cde/programs/dtksh/ksh93/src/lib/libast/sfio/sfseek.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 librararies 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 /* $XConsortium: sfseek.c /main/3 1995/11/01 18:35:35 rswiston $ */
  24 /***************************************************************
  25 *                                                              *
  26 *                      AT&T - PROPRIETARY                      *
  27 *                                                              *
  28 *         THIS IS PROPRIETARY SOURCE CODE LICENSED BY          *
  29 *                          AT&T CORP.                          *
  30 *                                                              *
  31 *                Copyright (c) 1995 AT&T Corp.                 *
  32 *                     All Rights Reserved                      *
  33 *                                                              *
  34 *           This software is licensed by AT&T Corp.            *
  35 *       under the terms and conditions of the license in       *
  36 *       http://www.research.att.com/orgs/ssr/book/reuse        *
  37 *                                                              *
  38 *               This software was created by the               *
  39 *           Software Engineering Research Department           *
  40 *                    AT&T Bell Laboratories                    *
  41 *                                                              *
  42 *               For further information contact                *
  43 *                     gsf@research.att.com                     *
  44 *                                                              *
  45 ***************************************************************/
  46 #include        "sfhdr.h"
  47
  48 /*      Set the IO pointer to a specific location in the stream
  49 **
  50 **      Written by Kiem-Phong Vo (06/27/90)
  51 */
  52
  53 #if __STD_C
  54 long sfseek(reg Sfio_t* f, reg long p, reg int type)
  55 #else
  56 long sfseek(f,p,type)
  57 reg Sfio_t      *f;     /* seek to a new location in this stream */
  58 reg long        p;      /* place to seek to */
  59 int             type;   /* 0: from org, 1: from here, 2: from end */
  60 #endif
  61 {
  62         reg long        r, s;
  63         reg int         mode, local;
  64
  65         GETLOCAL(f,local);
  66
  67         /* set and initialize the stream to a definite mode */
  68         if(SFMODE(f,local) != (mode = f->mode&SF_RDWR) && _sfmode(f,mode,local) < 0 )
  69                 return -1L;
  70
  71         if(type < 0 || type > 2 || f->extent < 0L)
  72                 return -1L;
  73
  74         /* throw away ungetc data */
  75         if(f->disc == _Sfudisc)
  76                 (void)sfclose((*_Sfstack)(f,NIL(Sfio_t*)));
  77
  78         /* lock the stream for internal manipulations */
  79         SFLOCK(f,local);
  80
  81         /* clear error and eof bits */
  82         f->flags &= ~(SF_EOF|SF_ERROR);
  83
  84         while(f->flags&SF_STRING)
  85         {       SFSTRSIZE(f);
  86
  87                 if(type == 1)
  88                         r = p + (f->next - f->data);
  89                 else if(type == 2)
  90                         r = p + f->extent;
  91                 else    r = p;
  92
  93                 if(r >= 0 && r <= f->size)
  94                 {       p = r;
  95                         f->next = f->data+p;
  96                         f->here = p;
  97                         if(p > f->extent)
  98                                 memclear((char*)(f->data+f->extent),(int)(p-f->extent));
  99                         goto done;
 100                 }
 101
 102                 /* check exception handler, note that this may pop stream */
 103                 if(SFSK(f,r,0,f->disc) != 0)
 104                 {       p = -1L;
 105                         goto done;
 106                 }
 107         }
 108
 109         /* flush any pending write data */
 110         if((f->mode&SF_WRITE) && f->next > f->data && SFSYNC(f) < 0)
 111         {       p = -1L;
 112                 goto done;
 113         }
 114
 115         /* currently known seek location */
 116         if((f->flags&(SF_SHARE|SF_PUBLIC)) == (SF_SHARE|SF_PUBLIC))
 117         {       s = SFSK(f,0L,1,f->disc);
 118                 if(s == f->here)
 119                         goto logical_seek;
 120         }
 121         else
 122         { logical_seek :
 123                 s = f->here + ((f->mode&SF_READ) ? f->next-f->endb : f->next-f->data);
 124         }
 125
 126         /* no need to do anything */
 127         if(!(f->flags&SF_SHARE) && type == 0 && s == p)
 128                 goto done;
 129
 130 #ifdef MAP_TYPE
 131         if(f->flags&SF_MMAP)
 132         {       /* move buffer pointer if possible */
 133                 p += type == 0 ? 0L : type == 1 ? s : f->extent;
 134                 if(p >= (f->here - (f->endb-f->data)) && p < f->here)
 135                         f->next = f->endb - (f->here - p);
 136                 else if(p >= 0)
 137                 {       if(!(f->flags&SF_SHARE) || SFSK(f,p,0,f->disc) == p)
 138                                 f->here = p;
 139
 140                         /* map is now invalid */
 141                         if(f->data)
 142                         {       (void)munmap((caddr_t)f->data,f->endb-f->data);
 143                                 f->endb = f->endr = f->endw =
 144                                 f->next = f->data = NIL(uchar*);
 145                         }
 146                 }
 147
 148                 goto done;
 149         }
 150 #endif
 151
 152         if(type == 1 && p == 0 && !(f->flags&(SF_APPEND|SF_SHARE)) )
 153         {       /* certify current location only */
 154                 if((p = SFSK(f,f->here,0,f->disc)) != f->here)
 155                         p = -1L;
 156                 else    p = s;
 157                 goto done;
 158         }
 159
 160         if(f->mode&SF_WRITE)
 161         {       if(!(f->flags&SF_SHARE) && type < 2 && ((r = type == 0 ? p : p+s)) == s)
 162                 {       /* at where we are supposed to be */
 163                         p = r;
 164                         goto done;
 165                 }
 166         }
 167         else if(type < 2 && !(f->flags&(SF_SHARE|SF_APPEND)) &&
 168                 (r = p + (type == 0 ? 0L : s)) > f->here && r < f->extent)
 169         {       /* move forward by reading */
 170                 if(f->next == f->endb)
 171                         f->endb = f->endr = f->next = f->data;
 172                 if(r < (s + (f->size - (f->endb-f->data))))
 173                         (void)SFFILBUF(f,-1);
 174         }
 175
 176         if(type < 2)
 177         {       /* place to seek to */
 178                 p += type == 0 ? 0L : s;
 179
 180                 if((f->mode&SF_READ) && !(f->flags&(SF_SHARE|SF_APPEND)) &&
 181                    p >= (f->here - (f->endb-f->data)) && p <= f->here)
 182                 {       /* still in bound, safe to just move the pointer */
 183                         f->next = f->endb - (f->here-p);
 184                         goto done;
 185                 }
 186         }
 187         else
 188         {       if((p = SFSK(f,p,2,f->disc)) < 0)
 189                         goto done;
 190                 f->here = p;
 191         }
 192
 193         if(f->mode&SF_READ)
 194         {       /* any buffered data is invalid */
 195                 f->next = f->endr = f->endb = f->data;
 196
 197                 /* seek to a rounded boundary to improve performance */
 198                 if(f->size > 1 && p < f->extent && (r = (p/f->size)*f->size) < p &&
 199                    SFSK(f,r,0,f->disc) == r)
 200                 {       f->here = r;
 201                         SFFILBUF(f,-1);
 202                         if(f->here < p)
 203                                 p = -1L;
 204                         else    f->next = f->endb - (f->here-p);
 205                         goto done;
 206                 }
 207         }
 208
 209         /* if get here must do a seek */
 210         if(type < 2 && (p = SFSK(f,p,0,f->disc)) >= 0)
 211                 f->here = p;
 212
 213 done :
 214         SFOPEN(f,local);
 215         return p;
 216 }