misc/mntent_r.c

   1 /* Utilities for reading/writing fstab, mtab, etc.
   2    Copyright (C) 1995-2000, 2001, 2002, 2003, 2006, 2010, 2011
   3    Free Software Foundation, Inc.
   4    This file is part of the GNU C Library.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #include <alloca.h>
  21 #include <mntent.h>
  22 #include <stdio.h>
  23 #include <stdio_ext.h>
  24 #include <string.h>
  25 #include <sys/types.h>
  26
  27 #define flockfile(s) _IO_flockfile (s)
  28 #define funlockfile(s) _IO_funlockfile (s)
  29
  30 #undef __setmntent
  31 #undef __endmntent
  32 #undef __getmntent_r
  33
  34 /* Prepare to begin reading and/or writing mount table entries from the
  35    beginning of FILE.  MODE is as for `fopen'.  */
  36 FILE *
  37 __setmntent (const char *file, const char *mode)
  38 {
  39   /* Extend the mode parameter with "c" to disable cancellation in the
  40      I/O functions and "e" to set FD_CLOEXEC.  */
  41   size_t modelen = strlen (mode);
  42   char newmode[modelen + 3];
  43   memcpy (mempcpy (newmode, mode, modelen), "ce", 3);
  44   FILE *result = fopen (file, newmode);
  45
  46   if (result != NULL)
  47     /* We do the locking ourselves.  */
  48     __fsetlocking (result, FSETLOCKING_BYCALLER);
  49
  50   return result;
  51 }
  52 INTDEF(__setmntent)
  53 weak_alias (__setmntent, setmntent)
  54
  55
  56 /* Close a stream opened with `setmntent'.  */
  57 int
  58 __endmntent (FILE *stream)
  59 {
  60   if (stream)           /* SunOS 4.x allows for NULL stream */
  61     fclose (stream);
  62   return 1;             /* SunOS 4.x says to always return 1 */
  63 }
  64 INTDEF(__endmntent)
  65 weak_alias (__endmntent, endmntent)
  66
  67
  68 /* Since the values in a line are separated by spaces, a name cannot
  69    contain a space.  Therefore some programs encode spaces in names
  70    by the strings "\040".  We undo the encoding when reading an entry.
  71    The decoding happens in place.  */
  72 static char *
  73 decode_name (char *buf)
  74 {
  75   char *rp = buf;
  76   char *wp = buf;
  77
  78   do
  79     if (rp[0] == '\\' && rp[1] == '0' && rp[2] == '4' && rp[3] == '0')
  80       {
  81         /* \040 is a SPACE.  */
  82         *wp++ = ' ';
  83         rp += 3;
  84       }
  85     else if (rp[0] == '\\' && rp[1] == '0' && rp[2] == '1' && rp[3] == '1')
  86       {
  87         /* \011 is a TAB.  */
  88         *wp++ = '\t';
  89         rp += 3;
  90       }
  91     else if (rp[0] == '\\' && rp[1] == '0' && rp[2] == '1' && rp[3] == '2')
  92       {
  93         /* \012 is a NEWLINE.  */
  94         *wp++ = '\n';
  95         rp += 3;
  96       }
  97     else if (rp[0] == '\\' && rp[1] == '\\')
  98       {
  99         /* We have to escape \\ to be able to represent all characters.  */
 100         *wp++ = '\\';
 101         rp += 1;
 102       }
 103     else if (rp[0] == '\\' && rp[1] == '1' && rp[2] == '3' && rp[3] == '4')
 104       {
 105         /* \134 is also \\.  */
 106         *wp++ = '\\';
 107         rp += 3;
 108       }
 109     else
 110       *wp++ = *rp;
 111   while (*rp++ != '\0');
 112
 113   return buf;
 114 }
 115
 116
 117 /* Read one mount table entry from STREAM.  Returns a pointer to storage
 118    reused on the next call, or null for EOF or error (use feof/ferror to
 119    check).  */
 120 struct mntent *
 121 __getmntent_r (FILE *stream, struct mntent *mp, char *buffer, int bufsiz)
 122 {
 123   char *cp;
 124   char *head;
 125
 126   flockfile (stream);
 127   do
 128     {
 129       char *end_ptr;
 130
 131       if (fgets_unlocked (buffer, bufsiz, stream) == NULL)
 132         {
 133           funlockfile (stream);
 134           return NULL;
 135         }
 136
 137       end_ptr = strchr (buffer, '\n');
 138       if (end_ptr != NULL)      /* chop newline */
 139         *end_ptr = '\0';
 140       else
 141         {
 142           /* Not the whole line was read.  Do it now but forget it.  */
 143           char tmp[1024];
 144           while (fgets_unlocked (tmp, sizeof tmp, stream) != NULL)
 145             if (strchr (tmp, '\n') != NULL)
 146               break;
 147         }
 148
 149       head = buffer + strspn (buffer, " \t");
 150       /* skip empty lines and comment lines:  */
 151     }
 152   while (head[0] == '\0' || head[0] == '#');
 153
 154   cp = __strsep (&head, " \t");
 155   mp->mnt_fsname = cp != NULL ? decode_name (cp) : (char *) "";
 156   if (head)
 157     head += strspn (head, " \t");
 158   cp = __strsep (&head, " \t");
 159   mp->mnt_dir = cp != NULL ? decode_name (cp) : (char *) "";
 160   if (head)
 161     head += strspn (head, " \t");
 162   cp = __strsep (&head, " \t");
 163   mp->mnt_type = cp != NULL ? decode_name (cp) : (char *) "";
 164   if (head)
 165     head += strspn (head, " \t");
 166   cp = __strsep (&head, " \t");
 167   mp->mnt_opts = cp != NULL ? decode_name (cp) : (char *) "";
 168   switch (head ? sscanf (head, " %d %d ", &mp->mnt_freq, &mp->mnt_passno) : 0)
 169     {
 170     case 0:
 171       mp->mnt_freq = 0;
 172     case 1:
 173       mp->mnt_passno = 0;
 174     case 2:
 175       break;
 176     }
 177   funlockfile (stream);
 178
 179   return mp;
 180 }
 181 INTDEF(__getmntent_r)
 182 weak_alias (__getmntent_r, getmntent_r)
 183
 184
 185 /* We have to use an encoding for names if they contain spaces or tabs.
 186    To be able to represent all characters we also have to escape the
 187    backslash itself.  This "function" must be a macro since we use
 188    `alloca'.  */
 189 #define encode_name(name) \
 190   do {                                                                        \
 191     const char *rp = name;                                                    \
 192                                                                               \
 193     while (*rp != '\0')                                                       \
 194       if (*rp == ' ' || *rp == '\t' || *rp == '\n' || *rp == '\\')            \
 195         break;                                                                \
 196       else                                                                    \
 197         ++rp;                                                                 \
 198                                                                               \
 199     if (*rp != '\0')                                                          \
 200       {                                                                       \
 201         /* In the worst case the length of the string can increase to         \
 202            four times the current length.  */                                 \
 203         char *wp;                                                             \
 204                                                                               \
 205         rp = name;                                                            \
 206         name = wp = (char *) alloca (strlen (name) * 4 + 1);                  \
 207                                                                               \
 208         do                                                                    \
 209           if (*rp == ' ')                                                     \
 210             {                                                                 \
 211               *wp++ = '\\';                                                   \
 212               *wp++ = '0';                                                    \
 213               *wp++ = '4';                                                    \
 214               *wp++ = '0';                                                    \
 215             }                                                                 \
 216           else if (*rp == '\t')                                               \
 217             {                                                                 \
 218               *wp++ = '\\';                                                   \
 219               *wp++ = '0';                                                    \
 220               *wp++ = '1';                                                    \
 221               *wp++ = '1';                                                    \
 222             }                                                                 \
 223           else if (*rp == '\n')                                               \
 224             {                                                                 \
 225               *wp++ = '\\';                                                   \
 226               *wp++ = '0';                                                    \
 227               *wp++ = '1';                                                    \
 228               *wp++ = '2';                                                    \
 229             }                                                                 \
 230           else if (*rp == '\\')                                               \
 231             {                                                                 \
 232               *wp++ = '\\';                                                   \
 233               *wp++ = '\\';                                                   \
 234             }                                                                 \
 235           else                                                                \
 236             *wp++ = *rp;                                                      \
 237         while (*rp++ != '\0');                                                \
 238       }                                                                       \
 239   } while (0)
 240
 241
 242 /* Write the mount table entry described by MNT to STREAM.
 243    Return zero on success, nonzero on failure.  */
 244 int
 245 __addmntent (FILE *stream, const struct mntent *mnt)
 246 {
 247   struct mntent mntcopy = *mnt;
 248   if (fseek (stream, 0, SEEK_END))
 249     return 1;
 250
 251   /* Encode spaces and tabs in the names.  */
 252   encode_name (mntcopy.mnt_fsname);
 253   encode_name (mntcopy.mnt_dir);
 254   encode_name (mntcopy.mnt_type);
 255   encode_name (mntcopy.mnt_opts);
 256
 257   return (fprintf (stream, "%s %s %s %s %d %d\n",
 258                    mntcopy.mnt_fsname,
 259                    mntcopy.mnt_dir,
 260                    mntcopy.mnt_type,
 261                    mntcopy.mnt_opts,
 262                    mntcopy.mnt_freq,
 263                    mntcopy.mnt_passno) < 0
 264           || fflush (stream) != 0);
 265 }
 266 weak_alias (__addmntent, addmntent)
 267
 268
 269 /* Search MNT->mnt_opts for an option matching OPT.
 270    Returns the address of the substring, or null if none found.  */
 271 char *
 272 __hasmntopt (const struct mntent *mnt, const char *opt)
 273 {
 274   const size_t optlen = strlen (opt);
 275   char *rest = mnt->mnt_opts, *p;
 276
 277   while ((p = strstr (rest, opt)) != NULL)
 278     {
 279       if ((p == rest || p[-1] == ',')
 280           && (p[optlen] == '\0' || p[optlen] == '=' || p[optlen] == ','))
 281         return p;
 282
 283       rest = strchr (p, ',');
 284       if (rest == NULL)
 285         break;
 286       ++rest;
 287     }
 288
 289   return NULL;
 290 }
 291 weak_alias (__hasmntopt, hasmntopt)