external/bsd/ntp/dist/sntp/libopts/compat/pathfind.c

   1 /*      $NetBSD$        */
   2
   3 /*  -*- Mode: C -*-  */
   4
   5 /* pathfind.c --- find a FILE  MODE along PATH */
   6
   7 /*
   8  * Author:           Gary V Vaughan <gvaughan@oranda.demon.co.uk>
   9  * Time-stamp:       "2006-09-23 19:46:16 bkorb"
  10  *            by: bkorb
  11  *
  12  * Id: 8ce7ddfe2378f0b75c91c0ab348a6ad81634fb01
  13  */
  14
  15 /* Code: */
  16
  17 #include "compat.h"
  18 #ifndef HAVE_PATHFIND
  19 #if defined(__windows__) && !defined(__CYGWIN__)
  20 char*
  21 pathfind( char const*  path,
  22           char const*  fileName,
  23           char const*  mode )
  24 {
  25     return NULL;
  26 }
  27 #else
  28
  29 static char* make_absolute( char const *string, char const *dot_path );
  30 static char* canonicalize_pathname( char *path );
  31 static char* extract_colon_unit( char* dir, char const *string, int *p_index );
  32
  33
  34 /*=export_func pathfind
  35  *
  36  * what: fild a file in a list of directories
  37  *
  38  * ifndef: HAVE_PATHFIND
  39  *
  40  * arg:  + char const* + path + colon separated list of search directories +
  41  * arg:  + char const* + file + the name of the file to look for +
  42  * arg:  + char const* + mode + the mode bits that must be set to match +
  43  *
  44  * ret_type:  char*
  45  * ret_desc:  the path to the located file
  46  *
  47  * doc:
  48  *
  49  * pathfind looks for a a file with name "FILE" and "MODE" access
  50  * along colon delimited "PATH", and returns the full pathname as a
  51  * string, or NULL if not found.  If "FILE" contains a slash, then
  52  * it is treated as a relative or absolute path and "PATH" is ignored.
  53  *
  54  * @strong{NOTE}: this function is compiled into @file{libopts} only if
  55  * it is not natively supplied.
  56  *
  57  * The "MODE" argument is a string of option letters chosen from the
  58  * list below:
  59  * @example
  60  *          Letter    Meaning
  61  *          r         readable
  62  *          w         writable
  63  *          x         executable
  64  *          f         normal file       (NOT IMPLEMENTED)
  65  *          b         block special     (NOT IMPLEMENTED)
  66  *          c         character special (NOT IMPLEMENTED)
  67  *          d         directory         (NOT IMPLEMENTED)
  68  *          p         FIFO (pipe)       (NOT IMPLEMENTED)
  69  *          u         set user ID bit   (NOT IMPLEMENTED)
  70  *          g         set group ID bit  (NOT IMPLEMENTED)
  71  *          k         sticky bit        (NOT IMPLEMENTED)
  72  *          s         size nonzero      (NOT IMPLEMENTED)
  73  * @end example
  74  *
  75  * example:
  76  * To find the "ls" command using the "PATH" environment variable:
  77  * @example
  78  *    #include <stdlib.h>
  79  *    char* pz_ls = pathfind( getenv("PATH"), "ls", "rx" );
  80  *    <<do whatever with pz_ls>>
  81  *    free( pz_ls );
  82  * @end example
  83  * The path is allocated with @code{malloc(3C)}, so you must @code{free(3C)}
  84  * the result.  Also, do not use unimplemented file modes.  :-)
  85  *
  86  * err:  returns NULL if the file is not found.
  87 =*/
  88 char*
  89 pathfind( char const*  path,
  90           char const*  fileName,
  91           char const*  mode )
  92 {
  93     int   p_index   = 0;
  94     int   mode_bits = 0;
  95     char* pathName  = NULL;
  96     char  zPath[ AG_PATH_MAX + 1 ];
  97
  98     if (strchr( mode, 'r' )) mode_bits |= R_OK;
  99     if (strchr( mode, 'w' )) mode_bits |= W_OK;
 100     if (strchr( mode, 'x' )) mode_bits |= X_OK;
 101
 102     /*
 103      *  FOR each non-null entry in the colon-separated path, DO ...
 104      */
 105     for (;;) {
 106         DIR*  dirP;
 107         char* colon_unit = extract_colon_unit( zPath, path, &p_index );
 108
 109         /*
 110          *  IF no more entries, THEN quit
 111          */
 112         if (colon_unit == NULL)
 113             break;
 114
 115         dirP = opendir( colon_unit );
 116
 117         /*
 118          *  IF the directory is inaccessable, THEN next directory
 119          */
 120         if (dirP == NULL)
 121             continue;
 122
 123         /*
 124          *  FOR every entry in the given directory, ...
 125          */
 126         for (;;) {
 127             struct dirent *entP = readdir( dirP );
 128
 129             if (entP == (struct dirent*)NULL)
 130                 break;
 131
 132             /*
 133              *  IF the file name matches the one we are looking for, ...
 134              */
 135             if (strcmp( entP->d_name, fileName ) == 0) {
 136                 char* pzFullName = make_absolute( fileName, colon_unit);
 137
 138                 /*
 139                  *  Make sure we can access it in the way we want
 140                  */
 141                 if (access( pzFullName, mode_bits ) >= 0) {
 142                     /*
 143                      *  We can, so normalize the name and return it below
 144                      */
 145                     pathName = canonicalize_pathname( pzFullName );
 146                 }
 147
 148                 free( (void*)pzFullName );
 149                 break;
 150             }
 151         }
 152
 153         closedir( dirP );
 154
 155         if (pathName != NULL)
 156             break;
 157     }
 158
 159     return pathName;
 160 }
 161
 162 /*
 163  * Turn STRING  (a pathname) into an  absolute  pathname, assuming  that
 164  * DOT_PATH contains the symbolic location of  `.'.  This always returns
 165  * a new string, even if STRING was an absolute pathname to begin with.
 166  */
 167 static char*
 168 make_absolute( char const *string, char const *dot_path )
 169 {
 170     char *result;
 171     int result_len;
 172
 173     if (!dot_path || *string == '/') {
 174         result = strdup( string );
 175     } else {
 176         if (dot_path && dot_path[0]) {
 177             result = malloc( 2 + strlen( dot_path ) + strlen( string ) );
 178             strcpy( result, dot_path );
 179             result_len = strlen( result );
 180             if (result[result_len - 1] != '/') {
 181                 result[result_len++] = '/';
 182                 result[result_len] = '\0';
 183             }
 184         } else {
 185             result = malloc( 3 + strlen( string ) );
 186             result[0] = '.'; result[1] = '/'; result[2] = '\0';
 187             result_len = 2;
 188         }
 189
 190         strcpy( result + result_len, string );
 191     }
 192
 193     return result;
 194 }
 195
 196 /*
 197  * Canonicalize PATH, and return a  new path.  The new path differs from
 198  * PATH in that:
 199  *
 200  *    Multiple `/'s     are collapsed to a single `/'.
 201  *    Leading `./'s     are removed.
 202  *    Trailing `/.'s    are removed.
 203  *    Trailing `/'s     are removed.
 204  *    Non-leading `../'s and trailing `..'s are handled by removing
 205  *                    portions of the path.
 206  */
 207 static char*
 208 canonicalize_pathname( char *path )
 209 {
 210     int i, start;
 211     char stub_char, *result;
 212
 213     /* The result cannot be larger than the input PATH. */
 214     result = strdup( path );
 215
 216     stub_char = (*path == '/') ? '/' : '.';
 217
 218     /* Walk along RESULT looking for things to compact. */
 219     i = 0;
 220     while (result[i]) {
 221         while (result[i] != '\0' && result[i] != '/')
 222             i++;
 223
 224         start = i++;
 225
 226         /* If we didn't find any  slashes, then there is nothing left to
 227          * do.
 228          */
 229         if (!result[start])
 230             break;
 231
 232         /* Handle multiple `/'s in a row. */
 233         while (result[i] == '/')
 234             i++;
 235
 236 #if !defined (apollo)
 237         if ((start + 1) != i)
 238 #else
 239         if ((start + 1) != i && (start != 0 || i != 2))
 240 #endif /* apollo */
 241         {
 242             strcpy( result + start + 1, result + i );
 243             i = start + 1;
 244         }
 245
 246         /* Handle backquoted `/'. */
 247         if (start > 0 && result[start - 1] == '\\')
 248             continue;
 249
 250         /* Check for trailing `/', and `.' by itself. */
 251         if ((start && !result[i])
 252             || (result[i] == '.' && !result[i+1])) {
 253             result[--i] = '\0';
 254             break;
 255         }
 256
 257         /* Check for `../', `./' or trailing `.' by itself. */
 258         if (result[i] == '.') {
 259             /* Handle `./'. */
 260             if (result[i + 1] == '/') {
 261                 strcpy( result + i, result + i + 1 );
 262                 i = (start < 0) ? 0 : start;
 263                 continue;
 264             }
 265
 266             /* Handle `../' or trailing `..' by itself. */
 267             if (result[i + 1] == '.' &&
 268                 (result[i + 2] == '/' || !result[i + 2])) {
 269                 while (--start > -1 && result[start] != '/')
 270                     ;
 271                 strcpy( result + start + 1, result + i + 2 );
 272                 i = (start < 0) ? 0 : start;
 273                 continue;
 274             }
 275         }
 276     }
 277
 278     if (!*result) {
 279         *result = stub_char;
 280         result[1] = '\0';
 281     }
 282
 283     return result;
 284 }
 285
 286 /*
 287  * Given a  string containing units of information separated  by colons,
 288  * return the next one  pointed to by (P_INDEX), or NULL if there are no
 289  * more.  Advance (P_INDEX) to the character after the colon.
 290  */
 291 static char*
 292 extract_colon_unit( char* pzDir, char const *string, int *p_index )
 293 {
 294     char*  pzDest = pzDir;
 295     int    ix     = *p_index;
 296
 297     if (string == NULL)
 298         return NULL;
 299
 300     if ((unsigned)ix >= strlen( string ))
 301         return NULL;
 302
 303     {
 304         char const* pzSrc = string + ix;
 305
 306         while (*pzSrc == ':')  pzSrc++;
 307
 308         for (;;) {
 309             char ch = (*(pzDest++) = *(pzSrc++));
 310             switch (ch) {
 311             case ':':
 312                 pzDest[-1] = NUL;
 313             case NUL:
 314                 goto copy_done;
 315             }
 316
 317             if ((pzDest - pzDir) >= AG_PATH_MAX)
 318                 break;
 319         } copy_done:;
 320
 321         ix = pzSrc - string;
 322     }
 323
 324     if (*pzDir == NUL)
 325         return NULL;
 326
 327     *p_index = ix;
 328     return pzDir;
 329 }
 330 #endif /* __windows__ / __CYGWIN__ */
 331 #endif /* HAVE_PATHFIND */
 332
 333 /*
 334  * Local Variables:
 335  * mode: C
 336  * c-file-style: "stroustrup"
 337  * indent-tabs-mode: nil
 338  * End:
 339  * end of compat/pathfind.c */