From fbf64f31f34a12a9fc983f74bec27e5fbbe85f34 Mon Sep 17 00:00:00 2001
From: Linus Nordberg <linus@nordberg.se>
Date: Tue, 9 Sep 2014 16:29:53 +0200
Subject: New hash tree implementation, using an ETS table for the hashes.

Also, add an untested entry storage implementation, using multiple
DETS tables.
---
 src/es.erl | 72 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 72 insertions(+)
 create mode 100644 src/es.erl

(limited to 'src/es.erl')

diff --git a/src/es.erl b/src/es.erl
new file mode 100644
index 0000000..9e8be8d
--- /dev/null
+++ b/src/es.erl
@@ -0,0 +1,72 @@
+%%% Copyright (c) 2014, NORDUnet A/S.
+%%% See LICENSE for licensing information.
+%%%
+%%% Entry storage.
+%%%
+%%% BUGS: Retrieving entries don't update list of tables. The effects
+%%% are that 1) dets:open_file is called for each retrieval and 2)
+%%% tables only read from won't get closed by close/1.
+
+-module(es).
+-export_type([entry_store/0]).
+-export([open/0, close/1, store/3, retrieve/2]).
+-import(lists, [filtermap/2, map/2, foreach/2, nth/2, flatten/1]).
+
+-record(entry_store, {tables :: list()}).       % [dets:tab_name()]
+-type entry_store() :: #entry_store{}.
+
+%%%%%%%%%%%%%%%%%%%%
+%% Public interface.
+-spec open() -> entry_store().
+open() ->
+    Files = filtermap(fun(F) -> dets:is_dets_file(F) end,
+                      filelib:wildcard("es*.dat")),
+    Tables = map(fun(F) -> list_to_atom(filename:basename(F, ".dat")) end,
+                       Files),
+    foreach(fun(T) -> T = open_file(T) end, Tables),
+    #entry_store{tables = Tables}.
+
+-spec close(entry_store()) -> ok.
+close(#entry_store{tables = Tables}) ->
+    foreach(fun(Tab) -> dets:close(Tab) end, Tables).
+
+-spec store(entry_store(), non_neg_integer(), binary()) -> entry_store().
+store(Store, Index, Entry) ->
+    {Tables, Tab} = get_table(Store#entry_store.tables, Index),
+    true = dets:insert_new(Tab, {Index, Entry}),
+    Store#entry_store{tables = Tables}.
+
+-spec retrieve(entry_store(), non_neg_integer()) -> binary() | notfound.
+retrieve(#entry_store{tables = Tables}, Index) ->
+    {_, Tab} = get_table(Tables, Index),
+    case dets:lookup(Tab, Index) of
+        [E] -> element(2, E);
+        [] -> notfound;
+        Error -> exit(Error)
+    end.
+
+%%%%%%%%%%%%%%%%%%%%
+%% Internal functions.
+%%-define(TABLE_SIZE, 25000000).                  % < 2e9 / 32 + 8
+-define(TABLE_SIZE, 256).                       % For testing.
+-define(AUTO_SAVE_INTERVAL, 30000).             % Milliseconds.
+
+-spec get_table(list(), non_neg_integer()) -> {list(), dets:tab_name()}.
+get_table(Tables, Index) ->
+    TableIndex = trunc(Index / ?TABLE_SIZE) + 1,
+    if TableIndex =< length(Tables) ->
+            {Tables, nth(TableIndex, Tables)};
+       true ->
+            Tab = open_file(list_to_atom(flatten(
+                                           io_lib:format("es~p", [TableIndex])))),
+            {Tables ++ [Tab], Tab} % Order is important, efficiency not.
+    end.
+
+-spec open_file(atom()) -> dets:tab_name().
+open_file(Name) ->
+    {ok, Tab} = dets:open_file(Name, [{type, set},
+                                      {file, atom_to_list(Name)++".dat"},
+                                      {auto_save, ?AUTO_SAVE_INTERVAL},
+                                      {min_no_slots, ?TABLE_SIZE},
+                                      {max_no_slots, ?TABLE_SIZE}]),
+    Tab.
-- 
cgit v1.1