include/qapi/visitor-impl.h

   1 /*
   2  * Core Definitions for QAPI Visitor implementations
   3  *
   4  * Copyright (C) 2012-2016 Red Hat, Inc.
   5  *
   6  * Author: Paolo Bonizni <pbonzini@redhat.com>
   7  *
   8  * This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
   9  * See the COPYING.LIB file in the top-level directory.
  10  *
  11  */
  12 #ifndef QAPI_VISITOR_IMPL_H
  13 #define QAPI_VISITOR_IMPL_H
  14
  15 #include "qapi/visitor.h"
  16
  17 /*
  18  * This file describes the callback interface for implementing a QAPI
  19  * visitor.  For the client interface, see visitor.h.  When
  20  * implementing the callbacks, it is easiest to declare a struct with
  21  * 'Visitor visitor;' as the first member.  A callback's contract
  22  * matches the corresponding public functions' contract unless stated
  23  * otherwise.  In the comments below, some callbacks are marked "must
  24  * be set for $TYPE visits to work"; if a visitor implementation omits
  25  * that callback, it should also document that it is only useful for a
  26  * subset of QAPI.
  27  */
  28
  29 /*
  30  * There are four classes of visitors; setting the class determines
  31  * how QAPI enums are visited, as well as what additional restrictions
  32  * can be asserted.  The values are intentionally chosen so as to
  33  * permit some assertions based on whether a given bit is set (that
  34  * is, some assertions apply to input and clone visitors, some
  35  * assertions apply to output and clone visitors).
  36  */
  37 typedef enum VisitorType {
  38     VISITOR_INPUT = 1,
  39     VISITOR_OUTPUT = 2,
  40     VISITOR_CLONE = 3,
  41     VISITOR_DEALLOC = 4,
  42 } VisitorType;
  43
  44 struct Visitor
  45 {
  46     /* Must be set to visit structs */
  47     void (*start_struct)(Visitor *v, const char *name, void **obj,
  48                          size_t size, Error **errp);
  49
  50     /* Optional; intended for input visitors */
  51     void (*check_struct)(Visitor *v, Error **errp);
  52
  53     /* Must be set to visit structs */
  54     void (*end_struct)(Visitor *v, void **obj);
  55
  56     /* Must be set; implementations may require @list to be non-null,
  57      * but must document it. */
  58     void (*start_list)(Visitor *v, const char *name, GenericList **list,
  59                        size_t size, Error **errp);
  60
  61     /* Must be set */
  62     GenericList *(*next_list)(Visitor *v, GenericList *tail, size_t size);
  63
  64     /* Optional; intended for input visitors */
  65     void (*check_list)(Visitor *v, Error **errp);
  66
  67     /* Must be set */
  68     void (*end_list)(Visitor *v, void **list);
  69
  70     /* Must be set by input and dealloc visitors to visit alternates;
  71      * optional for output visitors. */
  72     void (*start_alternate)(Visitor *v, const char *name,
  73                             GenericAlternate **obj, size_t size,
  74                             Error **errp);
  75
  76     /* Optional, needed for dealloc visitor */
  77     void (*end_alternate)(Visitor *v, void **obj);
  78
  79     /* Must be set */
  80     void (*type_int64)(Visitor *v, const char *name, int64_t *obj,
  81                        Error **errp);
  82
  83     /* Must be set */
  84     void (*type_uint64)(Visitor *v, const char *name, uint64_t *obj,
  85                         Error **errp);
  86
  87     /* Optional; fallback is type_uint64() */
  88     void (*type_size)(Visitor *v, const char *name, uint64_t *obj,
  89                       Error **errp);
  90
  91     /* Must be set */
  92     void (*type_bool)(Visitor *v, const char *name, bool *obj, Error **errp);
  93
  94     /* Must be set */
  95     void (*type_str)(Visitor *v, const char *name, char **obj, Error **errp);
  96
  97     /* Must be set to visit numbers */
  98     void (*type_number)(Visitor *v, const char *name, double *obj,
  99                         Error **errp);
 100
 101     /* Must be set to visit arbitrary QTypes */
 102     void (*type_any)(Visitor *v, const char *name, QObject **obj,
 103                      Error **errp);
 104
 105     /* Must be set to visit explicit null values.  */
 106     void (*type_null)(Visitor *v, const char *name, QNull **obj,
 107                       Error **errp);
 108
 109     /* Must be set for input visitors to visit structs, optional otherwise.
 110        The core takes care of the return type in the public interface. */
 111     void (*optional)(Visitor *v, const char *name, bool *present);
 112
 113     /* Must be set */
 114     VisitorType type;
 115
 116     /* Must be set for output visitors, optional otherwise. */
 117     void (*complete)(Visitor *v, void *opaque);
 118
 119     /* Must be set */
 120     void (*free)(Visitor *v);
 121 };
 122
 123 #endif