1 files changed, 103 insertions, 0 deletions
diff --git a/lib/freadahead.c b/lib/freadahead.c
new file mode 100644
index 0000000..829d03b
--- /dev/null
+++ b/lib/freadahead.c
@@ -0,0 +1,103 @@
+/* Retrieve information about a FILE stream.
+   Copyright (C) 2007-2022 Free Software Foundation, Inc.
+
+   This file is free software: you can redistribute it and/or modify
+   it under the terms of the GNU Lesser General Public License as
+   published by the Free Software Foundation; either version 2.1 of the
+   License, or (at your option) any later version.
+
+   This file is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
+
+#include <config.h>
+
+/* Specification.  */
+#include "freadahead.h"
+
+#include <stdlib.h>
+#include "stdio-impl.h"
+
+#if defined __DragonFly__
+/* Defined in libc, but not declared in <stdio.h>.  */
+extern size_t __sreadahead (FILE *);
+#endif
+
+/* This file is not used on systems that have the __freadahead function,
+   namely musl libc.  */
+
+size_t
+freadahead (FILE *fp)
+{
+#if defined _IO_EOF_SEEN || defined _IO_ftrylockfile || __GNU_LIBRARY__ == 1
+  /* GNU libc, BeOS, Haiku, Linux libc5 */
+  if (fp->_IO_write_ptr > fp->_IO_write_base)
+    return 0;
+  return (fp->_IO_read_end - fp->_IO_read_ptr)
+         + (fp->_flags & _IO_IN_BACKUP ? fp->_IO_save_end - fp->_IO_save_base :
+            0);
+#elif defined __sferror || defined __DragonFly__ || defined __ANDROID__
+  /* FreeBSD, NetBSD, OpenBSD, DragonFly, Mac OS X, Cygwin, Minix 3, Android */
+  if ((fp_->_flags & __SWR) != 0 || fp_->_r < 0)
+    return 0;
+# if defined __DragonFly__
+  return __sreadahead (fp);
+# else
+  return fp_->_r
+         + (HASUB (fp) ? fp_->_ur : 0);
+# endif
+#elif defined __EMX__               /* emx+gcc */
+  if ((fp->_flags & _IOWRT) != 0)
+    return 0;
+  /* Note: fp->_ungetc_count > 0 implies fp->_rcount <= 0,
+           fp->_ungetc_count = 0 implies fp->_rcount >= 0.  */
+  /* equivalent to
+     (fp->_ungetc_count == 0 ? fp->_rcount : fp->_ungetc_count - fp->_rcount) */
+  return (fp->_rcount > 0 ? fp->_rcount : fp->_ungetc_count - fp->_rcount);
+#elif defined __minix               /* Minix */
+  if ((fp_->_flags & _IOWRITING) != 0)
+    return 0;
+  return fp_->_count;
+#elif defined _IOERR                /* AIX, HP-UX, IRIX, OSF/1, Solaris, OpenServer, UnixWare, mingw, MSVC, NonStop Kernel, OpenVMS */
+  if ((fp_->_flag & _IOWRT) != 0)
+    return 0;
+  return fp_->_cnt;
+#elif defined __UCLIBC__            /* uClibc */
+# ifdef __STDIO_BUFFERS
+  if (fp->__modeflags & __FLAG_WRITING)
+    return 0;
+  return (fp->__bufread - fp->__bufpos)
+         + (fp->__modeflags & __FLAG_UNGOT ? 1 : 0);
+# else
+  return 0;
+# endif
+#elif defined __QNX__               /* QNX */
+  if ((fp->_Mode & 0x2000 /* _MWRITE */) != 0)
+    return 0;
+  /* fp->_Buf <= fp->_Next <= fp->_Rend,
+     and fp->_Rend may be overridden by fp->_Rsave. */
+  return ((fp->_Rsave ? fp->_Rsave : fp->_Rend) - fp->_Next)
+         + (fp->_Mode & 0x4000 /* _MBYTE */
+            ? (fp->_Back + sizeof (fp->_Back)) - fp->_Rback
+            : 0);
+#elif defined __MINT__              /* Atari FreeMiNT */
+  if (!fp->__mode.__read)
+    return 0;
+  return (fp->__pushed_back
+          ? fp->__get_limit - fp->__pushback_bufp + 1
+          : fp->__get_limit - fp->__bufp);
+#elif defined EPLAN9                /* Plan9 */
+  if (fp->state == 4 /* WR */ || fp->rp >= fp->wp)
+    return 0;
+  return fp->wp - fp->rp;
+#elif defined SLOW_BUT_NO_HACKS     /* users can define this */
+  abort ();
+  return 0;
+#else
+ #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."
+#endif
+}