rom/utility/nexttagitem.c

   1 /*
   2     Copyright © 1995-2007, The AROS Development Team. All rights reserved.
   3     $Id$    $Log
   4 */
   5 #include "intern.h"
   6
   7 /*****************************************************************************
   8
   9     NAME */
  10 #include <utility/tagitem.h>
  11 #include <proto/utility.h>
  12
  13         AROS_LH1(struct TagItem *, NextTagItem,
  14
  15 /*  SYNOPSIS */
  16         AROS_LHA(const struct TagItem **, tagListPtr, A0),
  17
  18 /*  LOCATION */
  19         struct Library *, UtilityBase, 8, Utility)
  20
  21 /*  FUNCTION
  22         Returns the address of the next tag-item in the list. This
  23         routine correctly handles TAG_END, TAG_DONE, TAG_MORE,
  24         TAG_IGNORE and TAG_SKIP.
  25
  26         TAG_END and TAG_DONE both terminate a TagItems-array (in
  27         fact, TAG_DONE is the same as TAG_END).
  28
  29         With TAG_MORE, you can redirect the processing to a new list
  30         of tags. Note that the processing will not return to the previous
  31         list when a TAG_END/TAG_DONE is encountered.
  32
  33         TAG_IGNORE disables the processing of an entry in the list.
  34         This entry is just ignored (We use this technique for filtering).
  35
  36         TAG_SKIP skips this tagitem, and the next number of tagitems as
  37         indicated in the tag's ti_Data field.
  38
  39     INPUTS
  40         tagListPtr - Pointer to an element in a taglist.
  41
  42     RESULT
  43         Next tag item or NULL if you reached the end of the list.
  44
  45     NOTES
  46         - TAG_MORE works like "go on with new list" instead of "read new
  47           list and go on with the current one".
  48
  49     EXAMPLE
  50
  51     BUGS
  52
  53     SEE ALSO
  54
  55     INTERNALS
  56
  57 *****************************************************************************/
  58 {
  59     AROS_LIBFUNC_INIT
  60
  61     if(!(*tagListPtr)) return NULL;
  62
  63 /*  Gosh, can't enable these because we get LOTS of hits at startup time
  64  *
  65  *  ASSERT_VALID_PTR(tagListPtr);
  66  *  ASSERT_VALID_PTR(*tagListPtr);
  67  */
  68
  69     while (TRUE)
  70     {
  71         switch ((*tagListPtr)->ti_Tag)
  72         {
  73         case TAG_MORE:
  74             if (!((*tagListPtr) = (struct TagItem *)(*tagListPtr)->ti_Data))
  75                 return NULL;
  76             continue;
  77
  78         case TAG_IGNORE:
  79             break;
  80
  81         case TAG_END:
  82             (*tagListPtr) = NULL;
  83             return NULL;
  84
  85         case TAG_SKIP:
  86             (*tagListPtr) += (*tagListPtr)->ti_Data + 1;
  87             continue;
  88
  89         default:
  90             /* Use post-increment (return will return the current value and
  91                 then tagListPtr will be incremented) */
  92             return (struct TagItem *)(*tagListPtr)++;
  93         }
  94
  95         (*tagListPtr) ++;
  96     }
  97
  98     AROS_LIBFUNC_EXIT
  99 } /* NextTagItem */