1 /* 2 * Copyright (c) 1983 Regents of the University of California. 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms are permitted 6 * provided that the above copyright notice and this paragraph are 7 * duplicated in all such forms and that any documentation, 8 * advertising materials, and other materials related to such 9 * distribution and use acknowledge that the software was developed 10 * by the University of California, Berkeley. The name of the 11 * University may not be used to endorse or promote products derived 12 * from this software without specific prior written permission. 13 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR 14 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED 15 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE. 16 */ 17 18 #if defined(LIBC_SCCS) && !defined(lint) 19 static char sccsid[] = "@(#)telldir.c 5.6 (Berkeley) 07/11/89"; 20 #endif /* LIBC_SCCS and not lint */ 21 22 #include <sys/param.h> 23 #include <dirent.h> 24 25 /* 26 * The option SINGLEUSE may be defined to say that a telldir 27 * cookie may be used only once before it is freed. This option 28 * is used to avoid having memory usage grow without bound. 29 */ 30 #define SINGLEUSE 31 32 /* 33 * One of these structures is malloced to describe the current directory 34 * position each time telldir is called. It records the current magic 35 * cookie returned by getdirentries and the offset within the buffer 36 * associated with that return value. 37 */ 38 struct ddloc { 39 struct ddloc *loc_next;/* next structure in list */ 40 long loc_index; /* key associated with structure */ 41 long loc_seek; /* magic cookie returned by getdirentries */ 42 long loc_loc; /* offset of entry in buffer */ 43 }; 44 45 #define NDIRHASH 32 /* Num of hash lists, must be a power of 2 */ 46 #define LOCHASH(i) ((i)&(NDIRHASH-1)) 47 48 static long dd_loccnt; /* Index of entry for sequential readdir's */ 49 static struct ddloc *dd_hash[NDIRHASH]; /* Hash list heads for ddlocs */ 50 51 /* 52 * return a pointer into a directory 53 */ 54 long 55 telldir(dirp) 56 DIR *dirp; 57 { 58 register int index; 59 register struct ddloc *lp; 60 61 if ((lp = (struct ddloc *)malloc(sizeof(struct ddloc))) == NULL) 62 return (-1); 63 index = dd_loccnt++; 64 lp->loc_index = index; 65 lp->loc_seek = dirp->dd_seek; 66 lp->loc_loc = dirp->dd_loc; 67 lp->loc_next = dd_hash[LOCHASH(index)]; 68 dd_hash[LOCHASH(index)] = lp; 69 return (index); 70 } 71 72 /* 73 * seek to an entry in a directory. 74 * Only values returned by "telldir" should be passed to seekdir. 75 */ 76 void 77 _seekdir(dirp, loc) 78 register DIR *dirp; 79 long loc; 80 { 81 register struct ddloc *lp; 82 register struct ddloc **prevlp; 83 struct dirent *dp; 84 extern long lseek(); 85 86 prevlp = &dd_hash[LOCHASH(loc)]; 87 lp = *prevlp; 88 while (lp != NULL) { 89 if (lp->loc_index == loc) 90 break; 91 prevlp = &lp->loc_next; 92 lp = lp->loc_next; 93 } 94 if (lp == NULL) 95 return; 96 if (lp->loc_loc == dirp->dd_loc && lp->loc_seek == dirp->dd_seek) 97 goto found; 98 (void) lseek(dirp->dd_fd, lp->loc_seek, 0); 99 dirp->dd_loc = 0; 100 while (dirp->dd_loc < lp->loc_loc) { 101 dp = readdir(dirp); 102 if (dp == NULL) 103 break; 104 } 105 found: 106 #ifdef SINGLEUSE 107 *prevlp = lp->loc_next; 108 free((caddr_t)lp); 109 #endif 110 } 111