unshift

/*
 *  call-seq:
 *     array.unshift(obj, ...)  -> array
 *  
 *  Prepends objects to the front of <i>array</i>.
 *  other elements up one.
 *     
 *     a = [ "b", "c", "d" ]
 *     a.unshift("a")   #=> ["a", "b", "c", "d"]
 *     a.unshift(1, 2)  #=> [ 1, 2, "a", "b", "c", "d"]
 */

static VALUE
rb_ary_unshift_m(argc, argv, ary)
    int argc;
    VALUE *argv;
    VALUE ary;
{
    long len = RARRAY(ary)->len;

    if (argc == 0) return ary;

    /* make rooms by setting the last item */
    rb_ary_store(ary, len + argc - 1, Qnil);

    /* sliding items */
    MEMMOVE(RARRAY(ary)->ptr + argc, RARRAY(ary)->ptr, VALUE, len);
    MEMCPY(RARRAY(ary)->ptr, argv, VALUE, argc);
    
    return ary;
}