From e25370368e98e6d8766e50b7f13e3543e1c3ef9b Mon Sep 17 00:00:00 2001

From: Kevin Wolf <kwolf@redhat.com>

Date: Mon, 9 Sep 2013 14:28:12 +0200

Subject: [PATCH 21/38] qapi: Flat unions with arbitrary discriminator

RH-Author: Kevin Wolf <kwolf@redhat.com>

Message-id: <1378736903-18489-22-git-send-email-kwolf@redhat.com>

Patchwork-id: 54208

O-Subject: [RHEL-7.0 qemu-kvm PATCH 21/32] qapi: Flat unions with arbitrary discriminator

Bugzilla: 1005818

RH-Acked-by: Fam Zheng <famz@redhat.com>

RH-Acked-by: Max Reitz <mreitz@redhat.com>

RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>

Bugzilla: 1005818

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>

(cherry picked from commit 50f2bdc75c5ee00617ad874c9ceac2cea660aa1e)

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

---

 docs/qapi-code-gen.txt | 22 ++++++++++++

 scripts/qapi-types.py  | 11 ++++--

 scripts/qapi-visit.py  | 90 +++++++++++++++++++++++++++++++++++++-------------

 3 files changed, 98 insertions(+), 25 deletions(-)

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>

---

 docs/qapi-code-gen.txt |   22 ++++++++++++

 scripts/qapi-types.py  |   11 +++++-

 scripts/qapi-visit.py  |   90 +++++++++++++++++++++++++++++++++++------------

 3 files changed, 98 insertions(+), 25 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

diff --git a/scripts/qapi-types.py b/scripts/qapi-types.py

index c0684a7..f139bfe 100644

--- a/scripts/qapi-types.py

+++ b/scripts/qapi-types.py

@@ -135,7 +135,9 @@ def generate_union(expr):

     name = expr['union']

     typeinfo = expr['data']

+

     base = expr.get('base')

+    discriminator = expr.get('discriminator')

     ret = mcgen('''

 struct %(name)s

@@ -158,8 +160,13 @@ 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('''

 };

diff --git a/scripts/qapi-visit.py b/scripts/qapi-visit.py

index be56ba4..b1c1ad6 100644

--- a/scripts/qapi-visit.py

+++ b/scripts/qapi-visit.py

@@ -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;

@@ -74,20 +103,14 @@ visit_start_struct(m, (void **)obj, "%(name)s", name, sizeof(%(name)s), &err;;

     ret += mcgen('''

 if (!err) {

     if (!obj || *obj) {

-''')

-    push_indent()

-    push_indent()

-

-    ret += generate_visit_struct_fields(field_prefix, members)

-    pop_indent()

-    ret += mcgen('''

-    error_propagate(errp, err);

-    err = NULL;

-}

-''')

+        visit_type_%(name)s_fields(m, obj, &err;;

+        error_propagate(errp, err);

+        err = NULL;

+    }

+''',

+        name=full_name)

     pop_indent()

-    pop_indent()

     ret += mcgen('''

         /* Always call end_struct if start_struct succeeded.  */

         visit_end_struct(m, &err;;

@@ -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(),

-- 

1.7.1