misc/mntent_r.c

   1 /* Utilities for reading/writing fstab, mtab, etc.
   2    Copyright (C) 1995-2000, 2001, 2002 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  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 #ifdef USE_IN_LIBIO
  28 # define flockfile(s) _IO_flockfile (s)
  29 # define funlockfile(s) _IO_funlockfile (s)
  30 #endif
  31
  32 #undef __setmntent
  33 #undef __endmntent
  34 #undef __getmntent_r
  35
  36 /* Prepare to begin reading and/or writing mount table entries from the
  37    beginning of FILE.  MODE is as for `fopen'.  */
  38 FILE *
  39 __setmntent (const char *file, const char *mode)
  40 {
  41   FILE *result = fopen (file, mode);
  42
  43   if (result != NULL)
  44     /* We do the locking ourselves.  */
  45     __fsetlocking (result, FSETLOCKING_BYCALLER);
  46
  47   return result;
  48 }
  49 INTDEF(__setmntent)
  50 weak_alias (__setmntent, setmntent)
  51
  52
  53 /* Close a stream opened with `setmntent'.  */
  54 int
  55 __endmntent (FILE *stream)
  56 {
  57   if (stream)           /* SunOS 4.x allows for NULL stream */
  58     fclose (stream);
  59   return 1;             /* SunOS 4.x says to always return 1 */
  60 }
  61 INTDEF(__endmntent)
  62 weak_alias (__endmntent, endmntent)
  63
  64
  65 /* Since the values in a line are separated by spaces, a name cannot
  66    contain a space.  Therefore some programs encode spaces in names
  67    by the strings "\040".  We undo the encoding when reading an entry.
  68    The decoding happens in place.  */
  69 static char *
  70 decode_name (char *buf)
  71 {
  72   char *rp = buf;
  73   char *wp = buf;
  74
  75   do
  76     if (rp[0] == '\\' && rp[1] == '0' && rp[2] == '4' && rp[3] == '0')
  77       {
  78         /* \040 is a SPACE.  */
  79         *wp++ = ' ';
  80         rp += 3;
  81       }
  82     else if (rp[0] == '\\' && rp[1] == '0' && rp[2] == '1' && rp[3] == '2')
  83       {
  84         /* \012 is a TAB.  */
  85         *wp++ = '\t';
  86         rp += 3;
  87       }
  88     else if (rp[0] == '\\' && rp[1] == '\\')
  89       {
  90         /* We have to escape \\ to be able to represent all characters.  */
  91         *wp++ = '\\';
  92         rp += 1;
  93       }
  94     else
  95       *wp++ = *rp;
  96   while (*rp++ != '\0');
  97
  98   return buf;
  99 }
 100
 101
 102 /* Read one mount table entry from STREAM.  Returns a pointer to storage
 103    reused on the next call, or null for EOF or error (use feof/ferror to
 104    check).  */
 105 struct mntent *
 106 __getmntent_r (FILE *stream, struct mntent *mp, char *buffer, int bufsiz)
 107 {
 108   char *cp;
 109   char *head;
 110
 111   flockfile (stream);
 112   do
 113     {
 114       char *end_ptr;
 115
 116       if (fgets_unlocked (buffer, bufsiz, stream) == NULL)
 117         {
 118           funlockfile (stream);
 119           return NULL;
 120         }
 121
 122       end_ptr = strchr (buffer, '\n');
 123       if (end_ptr != NULL)      /* chop newline */
 124         *end_ptr = '\0';
 125       else
 126         {
 127           /* Not the whole line was read.  Do it now but forget it.  */
 128           char tmp[1024];
 129           while (fgets_unlocked (tmp, sizeof tmp, stream) != NULL)
 130             if (strchr (tmp, '\n') != NULL)
 131               break;
 132         }
 133
 134       head = buffer + strspn (buffer, " \t");
 135       /* skip empty lines and comment lines:  */
 136     }
 137   while (head[0] == '\0' || head[0] == '#');
 138
 139   cp = __strsep (&head, " \t");
 140   mp->mnt_fsname = cp != NULL ? decode_name (cp) : (char *) "";
 141   if (head)
 142     head += strspn (head, " \t");
 143   cp = __strsep (&head, " \t");
 144   mp->mnt_dir = cp != NULL ? decode_name (cp) : (char *) "";
 145   if (head)
 146     head += strspn (head, " \t");
 147   cp = __strsep (&head, " \t");
 148   mp->mnt_type = cp != NULL ? decode_name (cp) : (char *) "";
 149   if (head)
 150     head += strspn (head, " \t");
 151   cp = __strsep (&head, " \t");
 152   mp->mnt_opts = cp != NULL ? decode_name (cp) : (char *) "";
 153   switch (head ? sscanf (head, " %d %d ", &mp->mnt_freq, &mp->mnt_passno) : 0)
 154     {
 155     case 0:
 156       mp->mnt_freq = 0;
 157     case 1:
 158       mp->mnt_passno = 0;
 159     case 2:
 160       break;
 161     }
 162   funlockfile (stream);
 163
 164   return mp;
 165 }
 166 INTDEF(__getmntent_r)
 167 weak_alias (__getmntent_r, getmntent_r)
 168
 169
 170 /* We have to use an encoding for names if they contain spaces or tabs.
 171    To be able to represent all characters we also have to escape the
 172    backslash itself.  This "function" must be a macro since we use
 173    `alloca'.  */
 174 #define encode_name(name) \
 175   do {                                                                        \
 176     const char *rp = name;                                                    \
 177                                                                               \
 178     while (*rp != '\0')                                                       \
 179       if (*rp == ' ' || *rp == '\t' || *rp == '\\')                           \
 180         break;                                                                \
 181       else                                                                    \
 182         ++rp;                                                                 \
 183                                                                               \
 184     if (*rp != '\0')                                                          \
 185       {                                                                       \
 186         /* In the worst case the length of the string can increase to         \
 187            founr times the current length.  */                                \
 188         char *wp;                                                             \
 189                                                                               \
 190         rp = name;                                                            \
 191         name = wp = (char *) alloca (strlen (name) * 4 + 1);                  \
 192                                                                               \
 193         do                                                                    \
 194           if (*rp == ' ')                                                     \
 195             {                                                                 \
 196               *wp++ = '\\';                                                   \
 197               *wp++ = '0';                                                    \
 198               *wp++ = '4';                                                    \
 199               *wp++ = '0';                                                    \
 200             }                                                                 \
 201           else if (*rp == '\t')                                               \
 202             {                                                                 \
 203               *wp++ = '\\';                                                   \
 204               *wp++ = '0';                                                    \
 205               *wp++ = '1';                                                    \
 206               *wp++ = '2';                                                    \
 207             }                                                                 \
 208           else if (*rp == '\\')                                               \
 209             {                                                                 \
 210               *wp++ = '\\';                                                   \
 211               *wp++ = '\\';                                                   \
 212             }                                                                 \
 213           else                                                                \
 214             *wp++ = *rp;                                                      \
 215         while (*rp++ != '\0');                                                \
 216       }                                                                       \
 217   } while (0)
 218
 219
 220 /* Write the mount table entry described by MNT to STREAM.
 221    Return zero on success, nonzero on failure.  */
 222 int
 223 __addmntent (FILE *stream, const struct mntent *mnt)
 224 {
 225   struct mntent mntcopy = *mnt;
 226   if (fseek (stream, 0, SEEK_END))
 227     return 1;
 228
 229   /* Encode spaces and tabs in the names.  */
 230   encode_name (mntcopy.mnt_fsname);
 231   encode_name (mntcopy.mnt_dir);
 232   encode_name (mntcopy.mnt_type);
 233   encode_name (mntcopy.mnt_opts);
 234
 235   return (fprintf (stream, "%s %s %s %s %d %d\n",
 236                    mntcopy.mnt_fsname,
 237                    mntcopy.mnt_dir,
 238                    mntcopy.mnt_type,
 239                    mntcopy.mnt_opts,
 240                    mntcopy.mnt_freq,
 241                    mntcopy.mnt_passno)
 242           < 0 ? 1 : 0);
 243 }
 244 weak_alias (__addmntent, addmntent)
 245
 246
 247 /* Search MNT->mnt_opts for an option matching OPT.
 248    Returns the address of the substring, or null if none found.  */
 249 char *
 250 __hasmntopt (const struct mntent *mnt, const char *opt)
 251 {
 252   const size_t optlen = strlen (opt);
 253   char *rest = mnt->mnt_opts, *p;
 254
 255   while ((p = strstr (rest, opt)) != NULL)
 256     {
 257       if (p == rest
 258           || (p[-1] == ','
 259               && (p[optlen] == '\0' ||
 260                   p[optlen] == '='  ||
 261                   p[optlen] == ',')))
 262         return p;
 263
 264       rest = strchr (rest, ',');
 265       if (rest == NULL)
 266         break;
 267       ++rest;
 268     }
 269
 270   return NULL;
 271 }
 272 weak_alias (__hasmntopt, hasmntopt)