Document

2 files changed, 32 insertions, 11 deletions

diff --git a/lib/data/data.ex b/lib/data/data.ex
new file mode 100644
index 0000000..2c6e629
--- /dev/null
+++ b/lib/data/data.ex
@@ -0,0 +1,14 @@
+defmodule SData do
+  @moduledoc """
+  Utility functions
+  """
+
+  @doc """
+  Calculate the hash of an Erlang term by first converting it to its
+  binary representation.
+  """
+  def term_hash(term) do
+    :crypto.hash(:sha256, (:erlang.term_to_binary term))
+  end
+
+end
diff --git a/lib/data/merklelist.ex b/lib/data/merklelist.ex
index 42b80fc..727f2a8 100644
--- a/lib/data/merklelist.ex
+++ b/lib/data/merklelist.ex
@@ -1,26 +1,33 @@
 defmodule SData.MerkleList do
+  @moduledoc """
+  A simple Merkle list store.
+
+  Future improvements:
+  - When messages are inserted other than at the top, all intermediate hashes
+    change. Keep track of the mapping from old hashes to new hashes so that get
+    requests can work even for hashes that are not valid anymore.
+  - group items in "pages" (bigger bundles)
+  """
+
   use GenServer
 
-  def start_link(cmp) do
-    GenServer.start_link(__MODULE__, cmp)
-  end
+  @doc """
+    Start a Merkle List storage process.
 
-  defp term_hash(term) do
-    :crypto.hash(:sha256, (:erlang.term_to_binary term))
-  end
 
-  @doc """
-    Initialize a Merkle List storage.
     `cmp` is a function that compares stored items and provides a total order.
-
     It must return:
       - `:after` if the first argument is more recent
       - `:duplicate` if the two items are the same
       - `:before` if the first argument is older
   """
+  def start_link(cmp) do
+    GenServer.start_link(__MODULE__, cmp)
+  end
+
   def init(cmp) do
     root_item = :root
-    root_hash = term_hash root_item
+    root_hash = SData.term_hash root_item
     state = %{
               root:  root_hash,
               top:   root_hash,
@@ -32,7 +39,7 @@ defmodule SData.MerkleList do
 
   defp state_push(item, state) do
     new_item = {item, state.top}
-    new_item_hash = term_hash new_item
+    new_item_hash = SData.term_hash new_item
     new_store = Map.put(state.store, new_item_hash, new_item)
     %{ state | :top => new_item_hash, :store => new_store }
   end