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, 59 Temple Place - Suite 330, Boston, MA
  20 02111-1307, 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 PARAMS ((const char *, int));
  99 static char **split_directories PARAMS ((const char *, int *));
 100 static void free_split_directories PARAMS ((char **));
 101
 102 static char *
 103 save_string (s, len)
 104      const char *s;
 105      int len;
 106 {
 107   char *result = malloc (len + 1);
 108
 109   memcpy (result, s, len);
 110   result[len] = 0;
 111   return result;
 112 }
 113
 114 /* Split a filename into component directories.  */
 115
 116 static char **
 117 split_directories (name, ptr_num_dirs)
 118      const char *name;
 119      int *ptr_num_dirs;
 120 {
 121   int num_dirs = 0;
 122   char **dirs;
 123   const char *p, *q;
 124   int ch;
 125
 126   /* Count the number of directories.  Special case MSDOS disk names as part
 127      of the initial directory.  */
 128   p = name;
 129 #ifdef HAVE_DOS_BASED_FILE_SYSTEM
 130   if (name[1] == ':' && IS_DIR_SEPARATOR (name[2]))
 131     {
 132       p += 3;
 133       num_dirs++;
 134     }
 135 #endif /* HAVE_DOS_BASED_FILE_SYSTEM */
 136
 137   while ((ch = *p++) != '\0')
 138     {
 139       if (IS_DIR_SEPARATOR (ch))
 140         {
 141           num_dirs++;
 142           while (IS_DIR_SEPARATOR (*p))
 143             p++;
 144         }
 145     }
 146
 147   dirs = (char **) malloc (sizeof (char *) * (num_dirs + 2));
 148   if (dirs == NULL)
 149     return NULL;
 150
 151   /* Now copy the directory parts.  */
 152   num_dirs = 0;
 153   p = name;
 154 #ifdef HAVE_DOS_BASED_FILE_SYSTEM
 155   if (name[1] == ':' && IS_DIR_SEPARATOR (name[2]))
 156     {
 157       dirs[num_dirs++] = save_string (p, 3);
 158       if (dirs[num_dirs - 1] == NULL)
 159         {
 160           free (dirs);
 161           return NULL;
 162         }
 163       p += 3;
 164     }
 165 #endif /* HAVE_DOS_BASED_FILE_SYSTEM */
 166
 167   q = p;
 168   while ((ch = *p++) != '\0')
 169     {
 170       if (IS_DIR_SEPARATOR (ch))
 171         {
 172           while (IS_DIR_SEPARATOR (*p))
 173             p++;
 174
 175           dirs[num_dirs++] = save_string (q, p - q);
 176           if (dirs[num_dirs - 1] == NULL)
 177             {
 178               dirs[num_dirs] = NULL;
 179               free_split_directories (dirs);
 180               return NULL;
 181             }
 182           q = p;
 183         }
 184     }
 185
 186   if (p - 1 - q > 0)
 187     dirs[num_dirs++] = save_string (q, p - 1 - q);
 188   dirs[num_dirs] = NULL;
 189
 190   if (dirs[num_dirs - 1] == NULL)
 191     {
 192       free_split_directories (dirs);
 193       return NULL;
 194     }
 195
 196   if (ptr_num_dirs)
 197     *ptr_num_dirs = num_dirs;
 198   return dirs;
 199 }
 200
 201 /* Release storage held by split directories.  */
 202
 203 static void
 204 free_split_directories (dirs)
 205      char **dirs;
 206 {
 207   int i = 0;
 208
 209   while (dirs[i] != NULL)
 210     free (dirs[i++]);
 211
 212   free ((char *) dirs);
 213 }
 214
 215 /* Given three strings PROGNAME, BIN_PREFIX, PREFIX, return a string that gets
 216    to PREFIX starting with the directory portion of PROGNAME and a relative
 217    pathname of the difference between BIN_PREFIX and PREFIX.
 218
 219    For example, if BIN_PREFIX is /alpha/beta/gamma/gcc/delta, PREFIX is
 220    /alpha/beta/gamma/omega/, and PROGNAME is /red/green/blue/gcc, then this
 221    function will return /red/green/blue/../../omega/.
 222
 223    If no relative prefix can be found, return NULL.  */
 224
 225 char *
 226 make_relative_prefix (progname, bin_prefix, prefix)
 227      const char *progname;
 228      const char *bin_prefix;
 229      const char *prefix;
 230 {
 231   char **prog_dirs, **bin_dirs, **prefix_dirs;
 232   int prog_num, bin_num, prefix_num;
 233   int i, n, common;
 234   int needed_len;
 235   char *ret, *ptr, *full_progname = NULL;
 236
 237   if (progname == NULL || bin_prefix == NULL || prefix == NULL)
 238     return NULL;
 239
 240   /* If there is no full pathname, try to find the program by checking in each
 241      of the directories specified in the PATH environment variable.  */
 242   if (lbasename (progname) == progname)
 243     {
 244       char *temp;
 245
 246       temp = getenv ("PATH");
 247       if (temp)
 248         {
 249           char *startp, *endp, *nstore;
 250           size_t prefixlen = strlen (temp) + 1;
 251           if (prefixlen < 2)
 252             prefixlen = 2;
 253
 254           nstore = (char *) alloca (prefixlen + strlen (progname) + 1);
 255
 256           startp = endp = temp;
 257           while (1)
 258             {
 259               if (*endp == PATH_SEPARATOR || *endp == 0)
 260                 {
 261                   if (endp == startp)
 262                     {
 263                       nstore[0] = '.';
 264                       nstore[1] = DIR_SEPARATOR;
 265                       nstore[2] = '\0';
 266                     }
 267                   else
 268                     {
 269                       strncpy (nstore, startp, endp - startp);
 270                       if (! IS_DIR_SEPARATOR (endp[-1]))
 271                         {
 272                           nstore[endp - startp] = DIR_SEPARATOR;
 273                           nstore[endp - startp + 1] = 0;
 274                         }
 275                       else
 276                         nstore[endp - startp] = 0;
 277                     }
 278                   strcat (nstore, progname);
 279                   if (! access (nstore, X_OK)
 280 #ifdef HAVE_HOST_EXECUTABLE_SUFFIX
 281                       || ! access (strcat (nstore, HOST_EXECUTABLE_SUFFIX), X_OK)
 282 #endif
 283                       )
 284                     {
 285                       progname = nstore;
 286                       break;
 287                     }
 288
 289                   if (*endp == 0)
 290                     break;
 291                   endp = startp = endp + 1;
 292                 }
 293               else
 294                 endp++;
 295             }
 296         }
 297     }
 298
 299   full_progname = lrealpath (progname);
 300   if (full_progname == NULL)
 301     return NULL;
 302
 303   prog_dirs = split_directories (full_progname, &prog_num);
 304   bin_dirs = split_directories (bin_prefix, &bin_num);
 305   free (full_progname);
 306   if (bin_dirs == NULL || prog_dirs == NULL)
 307     return NULL;
 308
 309   /* Remove the program name from comparison of directory names.  */
 310   prog_num--;
 311
 312   /* If we are still installed in the standard location, we don't need to
 313      specify relative directories.  Also, if argv[0] still doesn't contain
 314      any directory specifiers after the search above, then there is not much
 315      we can do.  */
 316   if (prog_num == bin_num)
 317     {
 318       for (i = 0; i < bin_num; i++)
 319         {
 320           if (strcmp (prog_dirs[i], bin_dirs[i]) != 0)
 321             break;
 322         }
 323
 324       if (prog_num <= 0 || i == bin_num)
 325         {
 326           free_split_directories (prog_dirs);
 327           free_split_directories (bin_dirs);
 328           prog_dirs = bin_dirs = (char **) 0;
 329           return NULL;
 330         }
 331     }
 332
 333   prefix_dirs = split_directories (prefix, &prefix_num);
 334   if (prefix_dirs == NULL)
 335     {
 336       free_split_directories (prog_dirs);
 337       free_split_directories (bin_dirs);
 338       return NULL;
 339     }
 340
 341   /* Find how many directories are in common between bin_prefix & prefix.  */
 342   n = (prefix_num < bin_num) ? prefix_num : bin_num;
 343   for (common = 0; common < n; common++)
 344     {
 345       if (strcmp (bin_dirs[common], prefix_dirs[common]) != 0)
 346         break;
 347     }
 348
 349   /* If there are no common directories, there can be no relative prefix.  */
 350   if (common == 0)
 351     {
 352       free_split_directories (prog_dirs);
 353       free_split_directories (bin_dirs);
 354       free_split_directories (prefix_dirs);
 355       return NULL;
 356     }
 357
 358   /* Two passes: first figure out the size of the result string, and
 359      then construct it.  */
 360   needed_len = 0;
 361   for (i = 0; i < prog_num; i++)
 362     needed_len += strlen (prog_dirs[i]);
 363   needed_len += sizeof (DIR_UP) * (bin_num - common);
 364   for (i = common; i < prefix_num; i++)
 365     needed_len += strlen (prefix_dirs[i]);
 366   needed_len += 1; /* Trailing NUL.  */
 367
 368   ret = (char *) malloc (needed_len);
 369   if (ret == NULL)
 370     return NULL;
 371
 372   /* Build up the pathnames in argv[0].  */
 373   *ret = '\0';
 374   for (i = 0; i < prog_num; i++)
 375     strcat (ret, prog_dirs[i]);
 376
 377   /* Now build up the ..'s.  */
 378   ptr = ret + strlen(ret);
 379   for (i = common; i < bin_num; i++)
 380     {
 381       strcpy (ptr, DIR_UP);
 382       ptr += sizeof (DIR_UP) - 1;
 383       *(ptr++) = DIR_SEPARATOR;
 384     }
 385   *ptr = '\0';
 386
 387   /* Put in directories to move over to prefix.  */
 388   for (i = common; i < prefix_num; i++)
 389     strcat (ret, prefix_dirs[i]);
 390
 391   free_split_directories (prog_dirs);
 392   free_split_directories (bin_dirs);
 393   free_split_directories (prefix_dirs);
 394
 395   return ret;
 396 }