cde/lib/tt/mini_isam/isindfreel.c

   1 /*
   2  * CDE - Common Desktop Environment
   3  *
   4  * Copyright (c) 1993-2012, The Open Group. All rights reserved.
   5  *
   6  * These libraries and programs are free software; you can
   7  * redistribute them and/or modify them under the terms of the GNU
   8  * Lesser General Public License as published by the Free Software
   9  * Foundation; either version 2 of the License, or (at your option)
  10  * any later version.
  11  *
  12  * These libraries and programs are distributed in the hope that
  13  * they will be useful, but WITHOUT ANY WARRANTY; without even the
  14  * implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
  15  * PURPOSE. See the GNU Lesser General Public License for more
  16  * details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with these libraries and programs; if not, write
  20  * to the Free Software Foundation, Inc., 51 Franklin Street, Fifth
  21  * Floor, Boston, MA 02110-1301 USA
  22  */
  23 /*%%  (c) Copyright 1993, 1994 Hewlett-Packard Company                   */
  24 /*%%  (c) Copyright 1993, 1994 International Business Machines Corp.     */
  25 /*%%  (c) Copyright 1993, 1994 Sun Microsystems, Inc.                    */
  26 /*%%  (c) Copyright 1993, 1994 Novell, Inc.                              */
  27 /*%%  $XConsortium: isindfreel.c /main/3 1995/10/23 11:41:03 rswiston $                                                          */
  28
  29 /*
  30  * Copyright (c) 1988 by Sun Microsystems, Inc.
  31  */
  32
  33 /*
  34  * isfreelist.c
  35  *
  36  * Description:
  37  *      Free list maintenance functions
  38  */
  39
  40 #include "isam_impl.h"
  41
  42 extern Bufhdr *_isdisk_fix();
  43
  44 /*
  45  * blkno = _isfreel_alloc()
  46  *
  47  * Allocate a new index page.
  48  */
  49
  50 Blkno
  51 _isindfreel_alloc(Fcb *fcb)
  52 {
  53     Bufhdr              *pbhdr;
  54     char                *p;
  55     int                 npointers;
  56     Blkno               blkno;
  57
  58     if (fcb->indfreelist == FREELIST_NOPAGE) {
  59
  60         /*
  61          * We must write something to the buffer, or we will get
  62          * segmentation fault when using mapped I/O.
  63          */
  64         fcb->indsize = _extend_file(fcb, fcb->indfd, fcb->indsize);
  65
  66         return (fcb->indsize - 1);
  67     }
  68
  69     pbhdr = _isdisk_fix(fcb, fcb->indfd, fcb->indfreelist, ISFIXWRITE);
  70     p = pbhdr->isb_buffer;
  71
  72     npointers = ldshort(p + FL_NPOINTERS_OFF);
  73
  74     if (npointers > 0) {
  75         blkno = ldblkno(p + FL_POINTERS_OFF + npointers * BLKNOSIZE);
  76         npointers--;
  77         stshort((short)npointers, p + FL_NPOINTERS_OFF);
  78
  79         return (ldblkno(p + FL_POINTERS_OFF + npointers * BLKNOSIZE));
  80     }
  81     else {
  82         blkno = fcb->indfreelist;
  83         fcb->indfreelist = ldblkno(p + FL_NEXT_OFF);
  84
  85         return (blkno);
  86     }
  87 }
  88
  89 /*
  90  * _isfreel_free()
  91  *
  92  * Free an index page.
  93  */
  94
  95 void
  96 _isindfreel_free(Fcb *fcb, Blkno blkno)
  97 {
  98     Bufhdr              *pbhdr;
  99     char                *p;
 100     int                 npointers;
 101
 102     if (fcb->indfreelist != FREELIST_NOPAGE) {
 103         pbhdr = _isdisk_fix(fcb, fcb->indfd, fcb->indfreelist, ISFIXWRITE);
 104         p = pbhdr->isb_buffer;
 105
 106         npointers = ldshort(p + FL_NPOINTERS_OFF);
 107
 108         if (npointers < FL_MAXNPOINTERS) {
 109             stblkno(blkno, p + FL_POINTERS_OFF + npointers * BLKNOSIZE);
 110             npointers++;
 111             stshort((short)npointers, p + FL_NPOINTERS_OFF);
 112
 113             return;
 114         }
 115     }
 116
 117
 118     pbhdr = _isdisk_fix(fcb, fcb->indfd, blkno, ISFIXWRITE);
 119     p = pbhdr->isb_buffer;
 120
 121     /* Mark page to indicate that it is in the free list. */
 122     stshort((short)PT_FREELIST, p + FL_TYPE_OFF);
 123
 124     stshort((short)0, p + FL_NPOINTERS_OFF);
 125     stblkno(fcb->indfreelist, p + FL_NEXT_OFF);
 126
 127     fcb->indfreelist = blkno;
 128 }