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Annotation of src/lib/libc/gen/getcwd.c, Revision 1.1.1.3

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

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