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Annotation of src/lib/libc/gen/getcwd.c, Revision 1.11

1.11    ! perry       1: /*     $NetBSD: getcwd.c,v 1.10 1998/02/03 18:23:44 perry Exp $        */
1.4       cgd         2:
1.1       cgd         3: /*
1.8       perry       4:  * Copyright (c) 1989, 1991, 1993, 1995
1.4       cgd         5:  *     The Regents of the University of California.  All rights reserved.
1.1       cgd         6:  *
1.8       perry       7:  * This code is derived from software contributed to Berkeley by
                      8:  * Jan-Simon Pendry.
                      9:  *
1.1       cgd        10:  * Redistribution and use in source and binary forms, with or without
                     11:  * modification, are permitted provided that the following conditions
                     12:  * are met:
                     13:  * 1. Redistributions of source code must retain the above copyright
                     14:  *    notice, this list of conditions and the following disclaimer.
                     15:  * 2. Redistributions in binary form must reproduce the above copyright
                     16:  *    notice, this list of conditions and the following disclaimer in the
                     17:  *    documentation and/or other materials provided with the distribution.
                     18:  * 3. All advertising materials mentioning features or use of this software
                     19:  *    must display the following acknowledgement:
                     20:  *     This product includes software developed by the University of
                     21:  *     California, Berkeley and its contributors.
                     22:  * 4. Neither the name of the University nor the names of its contributors
                     23:  *    may be used to endorse or promote products derived from this software
                     24:  *    without specific prior written permission.
                     25:  *
                     26:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
                     27:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
                     28:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
                     29:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
                     30:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
                     31:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
                     32:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
                     33:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
                     34:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
                     35:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
                     36:  * SUCH DAMAGE.
                     37:  */
                     38:
1.6       christos   39: #include <sys/cdefs.h>
1.1       cgd        40: #if defined(LIBC_SCCS) && !defined(lint)
1.4       cgd        41: #if 0
1.8       perry      42: static char sccsid[] = "@(#)getcwd.c   8.5 (Berkeley) 2/7/95";
1.4       cgd        43: #else
1.11    ! perry      44: __RCSID("$NetBSD: getcwd.c,v 1.10 1998/02/03 18:23:44 perry Exp $");
1.4       cgd        45: #endif
1.1       cgd        46: #endif /* LIBC_SCCS and not lint */
                     47:
1.7       jtc        48: #include "namespace.h"
1.1       cgd        49: #include <sys/param.h>
                     50: #include <sys/stat.h>
1.8       perry      51:
                     52: #include <dirent.h>
1.1       cgd        53: #include <errno.h>
1.8       perry      54: #include <fcntl.h>
1.1       cgd        55: #include <stdio.h>
                     56: #include <stdlib.h>
                     57: #include <string.h>
                     58: #include <unistd.h>
1.7       jtc        59:
                     60: #ifdef __weak_alias
                     61: __weak_alias(getcwd,_getcwd);
1.9       perry      62: __weak_alias(realpath,_realpath);
1.7       jtc        63: #endif
1.1       cgd        64:
1.8       perry      65: static char *getcwd_physical __P((char *, size_t));
                     66:
1.1       cgd        67: #define        ISDOT(dp) \
                     68:        (dp->d_name[0] == '.' && (dp->d_name[1] == '\0' || \
1.6       christos   69:            (dp->d_name[1] == '.' && dp->d_name[2] == '\0')))
1.1       cgd        70:
                     71: char *
                     72: getcwd(pt, size)
                     73:        char *pt;
                     74:        size_t size;
                     75: {
1.8       perry      76:        char *pwd;
                     77:        size_t pwdlen;
                     78:        dev_t dev;
                     79:        ino_t ino;
                     80:        struct stat s;
                     81:
                     82:        /* Check $PWD -- if it's right, it's fast. */
                     83:        if ((pwd = getenv("PWD")) != NULL && pwd[0] == '/' && !stat(pwd, &s)) {
                     84:                dev = s.st_dev;
                     85:                ino = s.st_ino;
                     86:                if (!stat(".", &s) && dev == s.st_dev && ino == s.st_ino) {
                     87:                        pwdlen = strlen(pwd);
                     88:                        if (size != 0) {
                     89:                                if (pwdlen + 1 > size) {
                     90:                                        errno = ERANGE;
                     91:                                        return (NULL);
                     92:                                }
                     93:                        } else if ((pt = malloc(pwdlen + 1)) == NULL)
                     94:                                return (NULL);
                     95:                        memmove(pt, pwd, pwdlen);
                     96:                        pt[pwdlen] = '\0';
                     97:                        return (pt);
                     98:                }
                     99:        }
                    100:
                    101:        return (getcwd_physical(pt, size));
                    102: }
                    103:
                    104: /*
                    105:  * char *realpath(const char *path, char resolved_path[MAXPATHLEN]);
                    106:  *
                    107:  * Find the real name of path, by removing all ".", ".." and symlink
                    108:  * components.  Returns (resolved) on success, or (NULL) on failure,
                    109:  * in which case the path which caused trouble is left in (resolved).
                    110:  */
                    111: char *
                    112: realpath(path, resolved)
                    113:        const char *path;
                    114:        char *resolved;
                    115: {
                    116:        struct stat sb;
                    117:        int fd, n, rootd, serrno;
                    118:        char *p, *q, wbuf[MAXPATHLEN];
                    119:
                    120:        /* Save the starting point. */
                    121:        if ((fd = open(".", O_RDONLY)) < 0) {
                    122:                (void)strcpy(resolved, ".");
                    123:                return (NULL);
                    124:        }
                    125:
                    126:        /*
                    127:         * Find the dirname and basename from the path to be resolved.
                    128:         * Change directory to the dirname component.
                    129:         * lstat the basename part.
                    130:         *     if it is a symlink, read in the value and loop.
                    131:         *     if it is a directory, then change to that directory.
                    132:         * get the current directory name and append the basename.
                    133:         */
                    134:        (void)strncpy(resolved, path, MAXPATHLEN - 1);
                    135:        resolved[MAXPATHLEN - 1] = '\0';
                    136: loop:
                    137:        q = strrchr(resolved, '/');
                    138:        if (q != NULL) {
                    139:                p = q + 1;
                    140:                if (q == resolved)
                    141:                        q = "/";
                    142:                else {
                    143:                        do {
                    144:                                --q;
                    145:                        } while (q > resolved && *q == '/');
                    146:                        q[1] = '\0';
                    147:                        q = resolved;
                    148:                }
                    149:                if (chdir(q) < 0)
                    150:                        goto err1;
                    151:        } else
                    152:                p = resolved;
                    153:
                    154:        /* Deal with the last component. */
                    155:        if (lstat(p, &sb) == 0) {
                    156:                if (S_ISLNK(sb.st_mode)) {
                    157:                        n = readlink(p, resolved, MAXPATHLEN);
                    158:                        if (n < 0)
                    159:                                goto err1;
                    160:                        resolved[n] = '\0';
                    161:                        goto loop;
                    162:                }
                    163:                if (S_ISDIR(sb.st_mode)) {
                    164:                        if (chdir(p) < 0)
                    165:                                goto err1;
                    166:                        p = "";
                    167:                }
                    168:        }
                    169:
                    170:        /*
                    171:         * Save the last component name and get the full pathname of
                    172:         * the current directory.
                    173:         */
1.9       perry     174:        (void)strncpy(wbuf, p, (sizeof(wbuf) - 1));
1.8       perry     175:
                    176:        /*
                    177:         * Call the inernal internal version of getcwd which
                    178:         * does a physical search rather than using the $PWD short-cut
                    179:         */
                    180:        if (getcwd_physical(resolved, MAXPATHLEN) == 0)
                    181:                goto err1;
                    182:
                    183:        /*
                    184:         * Join the two strings together, ensuring that the right thing
                    185:         * happens if the last component is empty, or the dirname is root.
                    186:         */
                    187:        if (resolved[0] == '/' && resolved[1] == '\0')
                    188:                rootd = 1;
                    189:        else
                    190:                rootd = 0;
                    191:
                    192:        if (*wbuf) {
                    193:                if (strlen(resolved) + strlen(wbuf) + rootd + 1 > MAXPATHLEN) {
                    194:                        errno = ENAMETOOLONG;
                    195:                        goto err1;
                    196:                }
                    197:                if (rootd == 0)
1.9       perry     198:                        (void)strcat(resolved, "/"); /* XXX: strcat is safe */
                    199:                (void)strcat(resolved, wbuf);   /* XXX: strcat is safe */
1.8       perry     200:        }
                    201:
                    202:        /* Go back to where we came from. */
                    203:        if (fchdir(fd) < 0) {
                    204:                serrno = errno;
                    205:                goto err2;
                    206:        }
                    207:
                    208:        /* It's okay if the close fails, what's an fd more or less? */
                    209:        (void)close(fd);
                    210:        return (resolved);
                    211:
                    212: err1:  serrno = errno;
                    213:        (void)fchdir(fd);
                    214: err2:  (void)close(fd);
                    215:        errno = serrno;
                    216:        return (NULL);
                    217: }
                    218:
                    219: static char *
                    220: getcwd_physical(pt, size)
                    221:        char *pt;
                    222:        size_t size;
                    223: {
1.10      perry     224:        struct dirent *dp;
                    225:        DIR *dir;
                    226:        dev_t dev;
                    227:        ino_t ino;
                    228:        int first;
                    229:        char *bpt, *bup;
1.1       cgd       230:        struct stat s;
                    231:        dev_t root_dev;
                    232:        ino_t root_ino;
                    233:        size_t ptsize, upsize;
                    234:        int save_errno;
                    235:        char *ept, *eup, *up;
                    236:
                    237:        /*
                    238:         * If no buffer specified by the user, allocate one as necessary.
                    239:         * If a buffer is specified, the size has to be non-zero.  The path
                    240:         * is built from the end of the buffer backwards.
                    241:         */
                    242:        if (pt) {
                    243:                ptsize = 0;
                    244:                if (!size) {
                    245:                        errno = EINVAL;
1.4       cgd       246:                        return (NULL);
1.1       cgd       247:                }
                    248:                ept = pt + size;
                    249:        } else {
1.4       cgd       250:                if ((pt = malloc(ptsize = 1024 - 4)) == NULL)
                    251:                        return (NULL);
1.1       cgd       252:                ept = pt + ptsize;
                    253:        }
                    254:        bpt = ept - 1;
                    255:        *bpt = '\0';
                    256:
                    257:        /*
                    258:         * Allocate bytes (1024 - malloc space) for the string of "../"'s.
                    259:         * Should always be enough (it's 340 levels).  If it's not, allocate
1.8       perry     260:         * as necessary.  Special case the first stat, it's ".", not "..".
1.1       cgd       261:         */
1.4       cgd       262:        if ((up = malloc(upsize = 1024 - 4)) == NULL)
1.1       cgd       263:                goto err;
                    264:        eup = up + MAXPATHLEN;
                    265:        bup = up;
                    266:        up[0] = '.';
                    267:        up[1] = '\0';
                    268:
                    269:        /* Save root values, so know when to stop. */
                    270:        if (stat("/", &s))
                    271:                goto err;
                    272:        root_dev = s.st_dev;
                    273:        root_ino = s.st_ino;
                    274:
                    275:        errno = 0;                      /* XXX readdir has no error return. */
                    276:
                    277:        for (first = 1;; first = 0) {
                    278:                /* Stat the current level. */
                    279:                if (lstat(up, &s))
                    280:                        goto err;
                    281:
                    282:                /* Save current node values. */
                    283:                ino = s.st_ino;
                    284:                dev = s.st_dev;
                    285:
                    286:                /* Check for reaching root. */
                    287:                if (root_dev == dev && root_ino == ino) {
                    288:                        *--bpt = '/';
                    289:                        /*
                    290:                         * It's unclear that it's a requirement to copy the
                    291:                         * path to the beginning of the buffer, but it's always
                    292:                         * been that way and stuff would probably break.
                    293:                         */
1.11    ! perry     294:                        bcopy(bpt, pt, (size_t)(ept - bpt));
1.1       cgd       295:                        free(up);
1.4       cgd       296:                        return (pt);
1.1       cgd       297:                }
                    298:
                    299:                /*
                    300:                 * Build pointer to the parent directory, allocating memory
                    301:                 * as necessary.  Max length is 3 for "../", the largest
                    302:                 * possible component name, plus a trailing NULL.
                    303:                 */
                    304:                if (bup + 3  + MAXNAMLEN + 1 >= eup) {
1.4       cgd       305:                        if ((up = realloc(up, upsize *= 2)) == NULL)
1.1       cgd       306:                                goto err;
1.4       cgd       307:                        bup = up;
1.1       cgd       308:                        eup = up + upsize;
                    309:                }
                    310:                *bup++ = '.';
                    311:                *bup++ = '.';
                    312:                *bup = '\0';
                    313:
                    314:                /* Open and stat parent directory. */
                    315:                if (!(dir = opendir(up)) || fstat(dirfd(dir), &s))
                    316:                        goto err;
                    317:
                    318:                /* Add trailing slash for next directory. */
                    319:                *bup++ = '/';
                    320:
                    321:                /*
                    322:                 * If it's a mount point, have to stat each element because
                    323:                 * the inode number in the directory is for the entry in the
                    324:                 * parent directory, not the inode number of the mounted file.
                    325:                 */
                    326:                save_errno = 0;
                    327:                if (s.st_dev == dev) {
                    328:                        for (;;) {
                    329:                                if (!(dp = readdir(dir)))
                    330:                                        goto notfound;
                    331:                                if (dp->d_fileno == ino)
                    332:                                        break;
                    333:                        }
                    334:                } else
                    335:                        for (;;) {
                    336:                                if (!(dp = readdir(dir)))
                    337:                                        goto notfound;
                    338:                                if (ISDOT(dp))
                    339:                                        continue;
1.11    ! perry     340:                                bcopy(dp->d_name, bup,
        !           341:                                    (size_t)(dp->d_namlen + 1));
1.1       cgd       342:
                    343:                                /* Save the first error for later. */
                    344:                                if (lstat(up, &s)) {
                    345:                                        if (!save_errno)
                    346:                                                save_errno = errno;
                    347:                                        errno = 0;
                    348:                                        continue;
                    349:                                }
                    350:                                if (s.st_dev == dev && s.st_ino == ino)
                    351:                                        break;
                    352:                        }
                    353:
                    354:                /*
                    355:                 * Check for length of the current name, preceding slash,
                    356:                 * leading slash.
                    357:                 */
                    358:                if (bpt - pt <= dp->d_namlen + (first ? 1 : 2)) {
                    359:                        size_t len, off;
                    360:
                    361:                        if (!ptsize) {
                    362:                                errno = ERANGE;
                    363:                                goto err;
                    364:                        }
                    365:                        off = bpt - pt;
                    366:                        len = ept - bpt;
1.4       cgd       367:                        if ((pt = realloc(pt, ptsize *= 2)) == NULL)
1.1       cgd       368:                                goto err;
                    369:                        bpt = pt + off;
                    370:                        ept = pt + ptsize;
1.5       jtc       371:                        bcopy(bpt, ept - len, len);
1.1       cgd       372:                        bpt = ept - len;
                    373:                }
                    374:                if (!first)
                    375:                        *--bpt = '/';
                    376:                bpt -= dp->d_namlen;
1.11    ! perry     377:                bcopy(dp->d_name, bpt, (size_t)dp->d_namlen);
1.1       cgd       378:                (void)closedir(dir);
                    379:
                    380:                /* Truncate any file name. */
                    381:                *bup = '\0';
                    382:        }
                    383:
                    384: notfound:
                    385:        /*
                    386:         * If readdir set errno, use it, not any saved error; otherwise,
                    387:         * didn't find the current directory in its parent directory, set
                    388:         * errno to ENOENT.
                    389:         */
                    390:        if (!errno)
                    391:                errno = save_errno ? save_errno : ENOENT;
                    392:        /* FALLTHROUGH */
                    393: err:
                    394:        if (ptsize)
                    395:                free(pt);
                    396:        free(up);
1.4       cgd       397:        return (NULL);
1.1       cgd       398: }

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