source: MondoRescue/branches/2.2.2/mindi-busybox/libbb/parse_mode.c@ 1247

/* vi: set sw=4 ts=4: */
/*
 * parse_mode implementation for busybox
 *
 * Copyright (C) 2003  Manuel Novoa III  <mjn3@codepoet.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 *
 */

/* http://www.opengroup.org/onlinepubs/007904975/utilities/chmod.html */

#include <stdlib.h>
#include <assert.h>
#include <sys/stat.h>
#include "libbb.h"

#define FILEMODEBITS    (S_ISUID | S_ISGID | S_ISVTX | S_IRWXU | S_IRWXG | S_IRWXO)

int bb_parse_mode(const char *s, mode_t *current_mode)
{
    static const mode_t who_mask[] = {
        S_ISUID | S_ISGID | S_ISVTX | S_IRWXU | S_IRWXG | S_IRWXO, /* a */
        S_ISUID | S_IRWXU,      /* u */
        S_ISGID | S_IRWXG,      /* g */
        S_IRWXO                 /* o */
    };

    static const mode_t perm_mask[] = {
        S_IRUSR | S_IRGRP | S_IROTH, /* r */
        S_IWUSR | S_IWGRP | S_IWOTH, /* w */
        S_IXUSR | S_IXGRP | S_IXOTH, /* x */
        S_IXUSR | S_IXGRP | S_IXOTH, /* X -- special -- see below */
        S_ISUID | S_ISGID,      /* s */
        S_ISVTX                 /* t */
    };

    static const char who_chars[] = "augo";
    static const char perm_chars[] = "rwxXst";

    const char *p;

    mode_t wholist;
    mode_t permlist;
    mode_t mask;
    mode_t new_mode;
    char op;

    assert(s);

    if (((unsigned int)(*s - '0')) < 8) {
        unsigned long tmp;
        char *e;

        tmp = strtol(s, &e, 8);
        if (*e || (tmp > 07777U)) { /* Check range and trailing chars. */
            return 0;
        }
        *current_mode = tmp;
        return 1;
    }

    mask = umask(0);
    umask(mask);

    new_mode = *current_mode;

    /* Note: We allow empty clauses, and hence empty modes.
     * We treat an empty mode as no change to perms. */

    while (*s) {    /* Process clauses. */

        if (*s == ',') {    /* We allow empty clauses. */
            ++s;
            continue;
        }

        /* Get a wholist. */
        wholist = 0;

    WHO_LIST:
        p = who_chars;
        do {
            if (*p == *s) {
                wholist |= who_mask[(int)(p-who_chars)];
                if (!*++s) {
                    return 0;
                }
                goto WHO_LIST;
            }
        } while (*++p);

        do {    /* Process action list. */
            if ((*s != '+') && (*s != '-')) {
                if (*s != '=') {
                    return 0;
                }
                /* Since op is '=', clear all bits corresponding to the
                 * wholist, of all file bits if wholist is empty. */
                permlist = ~FILEMODEBITS;
                if (wholist) {
                    permlist = ~wholist;
                }
                new_mode &= permlist;
            }
            op = *s++;

            /* Check for permcopy. */
            p = who_chars + 1;  /* Skip 'a' entry. */
            do {
                if (*p == *s) {
                    int i = 0;
                    permlist = who_mask[(int)(p-who_chars)]
                             & (S_IRWXU | S_IRWXG | S_IRWXO)
                             & new_mode;
                    do {
                        if (permlist & perm_mask[i]) {
                            permlist |= perm_mask[i];
                        }
                    } while (++i < 3);
                    ++s;
                    goto GOT_ACTION;
                }
            } while (*++p);

            /* It was not a permcopy, so get a permlist. */
            permlist = 0;

        PERM_LIST:
            p = perm_chars;
            do {
                if (*p == *s) {
                    if ((*p != 'X')
                        || (new_mode & (S_IFDIR | S_IXUSR | S_IXGRP | S_IXOTH))
                    ) {
                        permlist |= perm_mask[(int)(p-perm_chars)];
                    }
                    if (!*++s) {
                        break;
                    }
                    goto PERM_LIST;
                }
            } while (*++p);

        GOT_ACTION:
            if (permlist) { /* The permlist was nonempty. */
                mode_t tmp = ~mask;
                if (wholist) {
                    tmp = wholist;
                }
                permlist &= tmp;

                if (op == '-') {
                    new_mode &= ~permlist;
                } else {
                    new_mode |= permlist;
                }
            }
        } while (*s && (*s != ','));
    }

    *current_mode = new_mode;

    return 1;
}