From bbef4eda56de8610c5f0c174f71bcedb5dd0470f Mon Sep 17 00:00:00 2001
From: Robert Newson <robert.newson@cloudant.com>
Date: Sat, 12 Mar 2011 17:51:32 +0000
Subject: [PATCH] restore underflow check, remove ttl.

---
 src/monic_file.erl | 62 +++++++++++++++++++---------------------------
 1 file changed, 25 insertions(+), 37 deletions(-)

diff --git a/src/monic_file.erl b/src/monic_file.erl
index de91b86..cc8cf17 100644
--- a/src/monic_file.erl
+++ b/src/monic_file.erl
@@ -22,17 +22,13 @@
 %% gen_server API
 -export([init/1, terminate/2, code_change/3,handle_call/3, handle_cast/2, handle_info/2]).
 
--define(TTL, 2).
-
 -record(state, {
-    ttl=?TTL,
     tid,
     index_fd=nil,
     main_fd=nil,    
     next_index,
     next_key,
     reset_pos,
-    tref=nil,
     write_pos,
     writer=nil
 }).
@@ -82,13 +78,11 @@ init(Path) ->
         {ok, IndexFd, Hints} ->
             case load_main(Tid, Path, Hints) of
                 {ok, MainFd, {NextKey, NextLocation}} ->
-                    {ok, TRef} = timer:apply_interval(10000, gen_server, cast, [self(), ttl]),
                     {ok, #state{
                         index_fd=IndexFd,
                         main_fd=MainFd,
                         next_key=NextKey,
                         reset_pos=NextLocation,
-                        tref=TRef,
                         write_pos=NextLocation,                        
                         tid=Tid
                     }};
@@ -109,9 +103,9 @@ handle_call({start_writing, Size}, _From,
     Index = #index{cookie=Cookie, key=Key, flags=Flags, location=Pos, size=Size, version=Version},
     case monic_utils:pwrite_header(MainFd, Pos, Header) of
         ok ->
-            {reply, {ok, Ref}, reset_ttl(State#state{next_index=Index, write_pos=Pos + ?HEADER_SIZE, writer=Ref})};
+            {reply, {ok, Ref}, State#state{next_index=Index, write_pos=Pos + ?HEADER_SIZE, writer=Ref}};
         Else ->
-            {reply, Else, reset_ttl(abandon_write(State))}
+            {reply, Else, abandon_write(State)}
     end;
 handle_call({start_writing, _Size}, _From, State) ->
     {reply, {error, already_writing}, State};
@@ -122,20 +116,26 @@ handle_call({write, Ref, {Bin, Next}}, _From, #state{main_fd=Fd, write_pos=Pos,
             Pos1 = Pos + iolist_size(Bin),
             case Next of
                 done ->
-                    case file:datasync(Fd) of
-                        ok ->
-                            Index = State#state.next_index,
-                            monic_utils:write_index(State#state.index_fd, Index),
-                            ets:insert(State#state.tid, {Index#index.key, Index#index.cookie,
-                                Index#index.location, Index#index.size, Index#index.version}),
-                            {reply, {ok, {Index#index.key, Index#index.cookie}},
-                            reset_ttl(State#state{next_index=nil, next_key=State#state.next_key+1,
-                            reset_pos=Pos1, write_pos=Pos1, writer=nil})};
-                        Else ->
-                            {reply, Else, abandon_write(State)}
+                    Len = Pos1 - State#state.reset_pos,
+                    case Len < (State#state.next_index)#index.size of
+                        true ->
+                            {reply, {error, underflow}, abandon_write(State)};
+                        false ->
+                            case file:datasync(Fd) of
+                                ok ->
+                                    Index = State#state.next_index,
+                                    monic_utils:write_index(State#state.index_fd, Index),
+                                    ets:insert(State#state.tid, {Index#index.key, Index#index.cookie,
+                                    Index#index.location, Index#index.size, Index#index.version}),
+                                {reply, {ok, {Index#index.key, Index#index.cookie}},
+                                State#state{next_index=nil, next_key=State#state.next_key+1,
+                                reset_pos=Pos1, write_pos=Pos1, writer=nil}};
+                            Else ->
+                                {reply, Else, abandon_write(State)}
+                        end
                     end;
                 Next ->
-                    {reply, {continue, Next}, reset_ttl(State#state{write_pos=Pos1})}
+                    {reply, {continue, Next}, State#state{write_pos=Pos1}}
             end;
         {Else, _} ->
             {reply, Else, abandon_write(State)}
@@ -147,23 +147,19 @@ handle_call({read, Key, Cookie}, _From, #state{tid=Tid}=State) ->
     case info_int(Tid, Key, Cookie) of
         {ok, {Location, Size, _Version}} ->
             Self = self(),
-            {reply, {ok, fun() -> stream_out(Self, Location + ?HEADER_SIZE, Size) end}, reset_ttl(State)};
+            {reply, {ok, fun() -> stream_out(Self, Location + ?HEADER_SIZE, Size) end}, State};
         Else ->
             {reply, Else, State}
     end;
 handle_call({read_hunk, Location, Size}, _From, #state{main_fd=Fd}=State) ->
-    {reply, file:pread(Fd, Location, Size), reset_ttl(State)};
+    {reply, file:pread(Fd, Location, Size), State};
 
 handle_call({info, Key, Cookie}, _From, #state{tid=Tid}=State) ->
-    {reply, info_int(Tid, Key, Cookie), reset_ttl(State)};
+    {reply, info_int(Tid, Key, Cookie), State};
 
 handle_call(close, _From, State) ->
     {stop, normal, ok, cleanup(State)}.
 
-handle_cast(ttl, #state{ttl=0}=State) ->
-    {stop, normal, cleanup(State)};
-handle_cast(ttl, #state{ttl=Ttl}=State) ->
-    {noreply, State#state{ttl=Ttl-1}};
 handle_cast(_Msg, State) ->
     {noreply, State}.
 
@@ -277,12 +273,11 @@ info_int(Tid, Key, Cookie) ->
             {error, not_found}
     end.
 
-cleanup(#state{tid=Tid,tref=TRef,index_fd=IndexFd,main_fd=MainFd}=State) ->
+cleanup(#state{tid=Tid,index_fd=IndexFd,main_fd=MainFd}=State) ->
     close_int(IndexFd),
     close_int(MainFd),
     close_ets(Tid),
-    cancel_timer(TRef),
-    State#state{tid=nil,tref=nil,index_fd=nil,main_fd=nil}.
+    State#state{tid=nil,index_fd=nil,main_fd=nil}.
     
 close_int(nil) ->
     ok;
@@ -294,10 +289,3 @@ close_ets(nil) ->
 close_ets(Tid) ->
     ets:delete(Tid).
 
-cancel_timer(nil) ->
-    ok;
-cancel_timer(TRef) ->
-    timer:cancel(TRef).
-
-reset_ttl(State) ->
-    State#state{ttl=?TTL}.