Annotation of src/lib/libc/gen/getcwd.c, Revision 1.1
1.1 ! cgd 1: /*
! 2: * Copyright (c) 1989, 1991 The Regents of the University of California.
! 3: * All rights reserved.
! 4: *
! 5: * Redistribution and use in source and binary forms, with or without
! 6: * modification, are permitted provided that the following conditions
! 7: * are met:
! 8: * 1. Redistributions of source code must retain the above copyright
! 9: * notice, this list of conditions and the following disclaimer.
! 10: * 2. Redistributions in binary form must reproduce the above copyright
! 11: * notice, this list of conditions and the following disclaimer in the
! 12: * documentation and/or other materials provided with the distribution.
! 13: * 3. All advertising materials mentioning features or use of this software
! 14: * must display the following acknowledgement:
! 15: * This product includes software developed by the University of
! 16: * California, Berkeley and its contributors.
! 17: * 4. Neither the name of the University nor the names of its contributors
! 18: * may be used to endorse or promote products derived from this software
! 19: * without specific prior written permission.
! 20: *
! 21: * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
! 22: * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
! 23: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
! 24: * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
! 25: * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
! 26: * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
! 27: * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
! 28: * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
! 29: * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
! 30: * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
! 31: * SUCH DAMAGE.
! 32: */
! 33:
! 34: #if defined(LIBC_SCCS) && !defined(lint)
! 35: static char sccsid[] = "@(#)getcwd.c 5.11 (Berkeley) 2/24/91";
! 36: #endif /* LIBC_SCCS and not lint */
! 37:
! 38: #include <sys/param.h>
! 39: #include <sys/stat.h>
! 40: #include <errno.h>
! 41: #include <dirent.h>
! 42: #include <stdio.h>
! 43: #include <stdlib.h>
! 44: #include <string.h>
! 45: #include <unistd.h>
! 46:
! 47: #define ISDOT(dp) \
! 48: (dp->d_name[0] == '.' && (dp->d_name[1] == '\0' || \
! 49: dp->d_name[1] == '.' && dp->d_name[2] == '\0'))
! 50:
! 51: char *
! 52: getcwd(pt, size)
! 53: char *pt;
! 54: size_t size;
! 55: {
! 56: register struct dirent *dp;
! 57: register DIR *dir;
! 58: register dev_t dev;
! 59: register ino_t ino;
! 60: register int first;
! 61: register char *bpt, *bup;
! 62: struct stat s;
! 63: dev_t root_dev;
! 64: ino_t root_ino;
! 65: size_t ptsize, upsize;
! 66: int save_errno;
! 67: char *ept, *eup, *up;
! 68:
! 69: /*
! 70: * If no buffer specified by the user, allocate one as necessary.
! 71: * If a buffer is specified, the size has to be non-zero. The path
! 72: * is built from the end of the buffer backwards.
! 73: */
! 74: if (pt) {
! 75: ptsize = 0;
! 76: if (!size) {
! 77: errno = EINVAL;
! 78: return((char *)NULL);
! 79: }
! 80: ept = pt + size;
! 81: } else {
! 82: if (!(pt = (char *)malloc(ptsize = 1024 - 4)))
! 83: return((char *)NULL);
! 84: ept = pt + ptsize;
! 85: }
! 86: bpt = ept - 1;
! 87: *bpt = '\0';
! 88:
! 89: /*
! 90: * Allocate bytes (1024 - malloc space) for the string of "../"'s.
! 91: * Should always be enough (it's 340 levels). If it's not, allocate
! 92: * as necessary. Special * case the first stat, it's ".", not "..".
! 93: */
! 94: if (!(up = (char *)malloc(upsize = 1024 - 4)))
! 95: goto err;
! 96: eup = up + MAXPATHLEN;
! 97: bup = up;
! 98: up[0] = '.';
! 99: up[1] = '\0';
! 100:
! 101: /* Save root values, so know when to stop. */
! 102: if (stat("/", &s))
! 103: goto err;
! 104: root_dev = s.st_dev;
! 105: root_ino = s.st_ino;
! 106:
! 107: errno = 0; /* XXX readdir has no error return. */
! 108:
! 109: for (first = 1;; first = 0) {
! 110: /* Stat the current level. */
! 111: if (lstat(up, &s))
! 112: goto err;
! 113:
! 114: /* Save current node values. */
! 115: ino = s.st_ino;
! 116: dev = s.st_dev;
! 117:
! 118: /* Check for reaching root. */
! 119: if (root_dev == dev && root_ino == ino) {
! 120: *--bpt = '/';
! 121: /*
! 122: * It's unclear that it's a requirement to copy the
! 123: * path to the beginning of the buffer, but it's always
! 124: * been that way and stuff would probably break.
! 125: */
! 126: (void)bcopy(bpt, pt, ept - bpt);
! 127: free(up);
! 128: return(pt);
! 129: }
! 130:
! 131: /*
! 132: * Build pointer to the parent directory, allocating memory
! 133: * as necessary. Max length is 3 for "../", the largest
! 134: * possible component name, plus a trailing NULL.
! 135: */
! 136: if (bup + 3 + MAXNAMLEN + 1 >= eup) {
! 137: if (!(up = (char *)realloc(up, upsize *= 2)))
! 138: goto err;
! 139: eup = up + upsize;
! 140: }
! 141: *bup++ = '.';
! 142: *bup++ = '.';
! 143: *bup = '\0';
! 144:
! 145: /* Open and stat parent directory. */
! 146: if (!(dir = opendir(up)) || fstat(dirfd(dir), &s))
! 147: goto err;
! 148:
! 149: /* Add trailing slash for next directory. */
! 150: *bup++ = '/';
! 151:
! 152: /*
! 153: * If it's a mount point, have to stat each element because
! 154: * the inode number in the directory is for the entry in the
! 155: * parent directory, not the inode number of the mounted file.
! 156: */
! 157: save_errno = 0;
! 158: if (s.st_dev == dev) {
! 159: for (;;) {
! 160: if (!(dp = readdir(dir)))
! 161: goto notfound;
! 162: if (dp->d_fileno == ino)
! 163: break;
! 164: }
! 165: } else
! 166: for (;;) {
! 167: if (!(dp = readdir(dir)))
! 168: goto notfound;
! 169: if (ISDOT(dp))
! 170: continue;
! 171: bcopy(dp->d_name, bup, dp->d_namlen + 1);
! 172:
! 173: /* Save the first error for later. */
! 174: if (lstat(up, &s)) {
! 175: if (!save_errno)
! 176: save_errno = errno;
! 177: errno = 0;
! 178: continue;
! 179: }
! 180: if (s.st_dev == dev && s.st_ino == ino)
! 181: break;
! 182: }
! 183:
! 184: /*
! 185: * Check for length of the current name, preceding slash,
! 186: * leading slash.
! 187: */
! 188: if (bpt - pt <= dp->d_namlen + (first ? 1 : 2)) {
! 189: size_t len, off;
! 190:
! 191: if (!ptsize) {
! 192: errno = ERANGE;
! 193: goto err;
! 194: }
! 195: off = bpt - pt;
! 196: len = ept - bpt;
! 197: if (!(pt = (char *)realloc(pt, ptsize *= 2)))
! 198: goto err;
! 199: bpt = pt + off;
! 200: ept = pt + ptsize;
! 201: (void)bcopy(bpt, ept - len, len);
! 202: bpt = ept - len;
! 203: }
! 204: if (!first)
! 205: *--bpt = '/';
! 206: bpt -= dp->d_namlen;
! 207: bcopy(dp->d_name, bpt, dp->d_namlen);
! 208: (void)closedir(dir);
! 209:
! 210: /* Truncate any file name. */
! 211: *bup = '\0';
! 212: }
! 213:
! 214: notfound:
! 215: /*
! 216: * If readdir set errno, use it, not any saved error; otherwise,
! 217: * didn't find the current directory in its parent directory, set
! 218: * errno to ENOENT.
! 219: */
! 220: if (!errno)
! 221: errno = save_errno ? save_errno : ENOENT;
! 222: /* FALLTHROUGH */
! 223: err:
! 224: if (ptsize)
! 225: free(pt);
! 226: free(up);
! 227: return((char *)NULL);
! 228: }
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