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/* $OpenBSD: seekdir.c,v 1.13 2015/09/12 13:34:22 guenther Exp $ */ |
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/* |
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* Copyright (c) 2013 Ingo Schwarze <schwarze@openbsd.org> |
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* |
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* Permission to use, copy, modify, and distribute this software for any |
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* purpose with or without fee is hereby granted, provided that the above |
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* copyright notice and this permission notice appear in all copies. |
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* |
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES |
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF |
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR |
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES |
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN |
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF |
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. |
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*/ |
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#include <dirent.h> |
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#include <unistd.h> |
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#include "thread_private.h" |
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#include "telldir.h" |
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/* |
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* Seek to an entry in a directory. |
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* Only values returned by "telldir" should be passed to seekdir. |
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*/ |
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void |
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seekdir(DIR *dirp, long loc) |
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{ |
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struct dirent *dp; |
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/* |
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* First check whether the directory entry to seek for |
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* is still buffered in the directory structure in memory. |
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*/ |
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_MUTEX_LOCK(&dirp->dd_lock); |
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if (dirp->dd_size && dirp->dd_bufpos == loc) { |
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dirp->dd_loc = 0; |
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dirp->dd_curpos = loc; |
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_MUTEX_UNLOCK(&dirp->dd_lock); |
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return; |
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} |
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for (dirp->dd_loc = 0; |
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dirp->dd_loc < dirp->dd_size; |
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dirp->dd_loc += dp->d_reclen) { |
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dp = (struct dirent *)(dirp->dd_buf + dirp->dd_loc); |
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if (dp->d_off != loc) |
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continue; |
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/* |
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* Entry found in the buffer, use it. If readdir(3) |
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* follows, this will save us a getdents(2) syscall. |
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* Note that d_off is the offset of the _next_ entry, |
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* so advance dd_loc. |
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*/ |
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dirp->dd_loc += dp->d_reclen; |
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dirp->dd_curpos = loc; |
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_MUTEX_UNLOCK(&dirp->dd_lock); |
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return; |
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} |
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/* |
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* The entry is not in the buffer, prepare a call to getdents(2). |
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* In particular, invalidate dd_loc. |
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*/ |
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dirp->dd_loc = dirp->dd_size; |
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dirp->dd_bufpos = dirp->dd_curpos = lseek(dirp->dd_fd, loc, SEEK_SET); |
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_MUTEX_UNLOCK(&dirp->dd_lock); |
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} |
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DEF_WEAK(seekdir); |