ROX-Filer/src/modechange.c

   1 /*
   2  * $Id$
   3  *
   4  * ROX-Filer, filer for the ROX desktop project
   5  * Copyright (C) 2003, the ROX-Filer team.
   6  *
   7  * This program is free software; you can redistribute it and/or modify it
   8  * under the terms of the GNU General Public License as published by the Free
   9  * Software Foundation; either version 2 of the License, or (at your option)
  10  * any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful, but WITHOUT
  13  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  14  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  15  * more details.
  16  *
  17  * You should have received a copy of the GNU General Public License along with
  18  * this program; if not, write to the Free Software Foundation, Inc., 59 Temple
  19  * Place, Suite 330, Boston, MA  02111-1307  USA
  20  */
  21
  22 /* modechange.c -- file mode manipulation
  23  *
  24  * This rest of this file was taken from GNU FileUtils, with minor
  25  * modifications (eg changing the memory handling to use GLib).
  26  */
  27
  28 /* Written by David MacKenzie <djm@ai.mit.edu> */
  29
  30 /* The ASCII mode string is compiled into a linked list of `struct
  31    modechange', which can then be applied to each file to be changed.
  32    We do this instead of re-parsing the ASCII string for each file
  33    because the compiled form requires less computation to use; when
  34    changing the mode of many files, this probably results in a
  35    performance gain. */
  36
  37 #include "config.h"
  38
  39 #include <sys/types.h>
  40 #include <sys/stat.h>
  41 #include <string.h>
  42
  43 #include <glib.h>
  44
  45 #include "modechange.h"
  46
  47 #define isodigit(c) ((c) >= '0' && (c) <= '7')
  48
  49 /* Return a positive integer containing the value of the ASCII
  50    octal number S.  If S is not an octal number or is more than
  51    4 digits, return -1.  */
  52
  53 static int
  54 oatoi (const char *s)
  55 {
  56   register int i;
  57
  58   if (*s == 0 || strlen (s) > 4)
  59     return -1;
  60   for (i = 0; isodigit (*s); ++s)
  61     i = i * 8 + *s - '0';
  62   if (*s)
  63     return -1;
  64   return i;
  65 }
  66
  67 /* Return a linked list of file mode change operations created from
  68    MODE_STRING, an ASCII string that contains either an octal number
  69    specifying an absolute mode, or symbolic mode change operations with
  70    the form:
  71    [ugoa...][[+-=][rwxXstugo...]...][,...]
  72    MASKED_OPS is a bitmask indicating which symbolic mode operators (=+-)
  73    should not affect bits set in the umask when no users are given.
  74    Operators not selected in MASKED_OPS ignore the umask.
  75
  76    Return NULL if `mode_string' does not contain a valid
  77    representation of file mode change operations. */
  78
  79 struct mode_change *
  80 mode_compile (const char *mode_string, unsigned int masked_ops)
  81 {
  82   struct mode_change *head;     /* First element of the linked list. */
  83   struct mode_change *change;   /* An element of the linked list. */
  84   int i;                        /* General purpose temporary. */
  85   int umask_value;              /* The umask value (surprise). */
  86   unsigned short affected_bits; /* Which bits in the mode are operated on. */
  87   unsigned short affected_masked; /* `affected_bits' modified by umask. */
  88   unsigned ops_to_mask;         /* Operators to actually use umask on. */
  89
  90   i = oatoi (mode_string);
  91   if (i >= 0)
  92     {
  93       if (i > 07777)
  94         return NULL;
  95       head = g_new(struct mode_change, 1);
  96       head->next = NULL;
  97       head->op = '=';
  98       head->flags = 0;
  99       head->value = i;
 100       head->affected = 07777;   /* Affect all permissions. */
 101       return head;
 102     }
 103
 104   umask_value = umask (0);
 105   umask (umask_value);          /* Restore the old value. */
 106
 107   head = NULL;
 108   change = NULL;
 109   --mode_string;
 110
 111   /* One loop iteration for each "ugoa...=+-rwxXstugo...[=+-rwxXstugo...]". */
 112   do
 113     {
 114       affected_bits = 0;
 115       ops_to_mask = 0;
 116       /* Turn on all the bits in `affected_bits' for each group given. */
 117       for (++mode_string;; ++mode_string)
 118         switch (*mode_string)
 119           {
 120           case 'u':
 121             affected_bits |= 04700;
 122             break;
 123           case 'g':
 124             affected_bits |= 02070;
 125             break;
 126           case 'o':
 127             affected_bits |= 01007;
 128             break;
 129           case 'a':
 130             affected_bits |= 07777;
 131             break;
 132           default:
 133             goto no_more_affected;
 134           }
 135
 136     no_more_affected:
 137       /* If none specified, affect all bits, except perhaps those
 138          set in the umask. */
 139       if (affected_bits == 0)
 140         {
 141           affected_bits = 07777;
 142           ops_to_mask = masked_ops;
 143         }
 144
 145       while (*mode_string == '=' || *mode_string == '+' || *mode_string == '-')
 146         {
 147           /* Add the element to the tail of the list, so the operations
 148              are performed in the correct order. */
 149           if (head == NULL)
 150             {
 151               head = g_new(struct mode_change, 1);
 152               change = head;
 153             }
 154           else
 155             {
 156               change->next = g_new(struct mode_change, 1);
 157               change = change->next;
 158             }
 159
 160           change->next = NULL;
 161           change->op = *mode_string;    /* One of "=+-". */
 162           affected_masked = affected_bits;
 163           if (ops_to_mask & (*mode_string == '=' ? MODE_MASK_EQUALS
 164                              : *mode_string == '+' ? MODE_MASK_PLUS
 165                              : MODE_MASK_MINUS))
 166             affected_masked &= ~umask_value;
 167           change->affected = affected_masked;
 168           change->value = 0;
 169           change->flags = 0;
 170
 171           /* Set `value' according to the bits set in `affected_masked'. */
 172           for (++mode_string;; ++mode_string)
 173             switch (*mode_string)
 174               {
 175               case 'r':
 176                 change->value |= 00444 & affected_masked;
 177                 break;
 178               case 'w':
 179                 change->value |= 00222 & affected_masked;
 180                 break;
 181               case 'X':
 182                 change->flags |= MODE_X_IF_ANY_X;
 183                 /* Fall through. */
 184               case 'x':
 185                 change->value |= 00111 & affected_masked;
 186                 break;
 187               case 's':
 188                 /* Set the setuid/gid bits if `u' or `g' is selected. */
 189                 change->value |= 06000 & affected_masked;
 190                 break;
 191               case 't':
 192                 /* Set the "save text image" bit if `o' is selected. */
 193                 change->value |= 01000 & affected_masked;
 194                 break;
 195               case 'u':
 196                 /* Set the affected bits to the value of the `u' bits
 197                    on the same file.  */
 198                 if (change->value)
 199                   goto invalid;
 200                 change->value = 00700;
 201                 change->flags |= MODE_COPY_EXISTING;
 202                 break;
 203               case 'g':
 204                 /* Set the affected bits to the value of the `g' bits
 205                    on the same file.  */
 206                 if (change->value)
 207                   goto invalid;
 208                 change->value = 00070;
 209                 change->flags |= MODE_COPY_EXISTING;
 210                 break;
 211               case 'o':
 212                 /* Set the affected bits to the value of the `o' bits
 213                    on the same file.  */
 214                 if (change->value)
 215                   goto invalid;
 216                 change->value = 00007;
 217                 change->flags |= MODE_COPY_EXISTING;
 218                 break;
 219               default:
 220                 goto no_more_values;
 221               }
 222         no_more_values:;
 223         }
 224   } while (*mode_string == ',');
 225   if (*mode_string == 0)
 226     return head;
 227 invalid:
 228   mode_free (head);
 229   return NULL;
 230 }
 231
 232 /* Return file mode OLDMODE, adjusted as indicated by the list of change
 233    operations CHANGES.  If OLDMODE is a directory, the type `X'
 234    change affects it even if no execute bits were set in OLDMODE.
 235    The returned value has the S_IFMT bits cleared. */
 236
 237 unsigned short
 238 mode_adjust (unsigned int oldmode, const struct mode_change *changes)
 239 {
 240   unsigned short newmode;       /* The adjusted mode and one operand. */
 241   unsigned short value;         /* The other operand. */
 242
 243   newmode = oldmode & 07777;
 244
 245   for (; changes; changes = changes->next)
 246     {
 247       if (changes->flags & MODE_COPY_EXISTING)
 248         {
 249           /* Isolate in `value' the bits in `newmode' to copy, given in
 250              the mask `changes->value'. */
 251           value = newmode & changes->value;
 252
 253           if (changes->value & 00700)
 254             /* Copy `u' permissions onto `g' and `o'. */
 255             value |= (value >> 3) | (value >> 6);
 256           else if (changes->value & 00070)
 257             /* Copy `g' permissions onto `u' and `o'. */
 258             value |= (value << 3) | (value >> 3);
 259           else
 260             /* Copy `o' permissions onto `u' and `g'. */
 261             value |= (value << 3) | (value << 6);
 262
 263           /* In order to change only `u', `g', or `o' permissions,
 264              or some combination thereof, clear unselected bits.
 265              This can not be done in mode_compile because the value
 266              to which the `changes->affected' mask is applied depends
 267              on the old mode of each file. */
 268           value &= changes->affected;
 269         }
 270       else
 271         {
 272           value = changes->value;
 273           /* If `X', do not affect the execute bits if the file is not a
 274              directory and no execute bits are already set. */
 275           if ((changes->flags & MODE_X_IF_ANY_X)
 276               && !S_ISDIR (oldmode)
 277               && (newmode & 00111) == 0)
 278             value &= ~00111;    /* Clear the execute bits. */
 279         }
 280
 281       switch (changes->op)
 282         {
 283         case '=':
 284           /* Preserve the previous values in `newmode' of bits that are
 285              not affected by this change operation. */
 286           newmode = (newmode & ~changes->affected) | value;
 287           break;
 288         case '+':
 289           newmode |= value;
 290           break;
 291         case '-':
 292           newmode &= ~value;
 293           break;
 294         }
 295     }
 296   return newmode;
 297 }
 298
 299 /* Free the memory used by the list of file mode change operations
 300    CHANGES. */
 301
 302 void
 303 mode_free (register struct mode_change *changes)
 304 {
 305   register struct mode_change *next;
 306
 307   while (changes)
 308     {
 309       next = changes->next;
 310       g_free (changes);
 311       changes = next;
 312     }
 313 }