WIP: read_chunk #1

src/machi.proto

@@ -142,6 +142,25 @@ message Mpb_WriteChunkResp {
     required Mpb_GeneralStatusCode status = 1;
 }
 
+// read_chunk() request & response
+
+message Mpb_ReadChunkReq {
+    required string file = 1;
+    required uint64 offset = 2;
+    required uint32 size = 3;
+    // Use flag_checksum=non-zero to request the chunk's checksum also
+    optional uint32 flag_checksum = 4 [default=0];
+    // Use flag_no_chunk=non-zero to skip returning the chunk (which
+    // only makes sense if flag_checksum is set).
+    optional uint32 flag_no_chunk = 5 [default=0];
+}
+
+message Mpb_ReadChunkResp {
+    required Mpb_GeneralStatusCode status = 1;
+    optional bytes chunk = 2;
+    optional Mpb_ChunkCSum csum = 3;
+}
+
 //////////////////////////////////////////
 //
 // request & response wrapper
@@ -163,6 +182,7 @@ message Mpb_Request {
     optional Mpb_AuthReq auth = 11;
     optional Mpb_AppendChunkReq append_chunk = 12;
     optional Mpb_WriteChunkReq write_chunk = 13;
+    optional Mpb_ReadChunkReq read_chunk = 14;
 }
 
 message Mpb_Response {
@@ -183,4 +203,5 @@ message Mpb_Response {
     optional Mpb_AuthResp auth = 11;
     optional Mpb_AppendChunkResp append_chunk = 12;
     optional Mpb_WriteChunkResp write_chunk = 13;
+    optional Mpb_ReadChunkResp read_chunk = 14;
 }

src/machi_pb_high_client.erl

@@ -39,7 +39,8 @@
          echo/2, echo/3,
          auth/3, auth/4,
          append_chunk/6, append_chunk/7,
-         write_chunk/5, write_chunk/6
+         write_chunk/5, write_chunk/6,
+         read_chunk/4, read_chunk/5
         ]).
 
 %% gen_server callbacks
@@ -89,6 +90,12 @@ write_chunk(PidSpec, File, Offset, Chunk, CSum) ->
 write_chunk(PidSpec, File, Offset, Chunk, CSum, Timeout) ->
     send_sync(PidSpec, {write_chunk, File, Offset, Chunk, CSum}, Timeout).
 
+read_chunk(PidSpec, File, Offset, Size) ->
+    read_chunk(PidSpec, File, Offset, Size, ?DEFAULT_TIMEOUT).
+
+read_chunk(PidSpec, File, Offset, Size, Timeout) ->
+    send_sync(PidSpec, {read_chunk, File, Offset, Size}, Timeout).
+
 send_sync(PidSpec, Cmd, Timeout) ->
     gen_server:call(PidSpec, {send_sync, Cmd}, Timeout).
 
@@ -250,6 +257,30 @@ do_send_sync({write_chunk, File, Offset, Chunk, CSum},
     catch X:Y ->
             Res = {bummer, {X, Y, erlang:get_stacktrace()}},
             {Res, S#state{count=Count+1}}
+    end;
+do_send_sync({read_chunk, File, Offset, Size},
+             #state{sock=Sock, sock_id=Index, count=Count}=S) ->
+    try
+        ReqID = <<Index:64/big, Count:64/big>>,
+        Req = #mpb_readchunkreq{file=File,
+                                offset=Offset,
+                                size=Size},
+        R1a = #mpb_request{req_id=ReqID,
+                           read_chunk=Req},
+        Bin1a = machi_pb:encode_mpb_request(R1a),
+        ok = gen_tcp:send(Sock, Bin1a),
+        {ok, Bin1B} = gen_tcp:recv(Sock, 0),
+        case (catch machi_pb:decode_mpb_response(Bin1B)) of
+            #mpb_response{req_id=ReqID, read_chunk=R} when R /= undefined ->
+                Result = convert_read_chunk_resp(R),
+                {Result, S#state{count=Count+1}};
+            #mpb_response{req_id=ReqID, generic=G} when G /= undefined ->
+                #mpb_errorresp{code=Code, msg=Msg, extra=Extra} = G,
+                {{error, {Code, Msg, Extra}}, S#state{count=Count+1}}
+        end
+    catch X:Y ->
+            Res = {bummer, {X, Y, erlang:get_stacktrace()}},
+            {Res, S#state{count=Count+1}}
     end.
 
 convert_csum_req(none) ->
@@ -280,3 +311,8 @@ convert_write_chunk_resp(#mpb_writechunkresp{status='OK'}) ->
     ok;
 convert_write_chunk_resp(#mpb_writechunkresp{status=Status}) ->
     convert_general_status_code(Status).
+
+convert_read_chunk_resp(#mpb_readchunkresp{status='OK', chunk=Chunk}) ->
+    {ok, Chunk};
+convert_read_chunk_resp(#mpb_readchunkresp{status=Status}) ->
+    convert_general_status_code(Status).

test/machi_pb_high_client_test.erl

@@ -70,8 +70,15 @@ smoke_test2() ->
             {ok, {Off2, Size2, File2}} =
                 ?C:append_chunk(Clnt, PK, Prefix, Chunk2, CSum2, 1024),
             Chunk3 = ["This is a ", <<"test,">>, 32, [["Hello, world!"]]],
-            ok = ?C:write_chunk(Clnt, File2, Off2+iolist_size(Chunk2),
-                                Chunk3, none),
+            Off3 = Off2 + iolist_size(Chunk2),
+            Size3 = iolist_size(Chunk3),
+            ok = ?C:write_chunk(Clnt, File2, Off3, Chunk3, none),
+
+            Reads = [{Chunk1, File1, Off1, Size1},
+                     {Chunk2, File2, Off2, Size2},
+                     {Chunk3, File2, Off3, Size3}],
+            [{ok, Ch} = ?C:read_chunk(Clnt, Fl, Off, Sz) ||
+                {Ch, Fl, Off, Sz} <- Reads],
 
             ok
         after