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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>
This commit is contained in:
Kevin Wolf 2013-07-03 15:58:57 +02:00
parent 761d524dbc
commit 50f2bdc75c
3 changed files with 98 additions and 25 deletions
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22
docs/qapi-code-gen.txt
View File

@ -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

11
scripts/qapi-types.py
View File

@ -154,7 +154,9 @@ def generate_union(expr):
name = expr['union']
typeinfo = expr['data']
base = expr.get('base')
discriminator = expr.get('discriminator')
ret = mcgen('''
struct %(name)s
@ -177,8 +179,13 @@ struct %(name)s
''')
if base:
struct = find_struct(base)
ret += generate_struct_fields(struct['data'])
base_fields = find_struct(base)['data']
if discriminator:
base_fields = base_fields.copy()
del base_fields[discriminator]
ret += generate_struct_fields(base_fields)
else:
assert not discriminator
ret += mcgen('''
};

90
scripts/qapi-visit.py
View File

@ -17,8 +17,30 @@ import os
import getopt
import errno
def generate_visit_struct_fields(field_prefix, members):
def generate_visit_struct_fields(name, field_prefix, fn_prefix, members):
substructs = []
ret = ''
full_name = name if not fn_prefix else "%s_%s" % (name, fn_prefix)
for argname, argentry, optional, structured in parse_args(members):
if structured:
if not fn_prefix:
nested_fn_prefix = argname
else:
nested_fn_prefix = "%s_%s" % (fn_prefix, argname)
nested_field_prefix = "%s%s." % (field_prefix, argname)
ret += generate_visit_struct_fields(name, nested_field_prefix,
nested_fn_prefix, argentry)
ret += mcgen('''
static void visit_type_%(full_name)s_fields(Visitor *m, %(name)s ** obj, Error **errp)
{
Error *err = NULL;
''',
name=name, full_name=full_name)
push_indent()
for argname, argentry, optional, structured in parse_args(members):
if optional:
@ -31,7 +53,7 @@ if (obj && (*obj)->%(prefix)shas_%(c_name)s) {
push_indent()
if structured:
ret += generate_visit_struct_body(field_prefix + argname, argname, argentry)
ret += generate_visit_struct_body(full_name, argname, argentry)
else:
ret += mcgen('''
visit_type_%(type)s(m, obj ? &(*obj)->%(c_prefix)s%(c_name)s : NULL, "%(name)s", &err);
@ -47,6 +69,12 @@ visit_type_%(type)s(m, obj ? &(*obj)->%(c_prefix)s%(c_name)s : NULL, "%(name)s",
visit_end_optional(m, &err);
''')
pop_indent()
ret += mcgen('''
error_propagate(errp, err);
}
''')
return ret
@ -56,8 +84,9 @@ if (!error_is_set(errp)) {
''')
push_indent()
full_name = name if not field_prefix else "%s_%s" % (field_prefix, name)
if len(field_prefix):
field_prefix = field_prefix + "."
ret += mcgen('''
Error **errp = &err; /* from outer scope */
Error *err = NULL;
@ -74,19 +103,13 @@ visit_start_struct(m, (void **)obj, "%(name)s", name, sizeof(%(name)s), &err);
ret += mcgen('''
if (!err) {
if (!obj || *obj) {
''')
push_indent()
push_indent()
visit_type_%(name)s_fields(m, obj, &err);
error_propagate(errp, err);
err = NULL;
}
''',
name=full_name)
ret += generate_visit_struct_fields(field_prefix, members)
pop_indent()
ret += mcgen('''
error_propagate(errp, err);
err = NULL;
}
''')
pop_indent()
pop_indent()
ret += mcgen('''
/* Always call end_struct if start_struct succeeded. */
@ -98,7 +121,9 @@ if (!err) {
return ret
def generate_visit_struct(name, members):
ret = mcgen('''
ret = generate_visit_struct_fields(name, "", "", members)
ret += mcgen('''
void visit_type_%(name)s(Visitor *m, %(name)s ** obj, const char *name, Error **errp)
{
@ -157,9 +182,17 @@ def generate_visit_union(expr):
members = expr['data']
base = expr.get('base')
discriminator = expr.get('discriminator')
ret = generate_visit_enum('%sKind' % name, members.keys())
if base:
base_fields = find_struct(base)['data']
if discriminator:
base_fields = base_fields.copy()
del base_fields[discriminator]
ret += generate_visit_struct_fields(name, "", "", base_fields)
ret += mcgen('''
void visit_type_%(name)s(Visitor *m, %(name)s ** obj, const char *name, Error **errp)
@ -179,23 +212,34 @@ void visit_type_%(name)s(Visitor *m, %(name)s ** obj, const char *name, Error **
push_indent()
if base:
struct = find_struct(base)
push_indent()
ret += generate_visit_struct_fields("", struct['data'])
pop_indent()
ret += mcgen('''
visit_type_%(name)s_fields(m, obj, &err);
''',
name=name)
pop_indent()
ret += mcgen('''
visit_type_%(name)sKind(m, &(*obj)->kind, "type", &err);
visit_type_%(name)sKind(m, &(*obj)->kind, "%(type)s", &err);
if (!err) {
switch ((*obj)->kind) {
''',
name=name)
name=name, type="type" if not discriminator else discriminator)
for key in members:
if not discriminator:
fmt = 'visit_type_%(c_type)s(m, &(*obj)->%(c_name)s, "data", &err);'
else:
fmt = '''visit_start_implicit_struct(m, (void**) &(*obj)->%(c_name)s, sizeof(%(c_type)s), &err);
if (!err) {
visit_type_%(c_type)s_fields(m, &(*obj)->%(c_name)s, &err);
error_propagate(errp, err);
err = NULL;
visit_end_implicit_struct(m, &err);
}'''
ret += mcgen('''
case %(abbrev)s_KIND_%(enum)s:
visit_type_%(c_type)s(m, &(*obj)->%(c_name)s, "data", &err);
''' + fmt + '''
break;
''',
abbrev = de_camel_case(name).upper(),