Support encoding of strings

contractabi.nimble

@@ -4,4 +4,5 @@ description = "ABI Encoding for Ethereum contracts"
 license = "MIT"
 
 requires "stint"
+requires "stew"
 requires "upraises >= 0.1.0 & < 0.2.0"

contractabi/encoding.nim

@@ -1,5 +1,6 @@
 import pkg/stint
 import pkg/upraises
+import pkg/stew/byteutils
 
 export stint
 
@@ -110,6 +111,9 @@ func encode[T](encoder: var AbiEncoder, value: seq[T]) =
   encoder.finishTuple()
   encoder.setDynamic()
 
+func encode(encoder: var AbiEncoder, value: string) =
+  encoder.encode(value.toBytes)
+
 func write*[T](encoder: var AbiEncoder, value: T) =
   var writer = AbiEncoder.init()
   writer.encode(value)

tests/testEncoding.nim

@@ -1,6 +1,7 @@
 
 import std/unittest
 import pkg/stint
+import pkg/stew/byteutils
 import contractabi
 import ./examples
 
@@ -154,5 +155,8 @@ suite "ABI encoding":
       AbiEncoder.encode(32'u8) & # offset in tuple
       AbiEncoder.encode(a)
 
+  test "encodes strings as UTF-8 byte sequence":
+    check AbiEncoder.encode("hello!☺") == AbiEncoder.encode("hello!☺".toBytes)
+
 # https://medium.com/b2expand/abi-encoding-explanation-4f470927092d
 # https://docs.soliditylang.org/en/v0.8.1/abi-spec.html#formal-specification-of-the-encoding