The semantics of the list visit are somewhat baroque, with the following pseudocode when FooList is used: start() for (prev = head; cur = next(prev); prev = &cur) { visit(&cur->value) } Note that these semantics (advance before visit) requires that the first call to next() return the list head, while all other calls return the next element of the list; that is, every visitor implementation is required to track extra state to decide whether to return the input as-is, or to advance. It also requires an argument of 'GenericList **' to next(), solely because the first iteration might need to modify the caller's GenericList head, so that all other calls have to do a layer of dereferencing. Thankfully, we only have two uses of list visits in the entire code base: one in spapr_drc (which completely avoids visit_next_list(), feeding in integers from a different source than uint8List), and one in qapi-visit.py. That is, all other list visitors are generated in qapi-visit.c, and share the same paradigm based on a qapi FooList type, so we can refactor how lists are laid out with minimal churn among clients. We can greatly simplify things by hoisting the special case into the start() routine, and flipping the order in the loop to visit before advance: start(head) for (tail = *head; tail; tail = next(tail)) { visit(&tail->value) } With the simpler semantics, visitors have less state to track, the argument to next() is reduced to 'GenericList *', and it also becomes obvious whether an input visitor is allocating a FooList during visit_start_list() (rather than the old way of not knowing if an allocation happened until the first visit_next_list()). As a minor drawback, we now allocate in two functions instead of one, and have to pass the size to both functions (unless we were to tweak the input visitors to cache the size to start_list for reuse during next_list, but that defeats the goal of less visitor state). The signature of visit_start_list() is chosen to match visit_start_struct(), with the new parameters after 'name'. The spapr_drc case is a virtual visit, done by passing NULL for list, similarly to how NULL is passed to visit_start_struct() when a qapi type is not used in those visits. It was easy to provide these semantics for qmp-output and dealloc visitors, and a bit harder for qmp-input (several prerequisite patches refactored things to make this patch straightforward). But it turned out that the string and opts visitors munge enough other state during visit_next_list() to make it easier to just document and require a GenericList visit for now; an assertion will remind us to adjust things if we need the semantics in the future. Several pre-requisite cleanup patches made the reshuffling of the various visitors easier; particularly the qmp input visitor. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1461879932-9020-24-git-send-email-eblake@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com>
383 lines
10 KiB
Python
383 lines
10 KiB
Python
#
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# QAPI visitor generator
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#
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# Copyright IBM, Corp. 2011
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# Copyright (C) 2014-2016 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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# Michael Roth <mdroth@linux.vnet.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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import re
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def gen_visit_decl(name, scalar=False):
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c_type = c_name(name) + ' *'
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if not scalar:
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c_type += '*'
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return mcgen('''
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void visit_type_%(c_name)s(Visitor *v, const char *name, %(c_type)sobj, Error **errp);
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''',
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c_name=c_name(name), c_type=c_type)
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def gen_visit_members_decl(name):
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return mcgen('''
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void visit_type_%(c_name)s_members(Visitor *v, %(c_name)s *obj, Error **errp);
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''',
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c_name=c_name(name))
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def gen_visit_object_members(name, base, members, variants):
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ret = mcgen('''
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void visit_type_%(c_name)s_members(Visitor *v, %(c_name)s *obj, Error **errp)
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{
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Error *err = NULL;
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''',
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c_name=c_name(name))
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if base:
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ret += mcgen('''
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visit_type_%(c_type)s_members(v, (%(c_type)s *)obj, &err);
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''',
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c_type=base.c_name())
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ret += gen_err_check()
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for memb in members:
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if memb.optional:
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ret += mcgen('''
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if (visit_optional(v, "%(name)s", &obj->has_%(c_name)s)) {
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''',
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name=memb.name, c_name=c_name(memb.name))
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push_indent()
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ret += mcgen('''
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visit_type_%(c_type)s(v, "%(name)s", &obj->%(c_name)s, &err);
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''',
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c_type=memb.type.c_name(), name=memb.name,
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c_name=c_name(memb.name))
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ret += gen_err_check()
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if memb.optional:
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pop_indent()
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ret += mcgen('''
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}
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''')
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if variants:
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ret += mcgen('''
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switch (obj->%(c_name)s) {
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''',
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c_name=c_name(variants.tag_member.name))
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for var in variants.variants:
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ret += mcgen('''
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case %(case)s:
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visit_type_%(c_type)s_members(v, &obj->u.%(c_name)s, &err);
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break;
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''',
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case=c_enum_const(variants.tag_member.type.name,
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var.name,
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variants.tag_member.type.prefix),
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c_type=var.type.c_name(), c_name=c_name(var.name))
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ret += mcgen('''
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default:
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abort();
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}
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''')
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# 'goto out' produced for base, for each member, and if variants were
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# present
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if base or members or variants:
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ret += mcgen('''
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out:
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''')
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ret += mcgen('''
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error_propagate(errp, err);
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}
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''')
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return ret
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def gen_visit_list(name, element_type):
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# FIXME: if *obj is NULL on entry, and the first visit_next_list()
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# assigns to *obj, while a later one fails, we should clean up *obj
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# rather than leaving it non-NULL. As currently written, the caller must
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# call qapi_free_FOOList() to avoid a memory leak of the partial FOOList.
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return mcgen('''
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void visit_type_%(c_name)s(Visitor *v, const char *name, %(c_name)s **obj, Error **errp)
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{
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Error *err = NULL;
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%(c_name)s *tail;
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size_t size = sizeof(**obj);
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visit_start_list(v, name, (GenericList **)obj, size, &err);
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if (err) {
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goto out;
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}
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for (tail = *obj; tail;
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tail = (%(c_name)s *)visit_next_list(v, (GenericList *)tail, size)) {
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visit_type_%(c_elt_type)s(v, NULL, &tail->value, &err);
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if (err) {
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break;
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}
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}
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visit_end_list(v);
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out:
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error_propagate(errp, err);
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}
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''',
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c_name=c_name(name), c_elt_type=element_type.c_name())
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def gen_visit_enum(name):
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return mcgen('''
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void visit_type_%(c_name)s(Visitor *v, const char *name, %(c_name)s *obj, Error **errp)
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{
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int value = *obj;
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visit_type_enum(v, name, &value, %(c_name)s_lookup, errp);
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*obj = value;
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}
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''',
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c_name=c_name(name))
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def gen_visit_alternate(name, variants):
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promote_int = 'true'
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ret = ''
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for var in variants.variants:
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if var.type.alternate_qtype() == 'QTYPE_QINT':
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promote_int = 'false'
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ret += mcgen('''
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void visit_type_%(c_name)s(Visitor *v, const char *name, %(c_name)s **obj, Error **errp)
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{
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Error *err = NULL;
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visit_start_alternate(v, name, (GenericAlternate **)obj, sizeof(**obj),
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%(promote_int)s, &err);
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if (err) {
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goto out;
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}
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switch ((*obj)->type) {
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''',
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c_name=c_name(name), promote_int=promote_int)
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for var in variants.variants:
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ret += mcgen('''
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case %(case)s:
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''',
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case=var.type.alternate_qtype())
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if isinstance(var.type, QAPISchemaObjectType):
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ret += mcgen('''
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visit_start_struct(v, name, NULL, 0, &err);
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if (err) {
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break;
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}
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visit_type_%(c_type)s_members(v, &(*obj)->u.%(c_name)s, &err);
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if (!err) {
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visit_check_struct(v, &err);
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}
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visit_end_struct(v);
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''',
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c_type=var.type.c_name(),
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c_name=c_name(var.name))
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else:
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ret += mcgen('''
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visit_type_%(c_type)s(v, name, &(*obj)->u.%(c_name)s, &err);
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''',
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c_type=var.type.c_name(),
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c_name=c_name(var.name))
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ret += mcgen('''
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break;
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''')
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ret += mcgen('''
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default:
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error_setg(&err, QERR_INVALID_PARAMETER_TYPE, name ? name : "null",
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"%(name)s");
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}
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visit_end_alternate(v);
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out:
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error_propagate(errp, err);
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}
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''',
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name=name)
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return ret
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def gen_visit_object(name, base, members, variants):
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# FIXME: if *obj is NULL on entry, and visit_start_struct() assigns to
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# *obj, but then visit_type_FOO_members() fails, we should clean up *obj
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# rather than leaving it non-NULL. As currently written, the caller must
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# call qapi_free_FOO() to avoid a memory leak of the partial FOO.
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return mcgen('''
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void visit_type_%(c_name)s(Visitor *v, const char *name, %(c_name)s **obj, Error **errp)
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{
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Error *err = NULL;
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visit_start_struct(v, name, (void **)obj, sizeof(%(c_name)s), &err);
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if (err) {
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goto out;
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}
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if (!*obj) {
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goto out_obj;
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}
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visit_type_%(c_name)s_members(v, *obj, &err);
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if (err) {
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goto out_obj;
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}
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visit_check_struct(v, &err);
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out_obj:
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visit_end_struct(v);
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out:
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error_propagate(errp, err);
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}
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''',
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c_name=c_name(name))
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class QAPISchemaGenVisitVisitor(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._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._btin = guardstart('QAPI_VISIT_BUILTIN')
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def visit_end(self):
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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_VISIT_BUILTIN')
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self.decl = self._btin + self.decl
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self._btin = None
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def visit_enum_type(self, name, info, values, prefix):
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# Special case for our lone builtin enum type
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# TODO use something cleaner than existence of info
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if not info:
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self._btin += gen_visit_decl(name, scalar=True)
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if do_builtins:
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self.defn += gen_visit_enum(name)
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else:
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self.decl += gen_visit_decl(name, scalar=True)
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self.defn += gen_visit_enum(name)
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def visit_array_type(self, name, info, element_type):
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decl = gen_visit_decl(name)
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defn = gen_visit_list(name, element_type)
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if isinstance(element_type, QAPISchemaBuiltinType):
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self._btin += decl
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if do_builtins:
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self.defn += defn
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else:
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self.decl += decl
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self.defn += defn
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def visit_object_type(self, name, info, base, members, variants):
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# Nothing to do for the special empty builtin
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if name == 'q_empty':
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return
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self.decl += gen_visit_members_decl(name)
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self.defn += gen_visit_object_members(name, base, members, variants)
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# TODO Worth changing the visitor signature, so we could
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# directly use rather than repeat type.is_implicit()?
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if not name.startswith('q_'):
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# only explicit types need an allocating visit
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self.decl += gen_visit_decl(name)
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self.defn += gen_visit_object(name, base, members, variants)
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def visit_alternate_type(self, name, info, variants):
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self.decl += gen_visit_decl(name)
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self.defn += gen_visit_alternate(name, variants)
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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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# QAPISchemaGenVisitVisitor.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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* schema-defined QAPI visitor functions
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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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h_comment = '''
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/*
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* schema-defined QAPI visitor functions
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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-visit.c', 'qapi-visit.h',
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c_comment, h_comment)
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fdef.write(mcgen('''
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#include "qemu/osdep.h"
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#include "qemu-common.h"
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#include "qapi/error.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 "qapi/visitor.h"
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#include "qapi/qmp/qerror.h"
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#include "%(prefix)sqapi-types.h"
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''',
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prefix=prefix))
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schema = QAPISchema(input_file)
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gen = QAPISchemaGenVisitVisitor()
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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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