usr/src/lib/libc/port/stdio/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 (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21
  22 /*
  23  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
  24  * Use is subject to license terms.
  25  */
  26
  27 /*      Copyright (c) 1988 AT&T */
  28 /*        All Rights Reserved   */
  29
  30 #pragma ident   "%Z%%M% %I%     %E% SMI"
  31
  32 /*
  33  * Seek for standard library.  Coordinates with buffering.
  34  */
  35
  36 #pragma weak _fseek = fseek
  37
  38 #include "lint.h"
  39 #include "file64.h"
  40 #include "mtlib.h"
  41 #include <stdio.h>
  42 #include <errno.h>
  43 #include <thread.h>
  44 #include <synch.h>
  45 #include <unistd.h>
  46 #include <sys/types.h>
  47 #include "stdiom.h"
  48
  49 int
  50 fseek(FILE *iop, long offset, int ptrname)
  51 {
  52         off_t   p;
  53         rmutex_t *lk;
  54
  55         FLOCKFILE(lk, iop);
  56         iop->_flag &= ~_IOEOF;
  57
  58         if (!(iop->_flag & _IOREAD) && !(iop->_flag & (_IOWRT | _IORW))) {
  59                 errno = EBADF;
  60                 FUNLOCKFILE(lk);
  61                 return (-1);
  62         }
  63
  64         if (iop->_flag & _IOREAD) {
  65                 if (ptrname == 1 && iop->_base && !(iop->_flag&_IONBF)) {
  66                         offset -= iop->_cnt;
  67                 }
  68         } else if (iop->_flag & (_IOWRT | _IORW)) {
  69                 if (_fflush_u(iop) == EOF) {
  70                         FUNLOCKFILE(lk);
  71                         return (-1);
  72                 }
  73         }
  74         iop->_cnt = 0;
  75         iop->_ptr = iop->_base;
  76         if (iop->_flag & _IORW) {
  77                 iop->_flag &= ~(_IOREAD | _IOWRT);
  78         }
  79         p = lseek(FILENO(iop), (off_t)offset, ptrname);
  80         FUNLOCKFILE(lk);
  81         return ((p == (off_t)-1) ? -1: 0);
  82 }