6 files changed, 82 insertions, 71 deletions

diff --git a/include/qapi/visitor-impl.h b/include/qapi/visitor-impl.h
index c4af3e042f..6a1ddfbd9a 100644
--- a/include/qapi/visitor-impl.h
+++ b/include/qapi/visitor-impl.h
@@ -22,22 +22,23 @@ struct Visitor
                          size_t size, Error **errp);
     void (*end_struct)(Visitor *v, Error **errp);
 
-    void (*start_implicit_struct)(Visitor *v, void **obj, size_t size,
-                                  Error **errp);
-    /* May be NULL */
-    void (*end_implicit_struct)(Visitor *v);
-
     void (*start_list)(Visitor *v, const char *name, Error **errp);
     /* Must be set */
     GenericList *(*next_list)(Visitor *v, GenericList **list, size_t size);
     /* Must be set */
     void (*end_list)(Visitor *v);
 
+    /* Optional, needed for input and dealloc visitors.  */
+    void (*start_alternate)(Visitor *v, const char *name,
+                            GenericAlternate **obj, size_t size,
+                            bool promote_int, Error **errp);
+
+    /* Optional, needed for dealloc visitor.  */
+    void (*end_alternate)(Visitor *v);
+
+    /* Must be set. */
     void (*type_enum)(Visitor *v, const char *name, int *obj,
                       const char *const strings[], Error **errp);
-    /* May be NULL; only needed for input visitors. */
-    void (*get_next_type)(Visitor *v, const char *name, QType *type,
-                          bool promote_int, Error **errp);
 
     /* Must be set. */
     void (*type_int64)(Visitor *v, const char *name, int64_t *obj,
diff --git a/include/qapi/visitor.h b/include/qapi/visitor.h
index a6678b16ef..83cad74c88 100644
--- a/include/qapi/visitor.h
+++ b/include/qapi/visitor.h
@@ -27,17 +27,52 @@ typedef struct GenericList {
     char padding[];
 } GenericList;
 
+/* This struct is layout-compatible with all Alternate types
+ * created by the qapi generator. */
+typedef struct GenericAlternate {
+    QType type;
+    char padding[];
+} GenericAlternate;
+
 void visit_start_struct(Visitor *v, const char *name, void **obj,
                         size_t size, Error **errp);
 void visit_end_struct(Visitor *v, Error **errp);
-void visit_start_implicit_struct(Visitor *v, void **obj, size_t size,
-                                 Error **errp);
-void visit_end_implicit_struct(Visitor *v);
 
 void visit_start_list(Visitor *v, const char *name, Error **errp);
 GenericList *visit_next_list(Visitor *v, GenericList **list, size_t size);
 void visit_end_list(Visitor *v);
 
+/*
+ * Start the visit of an alternate @obj with the given @size.
+ *
+ * @name specifies the relationship to the containing struct (ignored
+ * for a top level visit, the name of the key if this alternate is
+ * part of an object, or NULL if this alternate is part of a list).
+ *
+ * @obj must not be NULL. Input visitors will allocate @obj and
+ * determine the qtype of the next thing to be visited, stored in
+ * (*@obj)->type.  Other visitors will leave @obj unchanged.
+ *
+ * If @promote_int, treat integers as QTYPE_FLOAT.
+ *
+ * If successful, this must be paired with visit_end_alternate(), even
+ * if visiting the contents of the alternate fails.
+ */
+void visit_start_alternate(Visitor *v, const char *name,
+                           GenericAlternate **obj, size_t size,
+                           bool promote_int, Error **errp);
+
+/*
+ * Finish visiting an alternate type.
+ *
+ * Must be called after a successful visit_start_alternate(), even if
+ * an error occurred in the meantime.
+ *
+ * TODO: Should all the visit_end_* interfaces take obj parameter, so
+ * that dealloc visitor need not track what was passed in visit_start?
+ */
+void visit_end_alternate(Visitor *v);
+
 /**
  * Check if an optional member @name of an object needs visiting.
  * For input visitors, set *@present according to whether the
@@ -46,14 +81,6 @@ void visit_end_list(Visitor *v);
  */
 bool visit_optional(Visitor *v, const char *name, bool *present);
 
-/**
- * Determine the qtype of the item @name in the current object visit.
- * For input visitors, set *@type to the correct qtype of a qapi
- * alternate type; for other visitors, leave *@type unchanged.
- * If @promote_int, treat integers as QTYPE_FLOAT.
- */
-void visit_get_next_type(Visitor *v, const char *name, QType *type,
-                         bool promote_int, Error **errp);
 void visit_type_enum(Visitor *v, const char *name, int *obj,
                      const char *const strings[], Error **errp);
 void visit_type_int(Visitor *v, const char *name, int64_t *obj, Error **errp);
diff --git a/qapi/qapi-dealloc-visitor.c b/qapi/qapi-dealloc-visitor.c
index 4eae555ace..69221794ec 100644
--- a/qapi/qapi-dealloc-visitor.c
+++ b/qapi/qapi-dealloc-visitor.c
@@ -76,16 +76,15 @@ static void qapi_dealloc_end_struct(Visitor *v, Error **errp)
     }
 }
 
-static void qapi_dealloc_start_implicit_struct(Visitor *v,
-                                               void **obj,
-                                               size_t size,
-                                               Error **errp)
+static void qapi_dealloc_start_alternate(Visitor *v, const char *name,
+                                         GenericAlternate **obj, size_t size,
+                                         bool promote_int, Error **errp)
 {
     QapiDeallocVisitor *qov = to_qov(v);
     qapi_dealloc_push(qov, obj);
 }
 
-static void qapi_dealloc_end_implicit_struct(Visitor *v)
+static void qapi_dealloc_end_alternate(Visitor *v)
 {
     QapiDeallocVisitor *qov = to_qov(v);
     void **obj = qapi_dealloc_pop(qov);
@@ -187,8 +186,8 @@ QapiDeallocVisitor *qapi_dealloc_visitor_new(void)
 
     v->visitor.start_struct = qapi_dealloc_start_struct;
     v->visitor.end_struct = qapi_dealloc_end_struct;
-    v->visitor.start_implicit_struct = qapi_dealloc_start_implicit_struct;
-    v->visitor.end_implicit_struct = qapi_dealloc_end_implicit_struct;
+    v->visitor.start_alternate = qapi_dealloc_start_alternate;
+    v->visitor.end_alternate = qapi_dealloc_end_alternate;
     v->visitor.start_list = qapi_dealloc_start_list;
     v->visitor.next_list = qapi_dealloc_next_list;
     v->visitor.end_list = qapi_dealloc_end_list;
diff --git a/qapi/qapi-visit-core.c b/qapi/qapi-visit-core.c
index f7b99807b0..856606b253 100644
--- a/qapi/qapi-visit-core.c
+++ b/qapi/qapi-visit-core.c
@@ -30,21 +30,6 @@ void visit_end_struct(Visitor *v, Error **errp)
     v->end_struct(v, errp);
 }
 
-void visit_start_implicit_struct(Visitor *v, void **obj, size_t size,
-                                 Error **errp)
-{
-    if (v->start_implicit_struct) {
-        v->start_implicit_struct(v, obj, size, errp);
-    }
-}
-
-void visit_end_implicit_struct(Visitor *v)
-{
-    if (v->end_implicit_struct) {
-        v->end_implicit_struct(v);
-    }
-}
-
 void visit_start_list(Visitor *v, const char *name, Error **errp)
 {
     v->start_list(v, name, errp);
@@ -61,20 +46,29 @@ void visit_end_list(Visitor *v)
     v->end_list(v);
 }
 
-bool visit_optional(Visitor *v, const char *name, bool *present)
+void visit_start_alternate(Visitor *v, const char *name,
+                           GenericAlternate **obj, size_t size,
+                           bool promote_int, Error **errp)
 {
-    if (v->optional) {
-        v->optional(v, name, present);
+    assert(obj && size >= sizeof(GenericAlternate));
+    if (v->start_alternate) {
+        v->start_alternate(v, name, obj, size, promote_int, errp);
+    }
+}
+
+void visit_end_alternate(Visitor *v)
+{
+    if (v->end_alternate) {
+        v->end_alternate(v);
     }
-    return *present;
 }
 
-void visit_get_next_type(Visitor *v, const char *name, QType *type,
-                         bool promote_int, Error **errp)
+bool visit_optional(Visitor *v, const char *name, bool *present)
 {
-    if (v->get_next_type) {
-        v->get_next_type(v, name, type, promote_int, errp);
+    if (v->optional) {
+        v->optional(v, name, present);
     }
+    return *present;
 }
 
 void visit_type_enum(Visitor *v, const char *name, int *obj,
diff --git a/qapi/qmp-input-visitor.c b/qapi/qmp-input-visitor.c
index 26216604cc..e6598327c3 100644
--- a/qapi/qmp-input-visitor.c
+++ b/qapi/qmp-input-visitor.c
@@ -143,14 +143,6 @@ static void qmp_input_end_struct(Visitor *v, Error **errp)
     qmp_input_pop(qiv, errp);
 }
 
-static void qmp_input_start_implicit_struct(Visitor *v, void **obj,
-                                            size_t size, Error **errp)
-{
-    if (obj) {
-        *obj = g_malloc0(size);
-    }
-}
-
 static void qmp_input_start_list(Visitor *v, const char *name, Error **errp)
 {
     QmpInputVisitor *qiv = to_qiv(v);
@@ -202,19 +194,22 @@ static void qmp_input_end_list(Visitor *v)
     qmp_input_pop(qiv, &error_abort);
 }
 
-static void qmp_input_get_next_type(Visitor *v, const char *name, QType *type,
-                                    bool promote_int, Error **errp)
+static void qmp_input_start_alternate(Visitor *v, const char *name,
+                                      GenericAlternate **obj, size_t size,
+                                      bool promote_int, Error **errp)
 {
     QmpInputVisitor *qiv = to_qiv(v);
     QObject *qobj = qmp_input_get_object(qiv, name, false);
 
     if (!qobj) {
+        *obj = NULL;
         error_setg(errp, QERR_MISSING_PARAMETER, name ? name : "null");
         return;
     }
-    *type = qobject_type(qobj);
-    if (promote_int && *type == QTYPE_QINT) {
-        *type = QTYPE_QFLOAT;
+    *obj = g_malloc0(size);
+    (*obj)->type = qobject_type(qobj);
+    if (promote_int && (*obj)->type == QTYPE_QINT) {
+        (*obj)->type = QTYPE_QFLOAT;
     }
 }
 
@@ -345,10 +340,10 @@ QmpInputVisitor *qmp_input_visitor_new(QObject *obj)
 
     v->visitor.start_struct = qmp_input_start_struct;
     v->visitor.end_struct = qmp_input_end_struct;
-    v->visitor.start_implicit_struct = qmp_input_start_implicit_struct;
     v->visitor.start_list = qmp_input_start_list;
     v->visitor.next_list = qmp_input_next_list;
     v->visitor.end_list = qmp_input_end_list;
+    v->visitor.start_alternate = qmp_input_start_alternate;
     v->visitor.type_enum = input_type_enum;
     v->visitor.type_int64 = qmp_input_type_int64;
     v->visitor.type_uint64 = qmp_input_type_uint64;
@@ -357,7 +352,6 @@ QmpInputVisitor *qmp_input_visitor_new(QObject *obj)
     v->visitor.type_number = qmp_input_type_number;
     v->visitor.type_any = qmp_input_type_any;
     v->visitor.optional = qmp_input_optional;
-    v->visitor.get_next_type = qmp_input_get_next_type;
 
     qmp_input_push(v, obj, NULL);
     qobject_incref(obj);
diff --git a/scripts/qapi-visit.py b/scripts/qapi-visit.py
index 3a3918f952..2308268a62 100644
--- a/scripts/qapi-visit.py
+++ b/scripts/qapi-visit.py
@@ -182,14 +182,11 @@ void visit_type_%(c_name)s(Visitor *v, const char *name, %(c_name)s **obj, Error
 {
     Error *err = NULL;
 
-    visit_start_implicit_struct(v, (void**) obj, sizeof(%(c_name)s), &err);
+    visit_start_alternate(v, name, (GenericAlternate **)obj, sizeof(**obj),
+                          %(promote_int)s, &err);
     if (err) {
         goto out;
     }
-    visit_get_next_type(v, name, &(*obj)->type, %(promote_int)s, &err);
-    if (err) {
-        goto out_obj;
-    }
     switch ((*obj)->type) {
 ''',
                  c_name=c_name(name), promote_int=promote_int)
@@ -227,8 +224,7 @@ void visit_type_%(c_name)s(Visitor *v, const char *name, %(c_name)s **obj, Error
         error_setg(&err, QERR_INVALID_PARAMETER_TYPE, name ? name : "null",
                    "%(name)s");
     }
-out_obj:
-    visit_end_implicit_struct(v);
+    visit_end_alternate(v);
 out:
     error_propagate(errp, err);
 }