Make get_by_indices() handle non-existing entries.

- Limit End to size - 1.
- Return [] for start < 0 and bound end < start.

1 files changed, 17 insertions, 9 deletions

diff --git a/src/db.erl b/src/db.erl
index d90282f..4bcdc1c 100644
--- a/src/db.erl
+++ b/src/db.erl
@@ -35,9 +35,7 @@ stop() ->
 add(LeafHash, EntryHash, Data, Index) ->
     gen_server:call(?MODULE, {add, {LeafHash, EntryHash, Data, Index}}).
 
--spec get_by_indices(non_neg_integer(),
-                     non_neg_integer(),
-                     {sorted, true|false}) ->
+-spec get_by_indices(integer(), integer(), {sorted, true|false}) ->
                             [{non_neg_integer(), binary(), binary()}].
 get_by_indices(Start, End, {sorted, Sorted}) ->
     gen_server:call(?MODULE, {get_by_indices, {Start, End, Sorted}}).
@@ -114,6 +112,21 @@ leafhash_for_index(Index) ->
 leafhash_for_entryhash(EntryHash) ->
     perm:readfile(entryhash_root_path(), EntryHash).
 
+get_by_indices_helper(Start, _End) when Start < 0 ->
+    [];
+get_by_indices_helper(Start, End) ->
+    EndBound = min(End, size() - 1),
+    case Start =< EndBound of
+        true ->
+            lists:map(fun (Index) ->
+                              LeafHash = leafhash_for_index(Index),
+                              Entry = entry_for_leafhash(LeafHash),
+                              {Index, LeafHash, Entry}
+                      end, lists:seq(Start, EndBound));
+        false ->
+            []
+    end.
+
 handle_call(stop, _From, State) ->
     {stop, normal, stopped, State};
 
@@ -127,12 +140,7 @@ handle_call({add, {LeafHash, EntryHash, Data, Index}}, _From, State) ->
     {reply, ok, State};
 
 handle_call({get_by_indices, {Start, End, _Sorted}}, _From, State) ->
-    R = lists:map(fun (Index) ->
-                          LeafHash = leafhash_for_index(Index),
-                          Entry = entry_for_leafhash(LeafHash),
-                          {Index, LeafHash, Entry}
-                  end, lists:seq(Start, End)),
-    {reply, R, State};
+    {reply, get_by_indices_helper(Start, End), State};
 
 handle_call({get_by_index, Index}, _From, State) ->
     LeafHash = leafhash_for_index(Index),