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[Qemu-devel] [PATCH v7 18/31] qapi: Add visit_type_null() visitor
From: |
Eric Blake |
Subject: |
[Qemu-devel] [PATCH v7 18/31] qapi: Add visit_type_null() visitor |
Date: |
Mon, 7 Dec 2015 20:55:08 -0700 |
Right now, qmp-output-visitor happens to produce a QNull result
if nothing is actually visited between the creation of the visitor
and the request for the resulting QObject. A stronger protocol
would require that a QMP output visit MUST visit something. But
to still be able to produce a JSON 'null' output, we need a new
visitor function that states our intentions.
This patch introduces the new visit_type_null() interface, and
a later patch will then wire it up into the qmp output visitor.
Signed-off-by: Eric Blake <address@hidden>
---
v7: new patch, based on discussion about spapr_drc.c
---
include/qapi/visitor-impl.h | 3 +++
include/qapi/visitor.h | 8 ++++++++
qapi/qapi-dealloc-visitor.c | 5 +++++
qapi/qapi-visit-core.c | 5 +++++
4 files changed, 21 insertions(+)
diff --git a/include/qapi/visitor-impl.h b/include/qapi/visitor-impl.h
index 27f776f..78a5ab1 100644
--- a/include/qapi/visitor-impl.h
+++ b/include/qapi/visitor-impl.h
@@ -75,6 +75,9 @@ struct Visitor
* visitors do not currently visit arbitrary types). */
void (*type_any)(Visitor *v, QObject **obj, const char *name,
Error **errp);
+ /* Must be provided to visit explicit null values (right now, only the
+ * dealloc visitor supports this). */
+ void (*type_null)(Visitor *v, const char *name, Error **errp);
/* May be NULL; most useful for input visitors. */
void (*optional)(Visitor *v, bool *present, const char *name);
diff --git a/include/qapi/visitor.h b/include/qapi/visitor.h
index 96a9535..2592dd1 100644
--- a/include/qapi/visitor.h
+++ b/include/qapi/visitor.h
@@ -267,6 +267,14 @@ void visit_type_number(Visitor *v, double *obj, const char
*name,
void visit_type_any(Visitor *v, QObject **obj, const char *name, Error **errp);
/**
+ * Visit a JSON null value tied to @name in the current object visit.
+ * @name will be NULL if this is visited as part of a list.
+ * No obj parameter is needed; rather, this is a witness that an
+ * explicit null value is expected rather than any other type.
+ */
+void visit_type_null(Visitor *v, const char *name, Error **errp);
+
+/**
* Mark the start of visiting the branches of a union. Return true if
* @data_present.
* FIXME: Should not be needed
diff --git a/qapi/qapi-dealloc-visitor.c b/qapi/qapi-dealloc-visitor.c
index e280d9f..e3a4493 100644
--- a/qapi/qapi-dealloc-visitor.c
+++ b/qapi/qapi-dealloc-visitor.c
@@ -162,6 +162,10 @@ static void qapi_dealloc_type_anything(Visitor *v, QObject
**obj,
}
}
+static void qapi_dealloc_type_null(Visitor *v, const char *name, Error **errp)
+{
+}
+
static void qapi_dealloc_type_enum(Visitor *v, int *obj,
const char *const strings[],
const char *name, Error **errp)
@@ -223,6 +227,7 @@ QapiDeallocVisitor *qapi_dealloc_visitor_new(void)
v->visitor.type_str = qapi_dealloc_type_str;
v->visitor.type_number = qapi_dealloc_type_number;
v->visitor.type_any = qapi_dealloc_type_anything;
+ v->visitor.type_null = qapi_dealloc_type_null;
v->visitor.start_union = qapi_dealloc_start_union;
QTAILQ_INIT(&v->stack);
diff --git a/qapi/qapi-visit-core.c b/qapi/qapi-visit-core.c
index 042ef07..36917f3 100644
--- a/qapi/qapi-visit-core.c
+++ b/qapi/qapi-visit-core.c
@@ -257,6 +257,11 @@ void visit_type_any(Visitor *v, QObject **obj, const char
*name,
v->type_any(v, obj, name, errp);
}
+void visit_type_null(Visitor *v, const char *name, Error **errp)
+{
+ v->type_null(v, name, errp);
+}
+
void output_type_enum(Visitor *v, int *obj, const char *const strings[],
const char *name, Error **errp)
{
--
2.4.3
- [Qemu-devel] [PATCH v7 01/31] qobject: Document more shortcomings in our number handling, (continued)
- [Qemu-devel] [PATCH v7 01/31] qobject: Document more shortcomings in our number handling, Eric Blake, 2015/12/07
- [Qemu-devel] [PATCH v7 11/31] qapi: Consolidate visitor small integer callbacks, Eric Blake, 2015/12/07
- [Qemu-devel] [PATCH v7 05/31] vl: Improve use of qapi visitor, Eric Blake, 2015/12/07
- [Qemu-devel] [PATCH v7 02/31] qapi: Avoid use of misnamed DO_UPCAST(), Eric Blake, 2015/12/07
- [Qemu-devel] [PATCH v7 10/31] qapi: Make all visitors supply uint64 callbacks, Eric Blake, 2015/12/07
- [Qemu-devel] [PATCH v7 12/31] qapi: Don't cast Enum* to int*, Eric Blake, 2015/12/07
- [Qemu-devel] [PATCH v7 15/31] qmp: Fix reference-counting of qnull on empty output visit, Eric Blake, 2015/12/07
- [Qemu-devel] [PATCH v7 13/31] qapi: Drop unused 'kind' for struct/enum visit, Eric Blake, 2015/12/07
- [Qemu-devel] [PATCH v7 18/31] qapi: Add visit_type_null() visitor,
Eric Blake <=
- [Qemu-devel] [PATCH v7 08/31] qapi: Track all failures between visit_start/stop, Eric Blake, 2015/12/07
- [Qemu-devel] [PATCH v7 07/31] qapi: Improve generated event use of qapi visitor, Eric Blake, 2015/12/07
- [Qemu-devel] [PATCH v7 14/31] qapi: Drop unused error argument for list and implicit struct, Eric Blake, 2015/12/07
- [Qemu-devel] [PATCH v7 22/31] qapi: Add type.is_empty() helper, Eric Blake, 2015/12/07
- [Qemu-devel] [PATCH v7 20/31] spapr_drc: Expose 'null' in qom-get when there is no fdt, Eric Blake, 2015/12/07
- [Qemu-devel] [PATCH v7 24/31] qapi: Eliminate empty visit_type_FOO_fields, Eric Blake, 2015/12/07
- [Qemu-devel] [PATCH v7 19/31] qmp: Tighten output visitor rules, Eric Blake, 2015/12/07
- [Qemu-devel] [PATCH v7 21/31] qapi: Simplify excess input reporting in input visitors, Eric Blake, 2015/12/07