| 1 | /* |
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| 2 | * Copyright (c) 1983 Regents of the University of California. |
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| 3 | * All rights reserved. |
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| 4 | * |
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| 5 | * Redistribution and use in source and binary forms, with or without |
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| 6 | * modification, are permitted provided that the following conditions |
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| 7 | * are met: |
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| 8 | * 1. Redistributions of source code must retain the above copyright |
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| 9 | * notice, this list of conditions and the following disclaimer. |
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| 10 | * 2. Redistributions in binary form must reproduce the above copyright |
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| 11 | * notice, this list of conditions and the following disclaimer in the |
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| 12 | * documentation and/or other materials provided with the distribution. |
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| 13 | * 3. All advertising materials mentioning features or use of this software |
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| 14 | * must display the following acknowledgement: |
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| 15 | * This product includes software developed by the University of |
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| 16 | * California, Berkeley and its contributors. |
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| 17 | * 4. Neither the name of the University nor the names of its contributors |
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| 18 | * may be used to endorse or promote products derived from this software |
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| 19 | * without specific prior written permission. |
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| 20 | * |
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| 21 | * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND |
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| 22 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
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| 23 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
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| 24 | * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE |
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| 25 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
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| 26 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
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| 27 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
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| 28 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
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| 29 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
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| 30 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
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| 31 | * SUCH DAMAGE. |
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| 32 | */ |
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| 33 | |
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| 34 | #if defined(LIBC_SCCS) && !defined(lint) |
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| 35 | static char sccsid[] = "@(#)telldir.c 5.9 (Berkeley) 2/23/91"; |
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| 36 | #endif /* LIBC_SCCS and not lint */ |
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| 37 | |
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| 38 | #include <sys/param.h> |
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| 39 | #include <dirent.h> |
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| 40 | #include <stdlib.h> |
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| 41 | #include <unistd.h> |
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| 42 | |
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| 43 | /* |
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| 44 | * The option SINGLEUSE may be defined to say that a telldir |
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| 45 | * cookie may be used only once before it is freed. This option |
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| 46 | * is used to avoid having memory usage grow without bound. |
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| 47 | */ |
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| 48 | #define SINGLEUSE |
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| 49 | |
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| 50 | /* |
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| 51 | * One of these structures is malloced to describe the current directory |
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| 52 | * position each time telldir is called. It records the current magic |
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| 53 | * cookie returned by getdirentries and the offset within the buffer |
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| 54 | * associated with that return value. |
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| 55 | */ |
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| 56 | struct ddloc { |
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| 57 | struct ddloc *loc_next;/* next structure in list */ |
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| 58 | long loc_index; /* key associated with structure */ |
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| 59 | long loc_seek; /* magic cookie returned by getdirentries */ |
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| 60 | long loc_loc; /* offset of entry in buffer */ |
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| 61 | }; |
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| 62 | |
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| 63 | #define NDIRHASH 32 /* Num of hash lists, must be a power of 2 */ |
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| 64 | #define LOCHASH(i) ((i)&(NDIRHASH-1)) |
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| 65 | |
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| 66 | static long dd_loccnt; /* Index of entry for sequential readdir's */ |
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| 67 | static struct ddloc *dd_hash[NDIRHASH]; /* Hash list heads for ddlocs */ |
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| 68 | |
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| 69 | /* |
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| 70 | * return a pointer into a directory |
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| 71 | */ |
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| 72 | long |
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| 73 | telldir(dirp) |
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| 74 | const DIR *dirp; |
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| 75 | { |
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| 76 | register int index; |
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| 77 | register struct ddloc *lp; |
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| 78 | |
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| 79 | if ((lp = (struct ddloc *)malloc(sizeof(struct ddloc))) == NULL) |
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| 80 | return (-1); |
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| 81 | index = dd_loccnt++; |
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| 82 | lp->loc_index = index; |
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| 83 | lp->loc_seek = dirp->dd_seek; |
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| 84 | lp->loc_loc = dirp->dd_loc; |
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| 85 | lp->loc_next = dd_hash[LOCHASH(index)]; |
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| 86 | dd_hash[LOCHASH(index)] = lp; |
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| 87 | return (index); |
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| 88 | } |
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| 89 | |
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| 90 | /* |
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| 91 | * seek to an entry in a directory. |
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| 92 | * Only values returned by "telldir" should be passed to seekdir. |
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| 93 | */ |
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| 94 | void |
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| 95 | _seekdir(dirp, loc) |
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| 96 | register DIR *dirp; |
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| 97 | long loc; |
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| 98 | { |
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| 99 | register struct ddloc *lp; |
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| 100 | register struct ddloc **prevlp; |
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| 101 | struct dirent *dp; |
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| 102 | extern long lseek(); |
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| 103 | |
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| 104 | prevlp = &dd_hash[LOCHASH(loc)]; |
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| 105 | lp = *prevlp; |
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| 106 | while (lp != NULL) { |
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| 107 | if (lp->loc_index == loc) |
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| 108 | break; |
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| 109 | prevlp = &lp->loc_next; |
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| 110 | lp = lp->loc_next; |
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| 111 | } |
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| 112 | if (lp == NULL) |
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| 113 | return; |
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| 114 | if (lp->loc_loc == dirp->dd_loc && lp->loc_seek == dirp->dd_seek) |
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| 115 | goto found; |
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| 116 | (void) lseek(dirp->dd_fd, lp->loc_seek, 0); |
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| 117 | dirp->dd_seek = lp->loc_seek; |
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| 118 | dirp->dd_loc = 0; |
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| 119 | while (dirp->dd_loc < lp->loc_loc) { |
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| 120 | dp = readdir(dirp); |
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| 121 | if (dp == NULL) |
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| 122 | break; |
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| 123 | } |
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| 124 | found: |
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| 125 | #ifdef SINGLEUSE |
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| 126 | *prevlp = lp->loc_next; |
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| 127 | free((caddr_t)lp); |
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| 128 | #endif |
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| 129 | } |
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