objective categorical abstract machine language personal data server
1# mist
2
3is a [Merkle Search Tree](https://atproto.com/specs/repository#mst-structure) implementation for atproto data repositories.
4
5## installation
6
7Add to your `dune-project`:
8
9```lisp
10(depends
11 mist
12 ipld) ; required dependency
13```
14
15## usage
16
17### working with TIDs
18
19TIDs are 13-character base32-encoded identifiers that combine a microsecond timestamp with a clock ID for ordering and uniqueness.
20
21```ocaml
22open Mist
23
24(* Generate a TID from current timestamp *)
25let tid = Tid.now ()
26(* => "3jzfcijpj2z23" *)
27
28(* Create TID from timestamp *)
29let tid = Tid.of_timestamp_ms 1609459200000L
30 ~clockid:123
31
32(* Parse TID from string *)
33let tid = Tid.of_string "3jzfcijpj2z23"
34
35(* Extract timestamp *)
36let (timestamp_us, clockid) = Tid.to_timestamp_us tid
37
38(* TIDs are comparable for ordering *)
39let is_later = Tid.compare tid1 tid2 > 0
40```
41
42### working with MSTs
43
44```ocaml
45open Lwt.Syntax
46
47(* Create a new MST with a blockstore and an empty root *)
48let blockstore = Mist.Storage.Memory_blockstore.create () in
49let* mst = Mst.create blockstore (Cid.of_string "")
50
51(* Add an entry *)
52let key = "app.bsky.feed.post/3jzfcijpj2z23" in
53let cid = Cid.of_string "bafy2bzaceb3z2z23" in
54let* mst = Mst.add mst key cid blockstore
55
56(* Get an entry *)
57let* value_opt = Mst.retrieve_node mst cid in
58match value_opt with
59| Some node -> (* found *)
60| None -> (* not found *)
61
62(* Delete an entry *)
63let* mst = Mst.delete mst key
64
65(* Get the root CID *)
66let root_cid = Cid.to_string mst.root
67```
68
69### inductive proof
70
71```ocaml
72(* Generate a map of all blocks needed to prove a given key *)
73let* proof = Mst.proof_for_key mst cid key in
74```
75
76### working with blob references
77
78```ocaml
79(* Parse blob reference from JSON *)
80let blob = Blob_ref.of_yojson json
81
82(* Access blob properties *)
83let cid = blob.ref in
84let mime_type = blob.mime_type in
85let size = blob.size
86
87(* Convert to IPLD representation *)
88let ipld = Blob_ref.to_ipld blob
89
90(* Convert back to JSON *)
91let json = Blob_ref.to_yojson blob
92```