lib/freadptr.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 "freadptr.h"
  21
  22 #include <stdlib.h>
  23
  24 #include "stdio-impl.h"
  25
  26 const char *
  27 freadptr (FILE *fp, size_t *sizep)
  28 {
  29   size_t size;
  30
  31   /* Keep this code in sync with freadahead!  */
  32 #if defined _IO_EOF_SEEN || __GNU_LIBRARY__ == 1 /* GNU libc, BeOS, Haiku, Linux libc5 */
  33   if (fp->_IO_write_ptr > fp->_IO_write_base)
  34     return NULL;
  35   size = fp->_IO_read_end - fp->_IO_read_ptr;
  36   if (size == 0)
  37     return NULL;
  38   *sizep = size;
  39   return (const char *) fp->_IO_read_ptr;
  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 NULL;
  44   size = fp_->_r;
  45   if (size == 0)
  46     return NULL;
  47   *sizep = size;
  48   return (const char *) fp_->_p;
  49 #elif defined __EMX__               /* emx+gcc */
  50   if ((fp->_flags & _IOWRT) != 0)
  51     return NULL;
  52   /* Note: fp->_ungetc_count > 0 implies fp->_rcount <= 0,
  53            fp->_ungetc_count = 0 implies fp->_rcount >= 0.  */
  54   if (fp->_rcount <= 0)
  55     return NULL;
  56   if (!(fp->_ungetc_count == 0))
  57     abort ();
  58   *sizep = fp->_rcount;
  59   return fp->_ptr;
  60 #elif defined __minix               /* Minix */
  61   if ((fp_->_flags & _IOWRITING) != 0)
  62     return NULL;
  63   size = fp_->_count;
  64   if (size == 0)
  65     return NULL;
  66   *sizep = size;
  67   return (const char *) fp_->_ptr;
  68 #elif defined _IOERR                /* AIX, HP-UX, IRIX, OSF/1, Solaris, OpenServer, mingw, MSVC, NonStop Kernel, OpenVMS */
  69   if ((fp_->_flag & _IOWRT) != 0)
  70     return NULL;
  71   size = fp_->_cnt;
  72   if (size == 0)
  73     return NULL;
  74   *sizep = size;
  75   return (const char *) fp_->_ptr;
  76 #elif defined __UCLIBC__            /* uClibc */
  77 # ifdef __STDIO_BUFFERS
  78   if (fp->__modeflags & __FLAG_WRITING)
  79     return NULL;
  80   if (fp->__modeflags & __FLAG_UNGOT)
  81     return NULL;
  82   size = fp->__bufread - fp->__bufpos;
  83   if (size == 0)
  84     return NULL;
  85   *sizep = size;
  86   return (const char *) fp->__bufpos;
  87 # else
  88   return NULL;
  89 # endif
  90 #elif defined __QNX__               /* QNX */
  91   if ((fp->_Mode & 0x2000 /* _MWRITE */) != 0)
  92     return NULL;
  93   /* fp->_Buf <= fp->_Next <= fp->_Rend */
  94   size = fp->_Rend - fp->_Next;
  95   if (size == 0)
  96     return NULL;
  97   *sizep = size;
  98   return (const char *) fp->_Next;
  99 #elif defined __MINT__              /* Atari FreeMiNT */
 100   if (!fp->__mode.__read)
 101     return NULL;
 102   size = fp->__get_limit - fp->__bufp;
 103   if (size == 0)
 104     return NULL;
 105   *sizep = size;
 106   return fp->__bufp;
 107 #elif defined EPLAN9                /* Plan9 */
 108   if (fp->state == 4 /* WR */)
 109     return NULL;
 110   if (fp->rp >= fp->wp)
 111     return NULL;
 112   *sizep = fp->wp - fp->rp;
 113   return fp->rp;
 114 #elif defined SLOW_BUT_NO_HACKS     /* users can define this */
 115   /* This implementation is correct on any ANSI C platform.  It is just
 116      awfully slow.  */
 117   return NULL;
 118 #else
 119  #error "Please port gnulib freadptr.c to your platform! Look at the definition of fflush, fread, getc, getc_unlocked on your system, then report this to bug-gnulib."
 120 #endif
 121 }