lib/fseeko.c

   1 /* An fseeko() function that, together with fflush(), is POSIX compliant.
   2    Copyright (C) 2007-2011 Free Software Foundation, Inc.
   3
   4    This program is free software; you can redistribute it and/or modify
   5    it under the terms of the GNU Lesser General Public License as published by
   6    the Free Software Foundation; either version 2, or (at your option)
   7    any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public License along
  15    with this program; if not, write to the Free Software Foundation,
  16    Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
  17
  18 #include <config.h>
  19
  20 /* Specification.  */
  21 #include <stdio.h>
  22
  23 /* Get off_t and lseek.  */
  24 #include <unistd.h>
  25
  26 #include "stdio-impl.h"
  27
  28 int
  29 fseeko (FILE *fp, off_t offset, int whence)
  30 #undef fseeko
  31 #if !HAVE_FSEEKO
  32 # undef fseek
  33 # define fseeko fseek
  34 #endif
  35 {
  36 #if LSEEK_PIPE_BROKEN
  37   /* mingw gives bogus answers rather than failure on non-seekable files.  */
  38   if (lseek (fileno (fp), 0, SEEK_CUR) == -1)
  39     return EOF;
  40 #endif
  41
  42   /* These tests are based on fpurge.c.  */
  43 #if defined _IO_ftrylockfile || __GNU_LIBRARY__ == 1 /* GNU libc, BeOS, Haiku, Linux libc5 */
  44   if (fp->_IO_read_end == fp->_IO_read_ptr
  45       && fp->_IO_write_ptr == fp->_IO_write_base
  46       && fp->_IO_save_base == NULL)
  47 #elif defined __sferror || defined __DragonFly__ /* FreeBSD, NetBSD, OpenBSD, DragonFly, MacOS X, Cygwin */
  48 # if defined __SL64 && defined __SCLE /* Cygwin */
  49   if ((fp->_flags & __SL64) == 0)
  50     {
  51       /* Cygwin 1.5.0 through 1.5.24 failed to open stdin in 64-bit
  52          mode; but has an fseeko that requires 64-bit mode.  */
  53       FILE *tmp = fopen ("/dev/null", "r");
  54       if (!tmp)
  55         return -1;
  56       fp->_flags |= __SL64;
  57       fp->_seek64 = tmp->_seek64;
  58       fclose (tmp);
  59     }
  60 # endif
  61   if (fp_->_p == fp_->_bf._base
  62       && fp_->_r == 0
  63       && fp_->_w == ((fp_->_flags & (__SLBF | __SNBF | __SRD)) == 0 /* fully buffered and not currently reading? */
  64                      ? fp_->_bf._size
  65                      : 0)
  66       && fp_ub._base == NULL)
  67 #elif defined __EMX__               /* emx+gcc */
  68   if (fp->_ptr == fp->_buffer
  69       && fp->_rcount == 0
  70       && fp->_wcount == 0
  71       && fp->_ungetc_count == 0)
  72 #elif defined _IOERR                /* AIX, HP-UX, IRIX, OSF/1, Solaris, OpenServer, mingw, NonStop Kernel */
  73   if (fp_->_ptr == fp_->_base
  74       && (fp_->_ptr == NULL || fp_->_cnt == 0))
  75 #elif defined __UCLIBC__            /* uClibc */
  76   if (((fp->__modeflags & __FLAG_WRITING) == 0
  77        || fp->__bufpos == fp->__bufstart)
  78       && ((fp->__modeflags & (__FLAG_READONLY | __FLAG_READING)) == 0
  79           || fp->__bufpos == fp->__bufread))
  80 #elif defined __QNX__               /* QNX */
  81   if ((fp->_Mode & 0x2000 /* _MWRITE */ ? fp->_Next == fp->_Buf : fp->_Next == fp->_Rend)
  82       && fp->_Rback == fp->_Back + sizeof (fp->_Back)
  83       && fp->_Rsave == NULL)
  84 #elif defined __MINT__              /* Atari FreeMiNT */
  85   if (fp->__bufp == fp->__buffer
  86       && fp->__get_limit == fp->__bufp
  87       && fp->__put_limit == fp->__bufp
  88       && !fp->__pushed_back)
  89 #else
  90   #error "Please port gnulib fseeko.c to your platform! Look at the code in fpurge.c, then report this to bug-gnulib."
  91 #endif
  92     {
  93       /* We get here when an fflush() call immediately preceded this one.  We
  94          know there are no buffers.
  95          POSIX requires us to modify the file descriptor's position.
  96          But we cannot position beyond end of file here.  */
  97       off_t pos =
  98         lseek (fileno (fp),
  99                whence == SEEK_END && offset > 0 ? 0 : offset,
 100                whence);
 101       if (pos == -1)
 102         {
 103 #if defined __sferror || defined __DragonFly__ /* FreeBSD, NetBSD, OpenBSD, DragonFly, MacOS X, Cygwin */
 104           fp_->_flags &= ~__SOFF;
 105 #endif
 106           return -1;
 107         }
 108
 109 #if defined _IO_ftrylockfile || __GNU_LIBRARY__ == 1 /* GNU libc, BeOS, Haiku, Linux libc5 */
 110       fp->_flags &= ~_IO_EOF_SEEN;
 111 #elif defined __sferror || defined __DragonFly__ /* FreeBSD, NetBSD, OpenBSD, DragonFly, MacOS X, Cygwin */
 112 # if defined __CYGWIN__
 113       /* fp_->_offset is typed as an integer.  */
 114       fp_->_offset = pos;
 115 # else
 116       /* fp_->_offset is an fpos_t.  */
 117       {
 118         /* Use a union, since on NetBSD, the compilation flags
 119            determine whether fpos_t is typedef'd to off_t or a struct
 120            containing a single off_t member.  */
 121         union
 122           {
 123             fpos_t f;
 124             off_t o;
 125           } u;
 126         u.o = pos;
 127         fp_->_offset = u.f;
 128       }
 129 # endif
 130       fp_->_flags |= __SOFF;
 131       fp_->_flags &= ~__SEOF;
 132 #elif defined __EMX__               /* emx+gcc */
 133       fp->_flags &= ~_IOEOF;
 134 #elif defined _IOERR                /* AIX, HP-UX, IRIX, OSF/1, Solaris, OpenServer, mingw, NonStop Kernel */
 135       fp->_flag &= ~_IOEOF;
 136 #elif defined __MINT__              /* Atari FreeMiNT */
 137       fp->__offset = pos;
 138       fp->__eof = 0;
 139 #endif
 140       /* If we were not requested to position beyond end of file, we're
 141          done.  */
 142       if (!(whence == SEEK_END && offset > 0))
 143         return 0;
 144     }
 145   return fseeko (fp, offset, whence);
 146 }