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authorKevin Wolf <kwolf@redhat.com>2013-07-03 15:58:57 +0200
committerKevin Wolf <kwolf@redhat.com>2013-07-26 21:09:37 +0200
commit50f2bdc75c5ee00617ad874c9ceac2cea660aa1e (patch)
tree331eee5391b95110ce3960b5623dcf8646f65e57 /docs
parent761d524dbcc5bb41213dd0f238f43c273bc2b077 (diff)
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qapi: Flat unions with arbitrary discriminator
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> Reviewed-by: Eric Blake <eblake@redhat.com>
Diffstat (limited to 'docs')
-rw-r--r--docs/qapi-code-gen.txt22
1 files changed, 22 insertions, 0 deletions
diff --git a/docs/qapi-code-gen.txt b/docs/qapi-code-gen.txt
index f6f8d33..11f19cf 100644
--- a/docs/qapi-code-gen.txt
+++ b/docs/qapi-code-gen.txt
@@ -103,6 +103,28 @@ And it looks like this on the wire:
"data" : { "backing-file": "/some/place/my-image",
"lazy-refcounts": true } }
+
+Flat union types avoid the nesting on the wire. They are used whenever a
+specific field of the base type is declared as the discriminator ('type' is
+then no longer generated). The discriminator must always be a string field.
+The above example can then be modified as follows:
+
+ { 'type': 'BlockdevCommonOptions',
+ 'data': { 'driver': 'str', 'readonly': 'bool' } }
+ { 'union': 'BlockdevOptions',
+ 'base': 'BlockdevCommonOptions',
+ 'discriminator': 'driver',
+ 'data': { 'raw': 'RawOptions',
+ 'qcow2': 'Qcow2Options' } }
+
+Resulting in this JSON object:
+
+ { "driver": "qcow2",
+ "readonly": false,
+ "backing-file": "/some/place/my-image",
+ "lazy-refcounts": true }
+
+
=== Commands ===
Commands are defined by using a list containing three members. The first