If the length of the array is unknown about node-struct

[bosconian-dynamics]

Struct arrays are analogous to C arrays - that is, there is no such thing as an array of undetermined length. You must either over-provision the length of your array to start with, or implement logic to expand/replace the arrays on your own. It's unlikely that the library will support such expansion logic moving forward as the means by which an array is expanded is dependent on the application itself.

Usually, expansion of an independent array is implemented by creating a new array of the desired size, copying the contents of the old array into the new one, and freeing the old array for garbage collection. Alternately, you can create a new array separately and use logic to create something of a "virtual index" that maps to the appropriate array - but you'll lose some of the performance benefits of using contiguous memory.

Changing the size of arrays within a struct at runtime is inadvisable as it will invalidate all previous instances of the struct by changing the offsets at which fields reside - so all previous instances of the struct would need to be converted each time any of their array fields grow.

[erakis]

Maybe you'd be better with something like smart-buffer and de-serializing your data as a stream.