lib/freadahead.c

   1 /* Retrieve information about a FILE stream.
   2    Copyright (C) 2007-2018 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 General Public License as published by
   6    the Free Software Foundation; either version 3 of the License, or
   7    (at your option) 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 General Public License for more details.
  13
  14    You should have received a copy of the GNU 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 size_t
  31 freadahead (FILE *fp)
  32 {
  33 #if defined _IO_EOF_SEEN || defined _IO_ftrylockfile || __GNU_LIBRARY__ == 1
  34   /* GNU libc, BeOS, Haiku, Linux libc5 */
  35   if (fp->_IO_write_ptr > fp->_IO_write_base)
  36     return 0;
  37   return (fp->_IO_read_end - fp->_IO_read_ptr)
  38          + (fp->_flags & _IO_IN_BACKUP ? fp->_IO_save_end - fp->_IO_save_base :
  39             0);
  40 #elif defined __sferror || defined __DragonFly__ || defined __ANDROID__
  41   /* FreeBSD, NetBSD, OpenBSD, DragonFly, Mac OS X, Cygwin, Minix 3, Android */
  42   if ((fp_->_flags & __SWR) != 0 || fp_->_r < 0)
  43     return 0;
  44 # if defined __DragonFly__
  45   return __sreadahead (fp);
  46 # else
  47   return fp_->_r
  48          + (HASUB (fp) ? fp_->_ur : 0);
  49 # endif
  50 #elif defined __EMX__               /* emx+gcc */
  51   if ((fp->_flags & _IOWRT) != 0)
  52     return 0;
  53   /* Note: fp->_ungetc_count > 0 implies fp->_rcount <= 0,
  54            fp->_ungetc_count = 0 implies fp->_rcount >= 0.  */
  55   /* equivalent to
  56      (fp->_ungetc_count == 0 ? fp->_rcount : fp->_ungetc_count - fp->_rcount) */
  57   return (fp->_rcount > 0 ? fp->_rcount : fp->_ungetc_count - fp->_rcount);
  58 #elif defined __minix               /* Minix */
  59   if ((fp_->_flags & _IOWRITING) != 0)
  60     return 0;
  61   return fp_->_count;
  62 #elif defined _IOERR                /* AIX, HP-UX, IRIX, OSF/1, Solaris, OpenServer, mingw, MSVC, NonStop Kernel, OpenVMS */
  63   if ((fp_->_flag & _IOWRT) != 0)
  64     return 0;
  65   return fp_->_cnt;
  66 #elif defined __UCLIBC__            /* uClibc */
  67 # ifdef __STDIO_BUFFERS
  68   if (fp->__modeflags & __FLAG_WRITING)
  69     return 0;
  70   return (fp->__bufread - fp->__bufpos)
  71          + (fp->__modeflags & __FLAG_UNGOT ? 1 : 0);
  72 # else
  73   return 0;
  74 # endif
  75 #elif defined __QNX__               /* QNX */
  76   if ((fp->_Mode & 0x2000 /* _MWRITE */) != 0)
  77     return 0;
  78   /* fp->_Buf <= fp->_Next <= fp->_Rend,
  79      and fp->_Rend may be overridden by fp->_Rsave. */
  80   return ((fp->_Rsave ? fp->_Rsave : fp->_Rend) - fp->_Next)
  81          + (fp->_Mode & 0x4000 /* _MBYTE */
  82             ? (fp->_Back + sizeof (fp->_Back)) - fp->_Rback
  83             : 0);
  84 #elif defined __MINT__              /* Atari FreeMiNT */
  85   if (!fp->__mode.__read)
  86     return 0;
  87   return (fp->__pushed_back
  88           ? fp->__get_limit - fp->__pushback_bufp + 1
  89           : fp->__get_limit - fp->__bufp);
  90 #elif defined EPLAN9                /* Plan9 */
  91   if (fp->state == 4 /* WR */ || fp->rp >= fp->wp)
  92     return 0;
  93   return fp->wp - fp->rp;
  94 #elif defined SLOW_BUT_NO_HACKS     /* users can define this */
  95   abort ();
  96   return 0;
  97 #else
  98  #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."
  99 #endif
 100 }