This is the critbit binary tree part of the https://github.com/openbook-dex/openbook-v2 codebase which is the most complex part and so to experiment it directly you can use this repo.

Here's my explanation on how the limits orders are stored https://pvnotpv.github.io/posts/openbook and how it works.

You need to set rust to 1.70 for it to work.

rustup override set 1.70
rustup default 1.70

The parent key is: 5
The here is: 5 4: 63
----
The parent key is: 4
The here is: 4 6: 62
Keep old parent, Inner prefix len: 63
----
The parent key is: 6
The here is: 6 7: 63
Keep old parent, Inner prefix len: 62
The here is: 6 7: 63
----
The parent key is: 6
The here is: 6 10: 60
Keep old parent, Inner prefix len: 62
----
The parent key is: 10
The here is: 10 15: 61
Keep old parent, Inner prefix len: 60
The here is: 10 15: 61
----
The parent key is: 10
The here is: 10 1: 60
Keep old parent, Inner prefix len: 60
The here is: 6 1: 61
Keep old parent, Inner prefix len: 62
----
The parent key is: 10
The here is: 10 18: 59
Keep old parent, Inner prefix len: 60
----
The parent key is: 18
The here is: 18 20: 61
Keep old parent, Inner prefix len: 59
The here is: 18 20: 61
----
The parent key is: 18
The here is: 18 25: 60
Keep old parent, Inner prefix len: 59
The here is: 20 25: 60
Keep old parent, Inner prefix len: 61
----
The parent key is: 18
The here is: 18 31: 60
Keep old parent, Inner prefix len: 59
The here is: 25 31: 61
Keep old parent, Inner prefix len: 60
The here is: 25 31: 61
----
The parent key is: 18
The here is: 18 40: 58
Keep old parent, Inner prefix len: 59
----
The parent key is: 40
The here is: 40 47: 61
Keep old parent, Inner prefix len: 58
The here is: 40 47: 61
----
The parent key is: 40
The here is: 40 42: 62
Keep old parent, Inner prefix len: 58
The here is: 47 42: 61
Keep old parent, Inner prefix len: 61
The here is: 40 42: 62
----
Root node: 0
Inner node: 0, 0: 22, 1: 21 , Key: 40
Leaf node: 1, Price: 4
Leaf node: 2, Price: 5
Inner node: 3, 0: 6, 1: 5 , Key: 7
Inner node: 4, 0: 1, 1: 2 , Key: 4
Leaf node: 5, Price: 7
Leaf node: 6, Price: 6
Inner node: 7, 0: 10, 1: 9 , Key: 15
Inner node: 8, 0: 11, 1: 12 , Key: 1
Leaf node: 9, Price: 15
Leaf node: 10, Price: 10
Leaf node: 11, Price: 1
Inner node: 12, 0: 4, 1: 3 , Key: 6
Inner node: 13, 0: 18, 1: 17 , Key: 25
Inner node: 14, 0: 8, 1: 7 , Key: 10
Leaf node: 15, Price: 20
Leaf node: 16, Price: 18
Inner node: 17, 0: 20, 1: 19 , Key: 31
Inner node: 18, 0: 16, 1: 15 , Key: 20
Leaf node: 19, Price: 31