lib/freadptr.c

   1 /* Retrieve information about a FILE stream.
   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 "freadptr.h"
  21
  22 #include <stdlib.h>
  23
  24 #include "stdio-impl.h"
  25
  26 /* This file is not used on systems that have the __freadptr function,
  27    namely musl libc.  */
  28
  29 const char *
  30 freadptr (FILE *fp, size_t *sizep)
  31 {
  32   size_t size;
  33
  34   /* Keep this code in sync with freadahead!  */
  35 #if defined _IO_EOF_SEEN || defined _IO_ftrylockfile || __GNU_LIBRARY__ == 1
  36   /* GNU libc, BeOS, Haiku, Linux libc5 */
  37   if (fp->_IO_write_ptr > fp->_IO_write_base)
  38     return NULL;
  39   size = fp->_IO_read_end - fp->_IO_read_ptr;
  40   if (size == 0)
  41     return NULL;
  42   *sizep = size;
  43   return (const char *) fp->_IO_read_ptr;
  44 #elif defined __sferror || defined __DragonFly__ || defined __ANDROID__
  45   /* FreeBSD, NetBSD, OpenBSD, DragonFly, Mac OS X, Cygwin, Minix 3, Android */
  46   if ((fp_->_flags & __SWR) != 0 || fp_->_r < 0)
  47     return NULL;
  48   size = fp_->_r;
  49   if (size == 0)
  50     return NULL;
  51   *sizep = size;
  52   return (const char *) fp_->_p;
  53 #elif defined __EMX__               /* emx+gcc */
  54   if ((fp->_flags & _IOWRT) != 0)
  55     return NULL;
  56   /* Note: fp->_ungetc_count > 0 implies fp->_rcount <= 0,
  57            fp->_ungetc_count = 0 implies fp->_rcount >= 0.  */
  58   if (fp->_rcount <= 0)
  59     return NULL;
  60   if (!(fp->_ungetc_count == 0))
  61     abort ();
  62   *sizep = fp->_rcount;
  63   return fp->_ptr;
  64 #elif defined __minix               /* Minix */
  65   if ((fp_->_flags & _IOWRITING) != 0)
  66     return NULL;
  67   size = fp_->_count;
  68   if (size == 0)
  69     return NULL;
  70   *sizep = size;
  71   return (const char *) fp_->_ptr;
  72 #elif defined _IOERR                /* AIX, HP-UX, IRIX, OSF/1, Solaris, OpenServer, UnixWare, mingw, MSVC, NonStop Kernel, OpenVMS */
  73   if ((fp_->_flag & _IOWRT) != 0)
  74     return NULL;
  75   size = fp_->_cnt;
  76   if (size == 0)
  77     return NULL;
  78   *sizep = size;
  79   return (const char *) fp_->_ptr;
  80 #elif defined __UCLIBC__            /* uClibc */
  81 # ifdef __STDIO_BUFFERS
  82   if (fp->__modeflags & __FLAG_WRITING)
  83     return NULL;
  84   if (fp->__modeflags & __FLAG_UNGOT)
  85     return NULL;
  86   size = fp->__bufread - fp->__bufpos;
  87   if (size == 0)
  88     return NULL;
  89   *sizep = size;
  90   return (const char *) fp->__bufpos;
  91 # else
  92   return NULL;
  93 # endif
  94 #elif defined __QNX__               /* QNX */
  95   if ((fp->_Mode & 0x2000 /* _MWRITE */) != 0)
  96     return NULL;
  97   /* fp->_Buf <= fp->_Next <= fp->_Rend */
  98   size = fp->_Rend - fp->_Next;
  99   if (size == 0)
 100     return NULL;
 101   *sizep = size;
 102   return (const char *) fp->_Next;
 103 #elif defined __MINT__              /* Atari FreeMiNT */
 104   if (!fp->__mode.__read)
 105     return NULL;
 106   size = fp->__get_limit - fp->__bufp;
 107   if (size == 0)
 108     return NULL;
 109   *sizep = size;
 110   return fp->__bufp;
 111 #elif defined EPLAN9                /* Plan9 */
 112   if (fp->state == 4 /* WR */)
 113     return NULL;
 114   if (fp->rp >= fp->wp)
 115     return NULL;
 116   *sizep = fp->wp - fp->rp;
 117   return fp->rp;
 118 #elif defined SLOW_BUT_NO_HACKS     /* users can define this */
 119   /* This implementation is correct on any ANSI C platform.  It is just
 120      awfully slow.  */
 121   return NULL;
 122 #else
 123  #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."
 124 #endif
 125 }