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authorKevin Wolf <kwolf@redhat.com>2013-09-19 11:56:36 +0200
committerKevin Wolf <kwolf@redhat.com>2013-10-11 16:50:01 +0200
commit622f557f5aaea1326c94ca4cddfa4eafeade3723 (patch)
treeca74eac5379e1003c4634119001400b737adb472 /docs
parent14d36307ffdf949df9c1dd7f435e138b36f63bb0 (diff)
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>
Diffstat (limited to 'docs')
-rw-r--r--docs/qapi-code-gen.txt17
1 files changed, 17 insertions, 0 deletions
diff --git a/docs/qapi-code-gen.txt b/docs/qapi-code-gen.txt
index 0ce045c0b3..91f44d01b9 100644
--- 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