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Annotation of src/lib/libc/gen/getcwd.c, Revision 1.5

1.5     ! jtc         1: /*     $NetBSD: getcwd.c,v 1.4 1995/02/27 04:12:20 cgd 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:
                     36: #if defined(LIBC_SCCS) && !defined(lint)
1.4       cgd        37: #if 0
                     38: static char sccsid[] = "@(#)getcwd.c   8.1 (Berkeley) 6/4/93";
                     39: #else
1.5     ! jtc        40: static char rcsid[] = "$NetBSD: getcwd.c,v 1.4 1995/02/27 04:12:20 cgd Exp $";
1.4       cgd        41: #endif
1.1       cgd        42: #endif /* LIBC_SCCS and not lint */
                     43:
                     44: #include <sys/param.h>
                     45: #include <sys/stat.h>
1.4       cgd        46:
1.1       cgd        47: #include <errno.h>
                     48: #include <dirent.h>
                     49: #include <stdio.h>
                     50: #include <stdlib.h>
                     51: #include <string.h>
                     52: #include <unistd.h>
                     53:
                     54: #define        ISDOT(dp) \
                     55:        (dp->d_name[0] == '.' && (dp->d_name[1] == '\0' || \
                     56:            dp->d_name[1] == '.' && dp->d_name[2] == '\0'))
                     57:
                     58: char *
                     59: getcwd(pt, size)
                     60:        char *pt;
                     61:        size_t size;
                     62: {
                     63:        register struct dirent *dp;
                     64:        register DIR *dir;
                     65:        register dev_t dev;
                     66:        register ino_t ino;
                     67:        register int first;
                     68:        register char *bpt, *bup;
                     69:        struct stat s;
                     70:        dev_t root_dev;
                     71:        ino_t root_ino;
                     72:        size_t ptsize, upsize;
                     73:        int save_errno;
                     74:        char *ept, *eup, *up;
                     75:
                     76:        /*
                     77:         * If no buffer specified by the user, allocate one as necessary.
                     78:         * If a buffer is specified, the size has to be non-zero.  The path
                     79:         * is built from the end of the buffer backwards.
                     80:         */
                     81:        if (pt) {
                     82:                ptsize = 0;
                     83:                if (!size) {
                     84:                        errno = EINVAL;
1.4       cgd        85:                        return (NULL);
1.1       cgd        86:                }
                     87:                ept = pt + size;
                     88:        } else {
1.4       cgd        89:                if ((pt = malloc(ptsize = 1024 - 4)) == NULL)
                     90:                        return (NULL);
1.1       cgd        91:                ept = pt + ptsize;
                     92:        }
                     93:        bpt = ept - 1;
                     94:        *bpt = '\0';
                     95:
                     96:        /*
                     97:         * Allocate bytes (1024 - malloc space) for the string of "../"'s.
                     98:         * Should always be enough (it's 340 levels).  If it's not, allocate
                     99:         * as necessary.  Special * case the first stat, it's ".", not "..".
                    100:         */
1.4       cgd       101:        if ((up = malloc(upsize = 1024 - 4)) == NULL)
1.1       cgd       102:                goto err;
                    103:        eup = up + MAXPATHLEN;
                    104:        bup = up;
                    105:        up[0] = '.';
                    106:        up[1] = '\0';
                    107:
                    108:        /* Save root values, so know when to stop. */
                    109:        if (stat("/", &s))
                    110:                goto err;
                    111:        root_dev = s.st_dev;
                    112:        root_ino = s.st_ino;
                    113:
                    114:        errno = 0;                      /* XXX readdir has no error return. */
                    115:
                    116:        for (first = 1;; first = 0) {
                    117:                /* Stat the current level. */
                    118:                if (lstat(up, &s))
                    119:                        goto err;
                    120:
                    121:                /* Save current node values. */
                    122:                ino = s.st_ino;
                    123:                dev = s.st_dev;
                    124:
                    125:                /* Check for reaching root. */
                    126:                if (root_dev == dev && root_ino == ino) {
                    127:                        *--bpt = '/';
                    128:                        /*
                    129:                         * It's unclear that it's a requirement to copy the
                    130:                         * path to the beginning of the buffer, but it's always
                    131:                         * been that way and stuff would probably break.
                    132:                         */
1.5     ! jtc       133:                        bcopy(bpt, pt, ept - bpt);
1.1       cgd       134:                        free(up);
1.4       cgd       135:                        return (pt);
1.1       cgd       136:                }
                    137:
                    138:                /*
                    139:                 * Build pointer to the parent directory, allocating memory
                    140:                 * as necessary.  Max length is 3 for "../", the largest
                    141:                 * possible component name, plus a trailing NULL.
                    142:                 */
                    143:                if (bup + 3  + MAXNAMLEN + 1 >= eup) {
1.4       cgd       144:                        if ((up = realloc(up, upsize *= 2)) == NULL)
1.1       cgd       145:                                goto err;
1.4       cgd       146:                        bup = up;
1.1       cgd       147:                        eup = up + upsize;
                    148:                }
                    149:                *bup++ = '.';
                    150:                *bup++ = '.';
                    151:                *bup = '\0';
                    152:
                    153:                /* Open and stat parent directory. */
                    154:                if (!(dir = opendir(up)) || fstat(dirfd(dir), &s))
                    155:                        goto err;
                    156:
                    157:                /* Add trailing slash for next directory. */
                    158:                *bup++ = '/';
                    159:
                    160:                /*
                    161:                 * If it's a mount point, have to stat each element because
                    162:                 * the inode number in the directory is for the entry in the
                    163:                 * parent directory, not the inode number of the mounted file.
                    164:                 */
                    165:                save_errno = 0;
                    166:                if (s.st_dev == dev) {
                    167:                        for (;;) {
                    168:                                if (!(dp = readdir(dir)))
                    169:                                        goto notfound;
                    170:                                if (dp->d_fileno == ino)
                    171:                                        break;
                    172:                        }
                    173:                } else
                    174:                        for (;;) {
                    175:                                if (!(dp = readdir(dir)))
                    176:                                        goto notfound;
                    177:                                if (ISDOT(dp))
                    178:                                        continue;
                    179:                                bcopy(dp->d_name, bup, dp->d_namlen + 1);
                    180:
                    181:                                /* Save the first error for later. */
                    182:                                if (lstat(up, &s)) {
                    183:                                        if (!save_errno)
                    184:                                                save_errno = errno;
                    185:                                        errno = 0;
                    186:                                        continue;
                    187:                                }
                    188:                                if (s.st_dev == dev && s.st_ino == ino)
                    189:                                        break;
                    190:                        }
                    191:
                    192:                /*
                    193:                 * Check for length of the current name, preceding slash,
                    194:                 * leading slash.
                    195:                 */
                    196:                if (bpt - pt <= dp->d_namlen + (first ? 1 : 2)) {
                    197:                        size_t len, off;
                    198:
                    199:                        if (!ptsize) {
                    200:                                errno = ERANGE;
                    201:                                goto err;
                    202:                        }
                    203:                        off = bpt - pt;
                    204:                        len = ept - bpt;
1.4       cgd       205:                        if ((pt = realloc(pt, ptsize *= 2)) == NULL)
1.1       cgd       206:                                goto err;
                    207:                        bpt = pt + off;
                    208:                        ept = pt + ptsize;
1.5     ! jtc       209:                        bcopy(bpt, ept - len, len);
1.1       cgd       210:                        bpt = ept - len;
                    211:                }
                    212:                if (!first)
                    213:                        *--bpt = '/';
                    214:                bpt -= dp->d_namlen;
                    215:                bcopy(dp->d_name, bpt, dp->d_namlen);
                    216:                (void)closedir(dir);
                    217:
                    218:                /* Truncate any file name. */
                    219:                *bup = '\0';
                    220:        }
                    221:
                    222: notfound:
                    223:        /*
                    224:         * If readdir set errno, use it, not any saved error; otherwise,
                    225:         * didn't find the current directory in its parent directory, set
                    226:         * errno to ENOENT.
                    227:         */
                    228:        if (!errno)
                    229:                errno = save_errno ? save_errno : ENOENT;
                    230:        /* FALLTHROUGH */
                    231: err:
                    232:        if (ptsize)
                    233:                free(pt);
                    234:        free(up);
1.4       cgd       235:        return (NULL);
1.1       cgd       236: }

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