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/* realpath.c - Return the canonicalized absolute pathname */

/* Written 2000 by Werner Almesberger */

#include <stdlib.h>

#include <unistd.h>

#include <string.h>

#include <limits.h>

#include <errno.h>

#include <sys/stat.h>

/* FIXME: buffer overrun possible, loops forever on cyclic symlinks */

/*

 * Canonical name: never ends with a slash

 */

static int resolve_path(char *path,char *result,char *pos)

{

    if (*path == '/') {

        *result = '/';

        pos = result+1;

        path++;

    }

    *pos = 0;

    if (!*path) return 0;

    while (1) {

        char *slash;

        struct stat st;

        slash = *path ? strchr(path,'/') : NULL;

        if (slash) *slash = 0;

        if (!path[0] || (path[0] == '.' &&

          (!path[1] || (path[1] == '.' && !path[2])))) {

            pos--;

            if (pos != result && path[0] && path[1])

                while (*--pos != '/');

        }

        else {

            strcpy(pos,path);

            if (lstat(result,&st) < 0) return -1;

            if (S_ISLNK(st.st_mode)) {

                char buf[PATH_MAX];

                if (readlink(result,buf,sizeof(buf)) < 0) return -1;

                *pos = 0;

                if (slash) {

                    *slash = '/';

                    strcat(buf,slash);

                }

                strcpy(path,buf);

                if (*path == '/') result[1] = 0;

                pos = strchr(result,0);

                continue;

            }

            pos = strchr(result,0);

        }

        if (slash) {

            *pos++ = '/';

            path = slash+1;

        }

        *pos = 0;

        if (!slash) break;

    }

    return 0;

}

char *realpath(const char *path,char *resolved_path)

{

    char cwd[PATH_MAX];

    char *path_copy;

    int res;

    if (!*path) {

        errno = ENOENT; /* SUSv2 */

        return NULL;

    }

    if (!getcwd(cwd,sizeof(cwd))) return NULL;

    strcpy(resolved_path,"/");

    if (resolve_path(cwd,resolved_path,resolved_path)) return NULL;

    strcat(resolved_path,"/");

    path_copy = strdup(path);

    if (!path_copy) return NULL;

    res = resolve_path(path_copy,resolved_path,strchr(resolved_path,0));

    free(path_copy);

    if (res) return NULL;

    return resolved_path;

}