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rel2abs.c

/*
 * Copyright (C) 1999-2004 Joachim Wieland <joe@mcknight.de>
 * Copyright (c) 1997 Shigio Yamaguchi. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by Shigio Yamaguchi.
 * 4. Neither the name of the author nor the names of any co-contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */
#include <errno.h>
#include <stdlib.h>
#include <string.h>
/*
 * rel2abs: convert an relative path name into absolute.
 *
 *    i)    path  relative path
 *    i)    base  base directory (must be absolute path)
 *    o)    result      result buffer
 *    i)    size  size of result buffer
 *    r)          != NULL: absolute path
 *                == NULL: error
 */
char *
rel2abs(path, base, result, size)
      const char *path;
      const char *base;
      char *result;
      const size_t size;
{
      const char *pp, *bp;
      /*
       * endp points the last position which is safe in the result buffer.
       */
      const char *endp = result + size - 1;
      char *rp;
      int length;

      if (*path == '/') {
            if (strlen(path) >= size)
                  goto erange;
            strcpy(result, path);
            goto finish;
      } else if (*base != '/' || !size) {
            errno = EINVAL;
            return (NULL);
      } else if (size == 1)
            goto erange;
      if (!strcmp(path, ".") || !strcmp(path, "./")) {
            if (strlen(base) >= size)
                  goto erange;
            strcpy(result, base);
            /*
             * rp points the last char.
             */
            rp = result + strlen(base) - 1;
            if (*rp == '/')
                  *rp = 0;
            else
                  rp++;
            /* rp point NULL char */
            if (*++path == '/') {
                  /*
                   * Append '/' to the tail of path name.
                   */
                  *rp++ = '/';
                  if (rp > endp)
                        goto erange;
                  *rp = 0;
            }
            goto finish;
      }
      bp = base + strlen(base);
      if (*(bp - 1) == '/')
            --bp;
      /*
       * up to root.
       */
      for (pp = path; *pp && *pp == '.'; ) {
            if (!strncmp(pp, "../", 3)) {
                  pp += 3;
                  while (bp > base && *--bp != '/')
                        ;
            } else if (!strncmp(pp, "./", 2)) {
                  pp += 2;
            } else if (!strncmp(pp, "..\0", 3)) {
                  pp += 2;
                  while (bp > base && *--bp != '/')
                        ;
            } else
                  break;
      }
      /*
       * down to leaf.
       */
      length = bp - base;
      if (length >= size)
            goto erange;
      strncpy(result, base, length);
      rp = result + length;
      if (*pp || *(pp - 1) == '/' || length == 0)
            *rp++ = '/';
      if (rp + strlen(pp) > endp)
            goto erange;
      strcpy(rp, pp);
finish:
      return result;
erange:
      errno = ERANGE;
      return (NULL);
}


/* the following code is by Joachim Wieland <jwieland@bigfoot.de> for jftpgw
 * */

#ifdef WITH_MAIN

#include <limits.h>
#include <stdio.h>

int main(int argc, char** argv) {
      char buf[PATH_MAX + 1];
      char* ret;

      if (argc != 3) {
            fprintf(stderr, "Usage: %s <relativepath> <basepath>\n\n",
                        argv[0]);
            return 1;
      }

      ret = rel2abs(argv[1], argv[2], buf, sizeof(buf) - 1);
      if (!ret) {
            /* an error occurred */
            ret = argv[2];
      }
      printf("%s\n", ret);

      return 0;
}

#endif /* WITH_MAIN */

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