cde/lib/tt/mini_isam/isindfreel.c

   1 /*%%  (c) Copyright 1993, 1994 Hewlett-Packard Company                   */
   2 /*%%  (c) Copyright 1993, 1994 International Business Machines Corp.     */
   3 /*%%  (c) Copyright 1993, 1994 Sun Microsystems, Inc.                    */
   4 /*%%  (c) Copyright 1993, 1994 Novell, Inc.                              */
   5 /*%%  $XConsortium: isindfreel.c /main/3 1995/10/23 11:41:03 rswiston $                                                          */
   6 #ifndef lint
   7 static char sccsid[] = "@(#)isindfreel.c 1.3 89/07/17 Copyr 1988 Sun Micro";
   8 #endif
   9
  10 /*
  11  * Copyright (c) 1988 by Sun Microsystems, Inc.
  12  */
  13
  14 /*
  15  * isfreelist.c
  16  *
  17  * Description:
  18  *      Free list maintenance functions
  19  */
  20
  21 #include "isam_impl.h"
  22
  23 extern Bufhdr *_isdisk_fix();
  24
  25 /*
  26  * blkno = _isfreel_alloc()
  27  *
  28  * Allocate a new index page.
  29  */
  30
  31 Blkno
  32 _isindfreel_alloc(fcb)
  33     Fcb                 *fcb;
  34 {
  35     Bufhdr              *pbhdr;
  36     char                *p;
  37     int                 npointers;
  38     Blkno               blkno;
  39
  40     if (fcb->indfreelist == FREELIST_NOPAGE) {
  41
  42         /*
  43          * We must write something to the buffer, or we will get
  44          * segmentation fault when using mapped I/O.
  45          */
  46         fcb->indsize = _extend_file(fcb, fcb->indfd, fcb->indsize);
  47
  48         return (fcb->indsize - 1);
  49     }
  50
  51     pbhdr = _isdisk_fix(fcb, fcb->indfd, fcb->indfreelist, ISFIXWRITE);
  52     p = pbhdr->isb_buffer;
  53
  54     npointers = ldshort(p + FL_NPOINTERS_OFF);
  55
  56     if (npointers > 0) {
  57         blkno = ldblkno(p + FL_POINTERS_OFF + npointers * BLKNOSIZE);
  58         npointers--;
  59         stshort((short)npointers, p + FL_NPOINTERS_OFF);
  60
  61         return (ldblkno(p + FL_POINTERS_OFF + npointers * BLKNOSIZE));
  62     }
  63     else {
  64         blkno = fcb->indfreelist;
  65         fcb->indfreelist = ldblkno(p + FL_NEXT_OFF);
  66
  67         return (blkno);
  68     }
  69 }
  70
  71 /*
  72  * _isfreel_free()
  73  *
  74  * Free an index page.
  75  */
  76
  77 void
  78 _isindfreel_free(fcb, blkno)
  79     Fcb                 *fcb;
  80     Blkno               blkno;
  81 {
  82     Bufhdr              *pbhdr;
  83     char                *p;
  84     int                 npointers;
  85
  86     if (fcb->indfreelist != FREELIST_NOPAGE) {
  87         pbhdr = _isdisk_fix(fcb, fcb->indfd, fcb->indfreelist, ISFIXWRITE);
  88         p = pbhdr->isb_buffer;
  89
  90         npointers = ldshort(p + FL_NPOINTERS_OFF);
  91
  92         if (npointers < FL_MAXNPOINTERS) {
  93             stblkno(blkno, p + FL_POINTERS_OFF + npointers * BLKNOSIZE);
  94             npointers++;
  95             stshort((short)npointers, p + FL_NPOINTERS_OFF);
  96
  97             return;
  98         }
  99     }
 100
 101
 102     pbhdr = _isdisk_fix(fcb, fcb->indfd, blkno, ISFIXWRITE);
 103     p = pbhdr->isb_buffer;
 104
 105     /* Mark page to indicate that it is in the free list. */
 106     stshort((short)PT_FREELIST, p + FL_TYPE_OFF);
 107
 108     stshort((short)0, p + FL_NPOINTERS_OFF);
 109     stblkno(fcb->indfreelist, p + FL_NEXT_OFF);
 110
 111     fcb->indfreelist = blkno;
 112 }