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Annotation of src/lib/libc/gen/getcwd.c, Revision 1.1

1.1     ! cgd         1: /*
        !             2:  * Copyright (c) 1989, 1991 The Regents of the University of California.
        !             3:  * All rights reserved.
        !             4:  *
        !             5:  * Redistribution and use in source and binary forms, with or without
        !             6:  * modification, are permitted provided that the following conditions
        !             7:  * are met:
        !             8:  * 1. Redistributions of source code must retain the above copyright
        !             9:  *    notice, this list of conditions and the following disclaimer.
        !            10:  * 2. Redistributions in binary form must reproduce the above copyright
        !            11:  *    notice, this list of conditions and the following disclaimer in the
        !            12:  *    documentation and/or other materials provided with the distribution.
        !            13:  * 3. All advertising materials mentioning features or use of this software
        !            14:  *    must display the following acknowledgement:
        !            15:  *     This product includes software developed by the University of
        !            16:  *     California, Berkeley and its contributors.
        !            17:  * 4. Neither the name of the University nor the names of its contributors
        !            18:  *    may be used to endorse or promote products derived from this software
        !            19:  *    without specific prior written permission.
        !            20:  *
        !            21:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
        !            22:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
        !            23:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
        !            24:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
        !            25:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
        !            26:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
        !            27:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
        !            28:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
        !            29:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
        !            30:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
        !            31:  * SUCH DAMAGE.
        !            32:  */
        !            33:
        !            34: #if defined(LIBC_SCCS) && !defined(lint)
        !            35: static char sccsid[] = "@(#)getcwd.c   5.11 (Berkeley) 2/24/91";
        !            36: #endif /* LIBC_SCCS and not lint */
        !            37:
        !            38: #include <sys/param.h>
        !            39: #include <sys/stat.h>
        !            40: #include <errno.h>
        !            41: #include <dirent.h>
        !            42: #include <stdio.h>
        !            43: #include <stdlib.h>
        !            44: #include <string.h>
        !            45: #include <unistd.h>
        !            46:
        !            47: #define        ISDOT(dp) \
        !            48:        (dp->d_name[0] == '.' && (dp->d_name[1] == '\0' || \
        !            49:            dp->d_name[1] == '.' && dp->d_name[2] == '\0'))
        !            50:
        !            51: char *
        !            52: getcwd(pt, size)
        !            53:        char *pt;
        !            54:        size_t size;
        !            55: {
        !            56:        register struct dirent *dp;
        !            57:        register DIR *dir;
        !            58:        register dev_t dev;
        !            59:        register ino_t ino;
        !            60:        register int first;
        !            61:        register char *bpt, *bup;
        !            62:        struct stat s;
        !            63:        dev_t root_dev;
        !            64:        ino_t root_ino;
        !            65:        size_t ptsize, upsize;
        !            66:        int save_errno;
        !            67:        char *ept, *eup, *up;
        !            68:
        !            69:        /*
        !            70:         * If no buffer specified by the user, allocate one as necessary.
        !            71:         * If a buffer is specified, the size has to be non-zero.  The path
        !            72:         * is built from the end of the buffer backwards.
        !            73:         */
        !            74:        if (pt) {
        !            75:                ptsize = 0;
        !            76:                if (!size) {
        !            77:                        errno = EINVAL;
        !            78:                        return((char *)NULL);
        !            79:                }
        !            80:                ept = pt + size;
        !            81:        } else {
        !            82:                if (!(pt = (char *)malloc(ptsize = 1024 - 4)))
        !            83:                        return((char *)NULL);
        !            84:                ept = pt + ptsize;
        !            85:        }
        !            86:        bpt = ept - 1;
        !            87:        *bpt = '\0';
        !            88:
        !            89:        /*
        !            90:         * Allocate bytes (1024 - malloc space) for the string of "../"'s.
        !            91:         * Should always be enough (it's 340 levels).  If it's not, allocate
        !            92:         * as necessary.  Special * case the first stat, it's ".", not "..".
        !            93:         */
        !            94:        if (!(up = (char *)malloc(upsize = 1024 - 4)))
        !            95:                goto err;
        !            96:        eup = up + MAXPATHLEN;
        !            97:        bup = up;
        !            98:        up[0] = '.';
        !            99:        up[1] = '\0';
        !           100:
        !           101:        /* Save root values, so know when to stop. */
        !           102:        if (stat("/", &s))
        !           103:                goto err;
        !           104:        root_dev = s.st_dev;
        !           105:        root_ino = s.st_ino;
        !           106:
        !           107:        errno = 0;                      /* XXX readdir has no error return. */
        !           108:
        !           109:        for (first = 1;; first = 0) {
        !           110:                /* Stat the current level. */
        !           111:                if (lstat(up, &s))
        !           112:                        goto err;
        !           113:
        !           114:                /* Save current node values. */
        !           115:                ino = s.st_ino;
        !           116:                dev = s.st_dev;
        !           117:
        !           118:                /* Check for reaching root. */
        !           119:                if (root_dev == dev && root_ino == ino) {
        !           120:                        *--bpt = '/';
        !           121:                        /*
        !           122:                         * It's unclear that it's a requirement to copy the
        !           123:                         * path to the beginning of the buffer, but it's always
        !           124:                         * been that way and stuff would probably break.
        !           125:                         */
        !           126:                        (void)bcopy(bpt, pt, ept - bpt);
        !           127:                        free(up);
        !           128:                        return(pt);
        !           129:                }
        !           130:
        !           131:                /*
        !           132:                 * Build pointer to the parent directory, allocating memory
        !           133:                 * as necessary.  Max length is 3 for "../", the largest
        !           134:                 * possible component name, plus a trailing NULL.
        !           135:                 */
        !           136:                if (bup + 3  + MAXNAMLEN + 1 >= eup) {
        !           137:                        if (!(up = (char *)realloc(up, upsize *= 2)))
        !           138:                                goto err;
        !           139:                        eup = up + upsize;
        !           140:                }
        !           141:                *bup++ = '.';
        !           142:                *bup++ = '.';
        !           143:                *bup = '\0';
        !           144:
        !           145:                /* Open and stat parent directory. */
        !           146:                if (!(dir = opendir(up)) || fstat(dirfd(dir), &s))
        !           147:                        goto err;
        !           148:
        !           149:                /* Add trailing slash for next directory. */
        !           150:                *bup++ = '/';
        !           151:
        !           152:                /*
        !           153:                 * If it's a mount point, have to stat each element because
        !           154:                 * the inode number in the directory is for the entry in the
        !           155:                 * parent directory, not the inode number of the mounted file.
        !           156:                 */
        !           157:                save_errno = 0;
        !           158:                if (s.st_dev == dev) {
        !           159:                        for (;;) {
        !           160:                                if (!(dp = readdir(dir)))
        !           161:                                        goto notfound;
        !           162:                                if (dp->d_fileno == ino)
        !           163:                                        break;
        !           164:                        }
        !           165:                } else
        !           166:                        for (;;) {
        !           167:                                if (!(dp = readdir(dir)))
        !           168:                                        goto notfound;
        !           169:                                if (ISDOT(dp))
        !           170:                                        continue;
        !           171:                                bcopy(dp->d_name, bup, dp->d_namlen + 1);
        !           172:
        !           173:                                /* Save the first error for later. */
        !           174:                                if (lstat(up, &s)) {
        !           175:                                        if (!save_errno)
        !           176:                                                save_errno = errno;
        !           177:                                        errno = 0;
        !           178:                                        continue;
        !           179:                                }
        !           180:                                if (s.st_dev == dev && s.st_ino == ino)
        !           181:                                        break;
        !           182:                        }
        !           183:
        !           184:                /*
        !           185:                 * Check for length of the current name, preceding slash,
        !           186:                 * leading slash.
        !           187:                 */
        !           188:                if (bpt - pt <= dp->d_namlen + (first ? 1 : 2)) {
        !           189:                        size_t len, off;
        !           190:
        !           191:                        if (!ptsize) {
        !           192:                                errno = ERANGE;
        !           193:                                goto err;
        !           194:                        }
        !           195:                        off = bpt - pt;
        !           196:                        len = ept - bpt;
        !           197:                        if (!(pt = (char *)realloc(pt, ptsize *= 2)))
        !           198:                                goto err;
        !           199:                        bpt = pt + off;
        !           200:                        ept = pt + ptsize;
        !           201:                        (void)bcopy(bpt, ept - len, len);
        !           202:                        bpt = ept - len;
        !           203:                }
        !           204:                if (!first)
        !           205:                        *--bpt = '/';
        !           206:                bpt -= dp->d_namlen;
        !           207:                bcopy(dp->d_name, bpt, dp->d_namlen);
        !           208:                (void)closedir(dir);
        !           209:
        !           210:                /* Truncate any file name. */
        !           211:                *bup = '\0';
        !           212:        }
        !           213:
        !           214: notfound:
        !           215:        /*
        !           216:         * If readdir set errno, use it, not any saved error; otherwise,
        !           217:         * didn't find the current directory in its parent directory, set
        !           218:         * errno to ENOENT.
        !           219:         */
        !           220:        if (!errno)
        !           221:                errno = save_errno ? save_errno : ENOENT;
        !           222:        /* FALLTHROUGH */
        !           223: err:
        !           224:        if (ptsize)
        !           225:                free(pt);
        !           226:        free(up);
        !           227:        return((char *)NULL);
        !           228: }

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