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Annotation of src/lib/libc/gen/getcwd.c, Revision 1.3.4.1

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)
1.3       jtc        35: /*static char *sccsid = "from: @(#)getcwd.c    5.11 (Berkeley) 2/24/91";*/
1.3.4.1 ! jtc        36: static char *rcsid = "$Id: getcwd.c,v 1.3 1993/08/26 00:44:36 jtc Exp $";
1.1       cgd        37: #endif /* LIBC_SCCS and not lint */
                     38:
1.3.4.1 ! jtc        39: #include "namespace.h"
1.1       cgd        40: #include <sys/param.h>
                     41: #include <sys/stat.h>
                     42: #include <errno.h>
                     43: #include <dirent.h>
                     44: #include <stdio.h>
                     45: #include <stdlib.h>
                     46: #include <string.h>
                     47: #include <unistd.h>
                     48:
                     49: #define        ISDOT(dp) \
                     50:        (dp->d_name[0] == '.' && (dp->d_name[1] == '\0' || \
                     51:            dp->d_name[1] == '.' && dp->d_name[2] == '\0'))
                     52:
                     53: char *
                     54: getcwd(pt, size)
                     55:        char *pt;
                     56:        size_t size;
                     57: {
                     58:        register struct dirent *dp;
                     59:        register DIR *dir;
                     60:        register dev_t dev;
                     61:        register ino_t ino;
                     62:        register int first;
                     63:        register char *bpt, *bup;
                     64:        struct stat s;
                     65:        dev_t root_dev;
                     66:        ino_t root_ino;
                     67:        size_t ptsize, upsize;
                     68:        int save_errno;
                     69:        char *ept, *eup, *up;
                     70:
                     71:        /*
                     72:         * If no buffer specified by the user, allocate one as necessary.
                     73:         * If a buffer is specified, the size has to be non-zero.  The path
                     74:         * is built from the end of the buffer backwards.
                     75:         */
                     76:        if (pt) {
                     77:                ptsize = 0;
                     78:                if (!size) {
                     79:                        errno = EINVAL;
                     80:                        return((char *)NULL);
                     81:                }
                     82:                ept = pt + size;
                     83:        } else {
                     84:                if (!(pt = (char *)malloc(ptsize = 1024 - 4)))
                     85:                        return((char *)NULL);
                     86:                ept = pt + ptsize;
                     87:        }
                     88:        bpt = ept - 1;
                     89:        *bpt = '\0';
                     90:
                     91:        /*
                     92:         * Allocate bytes (1024 - malloc space) for the string of "../"'s.
                     93:         * Should always be enough (it's 340 levels).  If it's not, allocate
                     94:         * as necessary.  Special * case the first stat, it's ".", not "..".
                     95:         */
                     96:        if (!(up = (char *)malloc(upsize = 1024 - 4)))
                     97:                goto err;
                     98:        eup = up + MAXPATHLEN;
                     99:        bup = up;
                    100:        up[0] = '.';
                    101:        up[1] = '\0';
                    102:
                    103:        /* Save root values, so know when to stop. */
                    104:        if (stat("/", &s))
                    105:                goto err;
                    106:        root_dev = s.st_dev;
                    107:        root_ino = s.st_ino;
                    108:
                    109:        errno = 0;                      /* XXX readdir has no error return. */
                    110:
                    111:        for (first = 1;; first = 0) {
                    112:                /* Stat the current level. */
                    113:                if (lstat(up, &s))
                    114:                        goto err;
                    115:
                    116:                /* Save current node values. */
                    117:                ino = s.st_ino;
                    118:                dev = s.st_dev;
                    119:
                    120:                /* Check for reaching root. */
                    121:                if (root_dev == dev && root_ino == ino) {
                    122:                        *--bpt = '/';
                    123:                        /*
                    124:                         * It's unclear that it's a requirement to copy the
                    125:                         * path to the beginning of the buffer, but it's always
                    126:                         * been that way and stuff would probably break.
                    127:                         */
                    128:                        (void)bcopy(bpt, pt, ept - bpt);
                    129:                        free(up);
                    130:                        return(pt);
                    131:                }
                    132:
                    133:                /*
                    134:                 * Build pointer to the parent directory, allocating memory
                    135:                 * as necessary.  Max length is 3 for "../", the largest
                    136:                 * possible component name, plus a trailing NULL.
                    137:                 */
                    138:                if (bup + 3  + MAXNAMLEN + 1 >= eup) {
                    139:                        if (!(up = (char *)realloc(up, upsize *= 2)))
                    140:                                goto err;
                    141:                        eup = up + upsize;
                    142:                }
                    143:                *bup++ = '.';
                    144:                *bup++ = '.';
                    145:                *bup = '\0';
                    146:
                    147:                /* Open and stat parent directory. */
                    148:                if (!(dir = opendir(up)) || fstat(dirfd(dir), &s))
                    149:                        goto err;
                    150:
                    151:                /* Add trailing slash for next directory. */
                    152:                *bup++ = '/';
                    153:
                    154:                /*
                    155:                 * If it's a mount point, have to stat each element because
                    156:                 * the inode number in the directory is for the entry in the
                    157:                 * parent directory, not the inode number of the mounted file.
                    158:                 */
                    159:                save_errno = 0;
                    160:                if (s.st_dev == dev) {
                    161:                        for (;;) {
                    162:                                if (!(dp = readdir(dir)))
                    163:                                        goto notfound;
                    164:                                if (dp->d_fileno == ino)
                    165:                                        break;
                    166:                        }
                    167:                } else
                    168:                        for (;;) {
                    169:                                if (!(dp = readdir(dir)))
                    170:                                        goto notfound;
                    171:                                if (ISDOT(dp))
                    172:                                        continue;
                    173:                                bcopy(dp->d_name, bup, dp->d_namlen + 1);
                    174:
                    175:                                /* Save the first error for later. */
                    176:                                if (lstat(up, &s)) {
                    177:                                        if (!save_errno)
                    178:                                                save_errno = errno;
                    179:                                        errno = 0;
                    180:                                        continue;
                    181:                                }
                    182:                                if (s.st_dev == dev && s.st_ino == ino)
                    183:                                        break;
                    184:                        }
                    185:
                    186:                /*
                    187:                 * Check for length of the current name, preceding slash,
                    188:                 * leading slash.
                    189:                 */
                    190:                if (bpt - pt <= dp->d_namlen + (first ? 1 : 2)) {
                    191:                        size_t len, off;
                    192:
                    193:                        if (!ptsize) {
                    194:                                errno = ERANGE;
                    195:                                goto err;
                    196:                        }
                    197:                        off = bpt - pt;
                    198:                        len = ept - bpt;
                    199:                        if (!(pt = (char *)realloc(pt, ptsize *= 2)))
                    200:                                goto err;
                    201:                        bpt = pt + off;
                    202:                        ept = pt + ptsize;
                    203:                        (void)bcopy(bpt, ept - len, len);
                    204:                        bpt = ept - len;
                    205:                }
                    206:                if (!first)
                    207:                        *--bpt = '/';
                    208:                bpt -= dp->d_namlen;
                    209:                bcopy(dp->d_name, bpt, dp->d_namlen);
                    210:                (void)closedir(dir);
                    211:
                    212:                /* Truncate any file name. */
                    213:                *bup = '\0';
                    214:        }
                    215:
                    216: notfound:
                    217:        /*
                    218:         * If readdir set errno, use it, not any saved error; otherwise,
                    219:         * didn't find the current directory in its parent directory, set
                    220:         * errno to ENOENT.
                    221:         */
                    222:        if (!errno)
                    223:                errno = save_errno ? save_errno : ENOENT;
                    224:        /* FALLTHROUGH */
                    225: err:
                    226:        if (ptsize)
                    227:                free(pt);
                    228:        free(up);
                    229:        return((char *)NULL);
                    230: }

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