struct(m, &err);
@@ -98,7 +117,9 @@ if (!err) {
     return ret
 
 def generate_visit_struct(name, members):
-    ret = mcgen('''
+    ret = generate_visit_struct_fields(name, "", members)
+
+    ret += mcgen('''
 
 void visit_type_%(name)s(Visitor *m, %(name)s ** obj, const char *name, Error **errp)
 {
@@ -156,13 +177,18 @@ def generate_visit_union(expr):
     name = expr['union']
     members = expr['data']
 
-    if expr.has_key('base'):
-        base = expr['base']
-    else:
-        base = None
+    struct = None
+    base = expr.get('base')
+    discriminator = expr.get('discriminator')
 
     ret = generate_visit_enum('%sKind' % name, members.keys())
 
+    if base:
+        struct = find_struct(base)
+        if discriminator:
+            del struct['data'][discriminator]
+        ret += generate_visit_struct_fields(name, "", struct['data'])
+
     ret += mcgen('''
 
 void visit_type_%(name)s(Visitor *m, %(name)s ** obj, const char *name, Error **errp)
@@ -182,23 +208,34 @@ void visit_type_%(name)s(Visitor *m, %(name)s ** obj, const char *name, Error **
     push_indent()
 
     if base:
-        struct = find_struct(base)
-        push_indent()
-        ret += generate_visit_struct_fields("", struct['data'])
-        pop_indent()
+        ret += mcgen('''
+    visit_type_%(name)s_fields(m, obj, &err);
+''',
+            name=name)
 
     pop_indent()
     ret += mcgen('''
-        visit_type_%(name)sKind(m, &(*obj)->kind, "type", &err);
+        visit_type_%(name)sKind(m, &(*obj)->kind, "%(type)s", &err);
         if (!err) {
             switch ((*obj)->kind) {
 ''',
-                 name=name)
+                 name=name, type="type" if not discriminator else discriminator)
 
     for key in members:
+        if not discriminator:
+            fmt = 'visit_type_%(c_type)s(m, &(*obj)->%(c_name)s, "data", &err);'
+        else:
+            fmt = '''visit_start_implicit_struct(m, (void**) &(*obj)->%(c_name)s, sizeof(%(c_type)s), &err);
+                if (!err) {
+                    visit_type_%(c_type)s_fields(m, &(*obj)->%(c_name)s, &err);
+                    error_propagate(errp, err);
+                    err = NULL;
+                    visit_end_implicit_struct(m, &err);
+                }'''
+
         ret += mcgen('''
             case %(abbrev)s_KIND_%(enum)s:
-                visit_type_%(c_type)s(m, &(*obj)->%(c_name)s, "data", &err);
+                ''' + fmt + '''
                 break;
 ''',
                 abbrev = de_camel_case(name).upper(),
-- 
1.8.1.4