First cut at adding DB support.

Including half crazy rewrite of most of the data structures.

1 files changed, 86 insertions, 0 deletions

diff --git a/src/db.erl b/src/db.erl
new file mode 100644
index 0000000..e1604d1
--- /dev/null
+++ b/src/db.erl
@@ -0,0 +1,86 @@
+-module(db).
+-behaviour(gen_server).
+
+%% API.
+-export([start_link/0, stop/0, init_tables/0]).
+-export([add/1, find/1]).
+%% API for testing.
+-export([dump/1, destroy_tables/0, info_tables/0, dump_to_file/1]).
+%% gen_server callbacks.
+-export([init/1, handle_call/3, terminate/2, handle_cast/2, handle_info/2,
+         code_change/3]).
+
+-include_lib("stdlib/include/qlc.hrl").
+-include("plop.hrl").
+
+%% @doc Run once, or rather every time you start on a new database.
+%% If run more than once, we'll get {aborted, {already_exists, TABLE}}.
+init_tables() ->
+    %% We've once upon a time invoked mnesia:create_schema/1 with the
+    %% nodes that will be part of the database.
+    RamCopies = [],
+    DiscCopies = [],
+    DiscOnlyCopies = [node()],
+    mnesia:start(),
+    mnesia:create_table(plop, [{type, set},
+                               {ram_copies, RamCopies},
+                               {disc_copies, DiscCopies},
+                               {disc_only_copies, DiscOnlyCopies},
+                               {attributes, record_info(fields, plop)}]),
+    mnesia:add_table_index(plop, hash).
+destroy_tables() ->
+    mnesia:delete_table(plop).
+info_tables() ->
+    mnesia:table_info(plop, all).
+dump_to_file(Filename) ->
+    mnesia:dump_to_textfile(Filename).
+
+init(_Args) ->
+    {ok, []}.                                   % TODO: return state
+
+start_link() ->
+    gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
+
+stop() ->
+    gen_server:call(?MODULE, stop).
+
+add(Entry) ->
+    gen_server:call(?MODULE, {add, Entry}).
+
+find(Hash) ->
+    gen_server:call(?MODULE, {find, Hash}).
+
+dump(Table) ->
+    gen_server:call(?MODULE, {dump, Table}).
+
+%%%%%%%%%%%%%%%%%%%%
+handle_cast(_Request, State) ->
+    {noreply, State}.
+
+handle_info(_Info, State) ->
+    {noreply, State}.
+
+code_change(_OldVsn, State, _Extra) ->
+    {ok, State}.
+
+terminate(_Reason, _State) ->
+    ok.
+
+%%%%%%%%%%%%%%%%%%%%
+handle_call(stop, _From, State) ->
+    {stop, normal, stopped, State};
+handle_call({add, Entry}, _From, State) ->
+    F = fun() ->
+                mnesia:write(Entry)
+        end,
+    Res = mnesia:transaction(F),
+    {reply, Res, State};
+handle_call({dump, Table}, _From, State) ->
+    F = fun() ->
+                Q = qlc:q([E || E <- mnesia:table(Table)]),
+                qlc:e(Q)
+        end,
+    Res = mnesia:transaction(F),
+    {reply, Res, State};
+handle_call({find, Hash}, _From, State) ->
+    {reply, mnesia:dirty_read({plop, Hash}), State}.