Move checksum file related code to machi_csum_table

src/machi_admin_util.erl

@@ -95,7 +95,7 @@ verify_file_checksums_common(Sock1, EpochID, File, ReadChunk) ->
     try
         case ?FLU_C:checksum_list(Sock1, EpochID, File) of
             {ok, InfoBin} ->
-                {Info, _} = machi_flu1:split_checksum_list_blob_decode(InfoBin),
+                {Info, _} = machi_checksums:split_checksum_list_blob_decode(InfoBin),
                 Res = lists:foldl(verify_chunk_checksum(File, ReadChunk),
                                   [], Info),
                 {ok, Res};

src/machi_csum_table.erl

@@ -0,0 +1,219 @@
+-module(machi_csum_table).
+
+-export([open/2,
+         find/3, write/4, trim/3,
+         sync/1,
+         calc_unwritten_bytes/1,
+         close/1, delete/1]).
+
+-export([encode_csum_file_entry/3, decode_csum_file_entry/1]).
+
+-include("machi.hrl").
+
+-ifdef(TEST).
+-export([split_checksum_list_blob_decode/1]).
+-endif.
+
+-record(machi_csum_table,
+        {file :: filename:filename(),
+         fd   :: file:descriptor(),
+         table :: ets:tid()}).
+
+-type table() :: #machi_csum_table{}.
+-type byte_sequence() :: { Offset :: non_neg_integer(),
+                           Size   :: pos_integer()|infinity }.
+
+-export_type([table/0]).
+
+-spec open(filename:filename(), proplists:proplists()) ->
+                  {ok, table()} | {error, file:posix()}.
+open(CSumFilename, _Opts) ->
+    T = ets:new(?MODULE, [private, ordered_set]),
+    C0 = #machi_csum_table{
+           file=CSumFilename,
+           table=T},
+    case file:read_file(CSumFilename) of
+        %% , [read, raw, binary]) of
+        {ok, Bin} ->
+            List = case split_checksum_list_blob_decode(Bin) of
+                       {List0, <<>>} ->
+                           List0;
+                       {List0, _Junk} ->
+                           %% Partially written, needs repair TODO
+                           %% [write(CSumFilename, List),
+                           List0
+                   end,
+            %% assuming all entries are strictly ordered by offset,
+            %% trim command should always come after checksum entry.
+            %% *if* by any chance that order cound not be kept, we
+            %% still can do ordering check and monotonic merge here.
+            ets:insert(T, List);
+        {error, enoent} ->
+            ok;
+        Error ->
+            throw(Error)
+    end,
+    {ok, Fd} = file:open(CSumFilename, [raw, binary, append]),
+    {ok, C0#machi_csum_table{fd=Fd}}.
+
+-spec find(table(), machi_dt:chunk_pos(), machi_dt:chunk_size()) ->
+                  {ok, machi_dt:chunk_csum()} | {error, trimmed|notfound}.
+find(#machi_csum_table{table=T}, Offset, Size) ->
+    case ets:lookup(T, Offset) of
+        [{Offset, Size, trimmed}] -> {error, trimmed};
+        [{Offset, Size, Checksum}] -> {ok, Checksum};
+        [{Offset, _, Checksum}] -> {ok, Checksum};
+        [] -> {error, notfound}
+    end.
+
+-spec write(table(), machi_dt:chunk_pos(), machi_dt:chunk_size(),
+            machi_dt:chunk_csum()) ->
+                   ok | {error, used|file:posix()}.
+write(#machi_csum_table{fd=Fd, table=T}, Offset, Size, CSum) ->
+    Binary = encode_csum_file_entry_bin(Offset, Size, CSum),
+    case file:write(Fd, Binary) of
+        ok ->
+            case ets:insert_new(T, {Offset, Size, CSum}) of
+                true ->
+                    ok;
+                false ->
+                    {error, written}
+            end;
+        Error ->
+            Error
+    end.
+
+-spec trim(table(), machi_dt:chunk_pos(), machi_dt:chunk_size()) ->
+                  ok | {error, file:posix()}.
+trim(#machi_csum_table{fd=Fd, table=T}, Offset, Size) ->
+    Binary = encode_csum_file_entry_bin(Offset, Size, trimmed),
+    case file:write(Fd, Binary) of
+        ok ->
+            true = ets:insert(T, {Offset, Size, trimmed}),
+            ok;
+        Error ->
+            Error
+    end.
+
+-spec sync(table()) -> ok | {error, file:posix()}.
+sync(#machi_csum_table{fd=Fd}) ->
+    file:sync(Fd).
+
+-spec calc_unwritten_bytes(table()) -> [byte_sequence()].
+calc_unwritten_bytes(#machi_csum_table{table=T}) ->
+    case lists:sort(ets:tab2list(T)) of
+        [] ->
+            [{?MINIMUM_OFFSET, infinity}];
+        Sorted ->
+            {LastOffset, _, _} = hd(Sorted),
+            build_unwritten_bytes_list(Sorted, LastOffset, [])
+    end.
+
+-spec close(table()) -> ok.
+close(#machi_csum_table{table=T, fd=Fd}) ->
+    true = ets:delete(T),
+    ok = file:close(Fd).
+
+-spec delete(table()) -> ok.
+delete(#machi_csum_table{file=F} = C) ->
+    catch close(C),
+    case file:delete(F) of
+        ok -> ok;
+        {error, enoent} -> ok;
+        E -> E
+    end.
+
+%% @doc Encode `Offset + Size + TaggedCSum' into an `iolist()' type for
+%% internal storage by the FLU.
+
+-spec encode_csum_file_entry(
+        machi_dt:file_offset(), machi_dt:chunk_size(), machi_dt:chunk_s()) ->
+        iolist().
+encode_csum_file_entry(Offset, Size, TaggedCSum) ->
+    Len = 8 + 4 + byte_size(TaggedCSum),
+    [<<$w, Len:8/unsigned-big, Offset:64/unsigned-big, Size:32/unsigned-big>>,
+     TaggedCSum].
+
+%% @doc Encode `Offset + Size + TaggedCSum' into an `binary()' type for
+%% internal storage by the FLU.
+
+-spec encode_csum_file_entry_bin(
+        machi_dt:file_offset(), machi_dt:chunk_size(), machi_dt:chunk_s()) ->
+        binary().
+encode_csum_file_entry_bin(Offset, Size, trimmed) ->
+    <<$t, Offset:64/unsigned-big, Size:32/unsigned-big>>;
+encode_csum_file_entry_bin(Offset, Size, TaggedCSum) ->
+    Len = 8 + 4 + byte_size(TaggedCSum),
+    <<$w, Len:8/unsigned-big, Offset:64/unsigned-big, Size:32/unsigned-big,
+      TaggedCSum/binary>>.
+
+%% @doc Decode a single `binary()' blob into an
+%%      `{Offset,Size,TaggedCSum}' tuple.
+%%
+%% The internal encoding (which is currently exposed to the outside world
+%% via this function and related ones) is:
+%%
+%% <ul>
+%% <li> 1 byte: record length
+%% </li>
+%% <li> 8 bytes (unsigned big-endian): byte offset
+%% </li>
+%% <li> 4 bytes (unsigned big-endian): chunk size
+%% </li>
+%% <li> all remaining bytes: tagged checksum (1st byte = type tag)
+%% </li>
+%% </ul>
+%%
+%% See `machi.hrl' for the tagged checksum types, e.g.,
+%% `?CSUM_TAG_NONE'.
+
+-spec decode_csum_file_entry(binary()) ->
+        error |
+        {machi_dt:file_offset(), machi_dt:chunk_size(), machi_dt:chunk_s()}.
+decode_csum_file_entry(<<_:8/unsigned-big, Offset:64/unsigned-big, Size:32/unsigned-big, TaggedCSum/binary>>) ->
+    {Offset, Size, TaggedCSum};
+decode_csum_file_entry(_Else) ->
+    error.
+
+%% @doc Split a `binary()' blob of `checksum_list' data into a list of
+%% `{Offset,Size,TaggedCSum}' tuples.
+
+-spec split_checksum_list_blob_decode(binary()) ->
+  {list({machi_dt:file_offset(), machi_dt:chunk_size(), machi_dt:chunk_s()}),
+   TrailingJunk::binary()}.
+split_checksum_list_blob_decode(Bin) ->
+    split_checksum_list_blob_decode(Bin, []).
+
+split_checksum_list_blob_decode(<<$w, Len:8/unsigned-big, Part:Len/binary, Rest/binary>>, Acc)->
+    One = <<Len:8/unsigned-big, Part/binary>>,
+    case decode_csum_file_entry(One) of
+        error ->
+            split_checksum_list_blob_decode(Rest, Acc);
+        DecOne ->
+            split_checksum_list_blob_decode(Rest, [DecOne|Acc])
+    end;
+split_checksum_list_blob_decode(<<$t, Offset:64/unsigned-big, Size:32/unsigned-big, Rest/binary>>, Acc) ->
+    %% trimmed offset
+    split_checksum_list_blob_decode(Rest, [{Offset, Size, trimmed}|Acc]);
+split_checksum_list_blob_decode(Rest, Acc) ->
+    {lists:reverse(Acc), Rest}.
+
+-spec build_unwritten_bytes_list( CsumData   :: [{ Offset   :: non_neg_integer(),
+                                                   Size     :: pos_integer(),
+                                                   Checksum :: binary() }],
+                                  LastOffset :: non_neg_integer(),
+                                  Acc        :: list() ) -> [byte_sequence()].
+% @private Given a <b>sorted</b> list of checksum data tuples, return a sorted
+% list of unwritten byte ranges. The output list <b>always</b> has at least one
+% entry: the last tuple in the list is guaranteed to be the current end of
+% bytes written to a particular file with the special space moniker
+% `infinity'.
+build_unwritten_bytes_list([], Last, Acc) ->
+    NewAcc = [ {Last, infinity} | Acc ],
+    lists:reverse(NewAcc);
+build_unwritten_bytes_list([{CurrentOffset, CurrentSize, _Csum}|Rest], LastOffset, Acc) when
+      CurrentOffset /= LastOffset ->
+    Hole = CurrentOffset - LastOffset,
+    build_unwritten_bytes_list(Rest, (CurrentOffset+CurrentSize), [{LastOffset, Hole}|Acc]);
+build_unwritten_bytes_list([{CO, CS, _Ck}|Rest], _LastOffset, Acc) ->
+    build_unwritten_bytes_list(Rest, CO + CS, Acc).

src/machi_file_proxy.erl

@@ -89,7 +89,7 @@
     eof_position = 0      :: non_neg_integer(),
     unwritten_bytes = []  :: [byte_sequence()],
     data_filehandle       :: file:filehandle(),
-    csum_filehandle       :: file:filehandle(),
+    csum_table            :: machi_csum_table:table(),
     tref                  :: reference(), %% timer ref
     ticks = 0             :: non_neg_integer(), %% ticks elapsed with no new operations
     ops = 0               :: non_neg_integer(), %% sum of all ops
@@ -196,10 +196,10 @@ init({Filename, DataDir}) ->
     {_, DPath} = machi_util:make_data_filename(DataDir, Filename),
     ok = filelib:ensure_dir(CsumFile),
     ok = filelib:ensure_dir(DPath),
-    UnwrittenBytes = parse_csum_file(CsumFile),
+    {ok, CsumTable} = machi_csum_table:open(CsumFile, []),
+    UnwrittenBytes = machi_csum_table:calc_unwritten_bytes(CsumTable),
     {Eof, infinity} = lists:last(UnwrittenBytes),
     {ok, FHd} = file:open(DPath, [read, write, binary, raw]),
-    {ok, FHc} = file:open(CsumFile, [append, binary, raw]),
     Tref = schedule_tick(),
     St = #state{
         filename        = Filename,
@@ -207,7 +207,7 @@ init({Filename, DataDir}) ->
         data_path       = DPath,
         csum_file       = CsumFile,
         data_filehandle = FHd,
-        csum_filehandle = FHc,
+        csum_table      = CsumTable,
         tref            = Tref,
         unwritten_bytes = UnwrittenBytes,
         eof_position    = Eof},
@@ -224,15 +224,15 @@ handle_call({sync, data}, _From, State = #state{ data_filehandle = FHd }) ->
     R = file:sync(FHd),
     {reply, R, State};
 
-handle_call({sync, csum}, _From, State = #state{ csum_filehandle = FHc }) ->
+handle_call({sync, csum}, _From, State = #state{ csum_table = T }) ->
-    R = file:sync(FHc),
+    R = machi_csum_table:sync(T),
     {reply, R, State};
 
 handle_call({sync, all}, _From, State = #state{filename = F,
                                                data_filehandle = FHd,
-                                               csum_filehandle = FHc
+                                               csum_table = T
                                               }) ->
-    R = file:sync(FHc),
+    R = machi_csum_table:sync(T),
     R1 = file:sync(FHd),
     Resp = case {R, R1} of
         {ok, ok} -> ok;
@@ -267,11 +267,17 @@ handle_call({read, Offset, Length}, _From,
 handle_call({read, Offset, Length}, _From,
             State = #state{filename = F,
                            data_filehandle = FH,
+                           csum_table = CsumTable,
                            unwritten_bytes = U,
                            reads = {T, Err}
                           }) ->
 
-    Checksum = get({Offset, Length}), %% N.B. Maybe be 'undefined'!
+    Checksum = case machi_csum_table:find(CsumTable, Offset, Length) of
+                   {ok, Checksum0} ->
+                       Checksum0;
+                   _ ->
+                       undefined
+               end,
 
     {Resp, NewErr} = case handle_read(FH, F, Checksum, Offset, Length, U) of
         {ok, Bytes, Csum} ->
@@ -296,7 +302,7 @@ handle_call({write, Offset, ClientMeta, Data}, _From,
                            filename = F,
                            writes = {T, Err},
                            data_filehandle = FHd,
-                           csum_filehandle = FHc
+                           csum_table = CsumTable
                           }) ->
 
     ClientCsumTag = proplists:get_value(client_csum_tag, ClientMeta, ?CSUM_TAG_NONE),
@@ -309,7 +315,7 @@ handle_call({write, Offset, ClientMeta, Data}, _From,
                         [ClientCsum, Bad]),
             {{error, bad_checksum}, Err + 1, U};
         TaggedCsum ->
-            case handle_write(FHd, FHc, F, TaggedCsum, Offset, Data, U) of
+            case handle_write(FHd, CsumTable, F, TaggedCsum, Offset, Data, U) of
                 {ok, NewU1} ->
                     {ok, Err, NewU1};
                 Error ->
@@ -336,7 +342,7 @@ handle_call({append, ClientMeta, Extra, Data}, _From,
                            filename = F,
                            appends = {T, Err},
                            data_filehandle = FHd,
-                           csum_filehandle = FHc
+                           csum_table = CsumTable
                           }) ->
 
     ClientCsumTag = proplists:get_value(client_csum_tag, ClientMeta, ?CSUM_TAG_NONE),
@@ -349,7 +355,7 @@ handle_call({append, ClientMeta, Extra, Data}, _From,
                         [ClientCsum, Bad]),
             {{error, bad_checksum}, Err + 1, U};
         TaggedCsum ->
-            case handle_write(FHd, FHc, F, TaggedCsum, EofP, Data, U) of
+            case handle_write(FHd, CsumTable, F, TaggedCsum, EofP, Data, U) of
                 {ok, NewU1} ->
                     {{ok, F, EofP}, Err, NewU1};
                 Error ->
@@ -450,7 +456,7 @@ handle_info(Req, State) ->
 % @private
 terminate(Reason, #state{filename = F,
                          data_filehandle = FHd,
-                         csum_filehandle = FHc,
+                         csum_table = T,
                          reads = {RT, RE},
                          writes = {WT, WE},
                          appends = {AT, AE}
@@ -461,9 +467,9 @@ terminate(Reason, #state{filename = F,
     lager:info(" Writes:  ~p/~p", [WT, WE]),
     lager:info("Appends:  ~p/~p", [AT, AE]),
     ok = file:sync(FHd),
-    ok = file:sync(FHc),
     ok = file:close(FHd),
-    ok = file:close(FHc),
+    ok = machi_csum_table:sync(T),
+    ok = machi_csum_table:close(T),
     ok.
 
 % @private
@@ -497,36 +503,6 @@ check_or_make_tagged_csum(OtherTag, _ClientCsum, _Data) ->
     lager:warning("Unknown checksum tag ~p", [OtherTag]),
     {error, bad_checksum}.
    
-encode_csum_file_entry(Offset, Size, TaggedCSum) ->
-    Len = 8 + 4 + byte_size(TaggedCSum),
-    [<<Len:8/unsigned-big, Offset:64/unsigned-big, Size:32/unsigned-big>>,
-     TaggedCSum].
-
-map_offsets_to_csums(CsumList) ->
-    lists:foreach(fun insert_offsets/1, CsumList).
-
-insert_offsets({Offset, Length, Checksum}) ->
-    put({Offset, Length}, Checksum).
-
--spec parse_csum_file( Filename :: string() ) -> [byte_sequence()].
-parse_csum_file(Filename) ->
-    %% using file:read_file works as long as the files are "small"
-    try
-        {ok, CsumData} = file:read_file(Filename),
-        {DecodedCsums, _Junk} = machi_flu1:split_checksum_list_blob_decode(CsumData),
-        Sort = lists:sort(DecodedCsums),
-        case Sort of
-        [] -> [{?MINIMUM_OFFSET, infinity}];
-        _ ->
-            map_offsets_to_csums(DecodedCsums),
-            {First, _, _} = hd(Sort),
-            build_unwritten_bytes_list(Sort, First, [])
-        end
-    catch
-        _:{badmatch, {error, enoent}} ->
-            [{?MINIMUM_OFFSET, infinity}]
-    end.
-   
 -spec handle_read(FHd        :: file:filehandle(),
                   Filename   :: string(),
                   TaggedCsum :: undefined|binary(),
@@ -593,7 +569,7 @@ do_read(FHd, Filename, TaggedCsum, Offset, Size) ->
     end.
 
 -spec handle_write( FHd        :: file:filehandle(),
-                    FHc        :: file:filehandle(),
+                    CsumTable  :: machi_csum_table:table(),
                     Filename   :: string(),
                     TaggedCsum :: binary(),
                     Offset     :: non_neg_integer(),
@@ -613,15 +589,19 @@ do_read(FHd, Filename, TaggedCsum, Offset, Size) ->
 % file, and the internal list of unwritten bytes is modified to reflect the
 % just-performed write.  This is then returned to the caller as 
 % `{ok, NewUnwritten}' where NewUnwritten is the revised unwritten byte list.
-handle_write(FHd, FHc, Filename, TaggedCsum, Offset, Data, U) ->
+handle_write(FHd, CsumTable, Filename, TaggedCsum, Offset, Data, U) ->
     Size = iolist_size(Data),
 
     case is_byte_range_unwritten(Offset, Size, U) of
         false ->
-            case get({Offset, Size}) of
+            case machi_csum_table:find(CsumTable, Offset, Size) of
-                undefined ->
+                {error, trimmed} = Error ->
+                    Error;
+                {error, notfound} ->
+                    %% Just unknown pair of {offset, size}
+                    %% given. Trust U and return as it is used
                     {error, written};
-                TaggedCsum ->
+                {ok, TaggedCsum} ->
                     case do_read(FHd, Filename, TaggedCsum, Offset, Size) of
                         eof ->
                             lager:warning("This should never happen: got eof while reading at offset ~p in file ~p that's supposedly written",
@@ -632,7 +612,7 @@ handle_write(FHd, FHc, Filename, TaggedCsum, Offset, Data, U) ->
                         _ ->
                             {error, written}
                     end;
-                OtherCsum ->
+                {ok, OtherCsum} ->
                     %% Got a checksum, but it doesn't match the data block's
                     lager:error("During a potential write at offset ~p in file ~p, a check for unwritten bytes gave us checksum ~p but the data we were trying to trying to write has checksum ~p",
                                 [Offset, Filename, OtherCsum, TaggedCsum]),
@@ -640,7 +620,7 @@ handle_write(FHd, FHc, Filename, TaggedCsum, Offset, Data, U) ->
             end;
         true ->
             try
-                do_write(FHd, FHc, Filename, TaggedCsum, Offset, Size, Data, U)
+                do_write(FHd, CsumTable, Filename, TaggedCsum, Offset, Size, Data, U)
             catch
                 %%% XXX FIXME: be more specific on badmatch that might
                 %%% occur around line 593 when we write the checksum
@@ -653,7 +633,7 @@ handle_write(FHd, FHc, Filename, TaggedCsum, Offset, Data, U) ->
 % @private Implements the disk writes for both the write and append
 % operation.
 -spec do_write( FHd        :: file:descriptor(),
-                FHc        :: file:descriptor(),
+                CsumTable  :: machi_csum_table:table(),
                 Filename   :: string(),
                 TaggedCsum :: binary(),
                 Offset     :: non_neg_integer(),
@@ -662,14 +642,12 @@ handle_write(FHd, FHc, Filename, TaggedCsum, Offset, Data, U) ->
                 Unwritten  :: [byte_sequence()]
               ) -> {ok, NewUnwritten :: [byte_sequence()]} |
                    {error, Reason :: term()}.
-do_write(FHd, FHc, Filename, TaggedCsum, Offset, Size, Data, U) ->
+do_write(FHd, CsumTable, Filename, TaggedCsum, Offset, Size, Data, U) ->
     case file:pwrite(FHd, Offset, Data) of
         ok ->
             lager:debug("Successful write in file ~p at offset ~p, length ~p",
                         [Filename, Offset, Size]),
-            EncodedCsum = encode_csum_file_entry(Offset, Size, TaggedCsum),
+            ok = machi_csum_table:write(CsumTable, Offset, Size, TaggedCsum),
-            ok = file:write(FHc, EncodedCsum),
-            put({Offset, Size}, TaggedCsum),
             NewU = update_unwritten(Offset, Size, U),
             lager:debug("Successful write to checksum file for ~p; unwritten bytes are now: ~p",
                         [Filename, NewU]),
@@ -756,22 +734,3 @@ update_byte_range(Offset, Size, {Pos, Space}) when Offset > Pos ->
     [{Pos, Offset - Pos}, {Offset+Size, ( (Pos+Space) - (Offset + Size) )}].
 
 
--spec build_unwritten_bytes_list( CsumData   :: [{ Offset   :: non_neg_integer(),
-                                                   Size     :: pos_integer(),
-                                                   Checksum :: binary() }],
-                                  LastOffset :: non_neg_integer(),
-                                  Acc        :: list() ) -> [byte_sequence()].
-% @private Given a <b>sorted</b> list of checksum data tuples, return a sorted
-% list of unwritten byte ranges. The output list <b>always</b> has at least one
-% entry: the last tuple in the list is guaranteed to be the current end of
-% bytes written to a particular file with the special space moniker
-% `infinity'.
-build_unwritten_bytes_list([], Last, Acc) ->
-    NewAcc = [ {Last, infinity} | Acc ],
-    lists:reverse(NewAcc);
-build_unwritten_bytes_list([{CurrentOffset, CurrentSize, _Csum}|Rest], LastOffset, Acc) when
-      CurrentOffset /= LastOffset ->
-    Hole = CurrentOffset - LastOffset,
-    build_unwritten_bytes_list(Rest, (CurrentOffset+CurrentSize), [{LastOffset, Hole}|Acc]);
-build_unwritten_bytes_list([{CO, CS, _Ck}|Rest], _LastOffset, Acc) ->
-    build_unwritten_bytes_list(Rest, CO + CS, Acc).

src/machi_flu1.erl

@@ -61,9 +61,6 @@
 -export([start_link/1, stop/1,
          update_wedge_state/3, wedge_myself/2]).
 -export([make_listener_regname/1, make_projection_server_regname/1]).
--export([encode_csum_file_entry/3, encode_csum_file_entry_bin/3,
-         decode_csum_file_entry/1,
-         split_checksum_list_blob/1, split_checksum_list_blob_decode/1]).
 
 -record(state, {
           flu_name        :: atom(),
@@ -707,99 +704,6 @@ make_listener_regname(BaseName) ->
 make_projection_server_regname(BaseName) ->
     list_to_atom(atom_to_list(BaseName) ++ "_pstore").
 
-%% @doc Encode `Offset + Size + TaggedCSum' into an `iolist()' type for
-%% internal storage by the FLU.
-
--spec encode_csum_file_entry(
-        machi_dt:file_offset(), machi_dt:chunk_size(), machi_dt:chunk_s()) ->
-        iolist().
-encode_csum_file_entry(Offset, Size, TaggedCSum) ->
-    Len = 8 + 4 + byte_size(TaggedCSum),
-    [<<Len:8/unsigned-big, Offset:64/unsigned-big, Size:32/unsigned-big>>,
-     TaggedCSum].
-
-%% @doc Encode `Offset + Size + TaggedCSum' into an `binary()' type for
-%% internal storage by the FLU.
-
--spec encode_csum_file_entry_bin(
-        machi_dt:file_offset(), machi_dt:chunk_size(), machi_dt:chunk_s()) ->
-        binary().
-encode_csum_file_entry_bin(Offset, Size, TaggedCSum) ->
-    Len = 8 + 4 + byte_size(TaggedCSum),
-    <<Len:8/unsigned-big, Offset:64/unsigned-big, Size:32/unsigned-big,
-      TaggedCSum/binary>>.
-
-%% @doc Decode a single `binary()' blob into an
-%%      `{Offset,Size,TaggedCSum}' tuple.
-%%
-%% The internal encoding (which is currently exposed to the outside world
-%% via this function and related ones) is:
-%%
-%% <ul>
-%% <li> 1 byte: record length
-%% </li>
-%% <li> 8 bytes (unsigned big-endian): byte offset
-%% </li>
-%% <li> 4 bytes (unsigned big-endian): chunk size
-%% </li>
-%% <li> all remaining bytes: tagged checksum (1st byte = type tag)
-%% </li>
-%% </ul>
-%%
-%% See `machi.hrl' for the tagged checksum types, e.g.,
-%% `?CSUM_TAG_NONE'.
-
--spec decode_csum_file_entry(binary()) ->
-        error |
-        {machi_dt:file_offset(), machi_dt:chunk_size(), machi_dt:chunk_s()}.
-decode_csum_file_entry(<<_:8/unsigned-big, Offset:64/unsigned-big, Size:32/unsigned-big, TaggedCSum/binary>>) ->
-    {Offset, Size, TaggedCSum};
-decode_csum_file_entry(_Else) ->
-    error.
-
-%% @doc Split a `binary()' blob of `checksum_list' data into a list of
-%% unparsed `binary()' blobs, one per entry.
-%%
-%% Decode the unparsed blobs with {@link decode_csum_file_entry/1}, if
-%% desired.
-%%
-%% The return value `TrailingJunk' is unparseable bytes at the end of
-%% the checksum list blob.
-
--spec split_checksum_list_blob(binary()) ->
-          {list(binary()), TrailingJunk::binary()}.
-split_checksum_list_blob(Bin) ->
-    split_checksum_list_blob(Bin, []).
-
-split_checksum_list_blob(<<Len:8/unsigned-big, Part:Len/binary, Rest/binary>>, Acc)->
-    case get(hack_length) of
-        Len -> ok;
-        _   -> put(hack_different, true)
-    end,
-    split_checksum_list_blob(Rest, [<<Len:8/unsigned-big, Part/binary>>|Acc]);
-split_checksum_list_blob(Rest, Acc) ->
-    {lists:reverse(Acc), Rest}.
-
-%% @doc Split a `binary()' blob of `checksum_list' data into a list of
-%% `{Offset,Size,TaggedCSum}' tuples.
-
--spec split_checksum_list_blob_decode(binary()) ->
-  {list({machi_dt:file_offset(), machi_dt:chunk_size(), machi_dt:chunk_s()}),
-   TrailingJunk::binary()}.
-split_checksum_list_blob_decode(Bin) ->
-    split_checksum_list_blob_decode(Bin, []).
-
-split_checksum_list_blob_decode(<<Len:8/unsigned-big, Part:Len/binary, Rest/binary>>, Acc)->
-    One = <<Len:8/unsigned-big, Part/binary>>,
-    case decode_csum_file_entry(One) of
-        error ->
-            split_checksum_list_blob_decode(Rest, Acc);
-        DecOne ->
-            split_checksum_list_blob_decode(Rest, [DecOne|Acc])
-    end;
-split_checksum_list_blob_decode(Rest, Acc) ->
-    {lists:reverse(Acc), Rest}.
-
 check_or_make_tagged_checksum(?CSUM_TAG_NONE, _Client_CSum, Chunk) ->
     %% TODO: If the client was foolish enough to use
     %% this type of non-checksum, then the client gets
@@ -859,9 +763,9 @@ timing_demo_test2() ->
     {HexUSec, _} =
     timer:tc(fun() ->
                      lists:foldl(fun(X, _) ->
-                                         B = encode_csum_file_entry_hex(X, 100, CSum),
+                                         B = machi_checksums:encode_csum_file_entry_hex(X, 100, CSum),
                                          %% file:write(ZZZ, [B, 10]),
-                                         decode_csum_file_entry_hex(list_to_binary(B))
+                                         machi_checksums:decode_csum_file_entry_hex(list_to_binary(B))
                                  end, x, Xs)
              end),
     io:format(user, "~.3f sec\n", [HexUSec / 1000000]),
@@ -872,14 +776,14 @@ timing_demo_test2() ->
     {NotSortedUSec, _} =
     timer:tc(fun() ->
                      lists:foldl(fun(X, _) ->
-                                         B = encode_csum_file_entry(X, 100, CSum),
+                                         B = machi_checksums:encode_csum_file_entry(X, 100, CSum),
-                                         decode_csum_file_entry(list_to_binary(B))
+                                         machi_checksums:decode_csum_file_entry(list_to_binary(B))
                                  end, x, Xs)
              end),
     io:format(user, "~.3f sec\n", [NotSortedUSec / 1000000]),
 
     NotHexList = lists:foldl(fun(X, Acc) ->
-                                 B = encode_csum_file_entry(X, 100, CSum),
+                                     B = machi_checksums:encode_csum_file_entry(X, 100, CSum),
                                  [B|Acc]
                          end, [], Xs),
     NotHexBin = iolist_to_binary(NotHexList),
@@ -890,7 +794,7 @@ timing_demo_test2() ->
     timer:tc(fun() ->
                      put(hack_length, 29),
                      put(hack_different, false),
-                     {Sorted, _Leftover} = split_checksum_list_blob(NotHexBin),
+                     {Sorted, _Leftover} = machi_checksums:split_checksum_list_blob(NotHexBin),
                      io:format(user, " Leftover ~p (hack_different ~p) ", [_Leftover, get(hack_different)]),
                      Sorted
              end),
@@ -964,7 +868,7 @@ sort_input_fun(FH, PrevStuff) ->
                                   true ->
                                        <<PrevStuff/binary, NewStuff/binary>>
                                end,
-                    {SplitRes, Leftover} = split_checksum_list_blob(AllStuff),
+                    {SplitRes, Leftover} = machi_checksums:split_checksum_list_blob(AllStuff),
                     {SplitRes, sort_input_fun(FH, Leftover)};
                 eof ->
                     end_of_input

test/machi_csum_table_test.erl

@@ -0,0 +1,29 @@
+-module(machi_csum_table_test).
+-compile(export_all).
+
+smoke_test() ->
+    Filename = "./temp-checksum-dumb-file",
+    {ok, MC} = machi_checksums:new(Filename),
+    {Offset, Size, Checksum} = {64, 34, <<"deadbeef">>},
+    {error, unwritten} = machi_checksums:find(MC, Offset, Size),
+    ok = machi_checksums:write(MC, Offset, Size, Checksum),
+    {ok, Checksum} = machi_checksums:find(MC, Offset, Size),
+    ok = machi_checksums:trim(MC, Offset, Size),
+    {error, trimmed} = machi_checksums:find(MC, Offset, Size),
+    ok = machi_checksums:destroy(MC),
+    ok = machi_checksums:delete_file(MC).
+
+close_test() ->
+    Filename = "./temp-checksum-dumb-file-2",
+    {ok, MC} = machi_checksums:new(Filename),
+    {Offset, Size, Checksum} = {64, 34, <<"deadbeef">>},
+    {error, unwritten} = machi_checksums:find(MC, Offset, Size),
+    ok = machi_checksums:write(MC, Offset, Size, Checksum),
+    {ok, Checksum} = machi_checksums:find(MC, Offset, Size),
+    ok = machi_checksums:destroy(MC),
+
+    {ok, MC2} = machi_checksums:new(Filename),
+    {ok, Checksum} = machi_checksums:find(MC2, Offset, Size),
+    ok = machi_checksums:trim(MC2, Offset, Size),
+    {error, trimmed} = machi_checksums:find(MC2, Offset, Size),
+    ok = machi_checksums:delete_file(MC2).