1 files changed, 89 insertions, 0 deletions

diff --git a/gl/lseek.c b/gl/lseek.c
new file mode 100644
index 00000000..e9a96ad2
--- /dev/null
+++ b/gl/lseek.c
@@ -0,0 +1,89 @@
+/* An lseek() function that detects pipes.
+   Copyright (C) 2007, 2009-2021 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 <unistd.h>
+
+#if defined _WIN32 && ! defined __CYGWIN__
+/* Windows platforms.  */
+/* Get GetFileType.  */
+# include <windows.h>
+/* Get _get_osfhandle.  */
+# if GNULIB_MSVC_NOTHROW
+#  include "msvc-nothrow.h"
+# else
+#  include <io.h>
+# endif
+#else
+# include <sys/stat.h>
+#endif
+#include <errno.h>
+
+#undef lseek
+
+off_t
+rpl_lseek (int fd, off_t offset, int whence)
+{
+#if defined _WIN32 && ! defined __CYGWIN__
+  /* mingw lseek mistakenly succeeds on pipes, sockets, and terminals.  */
+  HANDLE h = (HANDLE) _get_osfhandle (fd);
+  if (h == INVALID_HANDLE_VALUE)
+    {
+      errno = EBADF;
+      return -1;
+    }
+  if (GetFileType (h) != FILE_TYPE_DISK)
+    {
+      errno = ESPIPE;
+      return -1;
+    }
+#elif defined __APPLE__ && defined __MACH__ && defined SEEK_DATA
+  if (whence == SEEK_DATA)
+    {
+      /* If OFFSET points to data, macOS lseek+SEEK_DATA returns the
+         start S of the first data region that begins *after* OFFSET,
+         where the region from OFFSET to S consists of possibly-empty
+         data followed by a possibly-empty hole.  To work around this
+         portability glitch, check whether OFFSET is within data by
+         using lseek+SEEK_HOLE, and if so return to OFFSET by using
+         lseek+SEEK_SET.  Also, contrary to the macOS documentation,
+         lseek+SEEK_HOLE can fail with ENXIO if there are no holes on
+         or after OFFSET.  What a mess!  */
+      off_t next_hole = lseek (fd, offset, SEEK_HOLE);
+      if (next_hole < 0)
+        return errno == ENXIO ? offset : next_hole;
+      if (next_hole != offset)
+        whence = SEEK_SET;
+    }
+#else
+  /* BeOS lseek mistakenly succeeds on pipes...  */
+  struct stat statbuf;
+  if (fstat (fd, &statbuf) < 0)
+    return -1;
+  if (!S_ISREG (statbuf.st_mode))
+    {
+      errno = ESPIPE;
+      return -1;
+    }
+#endif
+#if _GL_WINDOWS_64_BIT_OFF_T || (defined __MINGW32__ && defined _FILE_OFFSET_BITS && (_FILE_OFFSET_BITS == 64))
+  return _lseeki64 (fd, offset, whence);
+#else
+  return lseek (fd, offset, whence);
+#endif
+}