source: trunk/src/gcc/libobjc/sendmsg.c@ 1519

/* GNU Objective C Runtime message lookup 
   Copyright (C) 1993, 1995, 1996, 1997, 1998,
   2001, 2002 Free Software Foundation, Inc.
   Contributed by Kresten Krab Thorup

This file is part of GNU CC.

GNU CC 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 2, or (at your option) any later version.

GNU CC 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.

You should have received a copy of the GNU General Public License along with
GNU CC; see the file COPYING.  If not, write to the Free Software
Foundation, 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */

/* As a special exception, if you link this library with files compiled with
   GCC to produce an executable, this does not cause the resulting executable
   to be covered by the GNU General Public License. This exception does not
   however invalidate any other reasons why the executable file might be
   covered by the GNU General Public License.  */

#include "tconfig.h"
#include "runtime.h"
#include "sarray.h"
#include "encoding.h"
#include "runtime-info.h"

/* this is how we hack STRUCT_VALUE to be 1 or 0 */
#define gen_rtx(args...) 1
#define gen_rtx_MEM(args...) 1
#define gen_rtx_REG(args...) 1
#define rtx int

#if ! defined (STRUCT_VALUE) || STRUCT_VALUE == 0
#define INVISIBLE_STRUCT_RETURN 1
#else
#define INVISIBLE_STRUCT_RETURN 0
#endif

/* The uninstalled dispatch table */
struct sarray *__objc_uninstalled_dtable = 0;   /* !T:MUTEX */

/* Hook for method forwarding. If it is set, is invoked to return a
   function that performs the real forwarding. Otherwise the libgcc
   based functions (__builtin_apply and friends) are used. */
IMP (*__objc_msg_forward) (SEL) = NULL;

/* Send +initialize to class */
static void __objc_send_initialize (Class);

static void __objc_install_dispatch_table_for_class (Class);

/* Forward declare some functions */
static void __objc_init_install_dtable (id, SEL);

/* Various forwarding functions that are used based upon the
   return type for the selector.
   __objc_block_forward for structures.
   __objc_double_forward for floats/doubles.
   __objc_word_forward for pointers or types that fit in registers.
   */
static double __objc_double_forward (id, SEL, ...);
static id __objc_word_forward (id, SEL, ...);
typedef struct { id many[8]; } __big;
#if INVISIBLE_STRUCT_RETURN 
static __big 
#else
static id
#endif
__objc_block_forward (id, SEL, ...);
static Method_t search_for_method_in_hierarchy (Class class, SEL sel);
Method_t search_for_method_in_list (MethodList_t list, SEL op);
id nil_method (id, SEL);

/* Given a selector, return the proper forwarding implementation. */
__inline__
IMP
__objc_get_forward_imp (SEL sel)
{
  /* If a custom forwarding hook was registered, try getting a forwarding
   * function from it.  */
  if (__objc_msg_forward)
    {
      IMP result;
      if ((result = __objc_msg_forward (sel)) != NULL) 
        return result;
    }

  /* In all other cases, use the default forwarding functions built using
   * __builtin_apply and friends.  */
    {
      const char *t = sel->sel_types;

      if (t && (*t == '[' || *t == '(' || *t == '{')
#ifdef OBJC_MAX_STRUCT_BY_VALUE
          && objc_sizeof_type (t) > OBJC_MAX_STRUCT_BY_VALUE
#endif
          )
        return (IMP)__objc_block_forward;
      else if (t && (*t == 'f' || *t == 'd'))
        return (IMP)__objc_double_forward;
      else
        return (IMP)__objc_word_forward;
    }
}

/* Given a class and selector, return the selector's implementation.  */
__inline__
IMP
get_imp (Class class, SEL sel)
{
  void *res = sarray_get_safe (class->dtable, (size_t) sel->sel_id);
  if (res == 0)
    {
      /* Not a valid method */
      if (class->dtable == __objc_uninstalled_dtable)
        {
          /* The dispatch table needs to be installed. */
          objc_mutex_lock (__objc_runtime_mutex);
          __objc_install_dispatch_table_for_class (class);
          objc_mutex_unlock (__objc_runtime_mutex);
          /* Call ourselves with the installed dispatch table
             and get the real method */
          res = get_imp (class, sel);
        }
      else
        {
          /* The dispatch table has been installed so the
             method just doesn't exist for the class.
             Return the forwarding implementation. */
          res = __objc_get_forward_imp (sel);
        }
    }
  return res;
}

/* Query if an object can respond to a selector, returns YES if the
object implements the selector otherwise NO.  Does not check if the
method can be forwarded. */
__inline__
BOOL
__objc_responds_to (id object, SEL sel)
{
  void *res;

  /* Install dispatch table if need be */
  if (object->class_pointer->dtable == __objc_uninstalled_dtable)
    {
      objc_mutex_lock (__objc_runtime_mutex);
      __objc_install_dispatch_table_for_class (object->class_pointer);
      objc_mutex_unlock (__objc_runtime_mutex);
    }

  /* Get the method from the dispatch table */
  res = sarray_get_safe (object->class_pointer->dtable, (size_t) sel->sel_id);
  return (res != 0);
}

/* This is the lookup function.  All entries in the table are either a 
   valid method *or* zero.  If zero then either the dispatch table
   needs to be installed or it doesn't exist and forwarding is attempted. */
__inline__
IMP
objc_msg_lookup (id receiver, SEL op)
{
  IMP result;
  if (receiver)
    {
      result = sarray_get_safe (receiver->class_pointer->dtable, 
                                (sidx)op->sel_id);
      if (result == 0)
        {
          /* Not a valid method */
          if (receiver->class_pointer->dtable == __objc_uninstalled_dtable)
            {
              /* The dispatch table needs to be installed.
                 This happens on the very first method call to the class. */
              __objc_init_install_dtable (receiver, op);

              /* Get real method for this in newly installed dtable */
              result = get_imp (receiver->class_pointer, op);
            }
          else
            {
              /* The dispatch table has been installed so the
                 method just doesn't exist for the class.
                 Attempt to forward the method. */
              result = __objc_get_forward_imp (op);
            }
        }
      return result;
    }
  else
    return (IMP)nil_method;
}

IMP
objc_msg_lookup_super (Super_t super, SEL sel)
{
  if (super->self)
    return get_imp (super->class, sel);
  else
    return (IMP)nil_method;
}