package octez-libs

  1. Overview
  2. Docs
package octez-libs
Legend:
Page
Library
Module
Module type
Parameter
Class
Class type
Source

Source file block_locator.ml

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
(*****************************************************************************)
(*                                                                           *)
(* Open Source License                                                       *)
(* Copyright (c) 2018 Dynamic Ledger Solutions, Inc. <contact@tezos.com>     *)
(* Copyright (c) 2019-2021 Nomadic Labs, <contact@nomadic-labs.com>          *)
(*                                                                           *)
(* Permission is hereby granted, free of charge, to any person obtaining a   *)
(* copy of this software and associated documentation files (the "Software"),*)
(* to deal in the Software without restriction, including without limitation *)
(* the rights to use, copy, modify, merge, publish, distribute, sublicense,  *)
(* and/or sell copies of the Software, and to permit persons to whom the     *)
(* Software is furnished to do so, subject to the following conditions:      *)
(*                                                                           *)
(* The above copyright notice and this permission notice shall be included   *)
(* in all copies or substantial portions of the Software.                    *)
(*                                                                           *)
(* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR*)
(* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,  *)
(* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL   *)
(* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER*)
(* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING   *)
(* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER       *)
(* DEALINGS IN THE SOFTWARE.                                                 *)
(*                                                                           *)
(*****************************************************************************)

type t = {
  head_hash : Tezos_crypto.Hashed.Block_hash.t;
  head_header : Block_header.t;
  history : Tezos_crypto.Hashed.Block_hash.t list;
}

let pp ppf {head_hash; history; _} =
  let repeats = 10 in
  let coef = 2 in
  (* list of hashes *)
  let rec pp_hash_list ppf (h_lst, acc, d, r) =
    match h_lst with
    | [] -> Format.fprintf ppf ""
    | hd :: tl ->
        let new_d = if r > 1 then d else d * coef in
        let new_r = if r > 1 then r - 1 else repeats in
        Format.fprintf
          ppf
          "%a (%i)\n%a"
          Tezos_crypto.Hashed.Block_hash.pp
          hd
          acc
          pp_hash_list
          (tl, acc - d, new_d, new_r)
  in
  Format.fprintf
    ppf
    "%a (head)\n%a"
    Tezos_crypto.Hashed.Block_hash.pp
    head_hash
    pp_hash_list
    (history, -1, 1, repeats - 1)

let pp_short ppf {head_hash; history; _} =
  Format.fprintf
    ppf
    "head: %a, %d predecessors"
    Tezos_crypto.Hashed.Block_hash.pp
    head_hash
    (List.length history)

let encoding_proj {head_header; history; _} = (head_header, history)

let encoding_inj (head_header, history) =
  {head_hash = Block_header.hash head_header; head_header; history}

let encoding =
  let open Data_encoding in
  def "block_locator" ~description:"A sparse block locator à la Bitcoin"
  @@ conv
       encoding_proj
       encoding_inj
       (obj2
          (req "current_head" (dynamic_size Block_header.encoding))
          (req
             "history"
             (Variable.list Tezos_crypto.Hashed.Block_hash.encoding)))

let bounded_encoding ~max_header_size ~max_length () =
  let open Data_encoding in
  conv
    encoding_proj
    encoding_inj
    (obj2
       (req
          "current_head"
          (dynamic_size
             (Block_header.bounded_encoding ~max_size:max_header_size ())))
       (req
          "history"
          (Variable.list ~max_length Tezos_crypto.Hashed.Block_hash.encoding)))

type seed = {sender_id : P2p_peer.Id.t; receiver_id : P2p_peer.Id.t}

(* Random generator for locator steps.

   We draw steps by sequence of 10. The first sequence's steps are of
   length 1 (consecutive). The second sequence's steps are of a random
   length between 1 and 2. The third sequence's steps are of a random
   length between 2 and 4, and so on...

   The sequence is deterministic for a given triple of sender,
   receiver and block hash. *)
module Step : sig
  type state

  val init : seed -> Tezos_crypto.Hashed.Block_hash.t -> state

  val next : state -> int * state
end = struct
  (* (step, counter, seed) .
     The seed is stored in a bigstring and should be mlocked *)
  type state = Int32.t * int * Bytes.t

  let update st b = Tezos_crypto.Hacl.Hash.SHA256.update st b

  let init seed head =
    let open Tezos_crypto.Hacl.Hash in
    let st = SHA256.init () in
    List.iter
      (update st)
      [
        P2p_peer.Id.to_bytes seed.sender_id;
        P2p_peer.Id.to_bytes seed.receiver_id;
        Tezos_crypto.Hashed.Block_hash.to_bytes head;
      ] ;
    (1l, 9, SHA256.finish st)

  let draw seed n =
    ( Int32.rem (TzEndian.get_int32 seed 0) n,
      Tezos_crypto.Hacl.Hash.SHA256.digest seed )

  let next (step, counter, seed) =
    let random_gap, seed =
      if step <= 1l then (0l, seed)
      else draw seed (Int32.succ (Int32.div step 2l))
    in
    let new_state =
      if counter = 0 then (Int32.mul step 2l, 9, seed)
      else (step, counter - 1, seed)
    in
    (Int32.to_int (Int32.sub step random_gap), new_state)
end

let estimated_length seed {head_hash; history; _} =
  let rec loop acc state = function
    | [] -> acc
    | _ :: hist ->
        let step, state = Step.next state in
        loop (acc + step) state hist
  in
  let state = Step.init seed head_hash in
  let step, state = Step.next state in
  loop step state history

let fold ~f ~init {head_hash; history; _} seed =
  let rec loop state acc = function
    | [] | [_] -> acc
    | block :: (pred :: rem as hist) ->
        let step, state = Step.next state in
        let acc = f acc ~block ~pred ~step ~strict_step:(rem <> []) in
        loop state acc hist
  in
  let state = Step.init seed head_hash in
  loop state init (head_hash :: history)

type step = {
  block : Tezos_crypto.Hashed.Block_hash.t;
  predecessor : Tezos_crypto.Hashed.Block_hash.t;
  step : int;
  strict_step : bool;
}

let pp_step ppf step =
  Format.fprintf ppf "%d%s" step.step (if step.strict_step then "" else " max")

let to_steps seed locator =
  fold locator seed ~init:[] ~f:(fun acc ~block ~pred ~step ~strict_step ->
      {block; predecessor = pred; step; strict_step} :: acc)

let fold_truncate ~f ~init ~save_point ~limit {head_hash; history; _} seed =
  let rec loop state step_sum acc = function
    | [] | [_] -> acc
    | block :: (pred :: rem as hist) ->
        let step, state = Step.next state in
        let new_step_sum = step + step_sum in
        if new_step_sum >= limit then
          f acc ~block ~pred:save_point ~step ~strict_step:false
        else
          let acc = f acc ~block ~pred ~step ~strict_step:(rem <> []) in
          loop state new_step_sum acc hist
  in
  let initial_state = Step.init seed head_hash in
  loop initial_state 0 init (head_hash :: history)

let to_steps_truncate ~limit ~save_point seed locator =
  fold_truncate
    locator
    seed
    ~init:[]
    ~save_point
    ~limit
    ~f:(fun acc ~block ~pred ~step ~strict_step ->
      {block; predecessor = pred; step; strict_step} :: acc)

let compute ~get_predecessor ~caboose ~size head_hash head_header seed =
  let open Error_monad.Lwt_syntax in
  let rec loop acc size state current_block_hash =
    if size = 0 then Lwt.return acc
    else
      let step, state = Step.next state in
      let* o = get_predecessor current_block_hash step in
      match o with
      | None ->
          if Tezos_crypto.Hashed.Block_hash.equal caboose current_block_hash
          then Lwt.return acc
          else Lwt.return (caboose :: acc)
      | Some predecessor ->
          if Tezos_crypto.Hashed.Block_hash.equal predecessor current_block_hash
          then (* caboose or genesis reached *)
            Lwt.return acc
          else loop (predecessor :: acc) (pred size) state predecessor
  in
  if size <= 0 then Lwt.return {head_hash; head_header; history = []}
  else
    let initial_state = Step.init seed head_hash in
    let* history = loop [] size initial_state head_hash in
    let history = List.rev history in
    Lwt.return {head_hash; head_header; history}

type validity = Unknown | Known_valid | Known_invalid

let unknown_prefix ~is_known locator =
  let open Error_monad.Lwt_syntax in
  let {head_hash; history; _} = locator in
  let rec loop hist acc =
    match hist with
    | [] -> Lwt.return (Unknown, locator)
    | h :: t -> (
        let* k = is_known h in
        match k with
        | Known_valid ->
            Lwt.return
              (Known_valid, {locator with history = List.rev (h :: acc)})
        | Known_invalid ->
            Lwt.return
              (Known_invalid, {locator with history = List.rev (h :: acc)})
        | Unknown -> loop t (h :: acc))
  in
  let* k = is_known head_hash in
  match k with
  | Known_valid -> Lwt.return (Known_valid, {locator with history = []})
  | Known_invalid -> Lwt.return (Known_invalid, {locator with history = []})
  | Unknown -> loop history []

let () = Data_encoding.Registration.register ~pp:pp_short encoding
OCaml

Innovation. Community. Security.

GitHub Discord Twitter Peertube RSS
About
Changelog Releases Industrial Users Academic Users Why OCaml
Ecosystem
Packages Community Events OCaml Planet Jobs
Resources
Install OCaml Get Started Platform Tools Language Manual Standard Library API Books Exercises Papers OCaml Playground Logo
Policies
Carbon Footprint Governance Privacy Code of Conduct