usr/src/lib/libbc/libc/stdio/common/fseek.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License, Version 1.0 only
   6  * (the "License").  You may not use this file except in compliance
   7  * with the License.
   8  *
   9  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
  10  * or http://www.opensolaris.org/os/licensing.
  11  * See the License for the specific language governing permissions
  12  * and limitations under the License.
  13  *
  14  * When distributing Covered Code, include this CDDL HEADER in each
  15  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  16  * If applicable, add the following below this CDDL HEADER, with the
  17  * fields enclosed by brackets "[]" replaced with your own identifying
  18  * information: Portions Copyright [yyyy] [name of copyright owner]
  19  *
  20  * CDDL HEADER END
  21  */
  22 /*
  23  * Copyright 1986 Sun Microsystems, Inc.  All rights reserved.
  24  * Use is subject to license terms.
  25  */
  26
  27 /*      Copyright (c) 1984 AT&T */
  28 /*        All Rights Reserved   */
  29
  30 #pragma ident   "%Z%%M% %I%     %E% SMI"  /* from S5R2 1.3 */
  31
  32 /*LINTLIBRARY*/
  33 /*
  34  * Seek for standard library.  Coordinates with buffering.
  35  */
  36 #include <stdio.h>
  37
  38 extern long lseek();
  39 extern int fflush();
  40
  41 int
  42 fseek(iop, offset, ptrname)
  43 register FILE *iop;
  44 long    offset;
  45 int     ptrname;
  46 {
  47         register int resync, c;
  48         long    p = -1;                 /* can't happen? */
  49
  50         iop->_flag &= ~_IOEOF;
  51         if(iop->_flag & _IOREAD) {
  52                 if(ptrname < 2 && iop->_base && !(iop->_flag&_IONBF)) {
  53                         c = iop->_cnt;
  54                         p = offset;
  55                         if(ptrname == 0) {
  56                                 long curpos = lseek(fileno(iop), 0L, 1);
  57                                 if (curpos == -1)
  58                                         return (-1);
  59                                 p += c - curpos;
  60                                 resync = offset&01;
  61                         } else {
  62                                 offset -= (long)c;
  63                                 resync = 0;
  64                         }
  65                         if(!(iop->_flag&_IORW) && c > 0 && p <= c &&
  66                                         p >= iop->_base - iop->_ptr) {
  67                                 iop->_ptr += (int)p;
  68                                 iop->_cnt -= (int)p;
  69                                 return(0);
  70                         }
  71                 } else
  72                         resync = 0;
  73                 if(iop->_flag & _IORW) {
  74                         iop->_ptr = iop->_base;
  75                         iop->_flag &= ~_IOREAD;
  76                         resync = 0;
  77                 }
  78                 p = lseek(fileno(iop), offset-resync, ptrname);
  79                 iop->_cnt = 0;
  80                 if (resync && p != -1)
  81                         if (getc(iop) == EOF)
  82                                 p = -1;
  83         } else if(iop->_flag & (_IOWRT | _IORW)) {
  84                 p = fflush(iop);
  85                 iop->_cnt = 0;
  86                 if(iop->_flag & _IORW) {
  87                         iop->_flag &= ~_IOWRT;
  88                         iop->_ptr = iop->_base;
  89                 }
  90                 return(lseek(fileno(iop), offset, ptrname) == -1 || p == EOF ?
  91                     -1 : 0);
  92         }
  93         return((p == -1)? -1: 0);
  94 }