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Annotation of src/lib/libc/gen/getcwd.c, Revision 1.6

1.6     ! christos    1: /*     $NetBSD: getcwd.c,v 1.5 1995/06/16 07:05:30 jtc Exp $   */
1.4       cgd         2:
1.1       cgd         3: /*
1.4       cgd         4:  * Copyright (c) 1989, 1991, 1993
                      5:  *     The Regents of the University of California.  All rights reserved.
1.1       cgd         6:  *
                      7:  * Redistribution and use in source and binary forms, with or without
                      8:  * modification, are permitted provided that the following conditions
                      9:  * are met:
                     10:  * 1. Redistributions of source code must retain the above copyright
                     11:  *    notice, this list of conditions and the following disclaimer.
                     12:  * 2. Redistributions in binary form must reproduce the above copyright
                     13:  *    notice, this list of conditions and the following disclaimer in the
                     14:  *    documentation and/or other materials provided with the distribution.
                     15:  * 3. All advertising materials mentioning features or use of this software
                     16:  *    must display the following acknowledgement:
                     17:  *     This product includes software developed by the University of
                     18:  *     California, Berkeley and its contributors.
                     19:  * 4. Neither the name of the University nor the names of its contributors
                     20:  *    may be used to endorse or promote products derived from this software
                     21:  *    without specific prior written permission.
                     22:  *
                     23:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
                     24:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
                     25:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
                     26:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
                     27:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
                     28:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
                     29:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
                     30:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
                     31:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
                     32:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
                     33:  * SUCH DAMAGE.
                     34:  */
                     35:
1.6     ! christos   36: #include <sys/cdefs.h>
1.1       cgd        37: #if defined(LIBC_SCCS) && !defined(lint)
1.4       cgd        38: #if 0
                     39: static char sccsid[] = "@(#)getcwd.c   8.1 (Berkeley) 6/4/93";
                     40: #else
1.6     ! christos   41: __RCSID("$NetBSD$");
1.4       cgd        42: #endif
1.1       cgd        43: #endif /* LIBC_SCCS and not lint */
                     44:
                     45: #include <sys/param.h>
                     46: #include <sys/stat.h>
1.4       cgd        47:
1.1       cgd        48: #include <errno.h>
                     49: #include <dirent.h>
                     50: #include <stdio.h>
                     51: #include <stdlib.h>
                     52: #include <string.h>
                     53: #include <unistd.h>
                     54:
                     55: #define        ISDOT(dp) \
                     56:        (dp->d_name[0] == '.' && (dp->d_name[1] == '\0' || \
1.6     ! christos   57:            (dp->d_name[1] == '.' && dp->d_name[2] == '\0')))
1.1       cgd        58:
                     59: char *
                     60: getcwd(pt, size)
                     61:        char *pt;
                     62:        size_t size;
                     63: {
                     64:        register struct dirent *dp;
                     65:        register DIR *dir;
                     66:        register dev_t dev;
                     67:        register ino_t ino;
                     68:        register int first;
                     69:        register char *bpt, *bup;
                     70:        struct stat s;
                     71:        dev_t root_dev;
                     72:        ino_t root_ino;
                     73:        size_t ptsize, upsize;
                     74:        int save_errno;
                     75:        char *ept, *eup, *up;
                     76:
                     77:        /*
                     78:         * If no buffer specified by the user, allocate one as necessary.
                     79:         * If a buffer is specified, the size has to be non-zero.  The path
                     80:         * is built from the end of the buffer backwards.
                     81:         */
                     82:        if (pt) {
                     83:                ptsize = 0;
                     84:                if (!size) {
                     85:                        errno = EINVAL;
1.4       cgd        86:                        return (NULL);
1.1       cgd        87:                }
                     88:                ept = pt + size;
                     89:        } else {
1.4       cgd        90:                if ((pt = malloc(ptsize = 1024 - 4)) == NULL)
                     91:                        return (NULL);
1.1       cgd        92:                ept = pt + ptsize;
                     93:        }
                     94:        bpt = ept - 1;
                     95:        *bpt = '\0';
                     96:
                     97:        /*
                     98:         * Allocate bytes (1024 - malloc space) for the string of "../"'s.
                     99:         * Should always be enough (it's 340 levels).  If it's not, allocate
                    100:         * as necessary.  Special * case the first stat, it's ".", not "..".
                    101:         */
1.4       cgd       102:        if ((up = malloc(upsize = 1024 - 4)) == NULL)
1.1       cgd       103:                goto err;
                    104:        eup = up + MAXPATHLEN;
                    105:        bup = up;
                    106:        up[0] = '.';
                    107:        up[1] = '\0';
                    108:
                    109:        /* Save root values, so know when to stop. */
                    110:        if (stat("/", &s))
                    111:                goto err;
                    112:        root_dev = s.st_dev;
                    113:        root_ino = s.st_ino;
                    114:
                    115:        errno = 0;                      /* XXX readdir has no error return. */
                    116:
                    117:        for (first = 1;; first = 0) {
                    118:                /* Stat the current level. */
                    119:                if (lstat(up, &s))
                    120:                        goto err;
                    121:
                    122:                /* Save current node values. */
                    123:                ino = s.st_ino;
                    124:                dev = s.st_dev;
                    125:
                    126:                /* Check for reaching root. */
                    127:                if (root_dev == dev && root_ino == ino) {
                    128:                        *--bpt = '/';
                    129:                        /*
                    130:                         * It's unclear that it's a requirement to copy the
                    131:                         * path to the beginning of the buffer, but it's always
                    132:                         * been that way and stuff would probably break.
                    133:                         */
1.5       jtc       134:                        bcopy(bpt, pt, ept - bpt);
1.1       cgd       135:                        free(up);
1.4       cgd       136:                        return (pt);
1.1       cgd       137:                }
                    138:
                    139:                /*
                    140:                 * Build pointer to the parent directory, allocating memory
                    141:                 * as necessary.  Max length is 3 for "../", the largest
                    142:                 * possible component name, plus a trailing NULL.
                    143:                 */
                    144:                if (bup + 3  + MAXNAMLEN + 1 >= eup) {
1.4       cgd       145:                        if ((up = realloc(up, upsize *= 2)) == NULL)
1.1       cgd       146:                                goto err;
1.4       cgd       147:                        bup = up;
1.1       cgd       148:                        eup = up + upsize;
                    149:                }
                    150:                *bup++ = '.';
                    151:                *bup++ = '.';
                    152:                *bup = '\0';
                    153:
                    154:                /* Open and stat parent directory. */
                    155:                if (!(dir = opendir(up)) || fstat(dirfd(dir), &s))
                    156:                        goto err;
                    157:
                    158:                /* Add trailing slash for next directory. */
                    159:                *bup++ = '/';
                    160:
                    161:                /*
                    162:                 * If it's a mount point, have to stat each element because
                    163:                 * the inode number in the directory is for the entry in the
                    164:                 * parent directory, not the inode number of the mounted file.
                    165:                 */
                    166:                save_errno = 0;
                    167:                if (s.st_dev == dev) {
                    168:                        for (;;) {
                    169:                                if (!(dp = readdir(dir)))
                    170:                                        goto notfound;
                    171:                                if (dp->d_fileno == ino)
                    172:                                        break;
                    173:                        }
                    174:                } else
                    175:                        for (;;) {
                    176:                                if (!(dp = readdir(dir)))
                    177:                                        goto notfound;
                    178:                                if (ISDOT(dp))
                    179:                                        continue;
                    180:                                bcopy(dp->d_name, bup, dp->d_namlen + 1);
                    181:
                    182:                                /* Save the first error for later. */
                    183:                                if (lstat(up, &s)) {
                    184:                                        if (!save_errno)
                    185:                                                save_errno = errno;
                    186:                                        errno = 0;
                    187:                                        continue;
                    188:                                }
                    189:                                if (s.st_dev == dev && s.st_ino == ino)
                    190:                                        break;
                    191:                        }
                    192:
                    193:                /*
                    194:                 * Check for length of the current name, preceding slash,
                    195:                 * leading slash.
                    196:                 */
                    197:                if (bpt - pt <= dp->d_namlen + (first ? 1 : 2)) {
                    198:                        size_t len, off;
                    199:
                    200:                        if (!ptsize) {
                    201:                                errno = ERANGE;
                    202:                                goto err;
                    203:                        }
                    204:                        off = bpt - pt;
                    205:                        len = ept - bpt;
1.4       cgd       206:                        if ((pt = realloc(pt, ptsize *= 2)) == NULL)
1.1       cgd       207:                                goto err;
                    208:                        bpt = pt + off;
                    209:                        ept = pt + ptsize;
1.5       jtc       210:                        bcopy(bpt, ept - len, len);
1.1       cgd       211:                        bpt = ept - len;
                    212:                }
                    213:                if (!first)
                    214:                        *--bpt = '/';
                    215:                bpt -= dp->d_namlen;
                    216:                bcopy(dp->d_name, bpt, dp->d_namlen);
                    217:                (void)closedir(dir);
                    218:
                    219:                /* Truncate any file name. */
                    220:                *bup = '\0';
                    221:        }
                    222:
                    223: notfound:
                    224:        /*
                    225:         * If readdir set errno, use it, not any saved error; otherwise,
                    226:         * didn't find the current directory in its parent directory, set
                    227:         * errno to ENOENT.
                    228:         */
                    229:        if (!errno)
                    230:                errno = save_errno ? save_errno : ENOENT;
                    231:        /* FALLTHROUGH */
                    232: err:
                    233:        if (ptsize)
                    234:                free(pt);
                    235:        free(up);
1.4       cgd       236:        return (NULL);
1.1       cgd       237: }

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