libiberty/make-relative-prefix.c

   1 /* Relative (relocatable) prefix support.
   2    Copyright (C) 1987, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
   3    1999, 2000, 2001, 2002 Free Software Foundation, Inc.
   4
   5 This file is part of libiberty.
   6
   7 GCC is free software; you can redistribute it and/or modify it under
   8 the terms of the GNU General Public License as published by the Free
   9 Software Foundation; either version 2, or (at your option) any later
  10 version.
  11
  12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  14 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  15 for more details.
  16
  17 You should have received a copy of the GNU General Public License
  18 along with GCC; see the file COPYING.  If not, write to the Free
  19 Software Foundation, 51 Franklin Street - Fifth Floor, Boston, MA
  20 02110-1301, USA.  */
  21
  22 /*
  23
  24 @deftypefn Extension {const char*} make_relative_prefix (const char *@var{progname}, const char *@var{bin_prefix}, const char *@var{prefix})
  25
  26 Given three paths @var{progname}, @var{bin_prefix}, @var{prefix},
  27 return the path that is in the same position relative to
  28 @var{progname}'s directory as @var{prefix} is relative to
  29 @var{bin_prefix}.  That is, a string starting with the directory
  30 portion of @var{progname}, followed by a relative pathname of the
  31 difference between @var{bin_prefix} and @var{prefix}.
  32
  33 If @var{progname} does not contain any directory separators,
  34 @code{make_relative_prefix} will search @env{PATH} to find a program
  35 named @var{progname}.  Also, if @var{progname} is a symbolic link,
  36 the symbolic link will be resolved.
  37
  38 For example, if @var{bin_prefix} is @code{/alpha/beta/gamma/gcc/delta},
  39 @var{prefix} is @code{/alpha/beta/gamma/omega/}, and @var{progname} is
  40 @code{/red/green/blue/gcc}, then this function will return
  41 @code{/red/green/blue/../../omega/}.
  42
  43 The return value is normally allocated via @code{malloc}.  If no
  44 relative prefix can be found, return @code{NULL}.
  45
  46 @end deftypefn
  47
  48 */
  49
  50 #ifdef HAVE_CONFIG_H
  51 #include "config.h"
  52 #endif
  53
  54 #ifdef HAVE_STDLIB_H
  55 #include <stdlib.h>
  56 #endif
  57 #ifdef HAVE_UNISTD_H
  58 #include <unistd.h>
  59 #endif
  60
  61 #include <string.h>
  62
  63 #include "ansidecl.h"
  64 #include "libiberty.h"
  65
  66 #ifndef R_OK
  67 #define R_OK 4
  68 #define W_OK 2
  69 #define X_OK 1
  70 #endif
  71
  72 #ifndef DIR_SEPARATOR
  73 #  define DIR_SEPARATOR '/'
  74 #endif
  75
  76 #if defined (_WIN32) || defined (__MSDOS__) \
  77     || defined (__DJGPP__) || defined (__OS2__)
  78 #  define HAVE_DOS_BASED_FILE_SYSTEM
  79 #  define HAVE_HOST_EXECUTABLE_SUFFIX
  80 #  define HOST_EXECUTABLE_SUFFIX ".exe"
  81 #  ifndef DIR_SEPARATOR_2
  82 #    define DIR_SEPARATOR_2 '\\'
  83 #  endif
  84 #  define PATH_SEPARATOR ';'
  85 #else
  86 #  define PATH_SEPARATOR ':'
  87 #endif
  88
  89 #ifndef DIR_SEPARATOR_2
  90 #  define IS_DIR_SEPARATOR(ch) ((ch) == DIR_SEPARATOR)
  91 #else
  92 #  define IS_DIR_SEPARATOR(ch) \
  93         (((ch) == DIR_SEPARATOR) || ((ch) == DIR_SEPARATOR_2))
  94 #endif
  95
  96 #define DIR_UP ".."
  97
  98 static char *save_string (const char *, int);
  99 static char **split_directories (const char *, int *);
 100 static void free_split_directories (char **);
 101
 102 static char *
 103 save_string (const char *s, int len)
 104 {
 105   char *result = malloc (len + 1);
 106
 107   memcpy (result, s, len);
 108   result[len] = 0;
 109   return result;
 110 }
 111
 112 /* Split a filename into component directories.  */
 113
 114 static char **
 115 split_directories (const char *name, int *ptr_num_dirs)
 116 {
 117   int num_dirs = 0;
 118   char **dirs;
 119   const char *p, *q;
 120   int ch;
 121
 122   /* Count the number of directories.  Special case MSDOS disk names as part
 123      of the initial directory.  */
 124   p = name;
 125 #ifdef HAVE_DOS_BASED_FILE_SYSTEM
 126   if (name[1] == ':' && IS_DIR_SEPARATOR (name[2]))
 127     {
 128       p += 3;
 129       num_dirs++;
 130     }
 131 #endif /* HAVE_DOS_BASED_FILE_SYSTEM */
 132
 133   while ((ch = *p++) != '\0')
 134     {
 135       if (IS_DIR_SEPARATOR (ch))
 136         {
 137           num_dirs++;
 138           while (IS_DIR_SEPARATOR (*p))
 139             p++;
 140         }
 141     }
 142
 143   dirs = (char **) malloc (sizeof (char *) * (num_dirs + 2));
 144   if (dirs == NULL)
 145     return NULL;
 146
 147   /* Now copy the directory parts.  */
 148   num_dirs = 0;
 149   p = name;
 150 #ifdef HAVE_DOS_BASED_FILE_SYSTEM
 151   if (name[1] == ':' && IS_DIR_SEPARATOR (name[2]))
 152     {
 153       dirs[num_dirs++] = save_string (p, 3);
 154       if (dirs[num_dirs - 1] == NULL)
 155         {
 156           free (dirs);
 157           return NULL;
 158         }
 159       p += 3;
 160     }
 161 #endif /* HAVE_DOS_BASED_FILE_SYSTEM */
 162
 163   q = p;
 164   while ((ch = *p++) != '\0')
 165     {
 166       if (IS_DIR_SEPARATOR (ch))
 167         {
 168           while (IS_DIR_SEPARATOR (*p))
 169             p++;
 170
 171           dirs[num_dirs++] = save_string (q, p - q);
 172           if (dirs[num_dirs - 1] == NULL)
 173             {
 174               dirs[num_dirs] = NULL;
 175               free_split_directories (dirs);
 176               return NULL;
 177             }
 178           q = p;
 179         }
 180     }
 181
 182   if (p - 1 - q > 0)
 183     dirs[num_dirs++] = save_string (q, p - 1 - q);
 184   dirs[num_dirs] = NULL;
 185
 186   if (dirs[num_dirs - 1] == NULL)
 187     {
 188       free_split_directories (dirs);
 189       return NULL;
 190     }
 191
 192   if (ptr_num_dirs)
 193     *ptr_num_dirs = num_dirs;
 194   return dirs;
 195 }
 196
 197 /* Release storage held by split directories.  */
 198
 199 static void
 200 free_split_directories (char **dirs)
 201 {
 202   int i = 0;
 203
 204   while (dirs[i] != NULL)
 205     free (dirs[i++]);
 206
 207   free ((char *) dirs);
 208 }
 209
 210 /* Given three strings PROGNAME, BIN_PREFIX, PREFIX, return a string that gets
 211    to PREFIX starting with the directory portion of PROGNAME and a relative
 212    pathname of the difference between BIN_PREFIX and PREFIX.
 213
 214    For example, if BIN_PREFIX is /alpha/beta/gamma/gcc/delta, PREFIX is
 215    /alpha/beta/gamma/omega/, and PROGNAME is /red/green/blue/gcc, then this
 216    function will return /red/green/blue/../../omega/.
 217
 218    If no relative prefix can be found, return NULL.  */
 219
 220 char *
 221 make_relative_prefix (const char *progname,
 222                       const char *bin_prefix, const char *prefix)
 223 {
 224   char **prog_dirs, **bin_dirs, **prefix_dirs;
 225   int prog_num, bin_num, prefix_num;
 226   int i, n, common;
 227   int needed_len;
 228   char *ret, *ptr, *full_progname = NULL;
 229
 230   if (progname == NULL || bin_prefix == NULL || prefix == NULL)
 231     return NULL;
 232
 233   /* If there is no full pathname, try to find the program by checking in each
 234      of the directories specified in the PATH environment variable.  */
 235   if (lbasename (progname) == progname)
 236     {
 237       char *temp;
 238
 239       temp = getenv ("PATH");
 240       if (temp)
 241         {
 242           char *startp, *endp, *nstore;
 243           size_t prefixlen = strlen (temp) + 1;
 244           if (prefixlen < 2)
 245             prefixlen = 2;
 246
 247           nstore = (char *) alloca (prefixlen + strlen (progname) + 1);
 248
 249           startp = endp = temp;
 250           while (1)
 251             {
 252               if (*endp == PATH_SEPARATOR || *endp == 0)
 253                 {
 254                   if (endp == startp)
 255                     {
 256                       nstore[0] = '.';
 257                       nstore[1] = DIR_SEPARATOR;
 258                       nstore[2] = '\0';
 259                     }
 260                   else
 261                     {
 262                       strncpy (nstore, startp, endp - startp);
 263                       if (! IS_DIR_SEPARATOR (endp[-1]))
 264                         {
 265                           nstore[endp - startp] = DIR_SEPARATOR;
 266                           nstore[endp - startp + 1] = 0;
 267                         }
 268                       else
 269                         nstore[endp - startp] = 0;
 270                     }
 271                   strcat (nstore, progname);
 272                   if (! access (nstore, X_OK)
 273 #ifdef HAVE_HOST_EXECUTABLE_SUFFIX
 274                       || ! access (strcat (nstore, HOST_EXECUTABLE_SUFFIX), X_OK)
 275 #endif
 276                       )
 277                     {
 278                       progname = nstore;
 279                       break;
 280                     }
 281
 282                   if (*endp == 0)
 283                     break;
 284                   endp = startp = endp + 1;
 285                 }
 286               else
 287                 endp++;
 288             }
 289         }
 290     }
 291
 292   full_progname = lrealpath (progname);
 293   if (full_progname == NULL)
 294     return NULL;
 295
 296   prog_dirs = split_directories (full_progname, &prog_num);
 297   bin_dirs = split_directories (bin_prefix, &bin_num);
 298   free (full_progname);
 299   if (bin_dirs == NULL || prog_dirs == NULL)
 300     return NULL;
 301
 302   /* Remove the program name from comparison of directory names.  */
 303   prog_num--;
 304
 305   /* If we are still installed in the standard location, we don't need to
 306      specify relative directories.  Also, if argv[0] still doesn't contain
 307      any directory specifiers after the search above, then there is not much
 308      we can do.  */
 309   if (prog_num == bin_num)
 310     {
 311       for (i = 0; i < bin_num; i++)
 312         {
 313           if (strcmp (prog_dirs[i], bin_dirs[i]) != 0)
 314             break;
 315         }
 316
 317       if (prog_num <= 0 || i == bin_num)
 318         {
 319           free_split_directories (prog_dirs);
 320           free_split_directories (bin_dirs);
 321           prog_dirs = bin_dirs = (char **) 0;
 322           return NULL;
 323         }
 324     }
 325
 326   prefix_dirs = split_directories (prefix, &prefix_num);
 327   if (prefix_dirs == NULL)
 328     {
 329       free_split_directories (prog_dirs);
 330       free_split_directories (bin_dirs);
 331       return NULL;
 332     }
 333
 334   /* Find how many directories are in common between bin_prefix & prefix.  */
 335   n = (prefix_num < bin_num) ? prefix_num : bin_num;
 336   for (common = 0; common < n; common++)
 337     {
 338       if (strcmp (bin_dirs[common], prefix_dirs[common]) != 0)
 339         break;
 340     }
 341
 342   /* If there are no common directories, there can be no relative prefix.  */
 343   if (common == 0)
 344     {
 345       free_split_directories (prog_dirs);
 346       free_split_directories (bin_dirs);
 347       free_split_directories (prefix_dirs);
 348       return NULL;
 349     }
 350
 351   /* Two passes: first figure out the size of the result string, and
 352      then construct it.  */
 353   needed_len = 0;
 354   for (i = 0; i < prog_num; i++)
 355     needed_len += strlen (prog_dirs[i]);
 356   needed_len += sizeof (DIR_UP) * (bin_num - common);
 357   for (i = common; i < prefix_num; i++)
 358     needed_len += strlen (prefix_dirs[i]);
 359   needed_len += 1; /* Trailing NUL.  */
 360
 361   ret = (char *) malloc (needed_len);
 362   if (ret == NULL)
 363     return NULL;
 364
 365   /* Build up the pathnames in argv[0].  */
 366   *ret = '\0';
 367   for (i = 0; i < prog_num; i++)
 368     strcat (ret, prog_dirs[i]);
 369
 370   /* Now build up the ..'s.  */
 371   ptr = ret + strlen(ret);
 372   for (i = common; i < bin_num; i++)
 373     {
 374       strcpy (ptr, DIR_UP);
 375       ptr += sizeof (DIR_UP) - 1;
 376       *(ptr++) = DIR_SEPARATOR;
 377     }
 378   *ptr = '\0';
 379
 380   /* Put in directories to move over to prefix.  */
 381   for (i = common; i < prefix_num; i++)
 382     strcat (ret, prefix_dirs[i]);
 383
 384   free_split_directories (prog_dirs);
 385   free_split_directories (bin_dirs);
 386   free_split_directories (prefix_dirs);
 387
 388   return ret;
 389 }