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Annotation of src/lib/libc/gen/getcwd.c, Revision 1.2

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)
1.2     ! mycroft    35: /*static char sccsid[] = "from: @(#)getcwd.c   5.11 (Berkeley) 2/24/91";*/
        !            36: static char rcsid[] = "$Id: $";
1.1       cgd        37: #endif /* LIBC_SCCS and not lint */
                     38:
                     39: #include <sys/param.h>
                     40: #include <sys/stat.h>
                     41: #include <errno.h>
                     42: #include <dirent.h>
                     43: #include <stdio.h>
                     44: #include <stdlib.h>
                     45: #include <string.h>
                     46: #include <unistd.h>
                     47:
                     48: #define        ISDOT(dp) \
                     49:        (dp->d_name[0] == '.' && (dp->d_name[1] == '\0' || \
                     50:            dp->d_name[1] == '.' && dp->d_name[2] == '\0'))
                     51:
                     52: char *
                     53: getcwd(pt, size)
                     54:        char *pt;
                     55:        size_t size;
                     56: {
                     57:        register struct dirent *dp;
                     58:        register DIR *dir;
                     59:        register dev_t dev;
                     60:        register ino_t ino;
                     61:        register int first;
                     62:        register char *bpt, *bup;
                     63:        struct stat s;
                     64:        dev_t root_dev;
                     65:        ino_t root_ino;
                     66:        size_t ptsize, upsize;
                     67:        int save_errno;
                     68:        char *ept, *eup, *up;
                     69:
                     70:        /*
                     71:         * If no buffer specified by the user, allocate one as necessary.
                     72:         * If a buffer is specified, the size has to be non-zero.  The path
                     73:         * is built from the end of the buffer backwards.
                     74:         */
                     75:        if (pt) {
                     76:                ptsize = 0;
                     77:                if (!size) {
                     78:                        errno = EINVAL;
                     79:                        return((char *)NULL);
                     80:                }
                     81:                ept = pt + size;
                     82:        } else {
                     83:                if (!(pt = (char *)malloc(ptsize = 1024 - 4)))
                     84:                        return((char *)NULL);
                     85:                ept = pt + ptsize;
                     86:        }
                     87:        bpt = ept - 1;
                     88:        *bpt = '\0';
                     89:
                     90:        /*
                     91:         * Allocate bytes (1024 - malloc space) for the string of "../"'s.
                     92:         * Should always be enough (it's 340 levels).  If it's not, allocate
                     93:         * as necessary.  Special * case the first stat, it's ".", not "..".
                     94:         */
                     95:        if (!(up = (char *)malloc(upsize = 1024 - 4)))
                     96:                goto err;
                     97:        eup = up + MAXPATHLEN;
                     98:        bup = up;
                     99:        up[0] = '.';
                    100:        up[1] = '\0';
                    101:
                    102:        /* Save root values, so know when to stop. */
                    103:        if (stat("/", &s))
                    104:                goto err;
                    105:        root_dev = s.st_dev;
                    106:        root_ino = s.st_ino;
                    107:
                    108:        errno = 0;                      /* XXX readdir has no error return. */
                    109:
                    110:        for (first = 1;; first = 0) {
                    111:                /* Stat the current level. */
                    112:                if (lstat(up, &s))
                    113:                        goto err;
                    114:
                    115:                /* Save current node values. */
                    116:                ino = s.st_ino;
                    117:                dev = s.st_dev;
                    118:
                    119:                /* Check for reaching root. */
                    120:                if (root_dev == dev && root_ino == ino) {
                    121:                        *--bpt = '/';
                    122:                        /*
                    123:                         * It's unclear that it's a requirement to copy the
                    124:                         * path to the beginning of the buffer, but it's always
                    125:                         * been that way and stuff would probably break.
                    126:                         */
                    127:                        (void)bcopy(bpt, pt, ept - bpt);
                    128:                        free(up);
                    129:                        return(pt);
                    130:                }
                    131:
                    132:                /*
                    133:                 * Build pointer to the parent directory, allocating memory
                    134:                 * as necessary.  Max length is 3 for "../", the largest
                    135:                 * possible component name, plus a trailing NULL.
                    136:                 */
                    137:                if (bup + 3  + MAXNAMLEN + 1 >= eup) {
                    138:                        if (!(up = (char *)realloc(up, upsize *= 2)))
                    139:                                goto err;
                    140:                        eup = up + upsize;
                    141:                }
                    142:                *bup++ = '.';
                    143:                *bup++ = '.';
                    144:                *bup = '\0';
                    145:
                    146:                /* Open and stat parent directory. */
                    147:                if (!(dir = opendir(up)) || fstat(dirfd(dir), &s))
                    148:                        goto err;
                    149:
                    150:                /* Add trailing slash for next directory. */
                    151:                *bup++ = '/';
                    152:
                    153:                /*
                    154:                 * If it's a mount point, have to stat each element because
                    155:                 * the inode number in the directory is for the entry in the
                    156:                 * parent directory, not the inode number of the mounted file.
                    157:                 */
                    158:                save_errno = 0;
                    159:                if (s.st_dev == dev) {
                    160:                        for (;;) {
                    161:                                if (!(dp = readdir(dir)))
                    162:                                        goto notfound;
                    163:                                if (dp->d_fileno == ino)
                    164:                                        break;
                    165:                        }
                    166:                } else
                    167:                        for (;;) {
                    168:                                if (!(dp = readdir(dir)))
                    169:                                        goto notfound;
                    170:                                if (ISDOT(dp))
                    171:                                        continue;
                    172:                                bcopy(dp->d_name, bup, dp->d_namlen + 1);
                    173:
                    174:                                /* Save the first error for later. */
                    175:                                if (lstat(up, &s)) {
                    176:                                        if (!save_errno)
                    177:                                                save_errno = errno;
                    178:                                        errno = 0;
                    179:                                        continue;
                    180:                                }
                    181:                                if (s.st_dev == dev && s.st_ino == ino)
                    182:                                        break;
                    183:                        }
                    184:
                    185:                /*
                    186:                 * Check for length of the current name, preceding slash,
                    187:                 * leading slash.
                    188:                 */
                    189:                if (bpt - pt <= dp->d_namlen + (first ? 1 : 2)) {
                    190:                        size_t len, off;
                    191:
                    192:                        if (!ptsize) {
                    193:                                errno = ERANGE;
                    194:                                goto err;
                    195:                        }
                    196:                        off = bpt - pt;
                    197:                        len = ept - bpt;
                    198:                        if (!(pt = (char *)realloc(pt, ptsize *= 2)))
                    199:                                goto err;
                    200:                        bpt = pt + off;
                    201:                        ept = pt + ptsize;
                    202:                        (void)bcopy(bpt, ept - len, len);
                    203:                        bpt = ept - len;
                    204:                }
                    205:                if (!first)
                    206:                        *--bpt = '/';
                    207:                bpt -= dp->d_namlen;
                    208:                bcopy(dp->d_name, bpt, dp->d_namlen);
                    209:                (void)closedir(dir);
                    210:
                    211:                /* Truncate any file name. */
                    212:                *bup = '\0';
                    213:        }
                    214:
                    215: notfound:
                    216:        /*
                    217:         * If readdir set errno, use it, not any saved error; otherwise,
                    218:         * didn't find the current directory in its parent directory, set
                    219:         * errno to ENOENT.
                    220:         */
                    221:        if (!errno)
                    222:                errno = save_errno ? save_errno : ENOENT;
                    223:        /* FALLTHROUGH */
                    224: err:
                    225:        if (ptsize)
                    226:                free(pt);
                    227:        free(up);
                    228:        return((char *)NULL);
                    229: }

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