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author | Kevin Wolf <kwolf@redhat.com> | 2013-07-03 15:58:57 +0200 |
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committer | Kevin Wolf <kwolf@redhat.com> | 2013-07-26 21:09:37 +0200 |
commit | 50f2bdc75c5ee00617ad874c9ceac2cea660aa1e (patch) | |
tree | 331eee5391b95110ce3960b5623dcf8646f65e57 /docs | |
parent | 761d524dbcc5bb41213dd0f238f43c273bc2b077 (diff) | |
download | qemu-50f2bdc75c5ee00617ad874c9ceac2cea660aa1e.zip qemu-50f2bdc75c5ee00617ad874c9ceac2cea660aa1e.tar.gz qemu-50f2bdc75c5ee00617ad874c9ceac2cea660aa1e.tar.bz2 |
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.txt | 22 |
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 |