30594fe1cd
A previous patch (commit 1e6c1616) made it possible to
directly cast from a qapi flat union type to its base type.
However, it requires the use of a C cast, which turns off
compiler type-safety checks. Fortunately, no such casts
exist, just yet.
Regardless, add inline type-safe wrappers named
qapi_FOO_base() for any union type FOO that has a base,
which can be used for a safer upcast, and enhance the
testsuite to cover the new functionality.
A future patch will extend the upcast support to structs,
where such conversions do exist already.
Note that C makes const-correct upcasts annoying because
it lacks overloads; these functions cast away const so that
they can accept user pointers whether const or not, and the
result in turn can be assigned to normal or const pointers.
Alternatively, this could have been done with macros, but
type-safe macros are hairy, and not worthwhile here.
This patch just adds upcasts. None of our code needed to
downcast from a base qapi class to a child. Also, in the
case of grandchildren (such as BlockdevOptionsQcow2), the
caller will need to call two functions to get to the inner
base (although it wouldn't be too hard to generate a
qapi_FOO_base_base() if desired). If a user changes qapi
to alter the base class hierarchy, such as going from
'A -> C' to 'A -> B -> C', it will change the type of
'qapi_C_base()', and the compiler will point out the places
that are affected by the new base.
One alternative was proposed, but was deemed too ugly to use
in practice: the generators could output redundant
information using anonymous types:
| struct Child {
| union {
| struct {
| Type1 parent_member1;
| Type2 parent_member2;
| };
| Parent base;
| };
| };
With that ugly proposal, for a given qapi type, obj->member
and obj->base.member would refer to the same storage; allowing
convenience in working with members without needing 'base.'
allowing typesafe upcast without needing a C cast by accessing
'&obj->base', and allowing downcasts from the parent back to
the child possible through container_of(obj, Child, base).
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1445898903-12082-10-git-send-email-eblake@redhat.com>
[Commit message tweaked]
Signed-off-by: Markus Armbruster <armbru@redhat.com>
364 lines
9.5 KiB
Python
364 lines
9.5 KiB
Python
#
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# QAPI types generator
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#
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# Copyright IBM, Corp. 2011
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# Copyright (c) 2013-2015 Red Hat Inc.
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#
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# Authors:
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# Anthony Liguori <aliguori@us.ibm.com>
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# Markus Armbruster <armbru@redhat.com>
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#
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# This work is licensed under the terms of the GNU GPL, version 2.
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# See the COPYING file in the top-level directory.
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from qapi import *
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def gen_fwd_object_or_array(name):
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return mcgen('''
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typedef struct %(c_name)s %(c_name)s;
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''',
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c_name=c_name(name))
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def gen_array(name, element_type):
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return mcgen('''
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struct %(c_name)s {
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union {
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%(c_type)s value;
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uint64_t padding;
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};
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%(c_name)s *next;
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};
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''',
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c_name=c_name(name), c_type=element_type.c_type())
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def gen_struct_field(name, typ, optional):
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ret = ''
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if optional:
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ret += mcgen('''
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bool has_%(c_name)s;
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''',
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c_name=c_name(name))
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ret += mcgen('''
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%(c_type)s %(c_name)s;
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''',
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c_type=typ.c_type(), c_name=c_name(name))
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return ret
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def gen_struct_fields(local_members, base=None):
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ret = ''
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if base:
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ret += mcgen('''
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/* Members inherited from %(c_name)s: */
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''',
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c_name=base.c_name())
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for memb in base.members:
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ret += gen_struct_field(memb.name, memb.type, memb.optional)
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ret += mcgen('''
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/* Own members: */
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''')
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for memb in local_members:
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ret += gen_struct_field(memb.name, memb.type, memb.optional)
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return ret
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def gen_struct(name, base, members):
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ret = mcgen('''
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struct %(c_name)s {
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''',
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c_name=c_name(name))
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if base:
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ret += gen_struct_field('base', base, False)
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ret += gen_struct_fields(members)
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# Make sure that all structs have at least one field; this avoids
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# potential issues with attempting to malloc space for zero-length
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# structs in C, and also incompatibility with C++ (where an empty
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# struct is size 1).
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if not base and not members:
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ret += mcgen('''
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char qapi_dummy_field_for_empty_struct;
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''')
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ret += mcgen('''
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};
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''')
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return ret
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def gen_upcast(name, base):
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# C makes const-correctness ugly. We have to cast away const to let
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# this function work for both const and non-const obj.
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return mcgen('''
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static inline %(base)s *qapi_%(c_name)s_base(const %(c_name)s *obj)
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{
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return (%(base)s *)obj;
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}
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''',
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c_name=c_name(name), base=base.c_name())
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def gen_alternate_qtypes_decl(name):
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return mcgen('''
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extern const int %(c_name)s_qtypes[];
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''',
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c_name=c_name(name))
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def gen_alternate_qtypes(name, variants):
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ret = mcgen('''
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const int %(c_name)s_qtypes[QTYPE_MAX] = {
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''',
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c_name=c_name(name))
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for var in variants.variants:
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qtype = var.type.alternate_qtype()
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assert qtype
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ret += mcgen('''
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[%(qtype)s] = %(enum_const)s,
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''',
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qtype=qtype,
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enum_const=c_enum_const(variants.tag_member.type.name,
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var.name))
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ret += mcgen('''
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};
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''')
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return ret
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def gen_union(name, base, variants):
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ret = mcgen('''
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struct %(c_name)s {
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''',
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c_name=c_name(name))
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if base:
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ret += gen_struct_fields([], base)
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else:
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ret += mcgen('''
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%(c_type)s kind;
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''',
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c_type=c_name(variants.tag_member.type.name))
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# FIXME: What purpose does data serve, besides preventing a union that
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# has a branch named 'data'? We use it in qapi-visit.py to decide
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# whether to bypass the switch statement if visiting the discriminator
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# failed; but since we 0-initialize structs, and cannot tell what
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# branch of the union is in use if the discriminator is invalid, there
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# should not be any data leaks even without a data pointer. Or, if
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# 'data' is merely added to guarantee we don't have an empty union,
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# shouldn't we enforce that at .json parse time?
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ret += mcgen('''
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union { /* union tag is @%(c_name)s */
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void *data;
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''',
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# TODO ugly special case for simple union
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# Use same tag name in C as on the wire to get rid of
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# it, then: c_name=c_name(variants.tag_member.name)
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c_name=c_name(variants.tag_name or 'kind'))
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for var in variants.variants:
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# Ugly special case for simple union TODO get rid of it
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typ = var.simple_union_type() or var.type
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ret += mcgen('''
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%(c_type)s %(c_name)s;
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''',
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c_type=typ.c_type(),
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c_name=c_name(var.name))
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ret += mcgen('''
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};
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};
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''')
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return ret
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def gen_type_cleanup_decl(name):
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ret = mcgen('''
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void qapi_free_%(c_name)s(%(c_name)s *obj);
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''',
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c_name=c_name(name))
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return ret
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def gen_type_cleanup(name):
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ret = mcgen('''
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void qapi_free_%(c_name)s(%(c_name)s *obj)
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{
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QapiDeallocVisitor *qdv;
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Visitor *v;
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if (!obj) {
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return;
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}
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qdv = qapi_dealloc_visitor_new();
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v = qapi_dealloc_get_visitor(qdv);
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visit_type_%(c_name)s(v, &obj, NULL, NULL);
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qapi_dealloc_visitor_cleanup(qdv);
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}
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''',
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c_name=c_name(name))
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return ret
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class QAPISchemaGenTypeVisitor(QAPISchemaVisitor):
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def __init__(self):
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self.decl = None
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self.defn = None
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self._fwdecl = None
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self._fwdefn = None
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self._btin = None
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def visit_begin(self, schema):
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self.decl = ''
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self.defn = ''
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self._fwdecl = ''
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self._fwdefn = ''
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self._btin = guardstart('QAPI_TYPES_BUILTIN')
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def visit_end(self):
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self.decl = self._fwdecl + self.decl
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self._fwdecl = None
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self.defn = self._fwdefn + self.defn
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self._fwdefn = None
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# To avoid header dependency hell, we always generate
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# declarations for built-in types in our header files and
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# simply guard them. See also do_builtins (command line
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# option -b).
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self._btin += guardend('QAPI_TYPES_BUILTIN')
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self.decl = self._btin + self.decl
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self._btin = None
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def visit_needed(self, entity):
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# Visit everything except implicit objects
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return not (entity.is_implicit() and
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isinstance(entity, QAPISchemaObjectType))
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def _gen_type_cleanup(self, name):
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self.decl += gen_type_cleanup_decl(name)
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self.defn += gen_type_cleanup(name)
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def visit_enum_type(self, name, info, values, prefix):
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self._fwdecl += gen_enum(name, values, prefix)
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self._fwdefn += gen_enum_lookup(name, values, prefix)
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def visit_array_type(self, name, info, element_type):
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if isinstance(element_type, QAPISchemaBuiltinType):
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self._btin += gen_fwd_object_or_array(name)
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self._btin += gen_array(name, element_type)
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self._btin += gen_type_cleanup_decl(name)
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if do_builtins:
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self.defn += gen_type_cleanup(name)
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else:
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self._fwdecl += gen_fwd_object_or_array(name)
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self.decl += gen_array(name, element_type)
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self._gen_type_cleanup(name)
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def visit_object_type(self, name, info, base, members, variants):
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self._fwdecl += gen_fwd_object_or_array(name)
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if variants:
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assert not members # not implemented
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self.decl += gen_union(name, base, variants)
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# TODO Use gen_upcast on structs too, once they have sane layout
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if base:
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self.decl += gen_upcast(name, base)
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else:
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self.decl += gen_struct(name, base, members)
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self._gen_type_cleanup(name)
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def visit_alternate_type(self, name, info, variants):
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self._fwdecl += gen_fwd_object_or_array(name)
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self._fwdefn += gen_alternate_qtypes(name, variants)
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self.decl += gen_union(name, None, variants)
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self.decl += gen_alternate_qtypes_decl(name)
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self._gen_type_cleanup(name)
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# If you link code generated from multiple schemata, you want only one
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# instance of the code for built-in types. Generate it only when
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# do_builtins, enabled by command line option -b. See also
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# QAPISchemaGenTypeVisitor.visit_end().
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do_builtins = False
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(input_file, output_dir, do_c, do_h, prefix, opts) = \
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parse_command_line("b", ["builtins"])
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for o, a in opts:
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if o in ("-b", "--builtins"):
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do_builtins = True
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c_comment = '''
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/*
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* deallocation functions for schema-defined QAPI types
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*
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* Copyright IBM, Corp. 2011
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*
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* Authors:
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* Anthony Liguori <aliguori@us.ibm.com>
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* Michael Roth <mdroth@linux.vnet.ibm.com>
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*
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* This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
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* See the COPYING.LIB file in the top-level directory.
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*
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*/
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'''
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h_comment = '''
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/*
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* schema-defined QAPI types
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*
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* Copyright IBM, Corp. 2011
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*
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* Authors:
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* Anthony Liguori <aliguori@us.ibm.com>
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*
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* This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
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* See the COPYING.LIB file in the top-level directory.
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*
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*/
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'''
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(fdef, fdecl) = open_output(output_dir, do_c, do_h, prefix,
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'qapi-types.c', 'qapi-types.h',
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c_comment, h_comment)
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fdef.write(mcgen('''
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#include "qapi/dealloc-visitor.h"
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#include "%(prefix)sqapi-types.h"
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#include "%(prefix)sqapi-visit.h"
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''',
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prefix=prefix))
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fdecl.write(mcgen('''
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#include <stdbool.h>
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#include <stdint.h>
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#include "qapi/qmp/qobject.h"
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'''))
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schema = QAPISchema(input_file)
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gen = QAPISchemaGenTypeVisitor()
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schema.visit(gen)
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fdef.write(gen.defn)
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fdecl.write(gen.decl)
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close_output(fdef, fdecl)
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