ROX-Filer/src/modechange.c

   1 /*
   2  * $Id$
   3  *
   4  * ROX-Filer, filer for the ROX desktop project
   5  * Copyright (C) 2001, 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
  42 #include <glib.h>
  43
  44 #include "modechange.h"
  45
  46 #define isodigit(c) ((c) >= '0' && (c) <= '7')
  47
  48 /* Return a positive integer containing the value of the ASCII
  49    octal number S.  If S is not an octal number or is more than
  50    4 digits, return -1.  */
  51
  52 static int
  53 oatoi (const char *s)
  54 {
  55   register int i;
  56
  57   if (*s == 0 || strlen (s) > 4)
  58     return -1;
  59   for (i = 0; isodigit (*s); ++s)
  60     i = i * 8 + *s - '0';
  61   if (*s)
  62     return -1;
  63   return i;
  64 }
  65
  66 /* Return a linked list of file mode change operations created from
  67    MODE_STRING, an ASCII string that contains either an octal number
  68    specifying an absolute mode, or symbolic mode change operations with
  69    the form:
  70    [ugoa...][[+-=][rwxXstugo...]...][,...]
  71    MASKED_OPS is a bitmask indicating which symbolic mode operators (=+-)
  72    should not affect bits set in the umask when no users are given.
  73    Operators not selected in MASKED_OPS ignore the umask.
  74
  75    Return NULL if `mode_string' does not contain a valid
  76    representation of file mode change operations. */
  77
  78 struct mode_change *
  79 mode_compile (const char *mode_string, unsigned int masked_ops)
  80 {
  81   struct mode_change *head;     /* First element of the linked list. */
  82   struct mode_change *change;   /* An element of the linked list. */
  83   int i;                        /* General purpose temporary. */
  84   int umask_value;              /* The umask value (surprise). */
  85   unsigned short affected_bits; /* Which bits in the mode are operated on. */
  86   unsigned short affected_masked; /* `affected_bits' modified by umask. */
  87   unsigned ops_to_mask;         /* Operators to actually use umask on. */
  88
  89   i = oatoi (mode_string);
  90   if (i >= 0)
  91     {
  92       if (i > 07777)
  93         return NULL;
  94       head = g_new(struct mode_change, 1);
  95       head->next = NULL;
  96       head->op = '=';
  97       head->flags = 0;
  98       head->value = i;
  99       head->affected = 07777;   /* Affect all permissions. */
 100       return head;
 101     }
 102
 103   umask_value = umask (0);
 104   umask (umask_value);          /* Restore the old value. */
 105
 106   head = NULL;
 107   change = NULL;
 108   --mode_string;
 109
 110   /* One loop iteration for each "ugoa...=+-rwxXstugo...[=+-rwxXstugo...]". */
 111   do
 112     {
 113       affected_bits = 0;
 114       ops_to_mask = 0;
 115       /* Turn on all the bits in `affected_bits' for each group given. */
 116       for (++mode_string;; ++mode_string)
 117         switch (*mode_string)
 118           {
 119           case 'u':
 120             affected_bits |= 04700;
 121             break;
 122           case 'g':
 123             affected_bits |= 02070;
 124             break;
 125           case 'o':
 126             affected_bits |= 01007;
 127             break;
 128           case 'a':
 129             affected_bits |= 07777;
 130             break;
 131           default:
 132             goto no_more_affected;
 133           }
 134
 135     no_more_affected:
 136       /* If none specified, affect all bits, except perhaps those
 137          set in the umask. */
 138       if (affected_bits == 0)
 139         {
 140           affected_bits = 07777;
 141           ops_to_mask = masked_ops;
 142         }
 143
 144       while (*mode_string == '=' || *mode_string == '+' || *mode_string == '-')
 145         {
 146           /* Add the element to the tail of the list, so the operations
 147              are performed in the correct order. */
 148           if (head == NULL)
 149             {
 150               head = g_new(struct mode_change, 1);
 151               change = head;
 152             }
 153           else
 154             {
 155               change->next = g_new(struct mode_change, 1);
 156               change = change->next;
 157             }
 158
 159           change->next = NULL;
 160           change->op = *mode_string;    /* One of "=+-". */
 161           affected_masked = affected_bits;
 162           if (ops_to_mask & (*mode_string == '=' ? MODE_MASK_EQUALS
 163                              : *mode_string == '+' ? MODE_MASK_PLUS
 164                              : MODE_MASK_MINUS))
 165             affected_masked &= ~umask_value;
 166           change->affected = affected_masked;
 167           change->value = 0;
 168           change->flags = 0;
 169
 170           /* Set `value' according to the bits set in `affected_masked'. */
 171           for (++mode_string;; ++mode_string)
 172             switch (*mode_string)
 173               {
 174               case 'r':
 175                 change->value |= 00444 & affected_masked;
 176                 break;
 177               case 'w':
 178                 change->value |= 00222 & affected_masked;
 179                 break;
 180               case 'X':
 181                 change->flags |= MODE_X_IF_ANY_X;
 182                 /* Fall through. */
 183               case 'x':
 184                 change->value |= 00111 & affected_masked;
 185                 break;
 186               case 's':
 187                 /* Set the setuid/gid bits if `u' or `g' is selected. */
 188                 change->value |= 06000 & affected_masked;
 189                 break;
 190               case 't':
 191                 /* Set the "save text image" bit if `o' is selected. */
 192                 change->value |= 01000 & affected_masked;
 193                 break;
 194               case 'u':
 195                 /* Set the affected bits to the value of the `u' bits
 196                    on the same file.  */
 197                 if (change->value)
 198                   goto invalid;
 199                 change->value = 00700;
 200                 change->flags |= MODE_COPY_EXISTING;
 201                 break;
 202               case 'g':
 203                 /* Set the affected bits to the value of the `g' bits
 204                    on the same file.  */
 205                 if (change->value)
 206                   goto invalid;
 207                 change->value = 00070;
 208                 change->flags |= MODE_COPY_EXISTING;
 209                 break;
 210               case 'o':
 211                 /* Set the affected bits to the value of the `o' bits
 212                    on the same file.  */
 213                 if (change->value)
 214                   goto invalid;
 215                 change->value = 00007;
 216                 change->flags |= MODE_COPY_EXISTING;
 217                 break;
 218               default:
 219                 goto no_more_values;
 220               }
 221         no_more_values:;
 222         }
 223   } while (*mode_string == ',');
 224   if (*mode_string == 0)
 225     return head;
 226 invalid:
 227   mode_free (head);
 228   return NULL;
 229 }
 230
 231 /* Return file mode OLDMODE, adjusted as indicated by the list of change
 232    operations CHANGES.  If OLDMODE is a directory, the type `X'
 233    change affects it even if no execute bits were set in OLDMODE.
 234    The returned value has the S_IFMT bits cleared. */
 235
 236 unsigned short
 237 mode_adjust (unsigned int oldmode, const struct mode_change *changes)
 238 {
 239   unsigned short newmode;       /* The adjusted mode and one operand. */
 240   unsigned short value;         /* The other operand. */
 241
 242   newmode = oldmode & 07777;
 243
 244   for (; changes; changes = changes->next)
 245     {
 246       if (changes->flags & MODE_COPY_EXISTING)
 247         {
 248           /* Isolate in `value' the bits in `newmode' to copy, given in
 249              the mask `changes->value'. */
 250           value = newmode & changes->value;
 251
 252           if (changes->value & 00700)
 253             /* Copy `u' permissions onto `g' and `o'. */
 254             value |= (value >> 3) | (value >> 6);
 255           else if (changes->value & 00070)
 256             /* Copy `g' permissions onto `u' and `o'. */
 257             value |= (value << 3) | (value >> 3);
 258           else
 259             /* Copy `o' permissions onto `u' and `g'. */
 260             value |= (value << 3) | (value << 6);
 261
 262           /* In order to change only `u', `g', or `o' permissions,
 263              or some combination thereof, clear unselected bits.
 264              This can not be done in mode_compile because the value
 265              to which the `changes->affected' mask is applied depends
 266              on the old mode of each file. */
 267           value &= changes->affected;
 268         }
 269       else
 270         {
 271           value = changes->value;
 272           /* If `X', do not affect the execute bits if the file is not a
 273              directory and no execute bits are already set. */
 274           if ((changes->flags & MODE_X_IF_ANY_X)
 275               && !S_ISDIR (oldmode)
 276               && (newmode & 00111) == 0)
 277             value &= ~00111;    /* Clear the execute bits. */
 278         }
 279
 280       switch (changes->op)
 281         {
 282         case '=':
 283           /* Preserve the previous values in `newmode' of bits that are
 284              not affected by this change operation. */
 285           newmode = (newmode & ~changes->affected) | value;
 286           break;
 287         case '+':
 288           newmode |= value;
 289           break;
 290         case '-':
 291           newmode &= ~value;
 292           break;
 293         }
 294     }
 295   return newmode;
 296 }
 297
 298 /* Free the memory used by the list of file mode change operations
 299    CHANGES. */
 300
 301 void
 302 mode_free (register struct mode_change *changes)
 303 {
 304   register struct mode_change *next;
 305
 306   while (changes)
 307     {
 308       next = changes->next;
 309       g_free (changes);
 310       changes = next;
 311     }
 312 }