feat(trace): add Source, to read traces

src/trace/sidekick_trace.ml

@@ -23,6 +23,7 @@ open Sidekick_sigs
 module Entry_view = Entry_view
 module Entry_read = Entry_read
 module Sink = Sink
+module Source = Source
 module Entry_id = Entry_id
 
 type entry_id = Entry_id.t

src/trace/source.ml

@@ -0,0 +1,15 @@
+type tag = string
+
+module type S = sig
+  val get_entry : Entry_id.t -> tag * Ser_value.t
+  val iter_all : (Entry_id.t -> tag:tag -> Ser_value.t -> unit) -> unit
+end
+
+type t = (module S)
+
+let get_entry_exn (module S : S) id = S.get_entry id
+
+let get_entry (module S : S) id : _ option =
+  try Some (S.get_entry id) with Not_found -> None
+
+let iter_all (module S : S) f : unit = S.iter_all f

src/trace/source.mli

@@ -0,0 +1,22 @@
+(** Source to read a trace.
+
+    A source is an IO input source that allows the read of individual
+    entries of the trace, by providing their entry ID. It also allows to
+    iterate on entries in chronological order.
+*)
+
+type tag = string
+
+module type S = sig
+  val get_entry : Entry_id.t -> tag * Ser_value.t
+  (** @raise Not_found if there is no such entry *)
+
+  val iter_all : (Entry_id.t -> tag:tag -> Ser_value.t -> unit) -> unit
+  (** Iterate on all entries *)
+end
+
+type t = (module S)
+
+val get_entry : t -> Entry_id.t -> (tag * Ser_value.t) option
+val get_entry_exn : t -> Entry_id.t -> tag * Ser_value.t
+val iter_all : t -> (Entry_id.t -> tag:tag -> Ser_value.t -> unit) -> unit