1  /* Retrieve information about a FILE stream.
       2     Copyright (C) 2007-2022 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 "freadahead.h"
      21  
      22  #include <stdlib.h>
      23  #include "stdio-impl.h"
      24  
      25  #if defined __DragonFly__
      26  /* Defined in libc, but not declared in <stdio.h>.  */
      27  extern size_t __sreadahead (FILE *);
      28  #endif
      29  
      30  /* This file is not used on systems that have the __freadahead function,
      31     namely musl libc.  */
      32  
      33  size_t
      34  freadahead (FILE *fp)
      35  {
      36  #if defined _IO_EOF_SEEN || defined _IO_ftrylockfile || __GNU_LIBRARY__ == 1
      37    /* GNU libc, BeOS, Haiku, Linux libc5 */
      38    if (fp->_IO_write_ptr > fp->_IO_write_base)
      39      return 0;
      40    return (fp->_IO_read_end - fp->_IO_read_ptr)
      41           + (fp->_flags & _IO_IN_BACKUP ? fp->_IO_save_end - fp->_IO_save_base :
      42              0);
      43  #elif defined __sferror || defined __DragonFly__ || defined __ANDROID__
      44    /* FreeBSD, NetBSD, OpenBSD, DragonFly, Mac OS X, Cygwin, Minix 3, Android */
      45    if ((fp_->_flags & __SWR) != 0 || fp_->_r < 0)
      46      return 0;
      47  # if defined __DragonFly__
      48    return __sreadahead (fp);
      49  # else
      50    return fp_->_r
      51           + (HASUB (fp) ? fp_->_ur : 0);
      52  # endif
      53  #elif defined __EMX__               /* emx+gcc */
      54    if ((fp->_flags & _IOWRT) != 0)
      55      return 0;
      56    /* Note: fp->_ungetc_count > 0 implies fp->_rcount <= 0,
      57             fp->_ungetc_count = 0 implies fp->_rcount >= 0.  */
      58    /* equivalent to
      59       (fp->_ungetc_count == 0 ? fp->_rcount : fp->_ungetc_count - fp->_rcount) */
      60    return (fp->_rcount > 0 ? fp->_rcount : fp->_ungetc_count - fp->_rcount);
      61  #elif defined __minix               /* Minix */
      62    if ((fp_->_flags & _IOWRITING) != 0)
      63      return 0;
      64    return fp_->_count;
      65  #elif defined _IOERR                /* AIX, HP-UX, IRIX, OSF/1, Solaris, OpenServer, UnixWare, mingw, MSVC, NonStop Kernel, OpenVMS */
      66    if ((fp_->_flag & _IOWRT) != 0)
      67      return 0;
      68    return fp_->_cnt;
      69  #elif defined __UCLIBC__            /* uClibc */
      70  # ifdef __STDIO_BUFFERS
      71    if (fp->__modeflags & __FLAG_WRITING)
      72      return 0;
      73    return (fp->__bufread - fp->__bufpos)
      74           + (fp->__modeflags & __FLAG_UNGOT ? 1 : 0);
      75  # else
      76    return 0;
      77  # endif
      78  #elif defined __QNX__               /* QNX */
      79    if ((fp->_Mode & 0x2000 /* _MWRITE */) != 0)
      80      return 0;
      81    /* fp->_Buf <= fp->_Next <= fp->_Rend,
      82       and fp->_Rend may be overridden by fp->_Rsave. */
      83    return ((fp->_Rsave ? fp->_Rsave : fp->_Rend) - fp->_Next)
      84           + (fp->_Mode & 0x4000 /* _MBYTE */
      85              ? (fp->_Back + sizeof (fp->_Back)) - fp->_Rback
      86              : 0);
      87  #elif defined __MINT__              /* Atari FreeMiNT */
      88    if (!fp->__mode.__read)
      89      return 0;
      90    return (fp->__pushed_back
      91            ? fp->__get_limit - fp->__pushback_bufp + 1
      92            : fp->__get_limit - fp->__bufp);
      93  #elif defined EPLAN9                /* Plan9 */
      94    if (fp->state == 4 /* WR */ || fp->rp >= fp->wp)
      95      return 0;
      96    return fp->wp - fp->rp;
      97  #elif defined SLOW_BUT_NO_HACKS     /* users can define this */
      98    abort ();
      99    return 0;
     100  #else
     101   #error "Please port gnulib freadahead.c to your platform! Look at the definition of fflush, fread, ungetc on your system, then report this to bug-gnulib."
     102  #endif
     103  }