90 lines
2.8 KiB
C
90 lines
2.8 KiB
C
/* An lseek() function that detects pipes.
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Copyright (C) 2007, 2009-2022 Free Software Foundation, Inc.
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This file is free software: you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as
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published by the Free Software Foundation; either version 2.1 of the
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License, or (at your option) any later version.
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This file is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>. */
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#include <config.h>
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/* Specification. */
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#include <unistd.h>
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#if defined _WIN32 && ! defined __CYGWIN__
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/* Windows platforms. */
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/* Get GetFileType. */
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# include <windows.h>
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/* Get _get_osfhandle. */
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# if GNULIB_MSVC_NOTHROW
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# include "msvc-nothrow.h"
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# else
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# include <io.h>
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# endif
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#else
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# include <sys/stat.h>
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#endif
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#include <errno.h>
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#undef lseek
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off_t
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rpl_lseek (int fd, off_t offset, int whence)
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{
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#if defined _WIN32 && ! defined __CYGWIN__
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/* mingw lseek mistakenly succeeds on pipes, sockets, and terminals. */
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HANDLE h = (HANDLE) _get_osfhandle (fd);
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if (h == INVALID_HANDLE_VALUE)
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{
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errno = EBADF;
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return -1;
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}
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if (GetFileType (h) != FILE_TYPE_DISK)
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{
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errno = ESPIPE;
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return -1;
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}
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#elif defined __APPLE__ && defined __MACH__ && defined SEEK_DATA
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if (whence == SEEK_DATA)
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{
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/* If OFFSET points to data, macOS lseek+SEEK_DATA returns the
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start S of the first data region that begins *after* OFFSET,
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where the region from OFFSET to S consists of possibly-empty
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data followed by a possibly-empty hole. To work around this
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portability glitch, check whether OFFSET is within data by
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using lseek+SEEK_HOLE, and if so return to OFFSET by using
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lseek+SEEK_SET. Also, contrary to the macOS documentation,
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lseek+SEEK_HOLE can fail with ENXIO if there are no holes on
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or after OFFSET. What a mess! */
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off_t next_hole = lseek (fd, offset, SEEK_HOLE);
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if (next_hole < 0)
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return errno == ENXIO ? offset : next_hole;
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if (next_hole != offset)
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whence = SEEK_SET;
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}
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#else
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/* BeOS lseek mistakenly succeeds on pipes... */
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struct stat statbuf;
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if (fstat (fd, &statbuf) < 0)
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return -1;
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if (!S_ISREG (statbuf.st_mode))
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{
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errno = ESPIPE;
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return -1;
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}
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#endif
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#if _GL_WINDOWS_64_BIT_OFF_T || (defined __MINGW32__ && defined _FILE_OFFSET_BITS && (_FILE_OFFSET_BITS == 64))
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return _lseeki64 (fd, offset, whence);
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#else
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return lseek (fd, offset, whence);
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#endif
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}
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