@@ -1,7 +1,7 @@
= How to use the QAPI code generator =
Copyright IBM Corp. 2011
-Copyright (C) 2012-2015 Red Hat, Inc.
+Copyright (C) 2012-2016 Red Hat, Inc.
This work is licensed under the terms of the GNU GPL, version 2 or
later. See the COPYING file in the top-level directory.
@@ -721,29 +721,34 @@ the names of built-in types. Clients should examine member
== Code generation ==
-Schemas are fed into four scripts to generate all the code/files that,
+Schemas are fed into five scripts to generate all the code/files that,
paired with the core QAPI libraries, comprise everything required to
take JSON commands read in by a Client JSON Protocol server, unmarshal
the arguments into the underlying C types, call into the corresponding
-C function, and map the response back to a Client JSON Protocol
-response to be returned to the user.
+C function, map the response back to a Client JSON Protocol response
+to be returned to the user, and introspect the commands.
-As an example, we'll use the following schema, which describes a single
-complex user-defined type (which will produce a C struct, along with a list
-node structure that can be used to chain together a list of such types in
-case we want to accept/return a list of this type with a command), and a
-command which takes that type as a parameter and returns the same type:
+As an example, we'll use the following schema, which describes a
+single complex user-defined type, along with command which takes a
+list of that type as a parameter. The user is responsible for writing
+the implementation of qmp_my_command(); everything else is produced by
+the generator.
$ cat example-schema.json
{ 'struct': 'UserDefOne',
- 'data': { 'integer': 'int', 'string': 'str' } }
+ 'data': { 'integer': 'int', '*string': 'str' } }
{ 'command': 'my-command',
- 'data': {'arg1': 'UserDefOne'},
+ 'data': { 'arg1': ['UserDefOne'] },
'returns': 'UserDefOne' }
{ 'event': 'MY_EVENT' }
+For a more thorough look at generated code, the testsuite includes
+tests/qapi-schema/qapi-schema-tests.json that covers more examples of
+what the generator will accept, and compiles the resulting C code as
+part of 'make check-unit'.
+
=== scripts/qapi-types.py ===
Used to generate the C types defined by a schema. The following files are
@@ -776,7 +781,7 @@ Example:
qdv = qapi_dealloc_visitor_new();
v = qapi_dealloc_get_visitor(qdv);
- visit_type_UserDefOne(v, &obj, NULL, NULL);
+ visit_type_UserDefOne(v, NULL, &obj, NULL);
qapi_dealloc_visitor_cleanup(qdv);
}
@@ -791,7 +796,7 @@ Example:
qdv = qapi_dealloc_visitor_new();
v = qapi_dealloc_get_visitor(qdv);
- visit_type_UserDefOneList(v, &obj, NULL, NULL);
+ visit_type_UserDefOneList(v, NULL, &obj, NULL);
qapi_dealloc_visitor_cleanup(qdv);
}
$ cat qapi-generated/example-qapi-types.h
@@ -808,6 +813,7 @@ Example:
struct UserDefOne {
int64_t integer;
+ bool has_string;
char *string;
};
@@ -854,34 +860,42 @@ Example:
{
Error *err = NULL;
- visit_type_int(v, &(*obj)->integer, "integer", &err);
+ visit_type_int(v, "integer", &(*obj)->integer, &err);
if (err) {
goto out;
}
- visit_type_str(v, &(*obj)->string, "string", &err);
- if (err) {
- goto out;
- }
-
- out:
- error_propagate(errp, err);
- }
-
- void visit_type_UserDefOne(Visitor *v, UserDefOne **obj, const char *name, Error **errp)
- {
- Error *err = NULL;
-
- visit_start_struct(v, (void **)obj, "UserDefOne", name, sizeof(UserDefOne), &err);
- if (!err) {
- if (*obj) {
- visit_type_UserDefOne_fields(v, obj, errp);
+ if (visit_optional(v, "string", &(*obj)->has_string)) {
+ visit_type_str(v, "string", &(*obj)->string, &err);
+ if (err) {
+ goto out;
}
- visit_end_struct(v, &err);
}
+
+ out:
+ error_propagate(errp, err);
+ }
+
+ void visit_type_UserDefOne(Visitor *v, const char *name, UserDefOne **obj, Error **errp)
+ {
+ Error *err = NULL;
+
+ visit_start_struct(v, name, (void **)obj, "UserDefOne", sizeof(UserDefOne), &err);
+ if (err) {
+ goto out;
+ }
+ if (!*obj) {
+ goto out_obj;
+ }
+ visit_type_UserDefOne_fields(v, obj, &err);
+ out_obj:
+ error_propagate(errp, err);
+ err = NULL;
+ visit_end_struct(v, &err);
+ out:
error_propagate(errp, err);
}
- void visit_type_UserDefOneList(Visitor *v, UserDefOneList **obj, const char *name, Error **errp)
+ void visit_type_UserDefOneList(Visitor *v, const char *name, UserDefOneList **obj, Error **errp)
{
Error *err = NULL;
GenericList *i, **prev;
@@ -895,7 +909,7 @@ Example:
!err && (i = visit_next_list(v, prev, &err)) != NULL;
prev = &i) {
UserDefOneList *native_i = (UserDefOneList *)i;
- visit_type_UserDefOne(v, &native_i->value, NULL, &err);
+ visit_type_UserDefOne(v, NULL, &native_i->value, &err);
}
error_propagate(errp, err);
@@ -912,8 +926,8 @@ Example:
[Visitors for built-in types omitted...]
- void visit_type_UserDefOne(Visitor *v, UserDefOne **obj, const char *name, Error **errp);
- void visit_type_UserDefOneList(Visitor *v, UserDefOneList **obj, const char *name, Error **errp);
+ void visit_type_UserDefOne(Visitor *v, const char *name, UserDefOne **obj, Error **errp);
+ void visit_type_UserDefOneList(Visitor *v, const char *name, UserDefOneList **obj, Error **errp);
#endif
@@ -949,7 +963,7 @@ Example:
Visitor *v;
v = qmp_output_get_visitor(qov);
- visit_type_UserDefOne(v, &ret_in, "unused", &err);
+ visit_type_UserDefOne(v, "unused", &ret_in, &err);
if (err) {
goto out;
}
@@ -960,7 +974,7 @@ Example:
qmp_output_visitor_cleanup(qov);
qdv = qapi_dealloc_visitor_new();
v = qapi_dealloc_get_visitor(qdv);
- visit_type_UserDefOne(v, &ret_in, "unused", NULL);
+ visit_type_UserDefOne(v, "unused", &ret_in, NULL);
qapi_dealloc_visitor_cleanup(qdv);
}
@@ -971,10 +985,10 @@ Example:
QmpInputVisitor *qiv = qmp_input_visitor_new_strict(QOBJECT(args));
QapiDeallocVisitor *qdv;
Visitor *v;
- UserDefOne *arg1 = NULL;
+ UserDefOneList *arg1 = NULL;
v = qmp_input_get_visitor(qiv);
- visit_type_UserDefOne(v, &arg1, "arg1", &err);
+ visit_type_UserDefOne(v, "arg1", &arg1, &err);
if (err) {
goto out;
}
@@ -991,7 +1005,7 @@ Example:
qmp_input_visitor_cleanup(qiv);
qdv = qapi_dealloc_visitor_new();
v = qapi_dealloc_get_visitor(qdv);
- visit_type_UserDefOne(v, &arg1, "arg1", NULL);
+ visit_type_UserDefOne(v, "arg1", &arg1, NULL);
qapi_dealloc_visitor_cleanup(qdv);
}
@@ -1011,7 +1025,7 @@ Example:
#include "qapi/qmp/qdict.h"
#include "qapi/error.h"
- UserDefOne *qmp_my_command(UserDefOne *arg1, Error **errp);
+ UserDefOne *qmp_my_command(UserDefOneList *arg1, Error **errp);
#endif
@@ -1095,8 +1109,9 @@ Example:
"{\"arg-type\": \"0\", \"meta-type\": \"event\", \"name\": \"MY_EVENT\"}, "
"{\"arg-type\": \"1\", \"meta-type\": \"command\", \"name\": \"my-command\", \"ret-type\": \"2\"}, "
"{\"members\": [], \"meta-type\": \"object\", \"name\": \"0\"}, "
- "{\"members\": [{\"name\": \"arg1\", \"type\": \"2\"}], \"meta-type\": \"object\", \"name\": \"1\"}, "
- "{\"members\": [{\"name\": \"integer\", \"type\": \"int\"}, {\"name\": \"string\", \"type\": \"str\"}], \"meta-type\": \"object\", \"name\": \"2\"}, "
+ "{\"members\": [{\"name\": \"arg1\", \"type\": \"[2]\"}], \"meta-type\": \"object\", \"name\": \"1\"}, "
+ "{\"members\": [{\"name\": \"integer\", \"type\": \"int\"}, {\"default\": null, \"name\": \"string\", \"type\": \"str\"}], \"meta-type\": \"object\", \"name\": \"2\"}, "
+ "{\"element-type\": \"2\", \"meta-type\": \"array\", \"name\": \"[2]\"}, "
"{\"json-type\": \"int\", \"meta-type\": \"builtin\", \"name\": \"int\"}, "
"{\"json-type\": \"string\", \"meta-type\": \"builtin\", \"name\": \"str\"}]";
$ cat qapi-generated/example-qmp-introspect.h
Several commits have been changing the generator, but not updating the docs to match (an obvious one is commit 9f08c8ec that made list types lazy, and thereby dropped UserDefOneList). Rework the example to show slightly more output (we don't want to show too much; that's what the testsuite is for), and regenerate the output to match recent changes, including the previous patch's reordering of parameter positions. Reported-by: Marc-André Lureau <marcandre.lureau@redhat.com> Signed-off-by: Eric Blake <eblake@redhat.com> --- v9: new patch --- docs/qapi-code-gen.txt | 103 ++++++++++++++++++++++++++++--------------------- 1 file changed, 59 insertions(+), 44 deletions(-)