Commit c818408e authored by Eric Blake's avatar Eric Blake Committed by Markus Armbruster
Browse files

qapi: Implement boxed types for commands/events 



Turn on the ability to pass command and event arguments in
a single boxed parameter, which must name a non-empty type
(although the type can be a struct with all optional members).
For structs, it makes it possible to pass a single qapi type
instead of a breakout of all struct members (useful if the
arguments are already in a struct or if the number of members
is large); for other complex types, it is now possible to use
a union or alternate as the data for a command or event.

The empty type may be technically feasible if needed down the
road, but it's easier to forbid it now and relax things to allow
it later, than it is to allow it now and have to special case
how the generated 'q_empty' type is handled (see commit 7ce106a9
for reasons why nothing is generated for the empty type).  An
alternate type is never considered empty, but now that a boxed
type can be either an object or an alternate, we have to provide
a trivial QAPISchemaAlternateType.is_empty().  The new call to
arg_type.is_empty() during QAPISchemaCommand.check() requires
that we first check the type in question; but there is no chance
of introducing a cycle since objects do not refer back to commands.

We still have a split in syntax checking between ad-hoc parsing
up front (merely validates that 'boxed' has a sane value) and
during .check() methods (if 'boxed' is set, then 'data' must name
a non-empty user-defined type).

Generated code is unchanged, as long as no client uses the
new feature.

Signed-off-by: default avatarEric Blake <eblake@redhat.com>
Message-Id: <1468468228-27827-10-git-send-email-eblake@redhat.com>
Reviewed-by: default avatarMarkus Armbruster <armbru@redhat.com>
[Test files renamed to *-boxed-*]
Signed-off-by: default avatarMarkus Armbruster <armbru@redhat.com>
parent 48825ca4

docs/qapi-code-gen.txt

+25 −2
Original line number Diff line number Diff line
@@ -410,7 +410,7 @@ following example objects: 
=== Commands ===



Usage: { 'command': STRING, '*data': COMPLEX-TYPE-NAME-OR-DICT,

         '*returns': TYPE-NAME,

         '*returns': TYPE-NAME, '*boxed': true,

         '*gen': false, '*success-response': false }



Commands are defined by using a dictionary containing several members,
@@ -461,6 +461,20 @@ which would validate this Client JSON Protocol transaction: 
 => { "execute": "my-second-command" }

 <= { "return": [ { "value": "one" }, { } ] }



The generator emits a prototype for the user's function implementing

the command.  Normally, 'data' is a dictionary for an anonymous type,

or names a struct type (possibly empty, but not a union), and its

members are passed as separate arguments to this function.  If the

command definition includes a key 'boxed' with the boolean value true,

then 'data' is instead the name of any non-empty complex type

(struct, union, or alternate), and a pointer to that QAPI type is

passed as a single argument.



The generator also emits a marshalling function that extracts

arguments for the user's function out of an input QDict, calls the

user's function, and if it succeeded, builds an output QObject from

its return value.



In rare cases, QAPI cannot express a type-safe representation of a

corresponding Client JSON Protocol command.  You then have to suppress

generation of a marshalling function by including a key 'gen' with
@@ -484,7 +498,8 @@ use of this member. 


=== Events ===



Usage: { 'event': STRING, '*data': COMPLEX-TYPE-NAME-OR-DICT }

Usage: { 'event': STRING, '*data': COMPLEX-TYPE-NAME-OR-DICT,

         '*boxed': true }



Events are defined with the keyword 'event'.  It is not allowed to

name an event 'MAX', since the generator also produces a C enumeration
@@ -505,6 +520,14 @@ Resulting in this JSON object: 
  "data": { "b": "test string" },

  "timestamp": { "seconds": 1267020223, "microseconds": 435656 } }



The generator emits a function to send the event.  Normally, 'data' is

a dictionary for an anonymous type, or names a struct type (possibly

empty, but not a union), and its members are passed as separate

arguments to this function.  If the event definition includes a key

'boxed' with the boolean value true, then 'data' is instead the name of

any non-empty complex type (struct, union, or alternate), and a

pointer to that QAPI type is passed as a single argument.





== Client JSON Protocol introspection ==

scripts/qapi-commands.py

+2 −1
Original line number Diff line number Diff line
@@ -30,7 +30,8 @@ def gen_call(name, arg_type, boxed, ret_type): 


    argstr = ''

    if boxed:

        assert False    # not implemented

        assert arg_type and not arg_type.is_empty()

        argstr = '&arg, '

    elif arg_type:

        assert not arg_type.variants

        for memb in arg_type.members:

scripts/qapi-event.py

+4 −1
Original line number Diff line number Diff line
@@ -79,7 +79,10 @@ def gen_event_send(name, arg_type, boxed): 
    QObject *obj;

    Visitor *v;

''')

        if not boxed:

            ret += gen_param_var(arg_type)

    else:

        assert not boxed



    ret += mcgen('''

scripts/qapi.py

+50 −13
Original line number Diff line number Diff line
@@ -522,10 +522,14 @@ def check_type(expr_info, source, value, allow_array=False, 


def check_command(expr, expr_info):

    name = expr['command']

    boxed = expr.get('boxed', False)



    args_meta = ['struct']

    if boxed:

        args_meta += ['union', 'alternate']

    check_type(expr_info, "'data' for command '%s'" % name,

               expr.get('data'), allow_dict=True, allow_optional=True,

               allow_metas=['struct'])

               expr.get('data'), allow_dict=not boxed, allow_optional=True,

               allow_metas=args_meta)

    returns_meta = ['union', 'struct']

    if name in returns_whitelist:

        returns_meta += ['built-in', 'alternate', 'enum']
@@ -537,11 +541,15 @@ def check_command(expr, expr_info): 
def check_event(expr, expr_info):

    global events

    name = expr['event']

    boxed = expr.get('boxed', False)



    meta = ['struct']

    if boxed:

        meta += ['union', 'alternate']

    events.append(name)

    check_type(expr_info, "'data' for event '%s'" % name,

               expr.get('data'), allow_dict=True, allow_optional=True,

               allow_metas=['struct'])

               expr.get('data'), allow_dict=not boxed, allow_optional=True,

               allow_metas=meta)





def check_union(expr, expr_info):
@@ -694,6 +702,10 @@ def check_keys(expr_elem, meta, required, optional=[]): 
            raise QAPIExprError(info,

                                "'%s' of %s '%s' should only use false value"

                                % (key, meta, name))

        if key == 'boxed' and value is not True:

            raise QAPIExprError(info,

                                "'%s' of %s '%s' should only use true value"

                                % (key, meta, name))

    for key in required:

        if key not in expr:

            raise QAPIExprError(info,
@@ -725,10 +737,10 @@ def check_exprs(exprs): 
            add_struct(expr, info)

        elif 'command' in expr:

            check_keys(expr_elem, 'command', [],

                       ['data', 'returns', 'gen', 'success-response'])

                       ['data', 'returns', 'gen', 'success-response', 'boxed'])

            add_name(expr['command'], info, 'command')

        elif 'event' in expr:

            check_keys(expr_elem, 'event', [], ['data'])

            check_keys(expr_elem, 'event', [], ['data', 'boxed'])

            add_name(expr['event'], info, 'event')

        else:

            raise QAPIExprError(expr_elem['info'],
@@ -1163,6 +1175,9 @@ class QAPISchemaAlternateType(QAPISchemaType): 
    def visit(self, visitor):

        visitor.visit_alternate_type(self.name, self.info, self.variants)



    def is_empty(self):

        return False





class QAPISchemaCommand(QAPISchemaEntity):

    def __init__(self, name, info, arg_type, ret_type, gen, success_response,
@@ -1181,9 +1196,19 @@ class QAPISchemaCommand(QAPISchemaEntity): 
    def check(self, schema):

        if self._arg_type_name:

            self.arg_type = schema.lookup_type(self._arg_type_name)

            assert isinstance(self.arg_type, QAPISchemaObjectType)

            assert not self.arg_type.variants   # not implemented

            assert not self.boxed               # not implemented

            assert (isinstance(self.arg_type, QAPISchemaObjectType) or

                    isinstance(self.arg_type, QAPISchemaAlternateType))

            self.arg_type.check(schema)

            if self.boxed:

                if self.arg_type.is_empty():

                    raise QAPIExprError(self.info,

                                        "Cannot use 'boxed' with empty type")

            else:

                assert not isinstance(self.arg_type, QAPISchemaAlternateType)

                assert not self.arg_type.variants

        elif self.boxed:

            raise QAPIExprError(self.info,

                                "Use of 'boxed' requires 'data'")

        if self._ret_type_name:

            self.ret_type = schema.lookup_type(self._ret_type_name)

            assert isinstance(self.ret_type, QAPISchemaType)
@@ -1205,9 +1230,19 @@ class QAPISchemaEvent(QAPISchemaEntity): 
    def check(self, schema):

        if self._arg_type_name:

            self.arg_type = schema.lookup_type(self._arg_type_name)

            assert isinstance(self.arg_type, QAPISchemaObjectType)

            assert not self.arg_type.variants   # not implemented

            assert not self.boxed               # not implemented

            assert (isinstance(self.arg_type, QAPISchemaObjectType) or

                    isinstance(self.arg_type, QAPISchemaAlternateType))

            self.arg_type.check(schema)

            if self.boxed:

                if self.arg_type.is_empty():

                    raise QAPIExprError(self.info,

                                        "Cannot use 'boxed' with empty type")

            else:

                assert not isinstance(self.arg_type, QAPISchemaAlternateType)

                assert not self.arg_type.variants

        elif self.boxed:

            raise QAPIExprError(self.info,

                                "Use of 'boxed' requires 'data'")



    def visit(self, visitor):

        visitor.visit_event(self.name, self.info, self.arg_type, self.boxed)
@@ -1648,11 +1683,13 @@ extern const char *const %(c_name)s_lookup[]; 


def gen_params(arg_type, boxed, extra):

    if not arg_type:

        assert not boxed

        return extra

    ret = ''

    sep = ''

    if boxed:

        assert False     # not implemented

        ret += '%s arg' % arg_type.c_param_type()

        sep = ', '

    else:

        assert not arg_type.variants

        for memb in arg_type.members:

tests/Makefile.include

+5 −0
Original line number Diff line number Diff line
@@ -284,6 +284,10 @@ qapi-schema += args-alternate.json 
qapi-schema += args-any.json

qapi-schema += args-array-empty.json

qapi-schema += args-array-unknown.json

qapi-schema += args-bad-boxed.json

qapi-schema += args-boxed-anon.json

qapi-schema += args-boxed-empty.json

qapi-schema += args-boxed-string.json

qapi-schema += args-int.json

qapi-schema += args-invalid.json

qapi-schema += args-member-array-bad.json
@@ -317,6 +321,7 @@ qapi-schema += enum-wrong-data.json 
qapi-schema += escape-outside-string.json

qapi-schema += escape-too-big.json

qapi-schema += escape-too-short.json

qapi-schema += event-boxed-empty.json

qapi-schema += event-case.json

qapi-schema += event-nest-struct.json

qapi-schema += flat-union-array-branch.json