Module `Tjr_btree.Bin_prot_marshalling`

Marshal frames to blocks using binprot FIXME needs polish. Currently assumes that blk_ids are ints.

Bin_prot marshalling calculations for a type 

    type tree = 
      | N of k list * blk_id list 
      | L of (k*v) list [@@deriving bin_io]

  - a size (Bin_prot.Nat0.t) < 0x10000 = 65536 takes 3 bytes
  - for a sum type constructor, 1 byte (assuming <=256 total constructors)

  - if we assume that a block size is less than 65536 then any list
    stored in a block will require 3 bytes or less

  - for a node, we need:
    - 1 byte;  tag for N
    - 0 ; tag for pair
    - 3 bytes; tag for ks, which is just length of ks (assume <65536)
    - 3 bytes; tag for rs (assume...)
    - |ks| * k_size ; for ks
    - |rs| * r_size ; for rs; safe to assume r_size is 9 bytes
    - total: 7 + |ks|*(k_size+r_size) + r_size


  - for a leaf, we need:
    - 1 byte; tag for L
    - 3 bytes; tag for kvs list, which is length
    - |kvs| * kv_size; for kvs
    - total: 4 + |kvs|*kv_size

module Blk_id = Tjr_fs_shared.Blk_id_as_int

val int_size_is_63 : bool

module Make : functor (X : sig ... end) -> sig ... end

val make_constants : blk_sz:Tjr_fs_shared.Blk_sz.blk_sz -> k_size:int -> v_size:int -> Isa_btree.Constants.constants: Given the relevant sizes (blocks,keys,values), construct the B-tree size constants