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/* GNU Objective-C Runtime API - Modern API

   Copyright (C) 2010 Free Software Foundation, Inc.

   Contributed by Nicola Pero <nicola.pero@meta-innovation.com>

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it

under the terms of the GNU General Public License as published by the

Free Software Foundation; either version 3, or (at your option) any

later version.

GCC is distributed in the hope that it will be useful, but WITHOUT

ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public

License for more details.

Under Section 7 of GPL version 3, you are granted additional

permissions described in the GCC Runtime Library Exception, version

3.1, as published by the Free Software Foundation.

You should have received a copy of the GNU General Public License and

a copy of the GCC Runtime Library Exception along with this program;

see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see

<http://www.gnu.org/licenses/>.  */

#ifndef __objc_runtime_INCLUDE_GNU

#define __objc_runtime_INCLUDE_GNU

/*

  This file declares the "modern" GNU Objective-C Runtime API.

  This API replaced the "traditional" GNU Objective-C Runtime API

  (which used to be declared in objc/objc-api.h) which is the one

  supported by older versions of the GNU Objective-C Runtime.  The

  "modern" API is very similar to the API used by the modern

  Apple/NeXT runtime.

*/

#include "objc.h"

#include "objc-decls.h"

#ifdef __cplusplus

extern "C" {

#endif /* __cplusplus */

/* An 'Ivar' represents an instance variable.  It holds information

   about the name, type and offset of the instance variable.  */

typedef struct objc_ivar *Ivar;

/* A 'Property' represents a property.  It holds information about the

   name of the property, and its attributes.

   Compatibility Note: the Apple/NeXT runtime defines this as

   objc_property_t, so we define it that way as well, but obviously

   Property is the right name.  */

typedef struct objc_property *Property;

typedef struct objc_property *objc_property_t;

/* A 'Method' represents a method.  It holds information about the

   name, types and the IMP of the method.  */

typedef struct objc_method *Method;

/* A 'Category' represents a category.  It holds information about the

   name of the category, the class it belongs to, and the methods,

   protocols and such like provided by the category.  */

typedef struct objc_category *Category;

/* 'Protocol' is defined in objc/objc.h (which is included by this

   file).  */

/* Method descriptor returned by introspective Object methods.  At the

   moment, this is really just the first part of the more complete

   objc_method structure used internally by the runtime.  (PS: In the

   GNU Objective-C Runtime, selectors already include a type, so an

   objc_method_description does not add much to a SEL.  But in other

   runtimes, that is not the case, which is why

   objc_method_description exists).  */

struct objc_method_description

{

  SEL name;      /* Selector (name and signature) */

  char *types;   /* Type encoding */

};

/* The following are used in encode strings to describe the type of

   Ivars and Methods.  */

#define _C_ID       '@'

#define _C_CLASS    '#'

#define _C_SEL      ':'

#define _C_CHR      'c'

#define _C_UCHR     'C'

#define _C_SHT      's'

#define _C_USHT     'S'

#define _C_INT      'i'

#define _C_UINT     'I'

#define _C_LNG      'l'

#define _C_ULNG     'L'

#define _C_LNG_LNG  'q'

#define _C_ULNG_LNG 'Q'

#define _C_FLT      'f'

#define _C_DBL      'd'

#define _C_LNG_DBL  'D'

#define _C_BFLD     'b'

#define _C_BOOL     'B'

#define _C_VOID     'v'

#define _C_UNDEF    '?'

#define _C_PTR      '^'

#define _C_CHARPTR  '*'

#define _C_ARY_B    '['

#define _C_ARY_E    ']'

#define _C_UNION_B  '('

#define _C_UNION_E  ')'

#define _C_STRUCT_B '{'

#define _C_STRUCT_E '}'

#define _C_VECTOR   '!'

#define _C_COMPLEX  'j'

/* _C_ATOM is never generated by the compiler.  You can treat it as

   equivalent to "*".  */

#define _C_ATOM     '%'

/* The following are used in encode strings to describe some

   qualifiers of method and ivar types.  */

#define _C_CONST        'r'

#define _C_IN           'n'

#define _C_INOUT        'N'

#define _C_OUT          'o'

#define _C_BYCOPY       'O'

#define _C_BYREF        'R'

#define _C_ONEWAY       'V'

#define _C_GCINVISIBLE  '|'

/* The same when used as flags.  */

#define _F_CONST        0x01

#define _F_IN           0x01

#define _F_OUT          0x02

#define _F_INOUT        0x03

#define _F_BYCOPY       0x04

#define _F_BYREF        0x08

#define _F_ONEWAY       0x10

#define _F_GCINVISIBLE  0x20

/** Implementation: the following functions are defined inline.  */

/* Return the class of 'object', or Nil if the object is nil.  If

   'object' is a class, the meta class is returned; if 'object' is a

   meta class, the root meta class is returned (note that this is

   different from the traditional GNU Objective-C Runtime API function

   object_get_class(), which for a meta class would return the meta

   class itself).  This function is inline, so it is really fast and

   should be used instead of accessing object->class_pointer

   directly.  */

static inline Class

object_getClass (id object)

{

  if (object != nil)

    return object->class_pointer;

  else

    return Nil;

}

/** Implementation: the following functions are in selector.c.  */

/* Return the name of a given selector.  If 'selector' is NULL, return

   "<null selector>".  */

objc_EXPORT const char *sel_getName (SEL selector);

/* Return the type of a given selector.  Return NULL if selector is

   NULL.

   Compatibility Note: the Apple/NeXT runtime has untyped selectors,

   so it does not have this function, which is specific to the GNU

   Runtime.  */

objc_EXPORT const char *sel_getTypeEncoding (SEL selector);

/* This is the same as sel_registerName ().  Please use

   sel_registerName () instead.  */

objc_EXPORT SEL sel_getUid (const char *name);

/* Register a selector with a given name (but unspecified types).  If

   you know the types, it is better to call sel_registerTypedName().

   If a selector with this name and no types already exists, it is

   returned.  Note that this function should really be called

   'objc_registerSelector'.  Return NULL if 'name' is NULL.  */

objc_EXPORT SEL sel_registerName (const char *name);

/* Register a selector with a given name and types.  If a selector

   with this name and types already exists, it is returned.  Note that

   this function should really be called 'objc_registerTypedSelector',

   and it's called 'sel_registerTypedName' only for consistency with

   'sel_registerName'.  Return NULL if 'name' is NULL.

   Compatibility Note: the Apple/NeXT runtime has untyped selectors,

   so it does not have this function, which is specific to the GNU

   Runtime.  */

objc_EXPORT SEL sel_registerTypedName (const char *name, const char *type);

/* Return YES if first_selector is the same as second_selector, and NO

   if not.  */

objc_EXPORT BOOL sel_isEqual (SEL first_selector, SEL second_selector);

/* Return all the selectors with the supplied name.  In the GNU

   runtime, selectors are typed and there may be multiple selectors

   with the same name but a different type.  The return value of the

   function is a pointer to an area, allocated with malloc(), that

   contains all the selectors with the supplier name known to the

   runtime.  The list is terminated by NULL.  Optionally, if you pass

   a non-NULL 'numberOfReturnedSelectors' pointer, the unsigned int

   that it points to will be filled with the number of selectors

   returned.

   Compatibility Note: the Apple/NeXT runtime has untyped selectors,

   so it does not have this function, which is specific to the GNU

   Runtime.  */

objc_EXPORT SEL * sel_copyTypedSelectorList (const char *name,

                                             unsigned int *numberOfReturnedSelectors);

/* Return a selector with name 'name' and a non-zero type encoding, if

   there is a single selector with a type, and with that name,

   registered with the runtime.  If there is no such selector, or if

   there are multiple selectors with the same name but conflicting

   types, NULL is returned.  Return NULL if 'name' is NULL.

   This is useful if you have the name of the selector, and would

   really like to get a selector for it that includes the type

   encoding.  Unfortunately, if the program contains multiple selector

   with the same name but different types, sel_getTypedSelector can

   not possibly know which one you need, and so will return NULL.

   Compatibility Note: the Apple/NeXT runtime has untyped selectors,

   so it does not have this function, which is specific to the GNU

   Runtime.  */

objc_EXPORT SEL sel_getTypedSelector (const char *name);

/** Implementation: the following functions are in objects.c.  */

/* Create an instance of class 'class_', adding extraBytes to the size

   of the returned object.  This method allocates the appropriate

   amount of memory for the instance, initializes it to zero, then

   calls all the C++ constructors on appropriate C++ instance

   variables of the instance (if any) (TODO: The C++ constructors bit

   is not implemented yet).  */

objc_EXPORT id class_createInstance (Class class_, size_t extraBytes);

/* Copy an object and return the copy.  extraBytes should be identical

   to the extraBytes parameter that was passed when creating the

   original object.  */

objc_EXPORT id object_copy (id object, size_t extraBytes);

/* Dispose of an object.  This method calls the appropriate C++

   destructors on appropriate C++ instance variables of the instance

   (if any) (TODO: This is not implemented yet), then frees the memory

   for the instance.  */

objc_EXPORT id object_dispose (id object);

/* Return the name of the class of 'object'.  If 'object' is 'nil',

   returns "Nil".  */

objc_EXPORT const char * object_getClassName (id object);

/* Change the class of object to be class_.  Return the previous class

   of object.  This is currently not really thread-safe.  */

objc_EXPORT Class object_setClass (id object, Class class_);

/** Implementation: the following functions are in ivars.c.  */

/* Return an instance variable given the class and the instance

   variable name.  This is an expensive function to call, so try to

   reuse the returned Ivar if you can.  */

objc_EXPORT Ivar class_getInstanceVariable (Class class_, const char *name);

/* Return a class variable given the class and the class variable

   name.  This is an expensive function to call, so try to reuse the

   returned Ivar if you can.

   This function always returns NULL since class variables are

   currently unavailable in Objective-C.  */

objc_EXPORT Ivar class_getClassVariable (Class class_, const char *name);

/* If the object was created in class_createInstance() with some

   extraBytes, returns a pointer to them.  If it was not, then the

   returned pointer may make no sense.  */

objc_EXPORT void * object_getIndexedIvars (id object);

/* Get the value of an instance variable of type 'id'.  The function

   returns the instance variable.  To get the value of the instance

   variable, you should pass as 'returnValue' a pointer to an 'id';

   the value will be copied there.  Note that 'returnValue' is really

   a 'void *', not a 'void **'.  This function really works only with

   instance variables of type 'id'; for other types of instance

   variables, access directly the data at (char *)object +

   ivar_getOffset (ivar).  */

objc_EXPORT Ivar object_getInstanceVariable (id object, const char *name, void **returnValue);

/* Set the value of an instance variable.  The value to set is passed

   in 'newValue' (which really is an 'id', not a 'void *').  The

   function returns the instance variable.  This function really works

   only with instance variables of type 'id'; for other types of

   instance variables, access directly the data at (char *)object +

   ivar_getOffset (ivar).  */

objc_EXPORT Ivar object_setInstanceVariable (id object, const char *name, void *newValue);

/* Get the value of an instance variable of type 'id' of the object

   'object'.  This is faster than object_getInstanceVariable if you

   already have the instance variable because it avoids the expensive

   call to class_getInstanceVariable that is done by

   object_getInstanceVariable.  */

objc_EXPORT id object_getIvar (id object, Ivar variable);

/* Set the value of an instance variable of type 'id' of the object

   'object'.  This is faster than object_setInstanceVariable if you

   already have the instance variable because it avoids the expensive

   call to class_getInstanceVariable that is done by

   object_setInstanceVariable.  */

objc_EXPORT void object_setIvar (id object, Ivar variable, id value);

/* Return the name of the instance variable.  Return NULL if

   'variable' is NULL.  */

objc_EXPORT const char * ivar_getName (Ivar variable);

/* Return the offset of the instance variable from the start of the

   object data.  Return 0 if 'variable' is NULL.  */

objc_EXPORT ptrdiff_t ivar_getOffset (Ivar variable);

/* Return the type encoding of the variable.  Return NULL if

   'variable' is NULL.  */

objc_EXPORT const char * ivar_getTypeEncoding (Ivar variable);

/* Return all the instance variables of the class.  The return value

   of the function is a pointer to an area, allocated with malloc(),

   that contains all the instance variables of the class.  It does not

   include instance variables of superclasses.  The list is terminated

   by NULL.  Optionally, if you pass a non-NULL

   'numberOfReturnedIvars' pointer, the unsigned int that it points to

   will be filled with the number of instance variables returned.

   Return NULL for classes still in construction (ie, allocated using

   objc_allocatedClassPair() but not yet registered with the runtime

   using objc_registerClassPair()).  */

objc_EXPORT Ivar * class_copyIvarList (Class class_, unsigned int *numberOfReturnedIvars);

/* Add an instance variable with name 'ivar_name' to class 'class_',

   where 'class_' is a class in construction that has been created

   using objc_allocateClassPair() and has not been registered with the

   runtime using objc_registerClassPair() yet.  You can not add

   instance variables to classes already registered with the runtime.

   'size' is the size of the instance variable, 'log_2_of_alignment'

   the alignment as a power of 2 (so 0 means alignment to a 1 byte

   boundary, 1 means alignment to a 2 byte boundary, 2 means alignment

   to a 4 byte boundary, etc), and 'type' the type encoding of the

   variable type.  You can use sizeof(), log2(__alignof__()) and

   @encode() to determine the right 'size', 'alignment' and 'type' for

   your instance variable.  For example, to add an instance variable

   name "my_variable" and of type 'id', you can use:

   class_addIvar (class, "my_variable", sizeof (id), log2 ( __alignof__ (id)),

                  @encode (id));

   Return YES if the variable was added, and NO if not.  In

   particular, return NO if 'class_' is Nil, or a meta-class or a

   class not in construction.  Return Nil also if 'ivar_name' or

   'type' is NULL, or 'size' is 0.

 */

objc_EXPORT BOOL class_addIvar (Class class_, const char * ivar_name, size_t size,

                                unsigned char log_2_of_alignment, const char *type);

/* Return the name of the property.  Return NULL if 'property' is

   NULL.  */

objc_EXPORT const char * property_getName (Property property);

/* Return the attributes of the property as a string.  Return NULL if

   'property' is NULL.  */

objc_EXPORT const char * property_getAttributes (Property property);

/* Return the property with name 'propertyName' of the class 'class_'.

   This function returns NULL if the required property can not be

   found.  Return NULL if 'class_' or 'propertyName' is NULL.

   Note that the traditional ABI does not store the list of properties

   of a class in a compiled module, so the traditional ABI will always

   return NULL.  */

objc_EXPORT Property class_getProperty (Class class_, const char *propertyName);

/* Return all the properties of the class.  The return value

   of the function is a pointer to an area, allocated with malloc(),

   that contains all the properties of the class.  It does not

   include properties of superclasses.  The list is terminated

   by NULL.  Optionally, if you pass a non-NULL

   'numberOfReturnedIvars' pointer, the unsigned int that it points to

   will be filled with the number of properties returned.

   Note that the traditional ABI does not store the list of properties

   of a class in a compiled module, so the traditional ABI will always

   return an empty list.  */

objc_EXPORT Property * class_copyPropertyList

(Class class_, unsigned int *numberOfReturnedProperties);

/* Return the ivar layout for class 'class_'.

   At the moment this function always returns NULL.  */

objc_EXPORT const char * class_getIvarLayout (Class class_);

/* Return the weak ivar layout for class 'class_'.

   At the moment this function always returns NULL.  */

objc_EXPORT const char * class_getWeakIvarLayout (Class class_);

/* Set the ivar layout for class 'class_'.

   At the moment, this function does nothing.  */

objc_EXPORT void class_setIvarLayout (Class class_, const char *layout);

/* Set the weak ivar layout for class 'class_'.

   At the moment, this function does nothing.  With the GNU runtime,

   you should use class_ivar_set_gcinvisible () to hide variables from

   the Garbage Collector.  */

objc_EXPORT void class_setWeakIvarLayout (Class class_, const char *layout);

/** Implementation: the following functions are in class.c.  */

/* Compatibility Note: The Apple/NeXT runtime does not have

   objc_get_unknown_class_handler and

   objc_setGetUnknownClassHandler().  They provide functionality that

   the traditional GNU Objective-C Runtime API used to provide via the

   _objc_lookup_class hook.  */

/* An 'objc_get_unknown_class_handler' function is used by

   objc_getClass() to get a class that is currently unknown to the

   compiler.  You could use it for example to have the class loaded by

   dynamically loading a library.  'class_name' is the name of the

   class.  The function should return the Class object if it manages to

   load the class, and Nil if not.  */

typedef Class (*objc_get_unknown_class_handler)(const char *class_name);

/* Sets a new handler function for getting unknown classes (to be used

   by objc_getClass () and related), and returns the previous one.

   This function is not safe to call in a multi-threaded environment

   because other threads may be trying to use the get unknown class

   handler while you change it!  */

objc_EXPORT

objc_get_unknown_class_handler

objc_setGetUnknownClassHandler (objc_get_unknown_class_handler new_handler);

/* Return the class with name 'name', if it is already registered with

   the runtime.  If it is not registered, and

   objc_setGetUnknownClassHandler() has been called to set a handler

   for unknown classes, the handler is called to give it a chance to

   load the class in some other way.  If the class is not known to the

   runtime and the handler is not set or returns Nil, objc_getClass()

   returns Nil.  */

objc_EXPORT Class objc_getClass (const char *name);

/* Return the class with name 'name', if it is already registered with

   the runtime.  Return Nil if not.  This function does not call the

   objc_get_unknown_class_handler function if the class is not

   found.  */

objc_EXPORT Class objc_lookUpClass (const char *name);

/* Return the meta class associated to the class with name 'name', if

   it is already registered with the runtime.  First, it finds the

   class using objc_getClass().  Then, it returns the associated meta

   class.  If the class could not be found using objc_getClass(),

   returns Nil.  */

objc_EXPORT Class objc_getMetaClass (const char *name);

/* This is identical to objc_getClass(), but if the class is not found,

   it aborts the process instead of returning Nil.  */

objc_EXPORT Class objc_getRequiredClass (const char *name);

/* If 'returnValue' is NULL, 'objc_getClassList' returns the number of

   classes currently registered with the runtime.  If 'returnValue' is

   not NULL, it should be a (Class *) pointer to an area of memory

   which can contain up to 'maxNumberOfClassesToReturn' Class records.

   'objc_getClassList' will fill the area pointed to by 'returnValue'

   with all the Classes registered with the runtime (or up to

   maxNumberOfClassesToReturn if there are more than

   maxNumberOfClassesToReturn).  The function return value is the

   number of classes actually returned in 'returnValue'.  */

objc_EXPORT int objc_getClassList (Class *returnValue, int maxNumberOfClassesToReturn);

/* Compatibility Note: The Apple/NeXT runtime also has

    Class objc_getFutureClass (const char *name);

    void objc_setFutureClass (Class class_, const char *name);

   the documentation is unclear on what they are supposed to do, and

   the GNU Objective-C Runtime currently does not provide them.  */

/* Return the name of the class 'class_', or the string "nil" if the

   class_ is Nil.  */

objc_EXPORT const char * class_getName (Class class_);

/* Return YES if 'class_' is a meta class, and NO if not.  If 'class_'

   is Nil, return NO.  */

objc_EXPORT BOOL class_isMetaClass (Class class_);

/* Return the superclass of 'class_'.  If 'class_' is Nil, or it is a

   root class, return Nil.  This function also works if 'class_' is a

   class being constructed, that is, a class returned by

   objc_allocateClassPair() but before it has been registered with the

   runtime using objc_registerClassPair().  */

objc_EXPORT Class class_getSuperclass (Class class_);

/* Return the 'version' number of the class, which is an integer that

   can be used to track changes in the class API, methods and

   variables.  If class_ is Nil, return 0.  If class_ is not Nil, the

   version is 0 unless class_setVersion() has been called to set a

   different one.

   Please note that internally the version is a long, but the API only

   allows you to set and retrieve int values.  */

objc_EXPORT int class_getVersion (Class class_);

/* Set the 'version' number of the class, which is an integer that can

   be used to track changes in the class API, methods and variables.

   If 'class_' is Nil, does nothing.

   This is typically used internally by "Foundation" libraries such as

   GNUstep Base to support serialization / deserialization of objects

   that work across changes in the classes.  If you are using such a

   library, you probably want to use their versioning API, which may

   be based on this one, but is integrated with the rest of the

   library.

   Please note that internally the version is a long, but the API only

   allows you to set and retrieve int values.  */

objc_EXPORT void class_setVersion (Class class_, int version);

/* Return the size in bytes (a byte is the size of a char) of an

   instance of the class.  If class_ is Nil, return 0; else it return

   a non-zero number (since the 'isa' instance variable is required

   for all classes).  */

objc_EXPORT size_t class_getInstanceSize (Class class_);

/* Change the implementation of the method.  It also searches all

   classes for any class implementing the method, and replaces the

   existing implementation with the new one.  For that to work,

   'method' must be a method returned by class_getInstanceMethod() or

   class_getClassMethod() as the matching is done by comparing the

   pointers; in that case, only the implementation in the class is

   modified.  Return the previous implementation that has been

   replaced.  If method or implementation is NULL, do nothing and

   return NULL.  */

objc_EXPORT IMP

method_setImplementation (Method method, IMP implementation);

/* Swap the implementation of two methods in a single, atomic

   operation.  This is equivalent to getting the implementation of

   each method and then calling method_setImplementation() on the

   other one.  For this to work, the two methods must have been

   returned by class_getInstanceMethod() or class_getClassMethod().

   If 'method_a' or 'method_b' is NULL, do nothing.  */

objc_EXPORT void

method_exchangeImplementations (Method method_a, Method method_b);

/* Create a new class/meta-class pair.  This function is called to

   create a new class at runtime.  The class is created with

   superclass 'superclass' (use 'Nil' to create a new root class) and

   name 'class_name'.  'extraBytes' can be used to specify some extra

   space for indexed variables to be added at the end of the class and

   meta-class objects (it is recommended that you set extraBytes to

   0).  Once you have created the class, it is not usable yet.  You

   need to add any instance variables (by using class_addIvar()), any

   instance methods (by using class_addMethod()) and any class methods

   (by using class_addMethod() on the meta-class, as in

   class_addMethod (object_getClass (class), method)) that are

   required, and then you need to call objc_registerClassPair() to

   activate the class.  If you need to create a hierarchy of classes,

   you need to create and register them one at a time.  You can not

   create a new class using another class in construction as

   superclass.  Return Nil if 'class-name' is NULL or if a class with

   that name already exists or 'superclass' is a class still in

   construction.

   Implementation Note: in the GNU runtime, allocating a class pair

   only creates the structures for the class pair, but does not

   register anything with the runtime.  The class is registered with

   the runtime only when objc_registerClassPair() is called.  In

   particular, if a class is in construction, objc_getClass() will not

   find it, the superclass will not know about it,

   class_getSuperclass() will return Nil and another thread may

   allocate a class pair with the same name; the conflict will only be

   detected when the classes are registered with the runtime.

 */

objc_EXPORT Class

objc_allocateClassPair (Class super_class, const char *class_name,

                        size_t extraBytes);

/* Register a class pair that was created with

   objc_allocateClassPair().  After you register a class, you can no

   longer make changes to its instance variables, but you can start

   creating instances of it.  Do nothing if 'class_' is NULL or if it

   is not a class allocated by objc_allocateClassPair() and still in

   construction.  */

objc_EXPORT void

objc_registerClassPair (Class class_);

/* Dispose of a class pair created using objc_allocateClassPair().

   Call this function if you started creating a new class with

   objc_allocateClassPair() but then want to abort the process.  You

   should not access 'class_' after calling this method.  Note that if

   'class_' has already been registered with the runtime via

   objc_registerClassPair(), this function does nothing; you can only

   dispose of class pairs that are still being constructed.  Do

   nothing if class is 'Nil' or if 'class_' is not a class being

   constructed.  */

objc_EXPORT void

objc_disposeClassPair (Class class_);

/* Compatibility Note: The Apple/NeXT runtime has the function

   objc_duplicateClass () but it's undocumented.  The GNU runtime does

   not have it.  */

/** Implementation: the following functions are in sendmsg.c.  */

/* Return the instance method with selector 'selector' of class

   'class_', or NULL if the class (or one of its superclasses) does

   not implement the method.  Return NULL if class_ is Nil or selector

   is NULL.  Calling this function may trigger a call to

   +resolveInstanceMethod:, but does not return a forwarding

   function.  */

objc_EXPORT Method class_getInstanceMethod (Class class_, SEL selector);

/* Return the class method with selector 'selector' of class 'class_',

   or NULL if the class (or one of its superclasses) does not

   implement the method.  Return NULL if class_ is Nil or selector is

   NULL.  Calling this function may trigger a call to

   +resolveClassMethod:, but does not return a forwarding

   function.  */

objc_EXPORT Method class_getClassMethod (Class class_, SEL selector);

/* Return the IMP (pointer to the function implementing a method) for

   the instance method with selector 'selector' in class 'class_'.

   This is the same routine that is used while messaging, and should

   be very fast.  Note that you most likely would need to cast the

   return function pointer to a function pointer with the appropriate

   arguments and return type before calling it.  To get a class

   method, you can pass the meta-class as the class_ argument (ie, use

   class_getMethodImplementation (object_getClass (class_),

   selector)).  Return NULL if class_ is Nil or selector is NULL.

   This function first looks for an existing method; if it is not

   found, it calls +resolveClassMethod: or +resolveInstanceMethod:

   (depending on whether a class or instance method is being looked

   up) if it is implemented.  If the method returns YES, then it tries

   the look up again (the assumption being that +resolveClassMethod:

   or resolveInstanceMethod: will add the method using

   class_addMethod()).  If it is still not found, it returns a

   forwarding function.  */

objc_EXPORT IMP class_getMethodImplementation (Class class_, SEL selector);

/* Compatibility Note: the Apple/NeXT runtime has the function

   class_getMethodImplementation_stret () which currently does not

   exist on the GNU runtime because the messaging implementation is

   different.  */

/* Return YES if class 'class_' has an instance method implementing

   selector 'selector', and NO if not.  Return NO if class_ is Nil or

   selector is NULL.  If you need to check a class method, use the

   meta-class as the class_ argument (ie, use class_respondsToSelector

   (object_getClass (class_), selector)).  */

objc_EXPORT BOOL class_respondsToSelector (Class class_, SEL selector);

/* Add a method to a class.  Use this function to add a new method to

   a class (potentially overriding a method with the same selector in

   the superclass); if you want to modify an existing method, use

   method_setImplementation() instead (or class_replaceMethod ()).

   This method adds an instance method to 'class_'; to add a class

   method, get the meta class first, then add the method to the meta

   class, that is, use

   class_addMethod (object_getClass (class_), selector,

   implementation, type);

   Return YES if the method was added, and NO if not.  Do nothing if

   one of the arguments is NULL.  */

objc_EXPORT BOOL class_addMethod (Class class_, SEL selector, IMP implementation,

                                  const char *method_types);

/* Replace a method in a class.  If the class already have a method

   with this 'selector', find it and use method_setImplementation() to

   replace the implementation with 'implementation' (method_types is

   ignored in that case).  If the class does not already have a method

   with this 'selector', call 'class_addMethod() to add it.

   Return the previous implementation of the method, or NULL if none

   was found.  Return NULL if any of the arguments is NULL.  */

objc_EXPORT IMP class_replaceMethod (Class class_, SEL selector, IMP implementation,

                                     const char *method_types);

/** Implementation: the following functions are in methods.c.  */

/* Return the selector for method 'method'.  Return NULL if 'method'

   is NULL.

   This function is misnamed; it should be called

   'method_getSelector'.  To get the actual name, get the selector,

   then the name from the selector (ie, use sel_getName

   (method_getName (method))).  */

objc_EXPORT SEL method_getName (Method method);

/* Return the IMP of the method.  Return NULL if 'method' is NULL.  */

objc_EXPORT IMP method_getImplementation (Method method);

/* Return the type encoding of the method.  Return NULL if 'method' is

   NULL.  */

objc_EXPORT const char * method_getTypeEncoding (Method method);

/* Return a method description for the method.  Return NULL if

   'method' is NULL.  */

objc_EXPORT struct objc_method_description * method_getDescription (Method method);

/* Return all the instance methods of the class.  The return value of

   the function is a pointer to an area, allocated with malloc(), that

   contains all the instance methods of the class.  It does not

   include instance methods of superclasses.  The list is terminated

   by NULL.  Optionally, if you pass a non-NULL

   'numberOfReturnedMethods' pointer, the unsigned int that it points

   to will be filled with the number of instance methods returned.  To

   get the list of class methods, pass the meta-class in the 'class_'

   argument, (ie, use class_copyMethodList (object_getClass (class_),

   &numberOfReturnedMethods)).  */

objc_EXPORT Method * class_copyMethodList (Class class_, unsigned int *numberOfReturnedMethods);

/** Implementation: the following functions are in encoding.c.  */

/* Return the number of arguments that the method 'method' expects.

   Note that all methods need two implicit arguments ('self' for the

   receiver, and '_cmd' for the selector).  Return 0 if 'method' is

   NULL.  */

objc_EXPORT unsigned int method_getNumberOfArguments (Method method);

/* Return the string encoding for the return type of method 'method'.

   The string is a standard zero-terminated string in an area of

   memory allocated with malloc(); you should free it with free() when

   you finish using it.  Return an empty string if method is NULL.  */

objc_EXPORT char * method_copyReturnType (Method method);

/* Return the string encoding for the argument type of method

   'method', argument number 'argumentNumber' ('argumentNumber' is 0

   for self, 1 for _cmd, and 2 or more for the additional arguments if

   any).  The string is a standard zero-terminated string in an area

   of memory allocated with malloc(); you should free it with free()

   when you finish using it.  Return an empty string if method is NULL

   or if 'argumentNumber' refers to a non-existing argument.  */

objc_EXPORT char * method_copyArgumentType (Method method, unsigned int argumentNumber);

/* Return the string encoding for the return type of method 'method'.

   The string is returned by copying it into the supplied

   'returnValue' string, which is of size 'returnValueSize'.  No more

   than 'returnValueSize' characters are copied; if the encoding is

   smaller than 'returnValueSize', the rest of 'returnValue' is filled

   with zeros.  If it is bigger, it is truncated (and would not be

   zero-terminated).  You should supply a big enough

   'returnValueSize'.  If the method is NULL, returnValue is set to a

   string of zeros.  */

objc_EXPORT void method_getReturnType (Method method, char *returnValue,

                                       size_t returnValueSize);

/* Return the string encoding for the argument type of method

   'method', argument number 'argumentNumber' ('argumentNumber' is 0

   for self, 1 for _cmd, and 2 or more for the additional arguments if

   any).  The string is returned by copying it into the supplied

   'returnValue' string, which is of size 'returnValueSize'.  No more

   than 'returnValueSize' characters are copied; if the encoding is

   smaller than 'returnValueSize', the rest of 'returnValue' is filled

   with zeros.  If it is bigger, it is truncated (and would not be

   zero-terminated).  You should supply a big enough

   'returnValueSize'.  If the method is NULL, returnValue is set to a

   string of zeros.  */

objc_EXPORT void method_getArgumentType (Method method, unsigned int argumentNumber,

                                         char *returnValue, size_t returnValueSize);

/** Implementation: the following functions are in protocols.c.  */

/* Return the protocol with name 'name', or nil if it the protocol is

   not known to the runtime.  */

objc_EXPORT Protocol *objc_getProtocol (const char *name);

/* Return all the protocols known to the runtime.  The return value of

   the function is a pointer to an area, allocated with malloc(), that

   contains all the protocols known to the runtime; the list is

   terminated by NULL.  You should free this area using free() once

   you no longer need it.  Optionally, if you pass a non-NULL

   'numberOfReturnedProtocols' pointer, the unsigned int that it

   points to will be filled with the number of protocols returned.  If

   there are no protocols known to the runtime, NULL is returned.  */

objc_EXPORT Protocol **objc_copyProtocolList (unsigned int *numberOfReturnedProtocols);

/* Add a protocol to a class, and return YES if it was done

   succesfully, and NO if not.  At the moment, NO should only happen

   if class_ or protocol are nil, if the protocol is not a Protocol

   object or if the class already conforms to the protocol.  */

objc_EXPORT BOOL class_addProtocol (Class class_, Protocol *protocol);

/* Return YES if the class 'class_' conforms to Protocol 'protocol',

   and NO if not.  This function does not check superclasses; if you

   want to check for superclasses (in the way that [NSObject

   +conformsToProtocol:] does) you need to iterate over the class

   hierarchy using class_getSuperclass(), and call

   class_conformsToProtocol() for each of them.  */

objc_EXPORT BOOL class_conformsToProtocol (Class class_, Protocol *protocol);

/* Return all the protocols that the class conforms to.  The return

   value of the function is a pointer to an area, allocated with

   malloc(), that contains all the protocols formally adopted by the

   class.  It does not include protocols adopted by superclasses.  The

   list is terminated by NULL.  Optionally, if you pass a non-NULL

   'numberOfReturnedProtocols' pointer, the unsigned int that it

   points to will be filled with the number of protocols returned.

   This function does not return protocols that superclasses conform

   to.  */

objc_EXPORT Protocol **class_copyProtocolList (Class class_, unsigned int *numberOfReturnedProtocols);

/* Return YES if protocol 'protocol' conforms to protocol

   'anotherProtocol', and NO if not.  Note that if one of the two

   protocols is nil, it returns NO.  */

objc_EXPORT BOOL protocol_conformsToProtocol (Protocol *protocol, Protocol *anotherProtocol);

/* Return YES if protocol 'protocol' is the same as protocol

   'anotherProtocol', and 'NO' if not.  Note that it returns YES if

   the two protocols are both nil.  */

objc_EXPORT BOOL protocol_isEqual (Protocol *protocol, Protocol *anotherProtocol);

/* Return the name of protocol 'protocol'.  If 'protocol' is nil or is

   not a Protocol, return NULL.  */

objc_EXPORT const char *protocol_getName (Protocol *protocol);

/* Return the method description for the method with selector

   'selector' in protocol 'protocol'; if 'requiredMethod' is YES, the

   function searches the list of required methods; if NO, the list of

   optional methods.  If 'instanceMethod' is YES, the function search

   for an instance method; if NO, for a class method.  If there is no

   matching method, an objc_method_description structure with both

   name and types set to NULL is returned.  This function will only

   find methods that are directly declared in the protocol itself, not

   in other protocols that this protocol adopts.

   Note that the traditional ABI does not store the list of optional

   methods of a protocol in a compiled module, so the traditional ABI