Fix type decoder to use lazy stream instead of pre-allocated list (#170)

* Fix type decoder to use lazy stream instead of pre-allocated list * Add regression test for bug fix * Refactor type decode to use `Stream.duplicate/2`
poanetwork · Jul 4, 2024 · 7882bf6 · 7882bf6
1 parent 26621a9
commit 7882bf6
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Showing 2 changed files with 48 additions and 4 deletions.
diff --git a/lib/abi/type_decoder.ex b/lib/abi/type_decoder.ex
@@ -253,7 +253,7 @@ defmodule ABI.TypeDecoder do
   end
 
   defp decode_type({:array, type, size}, data) do
-    types = List.duplicate(type, size)
+    types = Stream.duplicate(type, size)
     {tuple, bytes} = decode_type({:tuple, types}, data)
 
     {Tuple.to_list(tuple), bytes}
@@ -298,9 +298,9 @@ defmodule ABI.TypeDecoder do
   defp decode_type({:array, type}, data, full_data) do
     {offset, rest_bytes} = decode_uint(data, 256)
     <<_padding::binary-size(offset), rest_data::binary>> = full_data
-    {count, bytes} = decode_uint(rest_data, 256)
+    {size, bytes} = decode_uint(rest_data, 256)
 
-    types = List.duplicate(type, count)
+    types = Stream.duplicate(type, size)
 
     {tuple, _bytes} = decode_type({:tuple, types}, bytes)
     {Tuple.to_list(tuple), rest_bytes}
@@ -310,7 +310,7 @@ defmodule ABI.TypeDecoder do
     {offset, rest_bytes} = decode_uint(data, 256)
     <<_padding::binary-size(offset), rest_data::binary>> = full_data
 
-    types = List.duplicate(type, size)
+    types = Stream.duplicate(type, size)
 
     {tuple, _} = decode_type({:tuple, types}, rest_data)
 

diff --git a/test/abi/type_decoder_test.exs b/test/abi/type_decoder_test.exs
@@ -713,6 +713,50 @@ defmodule ABI.TypeDecoderTest do
       assert [0x123, "Hello, world!"] == TypeDecoder.decode(data, types)
       assert data == data |> TypeDecoder.decode(types) |> TypeEncoder.encode(types)
     end
+
+    test "handles huge number of list items while ABI decoding" do
+      selector = %FunctionSelector{
+        function: "swapExactTokensForTokens",
+        method_id: <<42, 68, 63, 174>>,
+        type: :function,
+        inputs_indexed: nil,
+        state_mutability: :non_payable,
+        input_names: ["amountIn", "amountOutMin", "path", "to", "deadline"],
+        types: [
+          {:uint, 256},
+          {:uint, 256},
+          {:tuple, [array: {:uint, 256}, array: {:uint, 8}, array: :address]},
+          :address,
+          {:uint, 256}
+        ],
+        returns: [uint: 256],
+        return_names: ["amountOut"]
+      }
+
+      data =
+        <<42, 68, 63, 174, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 110, 71, 248, 212, 138, 1, 180, 77,
+          243, 255, 243, 93, 37, 138, 16, 163, 174, 220, 17, 76, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+          0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 6, 212, 153, 236, 108, 99, 56, 0, 0, 0, 0, 0, 0,
+          0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 128, 0, 0,
+          0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1,
+          32, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+          0, 0, 0, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 143, 154, 114, 216, 245, 100, 121, 144,
+          58, 227, 134, 132, 158, 41, 13, 73, 56, 158, 65, 249, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+          0, 233, 25, 9, 44, 199, 203, 210, 9, 122, 227, 21, 143, 114, 218, 72, 74, 200, 19, 183,
+          75, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 137, 134, 203, 129, 146, 34, 242, 134, 159, 7,
+          202, 92, 60, 237, 11, 130, 38, 218, 44, 74, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 164,
+          168, 239, 101, 138, 224, 219, 204, 165, 88, 224, 178, 219, 217, 229, 25, 37, 24, 13, 50,
+          0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+          0, 0, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+          0, 0, 0, 0, 1, 245, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+          0, 0, 0, 0, 0, 0, 0, 1, 247, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+          0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 246, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+          0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 245>>
+
+      assert_raise MatchError, fn ->
+        TypeDecoder.decode(data, selector)
+      end
+    end
   end
 
   describe "with examples from solidity docs" do