Patchwork [10/18] qapi: Anonymous unions

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Submitter Kevin Wolf
Date July 23, 2013, 1:03 p.m.
Message ID <1374584606-5615-11-git-send-email-kwolf@redhat.com>
Download mbox | patch
Permalink /patch/261089/
State New
Headers show

Comments

Kevin Wolf - July 23, 2013, 1:03 p.m.
The discriminator for anonymous unions is the data type. This allows to
have a union type that allows both of these:

    { 'file': 'my_existing_block_device_id' }
    { 'file': { 'filename': '/tmp/mydisk.qcow2', 'read-only': true } }

Unions like this are specified in the schema with an empty dict as
discriminator. For this example you could take:

    { 'union': 'BlockRef',
      'discriminator': {},
      'data': { 'definition': 'BlockOptions'
                'reference': 'str' } }
    { 'type': 'ExampleObject',
      'data: { 'file': 'BlockRef' } }

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 docs/qapi-code-gen.txt      | 25 ++++++++++++++++++++++++
 include/qapi/qmp/qobject.h  |  1 +
 include/qapi/visitor-impl.h |  2 ++
 include/qapi/visitor.h      |  3 +++
 qapi/qapi-visit-core.c      |  9 +++++++++
 qapi/qmp-input-visitor.c    | 14 ++++++++++++++
 qobject/qjson.c             |  2 ++
 scripts/qapi-types.py       | 42 ++++++++++++++++++++++++++++++++++++++++
 scripts/qapi-visit.py       | 47 +++++++++++++++++++++++++++++++++++++++++++++
 scripts/qapi.py             | 15 +++++++++++++++
 10 files changed, 160 insertions(+)
Eric Blake - July 26, 2013, 3:42 p.m.
On 07/23/2013 07:03 AM, Kevin Wolf wrote:
> The discriminator for anonymous unions is the data type. This allows to
> have a union type that allows both of these:
> 
>     { 'file': 'my_existing_block_device_id' }
>     { 'file': { 'filename': '/tmp/mydisk.qcow2', 'read-only': true } }
> 
> Unions like this are specified in the schema with an empty dict as
> discriminator. For this example you could take:
> 
>     { 'union': 'BlockRef',
>       'discriminator': {},
>       'data': { 'definition': 'BlockOptions'

Missing comma.

>                 'reference': 'str' } }
>     { 'type': 'ExampleObject',
>       'data: { 'file': 'BlockRef' } }
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---

> +++ b/docs/qapi-code-gen.txt
> @@ -125,6 +125,31 @@ Resulting in this JSON object:
>     "lazy-refcounts": true }
>  
>  
> +A special type of unions are anonymous unions. They don't form a dictionary in
> +the wire format but allow the direct use of different types in their place. As
> +they aren't structured, they don't have any explicit discriminator but use
> +the (QObject) data type of their value as an implicit discriminator. This means
> +that they are restricted to using only one discriminator value per QObject
> +type. For example, you cannot have two different complex types in an anonymous
> +union, or two different integer types.
> +
> +Anonymous unions are declared using an empty dictionary as their discriminator.
> +The disriminator values never appear on the wire, they are only used in the

s/disriminator/discriminator/

> +generated C code. Anonymous unions cannot have a base type.
> +
> + { 'union': 'BlockRef',
> +   'discriminator': {},
> +   'data': { 'definition': 'BlockdevOptions'

Missing comma.

> +++ b/qobject/qjson.c
> @@ -260,6 +260,8 @@ static void to_json(const QObject *obj, QString *str, int pretty, int indent)
>          /* XXX: should QError be emitted? */
>      case QTYPE_NONE:
>          break;
> +    case QTYPE_MAX:
> +        abort();

There's another recent patch proposing the use of g_assert_not_reached():

https://lists.gnu.org/archive/html/qemu-devel/2013-07/msg04560.html

but I don't know if it is worth switching abort() over to this function
(and even if it was, there's enough other use of abort in the qapi code
that it would be better to switch it all as a separate patch).

Fix the typos, then you can add:
Reviewed-by: Eric Blake <eblake@redhat.com>

Patch

diff --git a/docs/qapi-code-gen.txt b/docs/qapi-code-gen.txt
index c187fda..ee8a13e 100644
--- a/docs/qapi-code-gen.txt
+++ b/docs/qapi-code-gen.txt
@@ -125,6 +125,31 @@  Resulting in this JSON object:
    "lazy-refcounts": true }
 
 
+A special type of unions are anonymous unions. They don't form a dictionary in
+the wire format but allow the direct use of different types in their place. As
+they aren't structured, they don't have any explicit discriminator but use
+the (QObject) data type of their value as an implicit discriminator. This means
+that they are restricted to using only one discriminator value per QObject
+type. For example, you cannot have two different complex types in an anonymous
+union, or two different integer types.
+
+Anonymous unions are declared using an empty dictionary as their discriminator.
+The disriminator values never appear on the wire, they are only used in the
+generated C code. Anonymous unions cannot have a base type.
+
+ { 'union': 'BlockRef',
+   'discriminator': {},
+   'data': { 'definition': 'BlockdevOptions'
+             'reference': 'str' } }
+
+This example allows using both of the following example objects:
+
+ { "file": "my_existing_block_device_id" }
+ { "file": { "driver": "file",
+             "readonly": false,
+             'filename': "/tmp/mydisk.qcow2" } }
+
+
 === Commands ===
 
 Commands are defined by using a list containing three members.  The first
diff --git a/include/qapi/qmp/qobject.h b/include/qapi/qmp/qobject.h
index 9124649..d0bbc7c 100644
--- a/include/qapi/qmp/qobject.h
+++ b/include/qapi/qmp/qobject.h
@@ -44,6 +44,7 @@  typedef enum {
     QTYPE_QFLOAT,
     QTYPE_QBOOL,
     QTYPE_QERROR,
+    QTYPE_MAX,
 } qtype_code;
 
 struct QObject;
diff --git a/include/qapi/visitor-impl.h b/include/qapi/visitor-impl.h
index 5c1297f..f3fa420 100644
--- a/include/qapi/visitor-impl.h
+++ b/include/qapi/visitor-impl.h
@@ -32,6 +32,8 @@  struct Visitor
 
     void (*type_enum)(Visitor *v, int *obj, const char *strings[],
                       const char *kind, const char *name, Error **errp);
+    void (*get_next_type)(Visitor *v, int *kind, const int *qobjects,
+                          const char *name, Error **errp);
 
     void (*type_int)(Visitor *v, int64_t *obj, const char *name, Error **errp);
     void (*type_bool)(Visitor *v, bool *obj, const char *name, Error **errp);
diff --git a/include/qapi/visitor.h b/include/qapi/visitor.h
index bd24f85..48a2a2e 100644
--- a/include/qapi/visitor.h
+++ b/include/qapi/visitor.h
@@ -13,6 +13,7 @@ 
 #ifndef QAPI_VISITOR_CORE_H
 #define QAPI_VISITOR_CORE_H
 
+#include "qapi/qmp/qobject.h"
 #include "qapi/error.h"
 #include <stdlib.h>
 
@@ -42,6 +43,8 @@  void visit_end_list(Visitor *v, Error **errp);
 void visit_start_optional(Visitor *v, bool *present, const char *name,
                           Error **errp);
 void visit_end_optional(Visitor *v, Error **errp);
+void visit_get_next_type(Visitor *v, int *obj, const int *qtypes,
+                         const char *name, Error **errp);
 void visit_type_enum(Visitor *v, int *obj, const char *strings[],
                      const char *kind, const char *name, Error **errp);
 void visit_type_int(Visitor *v, int64_t *obj, const char *name, Error **errp);
diff --git a/qapi/qapi-visit-core.c b/qapi/qapi-visit-core.c
index 9b4d51b..d6a4012 100644
--- a/qapi/qapi-visit-core.c
+++ b/qapi/qapi-visit-core.c
@@ -12,6 +12,7 @@ 
  */
 
 #include "qemu-common.h"
+#include "qapi/qmp/qobject.h"
 #include "qapi/qmp/qerror.h"
 #include "qapi/visitor.h"
 #include "qapi/visitor-impl.h"
@@ -98,6 +99,14 @@  void visit_end_optional(Visitor *v, Error **errp)
     }
 }
 
+void visit_get_next_type(Visitor *v, int *obj, const int *qtypes,
+                         const char *name, Error **errp)
+{
+    if (!error_is_set(errp) && v->get_next_type) {
+        v->get_next_type(v, obj, qtypes, name, errp);
+    }
+}
+
 void visit_type_enum(Visitor *v, int *obj, const char *strings[],
                      const char *kind, const char *name, Error **errp)
 {
diff --git a/qapi/qmp-input-visitor.c b/qapi/qmp-input-visitor.c
index 70864a1..bf42c04 100644
--- a/qapi/qmp-input-visitor.c
+++ b/qapi/qmp-input-visitor.c
@@ -208,6 +208,19 @@  static void qmp_input_end_list(Visitor *v, Error **errp)
     qmp_input_pop(qiv, errp);
 }
 
+static void qmp_input_get_next_type(Visitor *v, int *kind, const int *qobjects,
+                                    const char *name, Error **errp)
+{
+    QmpInputVisitor *qiv = to_qiv(v);
+    QObject *qobj = qmp_input_get_object(qiv, name, false);
+
+    if (!qobj) {
+        error_set(errp, QERR_MISSING_PARAMETER, name ? name : "null");
+        return;
+    }
+    *kind = qobjects[qobject_type(qobj)];
+}
+
 static void qmp_input_type_int(Visitor *v, int64_t *obj, const char *name,
                                Error **errp)
 {
@@ -317,6 +330,7 @@  QmpInputVisitor *qmp_input_visitor_new(QObject *obj)
     v->visitor.type_str = qmp_input_type_str;
     v->visitor.type_number = qmp_input_type_number;
     v->visitor.start_optional = qmp_input_start_optional;
+    v->visitor.get_next_type = qmp_input_get_next_type;
 
     qmp_input_push(v, obj, NULL);
     qobject_incref(obj);
diff --git a/qobject/qjson.c b/qobject/qjson.c
index 19085a1..6cf2511 100644
--- a/qobject/qjson.c
+++ b/qobject/qjson.c
@@ -260,6 +260,8 @@  static void to_json(const QObject *obj, QString *str, int pretty, int indent)
         /* XXX: should QError be emitted? */
     case QTYPE_NONE:
         break;
+    case QTYPE_MAX:
+        abort();
     }
 }
 
diff --git a/scripts/qapi-types.py b/scripts/qapi-types.py
index db2f533..57dff53 100644
--- a/scripts/qapi-types.py
+++ b/scripts/qapi-types.py
@@ -157,6 +157,40 @@  typedef enum %(name)s
 
     return lookup_decl + enum_decl
 
+def generate_anon_union_qtypes(expr):
+
+    name = expr['union']
+    members = expr['data']
+
+    ret = mcgen('''
+const int %(name)s_qtypes[QTYPE_MAX] = {
+''',
+    name=name)
+
+    for key in members:
+        qapi_type = members[key]
+        if builtin_type_qtypes.has_key(qapi_type):
+            qtype = builtin_type_qtypes[qapi_type]
+        elif find_struct(qapi_type):
+            qtype = "QTYPE_QDICT"
+        elif find_union(qapi_type):
+            qtype = "QTYPE_QDICT"
+        else:
+            assert False, "Invalid anonymous union member"
+
+        ret += mcgen('''
+    [ %(qtype)s ] = %(abbrev)s_KIND_%(enum)s,
+''',
+        qtype = qtype,
+        abbrev = de_camel_case(name).upper(),
+        enum = c_fun(de_camel_case(key),False).upper())
+
+    ret += mcgen('''
+};
+''')
+    return ret
+
+
 def generate_union(expr):
 
     name = expr['union']
@@ -196,6 +230,12 @@  struct %(name)s
     ret += mcgen('''
 };
 ''')
+    if discriminator == {}:
+        ret += mcgen('''
+extern const int %(name)s_qtypes[];
+''',
+            name=name)
+
 
     return ret
 
@@ -348,6 +388,8 @@  for expr in exprs:
         ret += generate_fwd_struct(expr['union'], expr['data']) + "\n"
         ret += generate_enum('%sKind' % expr['union'], expr['data'].keys())
         fdef.write(generate_enum_lookup('%sKind' % expr['union'], expr['data'].keys()))
+        if expr.get('discriminator') == {}:
+            fdef.write(generate_anon_union_qtypes(expr))
     else:
         continue
     fdecl.write(ret)
diff --git a/scripts/qapi-visit.py b/scripts/qapi-visit.py
index cd33e44..28539e2 100644
--- a/scripts/qapi-visit.py
+++ b/scripts/qapi-visit.py
@@ -172,6 +172,49 @@  void visit_type_%(name)s(Visitor *m, %(name)s * obj, const char *name, Error **e
 ''',
                  name=name)
 
+def generate_visit_anon_union(name, members):
+    ret = mcgen('''
+
+void visit_type_%(name)s(Visitor *m, %(name)s ** obj, const char *name, Error **errp)
+{
+    Error *err = NULL;
+
+    if (!error_is_set(errp)) {
+        visit_start_implicit_struct(m, (void**) obj, sizeof(%(name)s), &err);
+        visit_get_next_type(m, (int*) &(*obj)->kind, %(name)s_qtypes, name, &err);
+        switch ((*obj)->kind) {
+''',
+    name=name)
+
+    for key in members:
+        assert (members[key] in builtin_types
+            or find_struct(members[key])
+            or find_union(members[key])), "Invalid anonymous union member"
+
+        ret += mcgen('''
+        case %(abbrev)s_KIND_%(enum)s:
+            visit_type_%(c_type)s(m, &(*obj)->%(c_name)s, name, &err);
+            break;
+''',
+                abbrev = de_camel_case(name).upper(),
+                enum = c_fun(de_camel_case(key),False).upper(),
+                c_type = type_name(members[key]),
+                c_name = c_fun(key))
+
+    ret += mcgen('''
+        default:
+            abort();
+        }
+        error_propagate(errp, err);
+        err = NULL;
+        visit_end_implicit_struct(m, &err);
+    }
+}
+''')
+
+    return ret
+
+
 def generate_visit_union(expr):
 
     name = expr['union']
@@ -180,6 +223,10 @@  def generate_visit_union(expr):
     base = expr.get('base')
     discriminator = expr.get('discriminator')
 
+    if discriminator == {}:
+        assert not base
+        return generate_visit_anon_union(name, members)
+
     ret = generate_visit_enum('%sKind' % name, members.keys())
 
     if base:
diff --git a/scripts/qapi.py b/scripts/qapi.py
index 3a54c7f..38c808e 100644
--- a/scripts/qapi.py
+++ b/scripts/qapi.py
@@ -17,6 +17,21 @@  builtin_types = [
     'uint8', 'uint16', 'uint32', 'uint64'
 ]
 
+builtin_type_qtypes = {
+    'str':      'QTYPE_QSTRING',
+    'int':      'QTYPE_QINT',
+    'number':   'QTYPE_QFLOAT',
+    'bool':     'QTYPE_QBOOL',
+    'int8':     'QTYPE_QINT',
+    'int16':    'QTYPE_QINT',
+    'int32':    'QTYPE_QINT',
+    'int64':    'QTYPE_QINT',
+    'uint8':    'QTYPE_QINT',
+    'uint16':   'QTYPE_QINT',
+    'uint32':   'QTYPE_QINT',
+    'uint64':   'QTYPE_QINT',
+}
+
 def tokenize(data):
     while len(data):
         ch = data[0]