1158bb2a05
Rather than making the dealloc visitor track of stack of pointers remembered during visit_start_* in order to free them during visit_end_*, it's a lot easier to just make all callers pass the same pointer to visit_end_*. The generated code has access to the same pointer, while all other users are doing virtual walks and can pass NULL. The dealloc visitor is then greatly simplified. All three visit_end_*() functions intentionally take a void**, even though the visit_start_*() functions differ between void**, GenericList**, and GenericAlternate**. This is done for several reasons: when doing a virtual walk, passing NULL doesn't care what the type is, but when doing a generated walk, we already have to cast the caller's specific FOO* to call visit_start, while using void** lets us use visit_end without a cast. Also, an upcoming patch will add a clone visitor that wants to use the same implementation for all three visit_end callbacks, which is made easier if all three share the same signature. For visitors with already track per-object state (the QMP visitors via a stack, and the string visitors which do not allow nesting), add an assertion that the caller is indeed passing the same pointer to paired calls. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1465490926-28625-4-git-send-email-eblake@redhat.com> Reviewed-by: Markus Armbruster <armbru@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com>
110 lines
3.6 KiB
C
110 lines
3.6 KiB
C
/*
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* Core Definitions for QAPI Visitor implementations
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*
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* Copyright (C) 2012-2016 Red Hat, Inc.
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*
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* Author: Paolo Bonizni <pbonzini@redhat.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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#ifndef QAPI_VISITOR_IMPL_H
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#define QAPI_VISITOR_IMPL_H
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#include "qapi/visitor.h"
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/*
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* This file describes the callback interface for implementing a QAPI
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* visitor. For the client interface, see visitor.h. When
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* implementing the callbacks, it is easiest to declare a struct with
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* 'Visitor visitor;' as the first member. A callback's contract
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* matches the corresponding public functions' contract unless stated
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* otherwise. In the comments below, some callbacks are marked "must
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* be set for $TYPE visits to work"; if a visitor implementation omits
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* that callback, it should also document that it is only useful for a
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* subset of QAPI.
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*/
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/*
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* There are three classes of visitors; setting the class determines
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* how QAPI enums are visited, as well as what additional restrictions
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* can be asserted.
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*/
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typedef enum VisitorType {
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VISITOR_INPUT,
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VISITOR_OUTPUT,
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VISITOR_DEALLOC,
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} VisitorType;
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struct Visitor
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{
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/* Must be set to visit structs */
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void (*start_struct)(Visitor *v, const char *name, void **obj,
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size_t size, Error **errp);
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/* Optional; intended for input visitors */
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void (*check_struct)(Visitor *v, Error **errp);
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/* Must be set to visit structs */
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void (*end_struct)(Visitor *v, void **obj);
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/* Must be set; implementations may require @list to be non-null,
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* but must document it. */
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void (*start_list)(Visitor *v, const char *name, GenericList **list,
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size_t size, Error **errp);
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/* Must be set */
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GenericList *(*next_list)(Visitor *v, GenericList *tail, size_t size);
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/* Must be set */
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void (*end_list)(Visitor *v, void **list);
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/* Must be set by input and dealloc visitors to visit alternates;
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* optional for output visitors. */
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void (*start_alternate)(Visitor *v, const char *name,
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GenericAlternate **obj, size_t size,
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bool promote_int, Error **errp);
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/* Optional, needed for dealloc visitor */
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void (*end_alternate)(Visitor *v, void **obj);
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/* Must be set */
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void (*type_int64)(Visitor *v, const char *name, int64_t *obj,
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Error **errp);
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/* Must be set */
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void (*type_uint64)(Visitor *v, const char *name, uint64_t *obj,
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Error **errp);
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/* Optional; fallback is type_uint64() */
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void (*type_size)(Visitor *v, const char *name, uint64_t *obj,
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Error **errp);
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/* Must be set */
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void (*type_bool)(Visitor *v, const char *name, bool *obj, Error **errp);
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/* Must be set */
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void (*type_str)(Visitor *v, const char *name, char **obj, Error **errp);
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/* Must be set to visit numbers */
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void (*type_number)(Visitor *v, const char *name, double *obj,
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Error **errp);
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/* Must be set to visit arbitrary QTypes */
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void (*type_any)(Visitor *v, const char *name, QObject **obj,
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Error **errp);
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/* Must be set to visit explicit null values. */
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void (*type_null)(Visitor *v, const char *name, Error **errp);
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/* Must be set for input visitors, optional otherwise. The core
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* takes care of the return type in the public interface. */
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void (*optional)(Visitor *v, const char *name, bool *present);
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/* Must be set */
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VisitorType type;
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};
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#endif
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