/*
 * Copyright (c) 1997 Shigio Yamaguchi. All rights reserved.
 * Copyright (c) 1999 Tama Communications Corporation. 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.
 *
 * 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>
#include "pathconv.h" /* prototypes */
/*
 * 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(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;
        size_t 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;

        length = strlen(base);

        if (!strcmp(path, ".") || !strcmp(path, "./")) {
                if (length >= size)
                        goto erange;
                strcpy(result, base);
                /*
                 * rp points the last char.
                 */
                rp = result + length - 1;
                /*
                 * remove the last '/'.
                 */
                if (*rp == '/') {
                        if (length > 1)
                                *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 + length;
        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);
}