How to change the data with node API? Or how to write fast when I know the data offset or giving node? about mpack HOT 2 CLOSED

...//change node data externally
write_data_from_tree(writer, mpack_tree_root(tree));

void write_data_from_tree(mpack_writer_t* writer, mpack_node_t currentNode)
{
    mpack_node_data_t *value = currentNode.data;
    switch (value->type) {
        case mpack_type_missing:
            mpack_break("cannot write a missing value!");
            mpack_writer_flag_error(writer, mpack_error_bug);
            return;

        case mpack_type_nil:    mpack_write_nil   (writer);            return;
        case mpack_type_bool:   mpack_write_bool  (writer, value->value.b); return;
        case mpack_type_int:    mpack_write_int   (writer, value->value.i); return;
        case mpack_type_uint:   mpack_write_uint  (writer, value->value.u); return;

        case mpack_type_float:
            #if MPACK_FLOAT
            mpack_write_float
            #else
            mpack_write_raw_float
            #endif
                (writer, value->value.f);
            return;
        case mpack_type_double:
            #if MPACK_DOUBLE
            mpack_write_double
            #else
            mpack_write_raw_double
            #endif
                (writer, value->value.d);
            return;

        case mpack_type_str: mpack_write_str(writer, tree.data+value->value.offset, value->len); return;
        case mpack_type_bin: mpack_write_bin(writer, tree.data+value->value.offset, value->len); return;

        #if MPACK_EXTENSIONS
        case mpack_type_ext:
		#error data not include ext!
            mpack_start_ext(writer, mpack_tag_ext_exttype(&value), mpack_tag_ext_length(&value));
            return;
        #endif

        case mpack_type_array: 
			mpack_start_array(writer, value->len); 
			for(uint32_t i = 0; i < value->len; i++)
			{
				write_data_from_tree(writer, mpack_node(&tree, mpack_node_child(currentNode, i)));
			}
			mpack_finish_array(writer);
		return;
        case mpack_type_map:   
			mpack_start_map(writer, value->len);
			for(uint32_t i = 0; i < value->len; i++)
			{
				write_data_from_tree(writer, mpack_node(&tree, mpack_node_child(currentNode, i*2)));
                write_data_from_tree(writer, mpack_node(&tree, mpack_node_child(currentNode, i*2+1)));
            }
            mpack_finish_array(writer);
        return;
    }
    mpack_break("unrecognized type %i", (int)value.type);
    mpack_writer_flag_error(writer, mpack_error_bug);
}