encoding.c

gcc的组件

	while (*++type != '"')
	  /* do nothing */;
	return type + 1;
      }

    /* The following are one character type codes */
  case _C_CLASS:
  case _C_SEL:
  case _C_CHR:
  case _C_UCHR:
  case _C_CHARPTR:
  case _C_ATOM:
  case _C_SHT:
  case _C_USHT:
  case _C_INT:
  case _C_UINT:
  case _C_LNG:
  case _C_ULNG:
  case _C_LNG_LNG:
  case _C_ULNG_LNG:
  case _C_FLT:
  case _C_DBL:
  case _C_VOID:
  case _C_UNDEF:
    return ++type;
    break;

  case _C_ARY_B:
    /* skip digits, typespec and closing ']' */

    while (isdigit ((unsigned char)*++type))
      ;
    type = objc_skip_typespec (type);
    if (*type == _C_ARY_E)
      return ++type;
    else
      {
	objc_error (nil, OBJC_ERR_BAD_TYPE, "bad array type %s\n", type);
	return 0;
      }

  case _C_BFLD:
    /* The new encoding of bitfields is: b 'position' 'type' 'size' */
    while (isdigit ((unsigned char)*++type))
      ;	/* skip position */
    while (isdigit ((unsigned char)*++type))
      ;	/* skip type and size */
    return type;

  case _C_STRUCT_B:
    /* skip name, and elements until closing '}'  */

    while (*type != _C_STRUCT_E && *type++ != '=')
      ;
    while (*type != _C_STRUCT_E)
      {
	type = objc_skip_typespec (type);
      }
    return ++type;

  case _C_UNION_B:
    /* skip name, and elements until closing ')'  */

    while (*type != _C_UNION_E && *type++ != '=')
      ;
    while (*type != _C_UNION_E)
      {
	type = objc_skip_typespec (type);
      }
    return ++type;

  case _C_PTR:
    /* Just skip the following typespec */

    return objc_skip_typespec (++type);

  default:
    {
      objc_error (nil, OBJC_ERR_BAD_TYPE, "unknown type %s\n", type);
      return 0;
    }
  }
}

/*
  Skip an offset as part of a method encoding.  This is prepended by a
  '+' if the argument is passed in registers.
*/
inline const char *
objc_skip_offset (const char *type)
{
  if (*type == '+')
    type++;
  while (isdigit ((unsigned char) *++type))
    ;
  return type;
}

/*
  Skip an argument specification of a method encoding.
*/
const char *
objc_skip_argspec (const char *type)
{
  type = objc_skip_typespec (type);
  type = objc_skip_offset (type);
  return type;
}

/*
  Return the number of arguments that the method MTH expects.
  Note that all methods need two implicit arguments `self' and
  `_cmd'.
*/
int
method_get_number_of_arguments (struct objc_method *mth)
{
  int i = 0;
  const char *type = mth->method_types;
  while (*type)
    {
      type = objc_skip_argspec (type);
      i += 1;
    }
  return i - 1;
}

/*
  Return the size of the argument block needed on the stack to invoke
  the method MTH.  This may be zero, if all arguments are passed in
  registers.
*/

int
method_get_sizeof_arguments (struct objc_method *mth)
{
  const char *type = objc_skip_typespec (mth->method_types);
  return atoi (type);
}

/*
  Return a pointer to the next argument of ARGFRAME.  type points to
  the last argument.  Typical use of this look like:

  {
    char *datum, *type;
    for (datum = method_get_first_argument (method, argframe, &type);
         datum; datum = method_get_next_argument (argframe, &type))
      {
        unsigned flags = objc_get_type_qualifiers (type);
        type = objc_skip_type_qualifiers (type);
	if (*type != _C_PTR)
          [portal encodeData: datum ofType: type];
	else
	  {
	    if ((flags & _F_IN) == _F_IN)
              [portal encodeData: *(char **) datum ofType: ++type];
	  }
      }
  }
*/

char *
method_get_next_argument (arglist_t argframe, const char **type)
{
  const char *t = objc_skip_argspec (*type);

  if (*t == '\0')
    return 0;

  *type = t;
  t = objc_skip_typespec (t);

  if (*t == '+')
    return argframe->arg_regs + atoi (++t);
  else
    return argframe->arg_ptr + atoi (t);
}

/*
  Return a pointer to the value of the first argument of the method
  described in M with the given argumentframe ARGFRAME.  The type
  is returned in TYPE.  type must be passed to successive calls of
  method_get_next_argument.
*/
char *
method_get_first_argument (struct objc_method *m,
			   arglist_t argframe,
			   const char **type)
{
  *type = m->method_types;
  return method_get_next_argument (argframe, type);
}

/*
   Return a pointer to the ARGth argument of the method
   M from the frame ARGFRAME.  The type of the argument
   is returned in the value-result argument TYPE
*/

char *
method_get_nth_argument (struct objc_method *m,
			 arglist_t argframe, int arg,
			 const char **type)
{
  const char *t = objc_skip_argspec (m->method_types);

  if (arg > method_get_number_of_arguments (m))
    return 0;

  while (arg--)
    t = objc_skip_argspec (t);

  *type = t;
  t = objc_skip_typespec (t);

  if (*t == '+')
    return argframe->arg_regs + atoi (++t);
  else
    return argframe->arg_ptr + atoi (t);
}

unsigned
objc_get_type_qualifiers (const char *type)
{
  unsigned res = 0;
  BOOL flag = YES;

  while (flag)
    switch (*type++)
      {
      case _C_CONST:	res |= _F_CONST; break;
      case _C_IN:	res |= _F_IN; break;
      case _C_INOUT:	res |= _F_INOUT; break;
      case _C_OUT:	res |= _F_OUT; break;
      case _C_BYCOPY:	res |= _F_BYCOPY; break;
      case _C_BYREF:  res |= _F_BYREF; break;
      case _C_ONEWAY:	res |= _F_ONEWAY; break;
      case _C_GCINVISIBLE: res |= _F_GCINVISIBLE; break;
      default: flag = NO;
    }

  return res;
}


/* The following three functions can be used to determine how a
   structure is laid out by the compiler. For example:

  struct objc_struct_layout layout;
  int i;

  objc_layout_structure (type, &layout);
  while (objc_layout_structure_next_member (&layout))
    {
      int position, align;
      const char *type;

      objc_layout_structure_get_info (&layout, &position, &align, &type);
      printf ("element %d has offset %d, alignment %d\n",
              i++, position, align);
    }

  These functions are used by objc_sizeof_type and objc_alignof_type
  functions to compute the size and alignment of structures. The
  previous method of computing the size and alignment of a structure
  was not working on some architectures, particulary on AIX, and in
  the presence of bitfields inside the structure. */
void
objc_layout_structure (const char *type,
                           struct objc_struct_layout *layout)
{
  const char *ntype;

  if (*type++ != _C_STRUCT_B)
    {
      objc_error (nil, OBJC_ERR_BAD_TYPE,
                 "record type expected in objc_layout_structure, got %s\n",
                 type);
    }

  layout->original_type = type;

  /* Skip "<name>=" if any. Avoid embedded structures and unions. */
  ntype = type;
  while (*ntype != _C_STRUCT_E && *ntype != _C_STRUCT_B && *ntype != _C_UNION_B
         && *ntype++ != '=')
    /* do nothing */;

  /* If there's a "<name>=", ntype - 1 points to '='; skip the the name */
  if (*(ntype - 1) == '=')
    type = ntype;

  layout->type = type;
  layout->prev_type = NULL;
  layout->record_size = 0;
  layout->record_align = BITS_PER_UNIT;

  layout->record_align = MAX (layout->record_align, STRUCTURE_SIZE_BOUNDARY);
}


BOOL
objc_layout_structure_next_member (struct objc_struct_layout *layout)
{
  register int desired_align = 0;

  /* The following are used only if the field is a bitfield */
  register const char *bfld_type = 0;
  register int bfld_type_size, bfld_type_align = 0, bfld_field_size = 0;

  /* The current type without the type qualifiers */
  const char *type;

  /* Add the size of the previous field to the size of the record.  */
  if (layout->prev_type)
    {
      type = objc_skip_type_qualifiers (layout->prev_type);

      if (*type != _C_BFLD)
        layout->record_size += objc_sizeof_type (type) * BITS_PER_UNIT;
      else {
        /* Get the bitfield's type */
        for (bfld_type = type + 1;
             isdigit ((unsigned char)*bfld_type);
             bfld_type++)
          /* do nothing */;

        bfld_type_size = objc_sizeof_type (bfld_type) * BITS_PER_UNIT;
        bfld_type_align = objc_alignof_type (bfld_type) * BITS_PER_UNIT;
        bfld_field_size = atoi (objc_skip_typespec (bfld_type));
        layout->record_size += bfld_field_size;
      }
    }

  if (*layout->type == _C_STRUCT_E)
    return NO;

  /* Skip the variable name if any */
  if (*layout->type == '"')
    {
      for (layout->type++; *layout->type++ != '"';)
        /* do nothing */;
    }

  type = objc_skip_type_qualifiers (layout->type);

  if (*type != _C_BFLD)
    desired_align = objc_alignof_type (type) * BITS_PER_UNIT;
  else
    {
      desired_align = 1;
      /* Skip the bitfield's offset */
      for (bfld_type = type + 1;
           isdigit ((unsigned char) *bfld_type);
           bfld_type++)
        /* do nothing */;

      bfld_type_size = objc_sizeof_type (bfld_type) * BITS_PER_UNIT;
      bfld_type_align = objc_alignof_type (bfld_type) * BITS_PER_UNIT;
      bfld_field_size = atoi (objc_skip_typespec (bfld_type));
    }

#ifdef BIGGEST_FIELD_ALIGNMENT
  desired_align = MIN (desired_align, BIGGEST_FIELD_ALIGNMENT);
#endif
#ifdef ADJUST_FIELD_ALIGN
  desired_align = ADJUST_FIELD_ALIGN (type, desired_align);
#endif

  /* Record must have at least as much alignment as any field.
     Otherwise, the alignment of the field within the record
     is meaningless.  */
#ifndef PCC_BITFIELD_TYPE_MATTERS
  layout->record_align = MAX (layout->record_align, desired_align);
#else	/* PCC_BITFIELD_TYPE_MATTERS */
  if (*type == _C_BFLD)
    {
      /* For these machines, a zero-length field does not
         affect the alignment of the structure as a whole.
         It does, however, affect the alignment of the next field
         within the structure.  */
      if (bfld_field_size)
        layout->record_align = MAX (layout->record_align, desired_align);
      else
        desired_align = objc_alignof_type (bfld_type) * BITS_PER_UNIT;

      /* A named bit field of declared type `int'
         forces the entire structure to have `int' alignment.
         Q1: How is encoded this thing and how to check for it?
         Q2: How to determine maximum_field_alignment at runtime? */

/*	  if (DECL_NAME (field) != 0) */
      {
        int type_align = bfld_type_align;
#if 0
        if (maximum_field_alignment != 0)
          type_align = MIN (type_align, maximum_field_alignment);
        else if (DECL_PACKED (field))
          type_align = MIN (type_align, BITS_PER_UNIT);
#endif

        layout->record_align = MAX (layout->record_align, type_align);
      }
    }
  else
    layout->record_align = MAX (layout->record_align, desired_align);
#endif	/* PCC_BITFIELD_TYPE_MATTERS */

  /* Does this field automatically have alignment it needs
     by virtue of the fields that precede it and the record's
     own alignment?  */

  if (*type == _C_BFLD)
    layout->record_size = atoi (type + 1);
  else if (layout->record_size % desired_align != 0)
    {
      /* No, we need to skip space before this field.
         Bump the cumulative size to multiple of field alignment.  */
      layout->record_size = ROUND (layout->record_size, desired_align);
    }

  /* Jump to the next field in record. */

  layout->prev_type = layout->type;
  layout->type = objc_skip_typespec (layout->type);      /* skip component */

  return YES;
}


void objc_layout_finish_structure (struct objc_struct_layout *layout,
                                   unsigned int *size,
                                   unsigned int *align)
{
  if (layout->type && *layout->type == _C_STRUCT_E)
    {
      /* Work out the alignment of the record as one expression and store
         in the record type.  Round it up to a multiple of the record's
         alignment. */

#if defined (ROUND_TYPE_ALIGN) && ! defined (__sparc__)
      layout->record_align = ROUND_TYPE_ALIGN (layout->original_type,
                                               1,
                                               layout->record_align);
#else
      layout->record_align = MAX (1, layout->record_align);
#endif

#ifdef ROUND_TYPE_SIZE
      layout->record_size = ROUND_TYPE_SIZE (layout->original_type,
                                             layout->record_size,
                                             layout->record_align);
#else
      /* Round the size up to be a multiple of the required alignment */
      layout->record_size = ROUND (layout->record_size, layout->record_align);
#endif

      layout->type = NULL;
    }
  if (size)
    *size = layout->record_size / BITS_PER_UNIT;
  if (align)
    *align = layout->record_align / BITS_PER_UNIT;
}


void objc_layout_structure_get_info (struct objc_struct_layout *layout,
                                     unsigned int *offset,
                                     unsigned int *align,
                                     const char **type)
{
  if (offset)
    *offset = layout->record_size / BITS_PER_UNIT;
  if (align)
    *align = layout->record_align / BITS_PER_UNIT;
  if (type)
    *type = layout->prev_type;
}