object.h

/*
 * QEMU Object Model
 *
 *
 *  Anthony Liguori   <aliguori@us.ibm.com>
 *
 * This work is licensed under the terms of the GNU GPL, version 2 or later.
 * See the COPYING file in the top-level directory.
 *
 */

#ifndef OBJECT_H
#define OBJECT_H

#include <stdbool.h>
#include "glib.h"
#include "error.h"

struct TypeImpl;
typedef struct TypeImpl *Type;

typedef struct ObjectClass ObjectClass;
typedef struct Object Object;

typedef struct TypeInfo TypeInfo;

typedef struct InterfaceClass InterfaceClass;
typedef struct InterfaceInfo InterfaceInfo;

#define TYPE_OBJECT "object"

/**
 * SECTION:object.h
 * @title:Base Object Type System
 * @short_description: interfaces for creating new types and objects
 *
 * The QEMU Object Model provides a framework for registering user creatable
 * types and instantiating objects from those types.  QOM provides the following
 * features:
 *
 *  - System for dynamically registering types
 *  - Support for single-inheritance of types
 *  - Multiple inheritance of stateless interfaces
 *
 * <example>
 *   <title>Creating a minimal type</title>
 *   <programlisting>
 * #include "qdev.h"
 *
 * #define TYPE_MY_DEVICE "my-device"
 *
 * // No new virtual functions: we can reuse the typedef for the
 * // superclass.
 * typedef DeviceClass MyDeviceClass;
 * typedef struct MyDevice
 * {
 *     DeviceState parent;
 *
 *     int reg0, reg1, reg2;
 * } MyDevice;
 *
 * static const TypeInfo my_device_info = {
 *     .name = TYPE_MY_DEVICE,
 *     .parent = TYPE_DEVICE,
 *     .instance_size = sizeof(MyDevice),
 * };
 *
 * static void my_device_register_types(void)
 * {
 *     type_register_static(&my_device_info);
 * }
 *
 * type_init(my_device_register_types)
 *   </programlisting>
 * </example>
 *
 * In the above example, we create a simple type that is described by #TypeInfo.
 * #TypeInfo describes information about the type including what it inherits
 * from, the instance and class size, and constructor/destructor hooks.
 *
 * Alternatively several static types could be registered using helper macro
 * DEFINE_TYPES()
 *
 * <example>
 *   <programlisting>
 * static const TypeInfo device_types_info[] = {
 *     {
 *         .name = TYPE_MY_DEVICE_A,
 *         .parent = TYPE_DEVICE,
 *         .instance_size = sizeof(MyDeviceA),
 *     },
 *     {
 *         .name = TYPE_MY_DEVICE_B,
 *         .parent = TYPE_DEVICE,
 *         .instance_size = sizeof(MyDeviceB),
 *     },
 * };
 *
 * DEFINE_TYPES(device_types_info)
 *   </programlisting>
 * </example>
 *
 * Every type has an #ObjectClass associated with it.  #ObjectClass derivatives
 * are instantiated dynamically but there is only ever one instance for any
 * given type.  The #ObjectClass typically holds a table of function pointers
 * for the virtual methods implemented by this type.
 *
 * Using object_new(), a new #Object derivative will be instantiated.  You can
 * cast an #Object to a subclass (or base-class) type using
 * object_dynamic_cast().  You typically want to define macro wrappers around
 * OBJECT_CHECK() and OBJECT_CLASS_CHECK() to make it easier to convert to a
 * specific type:
 *
 * <example>
 *   <title>Typecasting macros</title>
 *   <programlisting>
 *    #define MY_DEVICE_GET_CLASS(obj) \
 *       OBJECT_GET_CLASS(MyDeviceClass, obj, TYPE_MY_DEVICE)
 *    #define MY_DEVICE_CLASS(klass) \
 *       OBJECT_CLASS_CHECK(MyDeviceClass, klass, TYPE_MY_DEVICE)
 *    #define MY_DEVICE(obj) \
 *       OBJECT_CHECK(MyDevice, obj, TYPE_MY_DEVICE)
 *   </programlisting>
 * </example>
 *
 * # Class Initialization #
 *
 * Before an object is initialized, the class for the object must be
 * initialized.  There is only one class object for all instance objects
 * that is created lazily.
 *
 * Classes are initialized by first initializing any parent classes (if
 * necessary).  After the parent class object has initialized, it will be
 * copied into the current class object and any additional storage in the
 * class object is zero filled.
 *
 * The effect of this is that classes automatically inherit any virtual
 * function pointers that the parent class has already initialized.  All
 * other fields will be zero filled.
 *
 * Once all of the parent classes have been initialized, #TypeInfo::class_init
 * is called to let the class being instantiated provide default initialize for
 * its virtual functions.  Here is how the above example might be modified
 * to introduce an overridden virtual function:
 *
 * <example>
 *   <title>Overriding a virtual function</title>
 *   <programlisting>
 * #include "qdev.h"
 *
 * void my_device_class_init(ObjectClass *klass, void *class_data)
 * {
 *     DeviceClass *dc = DEVICE_CLASS(klass);
 *     dc->reset = my_device_reset;
 * }
 *
 * static const TypeInfo my_device_info = {
 *     .name = TYPE_MY_DEVICE,
 *     .parent = TYPE_DEVICE,
 *     .instance_size = sizeof(MyDevice),
 *     .class_init = my_device_class_init,
 * };
 *   </programlisting>
 * </example>
 *
 * Introducing new virtual methods requires a class to define its own
 * struct and to add a .class_size member to the #TypeInfo.  Each method
 * will also have a wrapper function to call it easily:
 *
 * <example>
 *   <title>Defining an abstract class</title>
 *   <programlisting>
 * #include "qdev.h"
 *
 * typedef struct MyDeviceClass
 * {
 *     DeviceClass parent;
 *
 *     void (*frobnicate) (MyDevice *obj);
 * } MyDeviceClass;
 *
 * static const TypeInfo my_device_info = {
 *     .name = TYPE_MY_DEVICE,
 *     .parent = TYPE_DEVICE,
 *     .instance_size = sizeof(MyDevice),
 *     .abstract = true, // or set a default in my_device_class_init
 *     .class_size = sizeof(MyDeviceClass),
 * };
 *
 * void my_device_frobnicate(MyDevice *obj)
 * {
 *     MyDeviceClass *klass = MY_DEVICE_GET_CLASS(obj);
 *
 *     klass->frobnicate(obj);
 * }
 *   </programlisting>
 * </example>
 *
 * # Interfaces #
 *
 * Interfaces allow a limited form of multiple inheritance.  Instances are
 * similar to normal types except for the fact that are only defined by
 * their classes and never carry any state.  You can dynamically cast an object
 * to one of its #Interface types and vice versa.
 *
 * # Methods #
 *
 * A <emphasis>method</emphasis> is a function within the namespace scope of
 * a class. It usually operates on the object instance by passing it as a
 * strongly-typed first argument.
 * If it does not operate on an object instance, it is dubbed
 * <emphasis>class method</emphasis>.
 *
 * Methods cannot be overloaded. That is, the #ObjectClass and method name
 * uniquely identity the function to be called; the signature does not vary
 * except for trailing varargs.
 *
 * Methods are always <emphasis>virtual</emphasis>. Overriding a method in
 * #TypeInfo.class_init of a subclass leads to any user of the class obtained
 * via OBJECT_GET_CLASS() accessing the overridden function.
 * The original function is not automatically invoked. It is the responsibility
 * of the overriding class to determine whether and when to invoke the method
 * being overridden.
 *
 * To invoke the method being overridden, the preferred solution is to store
 * the original value in the overriding class before overriding the method.
 * This corresponds to |[ {super,base}.method(...) ]| in Java and C#
 * respectively; this frees the overriding class from hardcoding its parent
 * class, which someone might choose to change at some point.
 *
 * <example>
 *   <title>Overriding a virtual method</title>
 *   <programlisting>
 * typedef struct MyState MyState;
 *
 * typedef void (*MyDoSomething)(MyState *obj);
 *
 * typedef struct MyClass {
 *     ObjectClass parent_class;
 *
 *     MyDoSomething do_something;
 * } MyClass;
 *
 * static void my_do_something(MyState *obj)
 * {
 *     // do something
 * }
 *
 * static void my_class_init(ObjectClass *oc, void *data)
 * {
 *     MyClass *mc = MY_CLASS(oc);
 *
 *     mc->do_something = my_do_something;
 * }
 *
 * static const TypeInfo my_type_info = {
 *     .name = TYPE_MY,
 *     .parent = TYPE_OBJECT,
 *     .instance_size = sizeof(MyState),
 *     .class_size = sizeof(MyClass),
 *     .class_init = my_class_init,
 * };
 *
 * typedef struct DerivedClass {
 *     MyClass parent_class;
 *
 *     MyDoSomething parent_do_something;
 * } DerivedClass;
 *
 * static void derived_do_something(MyState *obj)
 * {
 *     DerivedClass *dc = DERIVED_GET_CLASS(obj);
 *
 *     // do something here
 *     dc->parent_do_something(obj);
 *     // do something else here
 * }
 *
 * static void derived_class_init(ObjectClass *oc, void *data)
 * {
 *     MyClass *mc = MY_CLASS(oc);
 *     DerivedClass *dc = DERIVED_CLASS(oc);
 *
 *     dc->parent_do_something = mc->do_something;
 *     mc->do_something = derived_do_something;
 * }
 *
 * static const TypeInfo derived_type_info = {
 *     .name = TYPE_DERIVED,
 *     .parent = TYPE_MY,
 *     .class_size = sizeof(DerivedClass),
 *     .class_init = derived_class_init,
 * };
 *   </programlisting>
 * </example>
 *
 * Alternatively, object_class_by_name() can be used to obtain the class and
 * its non-overridden methods for a specific type. This would correspond to
 * |[ MyClass::method(...) ]| in C++.
 *
 * The first example of such a QOM method was #CPUClass.reset,
 * another example is #DeviceClass.realize.
 */

/**
 * ObjectUnparent:
 * @obj: the object that is being removed from the composition tree
 *
 * Called when an object is being removed from the QOM composition tree.
 * The function should remove any backlinks from children objects to @obj.
 */
typedef void (ObjectUnparent)(Object *obj);

/**
 * ObjectFree:
 * @obj: the object being freed
 *
 * Called when an object's last reference is removed.
 */
typedef void (ObjectFree)(void *obj);

#define OBJECT_CLASS_CAST_CACHE 4

/**
 * ObjectClass:
 *
 * The base for all classes.  The only thing that #ObjectClass contains is an
 * integer type handle.
 */
struct ObjectClass
{
    /*< private >*/
    Type type;
    GSList *interfaces;

    const char *object_cast_cache[OBJECT_CLASS_CAST_CACHE];
    const char *class_cast_cache[OBJECT_CLASS_CAST_CACHE];

    ObjectUnparent *unparent;

    GHashTable *properties;
};

/**
 * Object:
 *
 * The base for all objects.  The first member of this object is a pointer to
 * a #ObjectClass.  Since C guarantees that the first member of a structure
 * always begins at byte 0 of that structure, as long as any sub-object places
 * its parent as the first member, we can cast directly to a #Object.
 *
 * As a result, #Object contains a reference to the objects type as its
 * first member.  This allows identification of the real type of the object at
 * run time.
 */
struct Object
{
    /*< private >*/
    ObjectClass *class;
    ObjectFree *free;
    GHashTable *properties;
    guint32 ref;
    Object *parent;
};

/**
 * TypeInfo:
 * @name: The name of the type.
 * @parent: The name of the parent type.
 * @instance_size: The size of the object (derivative of #Object).  If
 *   @instance_size is 0, then the size of the object will be the size of the
 *   parent object.
 * @instance_init: This function is called to initialize an object.  The parent
 *   class will have already been initialized so the type is only responsible
 *   for initializing its own members.
 * @instance_finalize: This function is called during object destruction.  This
 *   is called before the parent @instance_finalize function has been called.
 *   An object should only free the members that are unique to its type in this
 *   function.
 * @abstract: If this field is true, then the class is considered abstract and
 *   cannot be directly instantiated.
 * @class_size: The size of the class object (derivative of #ObjectClass)
 *   for this object.  If @class_size is 0, then the size of the class will be
 *   assumed to be the size of the parent class.  This allows a type to avoid
 *   implementing an explicit class type if they are not adding additional
 *   virtual functions.
 * @class_init: This function is called after all parent class initialization
 *   has occurred to allow a class to set its default virtual method pointers.
 *   This is also the function to use to override virtual methods from a parent
 *   class.
 * @class_base_init: This function is called for all base classes after all
 *   parent class initialization has occurred, but before the class itself
 *   is initialized.  This is the function to use to undo the effects of
 *   memcpy from the parent class to the descendants.
 * @class_finalize: This function is called during class destruction and is
 *   meant to release and dynamic parameters allocated by @class_init.
 * @class_data: Data to pass to the @class_init, @class_base_init and
 *   @class_finalize functions.  This can be useful when building dynamic
 *   classes.
 * @type_init_phase: If this filed is set to OBJECT_NEW_PHASE, then type will only
 *   be initialized during the first object of this type is creating.The other
 *   choice is TYPE_REGISTER_PHASE, that means type initialization will happen during
 *   type registration.
 * @interfaces: The list of interfaces associated with this type.  This
 *   should point to a static array that's terminated with a zero filled
 *   element.
 */

typedef enum TypeInitPhase
{
    OBJECT_NEW_PHASE = 0,
    TYPE_REGISTER_PHASE = 1
} TypeInitPhase;

struct TypeInfo
{
    const char *name;
    const char *parent;

    size_t instance_size;
    void (*instance_init)(Object *obj);
    void (*instance_finalize)(Object *obj);

    bool abstract;
    size_t class_size;

    void (*class_init)(ObjectClass *klass, void *data);
    void (*class_base_init)(ObjectClass *klass, void *data);
    void (*class_finalize)(ObjectClass *klass, void *data);
    void *class_data;

    TypeInitPhase type_init_phase; 

    InterfaceInfo *interfaces;
};

/**
 * OBJECT:
 * @obj: A derivative of #Object
 *
 * Converts an object to a #Object.  Since all objects are #Objects,
 * this function will always succeed.
 */
#define OBJECT(obj) \
    ((Object *)(obj))

/**
 * OBJECT_CLASS:
 * @class: A derivative of #ObjectClass.
 *
 * Converts a class to an #ObjectClass.  Since all objects are #Objects,
 * this function will always succeed.
 */
#define OBJECT_CLASS(class) \
    ((ObjectClass *)(class))

/**
 * GET_CLASS: 
 * @class_type: The class type want to get.
 * @name: class name.
 * 
 * This function will terminated if typname is NULL, or type has not registered
 * yet. If class member is null, it typically means type inititialization happens
 * in object new phase and no object of this type has created before.
 * created
 */
#define GET_CLASS(name) \
     (get_class_by_name((name), __FILE__, __LINE__, __func__))


/**
 * OBJECT_CHECK:
 * @type: The C type to use for the return value.
 * @obj: A derivative of @type to cast.
 * @name: The QOM typename of @type
 *
 * A type safe version of @object_dynamic_cast_assert.  Typically each class
 * will define a macro based on this type to perform type safe dynamic_casts to
 * this object type.
 *
 * If an invalid object is passed to this function, a run time assert will be
 * generated.
 */
#define OBJECT_CHECK(type, obj, name) \
    ((type *)object_dynamic_cast_assert(OBJECT(obj), (name), \
                                        __FILE__, __LINE__, __func__))

/**
 * OBJECT_CLASS_CHECK:
 * @class_type: The C type to use for the return value.
 * @class: A derivative class of @class_type to cast.
 * @name: the QOM typename of @class_type.
 *
 * A type safe version of @object_class_dynamic_cast_assert.  This macro is
 * typically wrapped by each type to perform type safe casts of a class to a
 * specific class type.
 */
#define OBJECT_CLASS_CHECK(class_type, class, name) \
    ((class_type *)object_class_dynamic_cast_assert(OBJECT_CLASS(class), (name), \
                                               __FILE__, __LINE__, __func__))

/**
 * OBJECT_GET_CLASS:
 * @class: The C type to use for the return value.
 * @obj: The object to obtain the class for.
 * @name: The QOM typename of @obj.
 *
 * This function will return a specific class for a given object.  Its generally
 * used by each type to provide a type safe macro to get a specific class type
 * from an object.
 */
#define OBJECT_GET_CLASS(class, obj, name) \
    OBJECT_CLASS_CHECK(class, object_get_class(OBJECT(obj)), name)

/**
 * InterfaceInfo:
 * @type: The name of the interface.
 *
 * The information associated with an interface.
 */
struct InterfaceInfo {
    const char *type;
};

/**
 * InterfaceClass:
 * @parent_class: the base class
 *
 * The class for all interfaces.  Subclasses of this class should only add
 * virtual methods.
 */
struct InterfaceClass
{
    ObjectClass parent_class;
    /*< private >*/
    ObjectClass *concrete_class;
    Type interface_type;
};

#define TYPE_INTERFACE "interface"

/**
 * INTERFACE_CLASS:
 * @klass: class to cast from
 * Returns: An #InterfaceClass or raise an error if cast is invalid
 */
#define INTERFACE_CLASS(klass) \
    OBJECT_CLASS_CHECK(InterfaceClass, klass, TYPE_INTERFACE)

/**
 * INTERFACE_CHECK:
 * @interface: the type to return
 * @obj: the object to convert to an interface
 * @name: the interface type name
 *
 * Returns: @obj casted to @interface if cast is valid, otherwise raise error.
 */
#define INTERFACE_CHECK(interface, obj, name) \
    ((interface *)object_dynamic_cast_assert(OBJECT((obj)), (name), \
                                             __FILE__, __LINE__, __func__))

/**
 *  register the object type
 */
void type_object_init(void);

/**
 * object_new:
 * @typename: The name of the type of the object to instantiate.
 *
 * This function will initialize a new object using heap allocated memory.
 * The returned object has a reference count of 1, and will be freed when
 * the last reference is dropped.
 *
 * Returns: The newly allocated and instantiated object.
 */
Object *object_new(const char *typename);


/**
 * object_new:
 * @typename: The name of the type of the object to instantiate.
 *
 * This function will initialize a new object using heap allocated memory.
 * The returned object has a reference count of 1, and will be freed when
 * the last reference is dropped.
 *
 * Returns: The newly allocated and instantiated object.
 */

Object **objects_new(const char *typename, int num_object);

/**
 * object_initialize:
 * @obj: A pointer to the memory to be used for the object.
 * @size: The maximum size available at @obj for the object.
 * @typename: The name of the type of the object to instantiate.
 *
 * This function will initialize an object.  The memory for the object should
 * have already been allocated.  The returned object has a reference count of 1,
 * and will be finalized when the last reference is dropped.
 */
void object_initialize(void *obj, size_t size, const char *typename);

/**
 * object_dynamic_cast:
 * @obj: The object to cast.
 * @typename: The @typename to cast to.
 *
 * This function will determine if @obj is-a @typename.  @obj can refer to an
 * object or an interface associated with an object.
 *
 * Returns: This function returns @obj on success or #NULL on failure.
 */
Object *object_dynamic_cast(Object *obj, const char *typename);

/**
 * object_dynamic_cast_assert:
 *
 * See object_dynamic_cast() for a description of the parameters of this
 * function.  The only difference in behavior is that this function asserts
 * instead of returning #NULL on failure if QOM cast debugging is enabled.
 * This function is not meant to be called directly, but only through
 * the wrapper macro OBJECT_CHECK.
 */
Object *object_dynamic_cast_assert(Object *obj, const char *typename,
                                   const char *file, int line, const char *func);

/**
 * object_get_class:
 * @obj: A derivative of #Object
 *
 * Returns: The #ObjectClass of the type associated with @obj.
 */
ObjectClass *object_get_class(Object *obj);

/**
 * object_get_typename:
 * @obj: A derivative of #Object.
 *
 * Returns: The QOM typename of @obj.
 */
const char *object_get_typename(const Object *obj);

/**
 * type_register_static:
 * @info: The #TypeInfo of the new type.
 *
 * @info and all of the strings it points to should exist for the life time
 * that the type is registered.
 *
 * Returns: the new #Type.
 */
Type type_register_static(const TypeInfo *info);

/**
 * type_register:
 * @info: The #TypeInfo of the new type
 *
 * Unlike type_register_static(), this call does not require @info or its
 * string members to continue to exist after the call returns.
 *
 * Returns: the new #Type.
 */
Type type_register(const TypeInfo *info);

/**
 * type_register_static_array:
 * @infos: The array of the new type #TypeInfo structures.
 * @nr_infos: number of entries in @infos
 *
 * @infos and all of the strings it points to should exist for the life time
 * that the type is registered.
 */
void type_register_static_array(const TypeInfo *infos, int nr_infos);

/**
 * void* get_class_by_name:
 * @typename: The QOM typename of the class to cast to.
 */
void *get_class_by_name(const char *typename,
                        const char *file, int line,
                        const char *func);

/**
 *  
 * bool is_compatible_type:
 * @typename: the name of the type to be tested. 
 * @target_typename: the name of the targert type. 
 */

bool is_compatible_type(const char *typename, const char *target_typename);

/**
 * object_class_dynamic_cast_assert:
 * @klass: The #ObjectClass to attempt to cast.
 * @typename: The QOM typename of the class to cast to.
 *
 * See object_class_dynamic_cast() for a description of the parameters
 * of this function.  The only difference in behavior is that this function
 * asserts instead of returning #NULL on failure if QOM cast debugging is
 * enabled.  This function is not meant to be called directly, but only through
 * the wrapper macros OBJECT_CLASS_CHECK and INTERFACE_CHECK.
 */
ObjectClass *object_class_dynamic_cast_assert(ObjectClass *klass,
                                              const char *typename,
                                              const char *file, int line,
                                              const char *func);

/**
 * object_class_dynamic_cast:
 * @klass: The #ObjectClass to attempt to cast.
 * @typename: The QOM typename of the class to cast to.
 *
 * Returns: If @typename is a class, this function returns @klass if
 * @typename is a subtype of @klass, else returns #NULL.
 *
 * If @typename is an interface, this function returns the interface
 * definition for @klass if @klass implements it unambiguously; #NULL
 * is returned if @klass does not implement the interface or if multiple
 * classes or interfaces on the hierarchy leading to @klass implement
 * it.  (FIXME: perhaps this can be detected at type definition time?)
 */
ObjectClass *object_class_dynamic_cast(ObjectClass *klass,
                                       const char *typename);

/**
 * object_class_get_parent:
 * @klass: The class to obtain the parent for.
 *
 * Returns: The parent for @klass or %NULL if none.
 */
ObjectClass *object_class_get_parent(ObjectClass *klass);

/**
 * object_class_get_name:
 * @klass: The class to obtain the QOM typename for.
 *
 * Returns: The QOM typename for @klass.
 */
const char *object_class_get_name(ObjectClass *klass);

/**
 * object_class_is_abstract:
 * @klass: The class to obtain the abstractness for.
 *
 * Returns: %true if @klass is abstract, %false otherwise.
 */
bool object_class_is_abstract(ObjectClass *klass);

/**
 * object_class_by_name:
 * @typename: The QOM typename to obtain the class for.
 *
 * Returns: The class for @typename or %NULL if not found.
 */
ObjectClass *object_class_by_name(const char *typename);

void object_class_foreach(void (*fn)(ObjectClass *klass, void *opaque),
                          const char *implements_type, bool include_abstract,
                          void *opaque);

/**
 * object_class_get_list:
 * @implements_type: The type to filter for, including its derivatives.
 * @include_abstract: Whether to include abstract classes.
 *
 * Returns: A singly-linked list of the classes in reverse hashtable order.
 */
GSList *object_class_get_list(const char *implements_type,
                              bool include_abstract);

/**
 * object_ref:
 * @obj: the object
 *
 * Increase the reference count of a object.  A object cannot be freed as long
 * as its reference count is greater than zero.
 */
void object_ref(Object *obj);

/**
 * object_unref:
 * @obj: the object
 *
 * Decrease the reference count of a object.  A object cannot be freed as long
 * as its reference count is greater than zero.
 */
void object_unref(Object *obj);

/**
 * object_type_register:
 *
 * Register object type. 
 */

void object_type_register(void);

#endif