basename

/*
 *  call-seq:
 *     File.basename(file_name [, suffix] ) -> base_name
 *  
 *  Returns the last component of the filename given in <i>file_name</i>,
 *  which must be formed using forward slashes (``<code>/</code>'')
 *  regardless of the separator used on the local file system. If
 *  <i>suffix</i> is given and present at the end of <i>file_name</i>,
 *  it is removed.
 *     
 *     File.basename("/home/gumby/work/ruby.rb")          #=> "ruby.rb"
 *     File.basename("/home/gumby/work/ruby.rb", ".rb")   #=> "ruby"
 */

static VALUE
rb_file_s_basename(argc, argv)
    int argc;
    VALUE *argv;
{
    VALUE fname, fext, basename;
    const char *name, *p;
#if defined DOSISH_DRIVE_LETTER || defined DOSISH_UNC
    const char *root;
#endif
    int f, n;

    if (rb_scan_args(argc, argv, "11", &fname, &fext) == 2) {
        StringValue(fext);
    }
    StringValue(fname);
    if (RSTRING(fname)->len == 0 || !*(name = RSTRING(fname)->ptr))
        return fname;
    name = skipprefix(name);
#if defined DOSISH_DRIVE_LETTER || defined DOSISH_UNC
    root = name;
#endif
    while (isdirsep(*name))
        name++;
    if (!*name) {
        p = name - 1;
        f = 1;
#if defined DOSISH_DRIVE_LETTER || defined DOSISH_UNC
        if (name != root) {
            /* has slashes */
        }
#ifdef DOSISH_DRIVE_LETTER
        else if (*p == ':') {
            p++;
            f = 0;
        }
#endif
#ifdef DOSISH_UNC
        else {
            p = "/";
        }
#endif
#endif
    }
    else {
        if (!(p = strrdirsep(name))) {
            p = name;
        }
        else {
            while (isdirsep(*p)) p++; /* skip last / */
        }
#if USE_NTFS
        n = ntfs_tail(p) - p;
#else
        n = chompdirsep(p) - p;
#endif
        if (NIL_P(fext) || !(f = rmext(p, n, StringValueCStr(fext)))) {
            f = n;
        }
        if (f == RSTRING_LEN(fname)) return fname;
    }
    basename = rb_str_new(p, f);
    OBJ_INFECT(basename, fname);
    return basename;
}