Fixed encoding of (multidimentional) dynamic arrays (#149)

* Fixed encoding of (multidimentional) dynamic arrays

* Added reference link

tests/test_contract_dsl.nim

@@ -34,6 +34,7 @@ contract(TestContract):
   proc getBool(): bool
   proc setBool(a: bool)
   proc setString(a: string)
+  proc g(a: seq[seq[UInt256]], b: seq[string])
 
 contract(TestContractWithConstructor):
   proc init(someArg1, someArg2: UInt256) {.constructor.}
@@ -47,7 +48,10 @@ suite "Contract DSL":
     checkData(c.getBool(), "0x12a7b914")
     checkData(c.setBool(true), "0x1e26fd330000000000000000000000000000000000000000000000000000000000000001")
     checkData(c.setBool(false), "0x1e26fd330000000000000000000000000000000000000000000000000000000000000000")
-    checkData(c.setString("hello"), "0x7fcaf6660000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000000568656c6c6f0000000000")
+    checkData(c.setString("hello"), "0x7fcaf6660000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000000568656c6c6f000000000000000000000000000000000000000000000000000000")
+
+    # Example taken from https://docs.soliditylang.org/en/latest/abi-spec.html#use-of-dynamic-types
+    checkData(c.g(@[@[1.u256, 2.u256], @[3.u256]], @["one", "two", "three"]), "0x2289b18c000000000000000000000000000000000000000000000000000000000000004000000000000000000000000000000000000000000000000000000000000001400000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000000000000000000000000000000000000004000000000000000000000000000000000000000000000000000000000000000a0000000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000000000000000000000000000000000000000100000000000000000000000000000000000000000000000000000000000000030000000000000000000000000000000000000000000000000000000000000003000000000000000000000000000000000000000000000000000000000000006000000000000000000000000000000000000000000000000000000000000000a000000000000000000000000000000000000000000000000000000000000000e000000000000000000000000000000000000000000000000000000000000000036f6e650000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000374776f000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000057468726565000000000000000000000000000000000000000000000000000000")
 
   test "Constructors":
     let s = DummySender()

web3/encoding.nim

@@ -58,8 +58,9 @@ func decode*(input: openarray[byte], baseOffset, offset: int, to: var Address):
 func encodeDynamic(v: openArray[byte]): seq[byte] =
   result = encode(v.len.u256)
   result.add(v)
-  for i in 0 ..< (v.len mod 32):
-    result.add(0)
+  let pad = v.len mod 32
+  if pad != 0:
+    result.setLen(result.len + 32 - pad)
 
 func encode*(x: DynamicBytes): seq[byte] {.inline.} =
   encodeDynamic(distinctBase x)
@@ -157,9 +158,9 @@ func encode*[T](x: openarray[T]): seq[byte] =
   when isDynamicType(T):
     result.setLen((1 + x.len) * 32)
     for i in 0 ..< x.len:
-      let offset = result.len
+      let offset = result.len - 32
       result &= encode(x[i])
-      result[i .. i + 31] = encode(offset.u256)
+      result[(i + 1) * 32 .. (i + 2) * 32 - 1] = encode(offset.u256)
   else:
     for i in 0 ..< x.len:
       result &= encode(x[i])