lib/fseeko.c

   1 /* An fseeko() function that, together with fflush(), is POSIX compliant.
   2    Copyright (C) 2007-2024 Free Software Foundation, Inc.
   3
   4    This file is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU Lesser General Public License as
   6    published by the Free Software Foundation; either version 2.1 of the
   7    License, or (at your option) any later version.
   8
   9    This file 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
  15    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  16
  17 #include <config.h>
  18
  19 /* Specification.  */
  20 #include <stdio.h>
  21
  22 /* Get off_t, lseek, _POSIX_VERSION.  */
  23 #include <unistd.h>
  24
  25 #include "stdio-impl.h"
  26
  27 int
  28 fseeko (FILE *fp, off_t offset, int whence)
  29 #undef fseeko
  30 #if !HAVE_FSEEKO
  31 # undef fseek
  32 # define fseeko fseek
  33 #endif
  34 #if _GL_WINDOWS_64_BIT_OFF_T
  35 # undef fseeko
  36 # if HAVE__FSEEKI64 && HAVE_DECL__FSEEKI64 /* msvc, mingw since msvcrt8.0, mingw64 */
  37 #  define fseeko _fseeki64
  38 # else /* mingw before msvcrt8.0 */
  39 #  define fseeko fseeko64
  40 # endif
  41 #endif
  42 {
  43 #if LSEEK_PIPE_BROKEN
  44   /* mingw gives bogus answers rather than failure on non-seekable files.  */
  45   if (lseek (fileno (fp), 0, SEEK_CUR) == -1)
  46     return EOF;
  47 #endif
  48
  49   /* These tests are based on fpurge.c.  */
  50 #if defined _IO_EOF_SEEN || defined _IO_ftrylockfile || __GNU_LIBRARY__ == 1
  51   /* GNU libc, BeOS, Haiku, Linux libc5 */
  52   if (fp->_IO_read_end == fp->_IO_read_ptr
  53       && fp->_IO_write_ptr == fp->_IO_write_base
  54       && fp->_IO_save_base == NULL)
  55 #elif defined __sferror || defined __DragonFly__ || defined __ANDROID__
  56   /* FreeBSD, NetBSD, OpenBSD, DragonFly, Mac OS X, Cygwin, Minix 3, Android */
  57 # if defined __SL64 && defined __SCLE /* Cygwin */
  58   if ((fp->_flags & __SL64) == 0)
  59     {
  60       /* Cygwin 1.5.0 through 1.5.24 failed to open stdin in 64-bit
  61          mode; but has an fseeko that requires 64-bit mode.  */
  62       FILE *tmp = fopen ("/dev/null", "r");
  63       if (!tmp)
  64         return -1;
  65       fp->_flags |= __SL64;
  66       fp->_seek64 = tmp->_seek64;
  67       fclose (tmp);
  68     }
  69 # endif
  70   if (fp_->_p == fp_->_bf._base
  71       && fp_->_r == 0
  72       && fp_->_w == ((fp_->_flags & (__SLBF | __SNBF | __SRD)) == 0 /* fully buffered and not currently reading? */
  73                      ? fp_->_bf._size
  74                      : 0)
  75       && fp_ub._base == NULL)
  76 #elif defined __EMX__               /* emx+gcc */
  77   if (fp->_ptr == fp->_buffer
  78       && fp->_rcount == 0
  79       && fp->_wcount == 0
  80       && fp->_ungetc_count == 0)
  81 #elif defined __minix               /* Minix */
  82   if (fp_->_ptr == fp_->_buf
  83       && (fp_->_ptr == NULL || fp_->_count == 0))
  84 #elif defined _IOERR                /* AIX, HP-UX, IRIX, OSF/1, Solaris, OpenServer, UnixWare, mingw, MSVC, NonStop Kernel, OpenVMS */
  85   if (fp_->_ptr == fp_->_base
  86       && (fp_->_ptr == NULL || fp_->_cnt == 0))
  87 #elif defined __UCLIBC__            /* uClibc */
  88   if (((fp->__modeflags & __FLAG_WRITING) == 0
  89        || fp->__bufpos == fp->__bufstart)
  90       && ((fp->__modeflags & (__FLAG_READONLY | __FLAG_READING)) == 0
  91           || fp->__bufpos == fp->__bufread))
  92 #elif defined __QNX__               /* QNX */
  93   if ((fp->_Mode & 0x2000 /* _MWRITE */ ? fp->_Next == fp->_Buf : fp->_Next == fp->_Rend)
  94       && fp->_Rback == fp->_Back + sizeof (fp->_Back)
  95       && fp->_Rsave == NULL)
  96 #elif defined __MINT__              /* Atari FreeMiNT */
  97   if (fp->__bufp == fp->__buffer
  98       && fp->__get_limit == fp->__bufp
  99       && fp->__put_limit == fp->__bufp
 100       && !fp->__pushed_back)
 101 #elif defined EPLAN9                /* Plan9 */
 102   if (fp->rp == fp->buf
 103       && fp->wp == fp->buf)
 104 #elif FUNC_FFLUSH_STDIN < 0 && 200809 <= _POSIX_VERSION
 105   /* Cross-compiling to some other system advertising conformance to
 106      POSIX.1-2008 or later.  Assume fseeko and fflush work as advertised.
 107      If this assumption is incorrect, please report the bug to
 108      bug-gnulib.  */
 109   if (0)
 110 #else
 111   #error "Please port gnulib fseeko.c to your platform! Look at the code in fseeko.c, then report this to bug-gnulib."
 112 #endif
 113     {
 114       /* We get here when an fflush() call immediately preceded this one (or
 115          if ftell() has created buffers but no I/O has occurred on a
 116          newly-opened stream).  We know there are no buffers.  */
 117       off_t pos = lseek (fileno (fp), offset, whence);
 118       if (pos == -1)
 119         {
 120 #if defined __sferror || defined __DragonFly__ || defined __ANDROID__
 121           /* FreeBSD, NetBSD, OpenBSD, DragonFly, Mac OS X, Cygwin, Minix 3, Android */
 122           fp_->_flags &= ~__SOFF;
 123 #endif
 124           return -1;
 125         }
 126
 127 #if defined _IO_EOF_SEEN || defined _IO_ftrylockfile || __GNU_LIBRARY__ == 1
 128       /* GNU libc, BeOS, Haiku, Linux libc5 */
 129       fp->_flags &= ~_IO_EOF_SEEN;
 130       fp->_offset = pos;
 131 #elif defined __sferror || defined __DragonFly__ || defined __ANDROID__
 132       /* FreeBSD, NetBSD, OpenBSD, DragonFly, Mac OS X, Cygwin, Minix 3, Android */
 133 # if defined __CYGWIN__ || (defined __NetBSD__ && __NetBSD_Version__ >= 600000000) || defined __minix
 134       /* fp_->_offset is typed as an integer.  */
 135       fp_->_offset = pos;
 136 # else
 137       /* fp_->_offset is an fpos_t.  */
 138       {
 139         /* Use a union, since on NetBSD, the compilation flags
 140            determine whether fpos_t is typedef'd to off_t or a struct
 141            containing a single off_t member.  */
 142         union
 143           {
 144             fpos_t f;
 145             off_t o;
 146           } u;
 147         u.o = pos;
 148         fp_->_offset = u.f;
 149       }
 150 # endif
 151       fp_->_flags |= __SOFF;
 152       fp_->_flags &= ~__SEOF;
 153 #elif defined __EMX__               /* emx+gcc */
 154       fp->_flags &= ~_IOEOF;
 155 #elif defined _IOERR                /* AIX, HP-UX, IRIX, OSF/1, Solaris, OpenServer, UnixWare, mingw, MSVC, NonStop Kernel, OpenVMS */
 156       fp_->_flag &= ~_IOEOF;
 157 #elif defined __MINT__              /* Atari FreeMiNT */
 158       fp->__offset = pos;
 159       fp->__eof = 0;
 160 #endif
 161       return 0;
 162     }
 163   return fseeko (fp, offset, whence);
 164 }