static inline
    SilcBuffer silc_buffer_srealloc_size(SilcStack stack,
                                         SilcBuffer sb, SilcUInt32 newsize);

    Same as silc_buffer_srealloc but moves moves the tail area
    automatically so that the buffer is ready to use without calling the
    silc_buffer_pull_tail.

    This routine use SilcStack are memory source.  If `stack' is NULL
    reverts back to normal allocating routine.