1 /* 2 * QEMU Object Model. 3 * 4 * Based on ideas by Avi Kivity <avi@redhat.com> 5 * 6 * Copyright (C) 2009 Red Hat Inc. 7 * 8 * Authors: 9 * Luiz Capitulino <lcapitulino@redhat.com> 10 * 11 * This work is licensed under the terms of the GNU LGPL, version 2.1 or later. 12 * See the COPYING.LIB file in the top-level directory. 13 * 14 * QObject Reference Counts Terminology 15 * ------------------------------------ 16 * 17 * - Returning references: A function that returns an object may 18 * return it as either a weak or a strong reference. If the reference 19 * is strong, you are responsible for calling QDECREF() on the reference 20 * when you are done. 21 * 22 * If the reference is weak, the owner of the reference may free it at 23 * any time in the future. Before storing the reference anywhere, you 24 * should call QINCREF() to make the reference strong. 25 * 26 * - Transferring ownership: when you transfer ownership of a reference 27 * by calling a function, you are no longer responsible for calling 28 * QDECREF() when the reference is no longer needed. In other words, 29 * when the function returns you must behave as if the reference to the 30 * passed object was weak. 31 */ 32 #ifndef QOBJECT_H 33 #define QOBJECT_H 34 35 #include <stddef.h> 36 #include <assert.h> 37 38 typedef enum { 39 QTYPE_NONE, 40 QTYPE_QINT, 41 QTYPE_QSTRING, 42 QTYPE_QDICT, 43 QTYPE_QLIST, 44 QTYPE_QFLOAT, 45 QTYPE_QBOOL, 46 QTYPE_QERROR, 47 } qtype_code; 48 49 struct QObject; 50 51 typedef struct QType { 52 qtype_code code; 53 void (*destroy)(struct QObject *); 54 } QType; 55 56 typedef struct QObject { 57 const QType *type; 58 size_t refcnt; 59 } QObject; 60 61 /* Objects definitions must include this */ 62 #define QObject_HEAD \ 63 QObject base 64 65 /* Get the 'base' part of an object */ 66 #define QOBJECT(obj) (&(obj)->base) 67 68 /* High-level interface for qobject_incref() */ 69 #define QINCREF(obj) \ 70 qobject_incref(QOBJECT(obj)) 71 72 /* High-level interface for qobject_decref() */ 73 #define QDECREF(obj) \ 74 qobject_decref(obj ? QOBJECT(obj) : NULL) 75 76 /* Initialize an object to default values */ 77 #define QOBJECT_INIT(obj, qtype_type) \ 78 obj->base.refcnt = 1; \ 79 obj->base.type = qtype_type 80 81 /** 82 * qobject_incref(): Increment QObject's reference count 83 */ 84 static inline void qobject_incref(QObject *obj) 85 { 86 if (obj) 87 obj->refcnt++; 88 } 89 90 /** 91 * qobject_decref(): Decrement QObject's reference count, deallocate 92 * when it reaches zero 93 */ 94 static inline void qobject_decref(QObject *obj) 95 { 96 if (obj && --obj->refcnt == 0) { 97 assert(obj->type != NULL); 98 assert(obj->type->destroy != NULL); 99 obj->type->destroy(obj); 100 } 101 } 102 103 /** 104 * qobject_type(): Return the QObject's type 105 */ 106 static inline qtype_code qobject_type(const QObject *obj) 107 { 108 assert(obj->type != NULL); 109 return obj->type->code; 110 } 111 112 #endif /* QOBJECT_H */ 113