1 /* 2 * Copyright (c) 1983 Regents of the University of California. 3 * All rights reserved. 4 * 5 * %sccs.include.redist.c% 6 */ 7 8 #if defined(LIBC_SCCS) && !defined(lint) 9 static char sccsid[] = "@(#)telldir.c 5.8 (Berkeley) 06/01/90"; 10 #endif /* LIBC_SCCS and not lint */ 11 12 #include <sys/param.h> 13 #include <dirent.h> 14 15 /* 16 * The option SINGLEUSE may be defined to say that a telldir 17 * cookie may be used only once before it is freed. This option 18 * is used to avoid having memory usage grow without bound. 19 */ 20 #define SINGLEUSE 21 22 /* 23 * One of these structures is malloced to describe the current directory 24 * position each time telldir is called. It records the current magic 25 * cookie returned by getdirentries and the offset within the buffer 26 * associated with that return value. 27 */ 28 struct ddloc { 29 struct ddloc *loc_next;/* next structure in list */ 30 long loc_index; /* key associated with structure */ 31 long loc_seek; /* magic cookie returned by getdirentries */ 32 long loc_loc; /* offset of entry in buffer */ 33 }; 34 35 #define NDIRHASH 32 /* Num of hash lists, must be a power of 2 */ 36 #define LOCHASH(i) ((i)&(NDIRHASH-1)) 37 38 static long dd_loccnt; /* Index of entry for sequential readdir's */ 39 static struct ddloc *dd_hash[NDIRHASH]; /* Hash list heads for ddlocs */ 40 41 /* 42 * return a pointer into a directory 43 */ 44 long 45 telldir(dirp) 46 DIR *dirp; 47 { 48 register int index; 49 register struct ddloc *lp; 50 51 if ((lp = (struct ddloc *)malloc(sizeof(struct ddloc))) == NULL) 52 return (-1); 53 index = dd_loccnt++; 54 lp->loc_index = index; 55 lp->loc_seek = dirp->dd_seek; 56 lp->loc_loc = dirp->dd_loc; 57 lp->loc_next = dd_hash[LOCHASH(index)]; 58 dd_hash[LOCHASH(index)] = lp; 59 return (index); 60 } 61 62 /* 63 * seek to an entry in a directory. 64 * Only values returned by "telldir" should be passed to seekdir. 65 */ 66 void 67 _seekdir(dirp, loc) 68 register DIR *dirp; 69 long loc; 70 { 71 register struct ddloc *lp; 72 register struct ddloc **prevlp; 73 struct dirent *dp; 74 extern long lseek(); 75 76 prevlp = &dd_hash[LOCHASH(loc)]; 77 lp = *prevlp; 78 while (lp != NULL) { 79 if (lp->loc_index == loc) 80 break; 81 prevlp = &lp->loc_next; 82 lp = lp->loc_next; 83 } 84 if (lp == NULL) 85 return; 86 if (lp->loc_loc == dirp->dd_loc && lp->loc_seek == dirp->dd_seek) 87 goto found; 88 (void) lseek(dirp->dd_fd, lp->loc_seek, 0); 89 dirp->dd_seek = lp->loc_seek; 90 dirp->dd_loc = 0; 91 while (dirp->dd_loc < lp->loc_loc) { 92 dp = readdir(dirp); 93 if (dp == NULL) 94 break; 95 } 96 found: 97 #ifdef SINGLEUSE 98 *prevlp = lp->loc_next; 99 free((caddr_t)lp); 100 #endif 101 } 102