61 lines
1.9 KiB
C
61 lines
1.9 KiB
C
/* Read block from given position in file without changing file pointer.
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POSIX version.
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Copyright (C) 1997 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Library General Public License as
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published by the Free Software Foundation; either version 2 of the
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License, or (at your option) any later version.
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The GNU C Library 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 GNU
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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with the GNU C Library; see the file COPYING.LIB. If not,
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write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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Boston, MA 02111-1307, USA. */
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#include <errno.h>
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#include <unistd.h>
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ssize_t
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__pread64 (int fd, void *buf, size_t nbyte, off64_t offset)
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{
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/* Since we must not change the file pointer preserve the value so that
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we can restore it later. */
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int save_errno;
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ssize_t result;
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off64_t old_offset = lseek64 (fd, 0, SEEK_CUR);
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if (old_offset == (off64_t) -1)
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return -1;
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/* Set to wanted position. */
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if (lseek64 (fd, offset, SEEK_SET) == (off64_t) -1)
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return -1;
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/* Write out the data. */
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result = read (fd, buf, nbyte);
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/* Now we have to restore the position. If this fails we have to
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return this as an error. But if the writing also failed we
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return this error. */
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save_errno = errno;
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if (lseek64 (fd, old_offset, SEEK_SET) == (off64_t) -1)
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{
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if (result == -1)
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__set_errno (save_errno);
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return -1;
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}
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__set_errno (save_errno);
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return result;
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}
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#ifndef __pread64
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weak_alias (__pread64, pread64)
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#endif
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