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Annotation of src/lib/libc/gen/getcwd.c, Revision 1.8

1.8     ! perry       1: /*     $NetBSD: getcwd.c,v 1.7 1997/07/21 14:07:04 jtc 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
1.8     ! perry      44: __RCSID("$NetBSD: getcwd.c,v 1.7 1997/07/21 14:07:04 jtc 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);
                     62: #endif
1.1       cgd        63:
1.8     ! perry      64: static char *getcwd_physical __P((char *, size_t));
        !            65:
1.1       cgd        66: #define        ISDOT(dp) \
                     67:        (dp->d_name[0] == '.' && (dp->d_name[1] == '\0' || \
1.6       christos   68:            (dp->d_name[1] == '.' && dp->d_name[2] == '\0')))
1.1       cgd        69:
                     70: char *
                     71: getcwd(pt, size)
                     72:        char *pt;
                     73:        size_t size;
                     74: {
1.8     ! perry      75:        char *pwd;
        !            76:        size_t pwdlen;
        !            77:        dev_t dev;
        !            78:        ino_t ino;
        !            79:        struct stat s;
        !            80:
        !            81:        /* Check $PWD -- if it's right, it's fast. */
        !            82:        if ((pwd = getenv("PWD")) != NULL && pwd[0] == '/' && !stat(pwd, &s)) {
        !            83:                dev = s.st_dev;
        !            84:                ino = s.st_ino;
        !            85:                if (!stat(".", &s) && dev == s.st_dev && ino == s.st_ino) {
        !            86:                        pwdlen = strlen(pwd);
        !            87:                        if (size != 0) {
        !            88:                                if (pwdlen + 1 > size) {
        !            89:                                        errno = ERANGE;
        !            90:                                        return (NULL);
        !            91:                                }
        !            92:                        } else if ((pt = malloc(pwdlen + 1)) == NULL)
        !            93:                                return (NULL);
        !            94:                        memmove(pt, pwd, pwdlen);
        !            95:                        pt[pwdlen] = '\0';
        !            96:                        return (pt);
        !            97:                }
        !            98:        }
        !            99:
        !           100:        return (getcwd_physical(pt, size));
        !           101: }
        !           102:
        !           103: /*
        !           104:  * char *realpath(const char *path, char resolved_path[MAXPATHLEN]);
        !           105:  *
        !           106:  * Find the real name of path, by removing all ".", ".." and symlink
        !           107:  * components.  Returns (resolved) on success, or (NULL) on failure,
        !           108:  * in which case the path which caused trouble is left in (resolved).
        !           109:  */
        !           110: char *
        !           111: realpath(path, resolved)
        !           112:        const char *path;
        !           113:        char *resolved;
        !           114: {
        !           115:        struct stat sb;
        !           116:        int fd, n, rootd, serrno;
        !           117:        char *p, *q, wbuf[MAXPATHLEN];
        !           118:
        !           119:        /* Save the starting point. */
        !           120:        if ((fd = open(".", O_RDONLY)) < 0) {
        !           121:                (void)strcpy(resolved, ".");
        !           122:                return (NULL);
        !           123:        }
        !           124:
        !           125:        /*
        !           126:         * Find the dirname and basename from the path to be resolved.
        !           127:         * Change directory to the dirname component.
        !           128:         * lstat the basename part.
        !           129:         *     if it is a symlink, read in the value and loop.
        !           130:         *     if it is a directory, then change to that directory.
        !           131:         * get the current directory name and append the basename.
        !           132:         */
        !           133:        (void)strncpy(resolved, path, MAXPATHLEN - 1);
        !           134:        resolved[MAXPATHLEN - 1] = '\0';
        !           135: loop:
        !           136:        q = strrchr(resolved, '/');
        !           137:        if (q != NULL) {
        !           138:                p = q + 1;
        !           139:                if (q == resolved)
        !           140:                        q = "/";
        !           141:                else {
        !           142:                        do {
        !           143:                                --q;
        !           144:                        } while (q > resolved && *q == '/');
        !           145:                        q[1] = '\0';
        !           146:                        q = resolved;
        !           147:                }
        !           148:                if (chdir(q) < 0)
        !           149:                        goto err1;
        !           150:        } else
        !           151:                p = resolved;
        !           152:
        !           153:        /* Deal with the last component. */
        !           154:        if (lstat(p, &sb) == 0) {
        !           155:                if (S_ISLNK(sb.st_mode)) {
        !           156:                        n = readlink(p, resolved, MAXPATHLEN);
        !           157:                        if (n < 0)
        !           158:                                goto err1;
        !           159:                        resolved[n] = '\0';
        !           160:                        goto loop;
        !           161:                }
        !           162:                if (S_ISDIR(sb.st_mode)) {
        !           163:                        if (chdir(p) < 0)
        !           164:                                goto err1;
        !           165:                        p = "";
        !           166:                }
        !           167:        }
        !           168:
        !           169:        /*
        !           170:         * Save the last component name and get the full pathname of
        !           171:         * the current directory.
        !           172:         */
        !           173:        (void)strcpy(wbuf, p);
        !           174:
        !           175:        /*
        !           176:         * Call the inernal internal version of getcwd which
        !           177:         * does a physical search rather than using the $PWD short-cut
        !           178:         */
        !           179:        if (getcwd_physical(resolved, MAXPATHLEN) == 0)
        !           180:                goto err1;
        !           181:
        !           182:        /*
        !           183:         * Join the two strings together, ensuring that the right thing
        !           184:         * happens if the last component is empty, or the dirname is root.
        !           185:         */
        !           186:        if (resolved[0] == '/' && resolved[1] == '\0')
        !           187:                rootd = 1;
        !           188:        else
        !           189:                rootd = 0;
        !           190:
        !           191:        if (*wbuf) {
        !           192:                if (strlen(resolved) + strlen(wbuf) + rootd + 1 > MAXPATHLEN) {
        !           193:                        errno = ENAMETOOLONG;
        !           194:                        goto err1;
        !           195:                }
        !           196:                if (rootd == 0)
        !           197:                        (void)strcat(resolved, "/");
        !           198:                (void)strcat(resolved, wbuf);
        !           199:        }
        !           200:
        !           201:        /* Go back to where we came from. */
        !           202:        if (fchdir(fd) < 0) {
        !           203:                serrno = errno;
        !           204:                goto err2;
        !           205:        }
        !           206:
        !           207:        /* It's okay if the close fails, what's an fd more or less? */
        !           208:        (void)close(fd);
        !           209:        return (resolved);
        !           210:
        !           211: err1:  serrno = errno;
        !           212:        (void)fchdir(fd);
        !           213: err2:  (void)close(fd);
        !           214:        errno = serrno;
        !           215:        return (NULL);
        !           216: }
        !           217:
        !           218: static char *
        !           219: getcwd_physical(pt, size)
        !           220:        char *pt;
        !           221:        size_t size;
        !           222: {
1.1       cgd       223:        register struct dirent *dp;
                    224:        register DIR *dir;
                    225:        register dev_t dev;
                    226:        register ino_t ino;
                    227:        register int first;
                    228:        register char *bpt, *bup;
                    229:        struct stat s;
                    230:        dev_t root_dev;
                    231:        ino_t root_ino;
                    232:        size_t ptsize, upsize;
                    233:        int save_errno;
                    234:        char *ept, *eup, *up;
                    235:
                    236:        /*
                    237:         * If no buffer specified by the user, allocate one as necessary.
                    238:         * If a buffer is specified, the size has to be non-zero.  The path
                    239:         * is built from the end of the buffer backwards.
                    240:         */
                    241:        if (pt) {
                    242:                ptsize = 0;
                    243:                if (!size) {
                    244:                        errno = EINVAL;
1.4       cgd       245:                        return (NULL);
1.1       cgd       246:                }
                    247:                ept = pt + size;
                    248:        } else {
1.4       cgd       249:                if ((pt = malloc(ptsize = 1024 - 4)) == NULL)
                    250:                        return (NULL);
1.1       cgd       251:                ept = pt + ptsize;
                    252:        }
                    253:        bpt = ept - 1;
                    254:        *bpt = '\0';
                    255:
                    256:        /*
                    257:         * Allocate bytes (1024 - malloc space) for the string of "../"'s.
                    258:         * Should always be enough (it's 340 levels).  If it's not, allocate
1.8     ! perry     259:         * as necessary.  Special case the first stat, it's ".", not "..".
1.1       cgd       260:         */
1.4       cgd       261:        if ((up = malloc(upsize = 1024 - 4)) == NULL)
1.1       cgd       262:                goto err;
                    263:        eup = up + MAXPATHLEN;
                    264:        bup = up;
                    265:        up[0] = '.';
                    266:        up[1] = '\0';
                    267:
                    268:        /* Save root values, so know when to stop. */
                    269:        if (stat("/", &s))
                    270:                goto err;
                    271:        root_dev = s.st_dev;
                    272:        root_ino = s.st_ino;
                    273:
                    274:        errno = 0;                      /* XXX readdir has no error return. */
                    275:
                    276:        for (first = 1;; first = 0) {
                    277:                /* Stat the current level. */
                    278:                if (lstat(up, &s))
                    279:                        goto err;
                    280:
                    281:                /* Save current node values. */
                    282:                ino = s.st_ino;
                    283:                dev = s.st_dev;
                    284:
                    285:                /* Check for reaching root. */
                    286:                if (root_dev == dev && root_ino == ino) {
                    287:                        *--bpt = '/';
                    288:                        /*
                    289:                         * It's unclear that it's a requirement to copy the
                    290:                         * path to the beginning of the buffer, but it's always
                    291:                         * been that way and stuff would probably break.
                    292:                         */
1.5       jtc       293:                        bcopy(bpt, pt, ept - bpt);
1.1       cgd       294:                        free(up);
1.4       cgd       295:                        return (pt);
1.1       cgd       296:                }
                    297:
                    298:                /*
                    299:                 * Build pointer to the parent directory, allocating memory
                    300:                 * as necessary.  Max length is 3 for "../", the largest
                    301:                 * possible component name, plus a trailing NULL.
                    302:                 */
                    303:                if (bup + 3  + MAXNAMLEN + 1 >= eup) {
1.4       cgd       304:                        if ((up = realloc(up, upsize *= 2)) == NULL)
1.1       cgd       305:                                goto err;
1.4       cgd       306:                        bup = up;
1.1       cgd       307:                        eup = up + upsize;
                    308:                }
                    309:                *bup++ = '.';
                    310:                *bup++ = '.';
                    311:                *bup = '\0';
                    312:
                    313:                /* Open and stat parent directory. */
                    314:                if (!(dir = opendir(up)) || fstat(dirfd(dir), &s))
                    315:                        goto err;
                    316:
                    317:                /* Add trailing slash for next directory. */
                    318:                *bup++ = '/';
                    319:
                    320:                /*
                    321:                 * If it's a mount point, have to stat each element because
                    322:                 * the inode number in the directory is for the entry in the
                    323:                 * parent directory, not the inode number of the mounted file.
                    324:                 */
                    325:                save_errno = 0;
                    326:                if (s.st_dev == dev) {
                    327:                        for (;;) {
                    328:                                if (!(dp = readdir(dir)))
                    329:                                        goto notfound;
                    330:                                if (dp->d_fileno == ino)
                    331:                                        break;
                    332:                        }
                    333:                } else
                    334:                        for (;;) {
                    335:                                if (!(dp = readdir(dir)))
                    336:                                        goto notfound;
                    337:                                if (ISDOT(dp))
                    338:                                        continue;
                    339:                                bcopy(dp->d_name, bup, dp->d_namlen + 1);
                    340:
                    341:                                /* Save the first error for later. */
                    342:                                if (lstat(up, &s)) {
                    343:                                        if (!save_errno)
                    344:                                                save_errno = errno;
                    345:                                        errno = 0;
                    346:                                        continue;
                    347:                                }
                    348:                                if (s.st_dev == dev && s.st_ino == ino)
                    349:                                        break;
                    350:                        }
                    351:
                    352:                /*
                    353:                 * Check for length of the current name, preceding slash,
                    354:                 * leading slash.
                    355:                 */
                    356:                if (bpt - pt <= dp->d_namlen + (first ? 1 : 2)) {
                    357:                        size_t len, off;
                    358:
                    359:                        if (!ptsize) {
                    360:                                errno = ERANGE;
                    361:                                goto err;
                    362:                        }
                    363:                        off = bpt - pt;
                    364:                        len = ept - bpt;
1.4       cgd       365:                        if ((pt = realloc(pt, ptsize *= 2)) == NULL)
1.1       cgd       366:                                goto err;
                    367:                        bpt = pt + off;
                    368:                        ept = pt + ptsize;
1.5       jtc       369:                        bcopy(bpt, ept - len, len);
1.1       cgd       370:                        bpt = ept - len;
                    371:                }
                    372:                if (!first)
                    373:                        *--bpt = '/';
                    374:                bpt -= dp->d_namlen;
                    375:                bcopy(dp->d_name, bpt, dp->d_namlen);
                    376:                (void)closedir(dir);
                    377:
                    378:                /* Truncate any file name. */
                    379:                *bup = '\0';
                    380:        }
                    381:
                    382: notfound:
                    383:        /*
                    384:         * If readdir set errno, use it, not any saved error; otherwise,
                    385:         * didn't find the current directory in its parent directory, set
                    386:         * errno to ENOENT.
                    387:         */
                    388:        if (!errno)
                    389:                errno = save_errno ? save_errno : ENOENT;
                    390:        /* FALLTHROUGH */
                    391: err:
                    392:        if (ptsize)
                    393:                free(pt);
                    394:        free(up);
1.4       cgd       395:        return (NULL);
1.1       cgd       396: }

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