Add reader and manifest abstractions for osiris_log

src/osiris.erl

@@ -231,6 +231,8 @@ init_reader(Pid, OffsetSpec, CounterSpec) ->
 init_reader(Pid, OffsetSpec, {_, _} = CounterSpec, Options)
     when is_pid(Pid) andalso node(Pid) =:= node() ->
     ?DEBUG("osiris: initialising reader. Spec: ~w", [OffsetSpec]),
+    %% TODO: the manifest mod is now present here. We could use that value
+    %% rather than reading from the application env.
     Ctx0 = osiris_util:get_reader_context(Pid),
     Ctx = Ctx0#{counter_spec => CounterSpec,
                 options => Options},

src/osiris.hrl

@@ -47,6 +47,18 @@
 -define(FILE_OPTS_WRITE, [raw, binary, write, read]).
 -define(INDEX_RECORD_SIZE_B, 29).
 
+%% record chunk_info does not map exactly to an index record (field 'num' differs)
+-record(chunk_info,
+        {id :: osiris:offset(),
+         timestamp :: non_neg_integer(),
+         epoch :: osiris:epoch(),
+         num :: non_neg_integer(),
+         type :: osiris_log:chunk_type(),
+         %% size of data + filter + trailer
+         size :: non_neg_integer(),
+         %% position in segment file
+         pos :: integer()
+        }).
 
 %% chunk types
 -define(CHNK_USER, 0).