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-rw-r--r--lib/lseek.c89
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diff --git a/lib/lseek.c b/lib/lseek.c
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+/* An lseek() function that detects pipes.
+ Copyright (C) 2007, 2009-2022 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 <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
+}