Shell/RPC: Implements `/block/<hash>/predecessors

src/client/client_node_rpcs.ml

@@ -178,6 +178,7 @@ module Blocks = struct
   }
   let net cctxt h = call_service1 cctxt Services.Blocks.net h ()
   let predecessor cctxt h = call_service1 cctxt Services.Blocks.predecessor h ()
+  let predecessors cctxt h l = call_service1 cctxt Services.Blocks.predecessors h l
   let hash cctxt h = call_service1 cctxt Services.Blocks.hash h ()
   let timestamp cctxt h = call_service1 cctxt Services.Blocks.timestamp h ()
   let fitness cctxt h = call_service1 cctxt Services.Blocks.fitness h ()

src/client/client_node_rpcs.mli

@@ -59,6 +59,9 @@ module Blocks : sig
   val predecessor:
     Client_commands.context ->
     block -> Block_hash.t Lwt.t
+  val predecessors:
+    Client_commands.context ->
+    block -> int -> Block_hash.t list Lwt.t
   val hash:
     Client_commands.context ->
     block -> Block_hash.t Lwt.t

src/node/shell/node.ml

@@ -432,10 +432,28 @@ module RPC = struct
         Block_hash.Map.empty (test_heads @ heads) in
     Lwt.return map
 
-  let predecessors net_state ignored len head =
+  let predecessors node len head =
+    let rec loop net_db acc len hash (block: State.Block_header.t) =
+      if Block_hash.equal block.shell.predecessor hash then
+        Lwt.return (List.rev acc)
+      else begin
+        if len = 0 then
+          Lwt.return (List.rev acc)
+        else
+          let hash = block.shell.predecessor in
+          Distributed_db.Block_header.read_exn net_db hash >>= fun block ->
+          loop net_db (hash :: acc) (len-1) hash block
+      end in
+    try
+      Distributed_db.read_block_exn
+        node.distributed_db head >>= fun (net_db, block) ->
+      loop net_db [] len head block
+    with Not_found -> Lwt.return_nil
+
+  let predecessors_bi state ignored len head =
     try
       let rec loop acc len hash =
-        State.Valid_block.read_exn net_state hash >>= fun block ->
+        State.Valid_block.read_exn state hash >>= fun block ->
         let bi = convert block in
         if Block_hash.equal bi.predecessor hash then
           Lwt.return (List.rev (bi :: acc))
@@ -455,7 +473,7 @@ module RPC = struct
          Distributed_db.read_block_exn
            node.distributed_db head >>= fun (net_db, _block) ->
          let net_state = Distributed_db.state net_db in
-         predecessors net_state ignored len head >|= fun predecessors ->
+         predecessors_bi net_state ignored len head >|= fun predecessors ->
          let ignored =
            List.fold_right
              (fun x s -> Block_hash.Set.add x.hash s)
@@ -463,8 +481,8 @@ module RPC = struct
          ignored, predecessors :: acc
       )
       (Block_hash.Set.empty, [])
-      heads >|= fun (_, blocks) ->
+      heads >>= fun (_, blocks) ->
-    List.rev blocks
+    Lwt.return (List.rev blocks)
 
   let block_watcher node =
     let stream, shutdown = Distributed_db.watch_block node.distributed_db in

src/node/shell/node.mli

@@ -43,6 +43,9 @@ module RPC : sig
     t -> (block_info Lwt_stream.t * Watcher.stopper)
   val heads: t -> block_info Block_hash.Map.t Lwt.t
 
+  val predecessors:
+    t -> int -> Block_hash.t -> Block_hash.t list Lwt.t
+
   val list:
     t -> int -> Block_hash.t list -> block_info list list Lwt.t
 

src/node/shell/node_rpc.ml

@@ -41,6 +41,13 @@ let register_bi_dir node dir =
       RPC.Answer.return bi.predecessor in
     RPC.register1 dir
       Services.Blocks.predecessor implementation in
+  let dir =
+    let implementation b len =
+      Node.RPC.block_info node b >>= fun bi ->
+      Node.RPC.predecessors node len bi.hash >>= fun hashes ->
+      RPC.Answer.return hashes in
+    RPC.register1 dir
+      Services.Blocks.predecessors implementation in
   let dir =
     let implementation b () =
       Node.RPC.block_info node b >>= fun bi ->
@@ -367,7 +374,8 @@ let get_protocols node hash () =
 
 let build_rpc_directory node =
   let dir = RPC.empty in
-  let dir = RPC.register0 dir Services.Blocks.list (list_blocks node) in
+  let dir =
+    RPC.register0 dir Services.Blocks.list (list_blocks node) in
   let dir = register_bi_dir node dir in
   let dir =
     let implementation block =

src/node/shell/node_rpc_services.ml

@@ -194,6 +194,15 @@ module Blocks = struct
       ~output: (obj1 (req "predecessor" Block_hash.encoding))
       RPC.Path.(block_path / "predecessor")
 
+  let predecessors =
+    RPC.service
+      ~description:
+        "...."
+      ~input: (obj1 (req "length" Data_encoding.uint16))
+      ~output: (obj1
+                  (req "blocks" (Data_encoding.list Block_hash.encoding)))
+      RPC.Path.(block_path / "predecessors")
+
   let hash =
     RPC.service
       ~description:"Returns the block's id."
@@ -378,8 +387,6 @@ module Blocks = struct
       ~output: (obj1 (req "blocks" (list (list block_info_encoding))))
       RPC.Path.(root / "blocks")
 
-
-
 end
 
 module Operations = struct

src/node/shell/node_rpc_services.mli

@@ -44,6 +44,8 @@ module Blocks : sig
     (unit, unit * block, unit, net) RPC.service
   val predecessor:
     (unit, unit * block, unit, Block_hash.t) RPC.service
+  val predecessors:
+    (unit, unit * block , int, Block_hash.t list) RPC.service
   val hash:
     (unit, unit * block, unit, Block_hash.t) RPC.service
   val timestamp: