Move everything to subdirectory

1 files changed, 387 insertions, 0 deletions

diff --git a/shard/lib/data/merklesearchtree.ex b/shard/lib/data/merklesearchtree.ex
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+++ b/shard/lib/data/merklesearchtree.ex
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+defmodule SData.MerkleSearchTree do
+  @moduledoc"""
+  A Merkle search tree.
+
+  A node of the tree is
+    {
+      level,
+      hash_of_node | nil,
+      [ 
+        { item_low_bound, hash_of_node | nil },
+        { item_low_bound, hash_of_node | nil },
+        ...
+      }
+    }
+  """
+
+  alias SData.PageStore, as: Store
+
+  @doc"""
+  Create a new Merkle search tree.
+
+  This structure can be used as a set with only true keys,
+  or as a map if a merge function is given.
+
+  `cmp` is a compare function for keys as defined in module `SData`.
+
+  `merge` is a function for merging two items that have the same key.
+  """
+  defstruct root: nil,
+            store: SData.LocalStore.new,
+            cmp: &SData.cmp_term/2,
+            merge: &SData.merge_true/2
+
+          
+  defmodule Page do
+    defstruct [:level, :low, :list]
+  end
+
+  defimpl SData.Page, for: Page do
+    def refs(page) do
+      refs = for {_, _, h} <- page.list, h != nil, do: h
+      if page.low != nil do
+        [ page.low | refs ]
+      else
+        refs
+      end
+    end
+  end
+
+
+  @doc"""
+    Insert an item into the search tree.
+  """
+  def insert(state, key, value \\ true) do
+    level = calc_level(key)
+    {hash, store} = insert_at(state, state.store, state.root, key, level, value)
+    %{ state | root: hash, store: store }
+  end
+
+  defp insert_at(s, store, root, key, level, value) do
+    {new_page, store} = if root == nil do
+      { %Page{ level: level, low: nil, list: [ { key, value, nil } ] }, store }
+    else
+      %Page{ level: plevel, low: low, list: lst } = Store.get(store, root)
+      [ { k0, _, _} | _ ] = lst
+      cond do
+        plevel < level ->
+          {low, high, store} = split(s, store, root, key)
+          { %Page{ level: level, low: low, list: [ { key, value, high } ] }, store }
+        plevel == level ->
+          store = Store.free(store, root)
+          case s.cmp.(key, k0) do
+            :before ->
+              {low2a, low2b, store} = split(s, store, low, key)
+              { %Page{ level: level, low: low2a, list: [ { key, value, low2b } | lst] }, store }
+            _ ->
+              {new_lst, store} = aux_insert_after_first(s, store, lst, key, value)
+              { %Page{ level: plevel, low: low, list: new_lst }, store }
+          end
+        plevel > level ->
+          store = Store.free(store, root)
+          case s.cmp.(key, k0) do
+            :before ->
+              {new_low, store} = insert_at(s, store, low, key, level, value)
+              { %Page{ level: plevel, low: new_low, list: lst }, store }
+            :after ->
+              {new_lst, store} = aux_insert_sub_after_first(s, store, lst, key, level, value)
+              { %Page{ level: plevel, low: low, list: new_lst }, store }
+          end
+      end
+    end
+    Store.put(store, new_page)    # returns {hash, store}
+  end
+
+  defp split(s, store, hash, key) do
+    if hash == nil do
+      {nil, nil, store}
+    else
+      %Page{ level: level, low: low, list: lst } = Store.get(store, hash) || Store.get(s.store, hash)
+      store = Store.free(store, hash)
+      [ { k0, _, _} | _ ] = lst
+      case s.cmp.(key, k0) do
+        :before ->
+          {lowlow, lowhi, store} = split(s, store, low, key)
+          newp2 = %Page{ level: level, low: lowhi, list: lst }
+          {newp2h, store} = Store.put(store, newp2)
+          {lowlow, newp2h, store}
+        :after ->
+          {lst1, p2, store} = split_aux(s, store, lst, key, level)
+          newp1 = %Page{ level: level, low: low, list: lst1}
+          {newp1h, store} = Store.put(store, newp1)
+          {newp1h, p2, store}
+      end 
+    end
+  end
+
+  defp split_aux(s, store, lst, key, level) do
+    case lst do
+      [ {k1, v1, r1} ] ->
+        if s.cmp.(k1, key) == :duplicate do
+          raise "Bad logic"
+        end
+        {r1l, r1h, store} = split(s, store, r1, key)
+        { [{k1, v1, r1l}], r1h, store }
+      [ {k1, v1, r1} = fst, {k2, v2, r2} = rst1 | rst ] ->
+        case s.cmp.(key, k2) do
+          :before ->
+            {r1l, r1h, store} = split(s, store, r1, key)
+            p2 = %Page{ level: level, low: r1h, list: [ {k2, v2, r2} | rst ] }
+            {p2h, store} = Store.put(store, p2)
+            { [{k1, v1, r1l}], p2h, store }
+          :after ->
+            {rst2, hi, store} = split_aux(s, store, [rst1 | rst], key, level)
+            { [ fst | rst2 ], hi, store }
+          :duplicate ->
+            raise "Bad logic"
+        end
+    end
+  end
+
+  defp aux_insert_after_first(s, store, lst, key, value) do
+    case lst do
+      [ {k1, v1, r1} ] ->
+        case s.cmp.(k1, key) do
+          :duplicate ->
+            { [ {k1, s.merge.(v1, value), r1} ], store }
+          :before ->
+            {r1a, r1b, new_store} = split(s, store, r1, key)
+            { [ {k1, v1, r1a}, {key, value, r1b} ], new_store }
+        end
+      [ {k1, v1, r1} = fst, {k2, v2, r2} = rst1 | rst ] ->
+        case s.cmp.(k1, key) do
+          :duplicate ->
+            { [ {k1, s.merge.(v1, value), r1}, rst1 | rst ], store }
+          :before ->
+            case s.cmp.(k2, key) do
+              :after ->
+                {r1a, r1b, new_store} = split(s, store, r1, key)
+                { [ {k1, v1, r1a}, {key, value, r1b}, {k2, v2, r2} | rst ], new_store }
+              _ ->
+                {rst2, new_store} = aux_insert_after_first(s, store, [rst1 | rst], key, value)
+                { [ fst | rst2 ], new_store }
+            end
+        end
+      end
+    end
+
+  defp aux_insert_sub_after_first(s, store, lst, key, level, value) do
+    case lst do
+      [ {k1, v1, r1} ] ->
+        if s.cmp.(k1, key) == :duplicate do
+          raise "Bad logic"
+        end
+        {r1new, store_new} = insert_at(s, store, r1, key, level, value)
+        { [{k1, v1, r1new}], store_new }
+      [ {k1, v1, r1} = fst, {k2, _, _} = rst1 | rst ] ->
+        if s.cmp.(k1, key) == :duplicate do
+          raise "Bad logic"
+        end
+        case s.cmp.(key, k2) do
+          :before ->
+            {r1new, store_new} = insert_at(s, store, r1, key, level, value)
+            { [{k1, v1, r1new}, rst1 | rst], store_new }
+          _ ->
+            {rst2, new_store} = aux_insert_sub_after_first(s, store, [rst1 |rst], key, level, value)
+            { [ fst | rst2 ], new_store }
+        end
+    end
+  end
+
+  @doc"""
+  Merge values from another MST in this MST.
+
+  The merge is not symmetrical in the sense that:
+  - new pages are added in the store of the first argument
+  - the callback is called for all items found in the second argument and not the first
+  """
+  def merge(to, from, callback \\ fn _, _ -> nil end) do
+    { store, root } = merge_aux(to, from, to.store, to.root, from.root, callback)
+    %{ to | store: store, root: root }
+  end
+
+  defp merge_aux(s1, s2, store, r1, r2, callback) do
+    case {r1, r2} do
+      _ when r1 == r2 -> { store, r1 }
+      {_, nil} ->
+        { store, r1 }
+      {nil, _} ->
+        store = Store.copy(store, s2.store, r2)
+        rec_callback(store, r2, callback)
+        { store, r2 }
+      _ ->
+        %Page{ level: level1, low: low1, list: lst1 } = Store.get(store, r1)
+        %Page{ level: level2, low: low2, list: lst2 } = Store.get(store, r2) || Store.get(s2.store, r2)
+        { level, low1, lst1, low2, lst2 } = cond do
+          level1 == level2 -> {level1, low1, lst1, low2, lst2}
+          level1 > level2 ->  {level1, low1, lst1, r2, []}
+          level2 > level1 ->  {level2, r1, [], low2, lst2}
+        end
+        { store, low, lst } = merge_aux_rec(s1, s2, store, low1, lst1, low2, lst2, callback)
+        page = %Page{ level: level, low: low, list: lst }
+        {hash, store} = Store.put(store, page)
+        {store, hash}
+    end
+  end
+
+  defp merge_aux_rec(s1, s2, store, low1, lst1, low2, lst2, callback) do
+    case {lst1, lst2} do
+      { [], [] } ->
+        {store, hash} = merge_aux(s1, s2, store, low1, low2, callback)
+        {store, hash, []}
+      { [], [ {k, v, r} | rst2 ] } ->
+        {low1l, low1h, store} = split(s1, store, low1, k)
+        {store, newlow} = merge_aux(s1, s2, store, low1l, low2, callback)
+        callback.(k, v)
+        {store, newr, newrst} = merge_aux_rec(s1, s2, store, low1h, [], r, rst2, callback)
+        {store, newlow, [ {k, v, newr} | newrst ]}
+      { [ {k, v, r} | rst1 ], [] } ->
+        {low2l, low2h, store} = split(s2, store, low2, k)
+        {store, newlow} = merge_aux(s1, s2, store, low1, low2l, callback)
+        {store, newr, newrst} = merge_aux_rec(s1, s2, store, r, rst1, low2h, [], callback)
+        {store, newlow, [ {k, v, newr} | newrst ]}
+      { [ {k1, v1, r1} | rst1 ], [ {k2, v2, r2} | rst2 ] } ->
+        case s1.cmp.(k1, k2) do
+          :before ->
+            {low2l, low2h, store} = split(s2, store, low2, k1)
+            {store, newlow} = merge_aux(s1, s2, store, low1, low2l, callback)
+            {store, newr, newrst} = merge_aux_rec(s1, s2, store, r1, rst1, low2h, lst2, callback)
+            {store, newlow, [ {k1, v1, newr} | newrst ]}
+          :after ->
+            {low1l, low1h, store} = split(s1, store, low1, k2)
+            {store, newlow} = merge_aux(s1, s2, store, low1l, low2, callback)
+            callback.(k2, v2)
+            {store, newr, newrst} = merge_aux_rec(s1, s2, store, low1h, lst1, r2, rst2, callback)
+            {store, newlow, [ {k2, v2, newr} | newrst ]}
+          :duplicate ->
+            {store, newlow} = merge_aux(s1, s2, store, low1, low2, callback)
+            newv = s1.merge.(v1, v2) ## TODO: callback here ??
+            {store, newr, newrst} = merge_aux_rec(s1, s2, store, r1, rst1, r2, rst2, callback)
+            {store, newlow, [ {k1, newv, newr} | newrst ]}
+        end
+    end
+  end
+
+  defp rec_callback(store, root, callback) do
+    case root do
+      nil -> nil
+      _ ->
+        %Page{ level: _, low: low, list: lst } = Store.get(store, root)
+        rec_callback(store, low, callback)
+        for {k, v, rst} <- lst do
+          callback.(k, v)
+          rec_callback(store, rst, callback)
+        end
+    end
+  end
+
+  @doc"""
+    Get value for a specific key in search tree.
+  """
+  def get(state, key) do
+    get(state, state.root, key)
+  end
+
+  defp get(s, root, key) do
+    case root do
+      nil -> nil
+      _ ->
+        %Page{ level: _, low: low, list: lst } = Store.get(s.store, root)
+        get_aux(s, low, lst, key)
+    end
+  end
+
+  defp get_aux(s, low, lst, key) do
+    case lst do
+      [] ->
+        get(s, low, key)
+      [ {k, v, low2} | rst ] ->
+        case s.cmp.(key, k) do
+          :duplicate -> v
+          :before ->
+            get(s, low, key)
+          :after -> 
+            get_aux(s, low2, rst, key)
+        end
+    end
+  end
+
+  @doc"""
+    Get the last n items of the tree, or the last n items
+    strictly before given upper bound if non nil
+  """
+  def last(state, top_bound, num) do
+    last(state, state.root, top_bound, num)
+  end
+
+  defp last(s, root, top_bound, num) do
+    case root do
+      nil -> []
+      _ ->
+        %Page{ level: _, low: low, list: lst } = Store.get(s.store, root)
+        last_aux(s, low, lst, top_bound, num)
+    end
+  end
+
+  defp last_aux(s, low, lst, top_bound, num) do
+    case lst do
+      [] ->
+        last(s, low, top_bound, num)
+      [ {k, v, low2} | rst ] ->
+        if top_bound == nil or s.cmp.(top_bound, k) == :after do
+          items = last_aux(s, low2, rst, top_bound, num)
+          items = if Enum.count(items) < num do
+            [ {k, v} | items ]
+          else
+            items
+          end
+          cnt = Enum.count items
+          if cnt < num do
+            last(s, low, top_bound, num - cnt) ++ items
+          else
+            items
+          end
+        else
+          last(s, low, top_bound, num)
+        end
+    end
+  end
+
+
+  @doc"""
+    Dump Merkle search tree structure.
+  """
+  def dump(state) do
+    dump(state.store, state.root, "")
+  end
+
+  defp dump(store, root, lvl) do
+    case root do
+      nil ->
+        IO.puts(lvl <> "nil")
+      _ ->
+        %Page{ level: level, low: low, list: lst} = Store.get(store, root)
+        IO.puts(lvl <> "#{root|>Base.encode16} (#{level})")
+        dump(store, low, lvl <> "  ")
+        for {k, v, r} <- lst do
+          IO.puts(lvl<>"- #{inspect k} => #{inspect v}")
+          dump(store, r, lvl <> "  ")
+        end
+    end
+  end
+
+  defp calc_level(key) do
+    key
+      |> SData.term_hash
+      |> Base.encode16
+      |> String.to_charlist
+      |> count_leading_zeroes
+  end
+
+  defp count_leading_zeroes('0' ++ rest) do
+    1 + count_leading_zeroes(rest)
+  end
+  defp count_leading_zeroes(_) do
+    0
+  end
+end