Add support for Ethereum addresses

contractabi/address.nim

@@ -0,0 +1,26 @@
+import pkg/stew/byteutils
+import pkg/questionable
+import pkg/upraises
+
+push: {.upraises: [].}
+
+type
+  Address* = distinct array[20, byte]
+
+func init*(_: type Address, bytes: array[20, byte]): Address =
+  Address(bytes)
+
+func init*(_: type Address, hex: string): ?Address =
+  try:
+    let bytes = array[20, byte].fromHex(hex)
+    some Address.init(bytes)
+  except ValueError:
+    none Address
+
+func toArray*(address: Address): array[20, byte] =
+  array[20, byte](address)
+
+func `$`*(address: Address): string =
+  "0x" & toHex(address.toArray)
+
+func `==`*(a, b: Address): bool {.borrow.}

contractabi/decoding.nim

@@ -5,6 +5,10 @@ import pkg/questionable/results
 import pkg/upraises
 import ./encoding
 import ./integers
+import ./address
+
+export stint
+export address
 
 push: {.upraises:[].}
 
@@ -114,6 +118,11 @@ func decode(decoder: var AbiDecoder, T: type enum): ?!T =
   else:
     failure "invalid enum value"
 
+func decode(decoder: var AbiDecoder, T: type Address): ?!T =
+  var bytes: array[20, byte]
+  bytes[0..<20] =(?decoder.read(20))[0..<20]
+  success T.init(bytes)
+
 func decode[I](decoder: var AbiDecoder, T: type array[I, byte]): ?!T =
   var arr: T
   arr[0..<arr.len] = ?decoder.read(arr.len, padRight)

contractabi/encoding.nim

@@ -2,8 +2,10 @@ import pkg/stint
 import pkg/upraises
 import pkg/stew/byteutils
 import ./integers
+import ./address
 
 export stint
+export address
 
 push: {.upraises:[].}
 
@@ -95,6 +97,9 @@ func encode(encoder: var AbiEncoder, value: bool) =
 func encode(encoder: var AbiEncoder, value: enum) =
   encoder.encode(uint64(ord(value)))
 
+func encode(encoder: var AbiEncoder, value: Address) =
+  encoder.padleft(value.toArray)
+
 func encode[I](encoder: var AbiEncoder, bytes: array[I, byte]) =
   encoder.padright(bytes)
 

tests/contractabi/examples.nim

@@ -1,6 +1,7 @@
 import std/random
 import std/sequtils
 import pkg/stint
+import pkg/contractabi/address
 
 randomize()
 
@@ -23,3 +24,6 @@ proc example*(T: type StUint): T =
 
 proc example*(T: type StInt): T =
   cast[T](StUint[T.bits].example)
+
+proc example*(T: type Address): T =
+  Address.init(array[20, byte].example)

tests/contractabi/testAddress.nim

@@ -0,0 +1,25 @@
+import std/unittest
+import pkg/contractabi/address
+import pkg/questionable
+
+suite "Address":
+
+  let address = Address.init [
+    0x1'u8, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8, 0x9, 0xa,
+    0x1   , 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8, 0x9, 0xa
+  ]
+
+  test "can be converted to string":
+    check $address == "0x0102030405060708090a0102030405060708090a"
+
+  test "can be parsed from string":
+    check:
+      Address.init("0x0102030405060708090a0102030405060708090a") == some address
+
+  test "parsing fails when string does not contain proper hex":
+    check:
+      Address.init("0xfoo2030405060708090a0102030405060708090a") == none Address
+
+  test "parsing fails when string does not contain 20 bytes":
+    check:
+      Address.init("0x0102030405060708090a010203040506070809") == none Address

tests/contractabi/testDecoding.nim

@@ -84,6 +84,9 @@ suite "ABI decoding":
     checkDecode(Int128)
     checkDecode(Int256)
 
+  test "decodes addresses":
+    checkDecode(Address.example)
+
   test "decodes byte arrays":
     checkDecode([1'u8, 2'u8, 3'u8])
     checkDecode(array[32, byte].example)

tests/contractabi/testEncoding.nim

@@ -59,6 +59,10 @@ suite "ABI encoding":
     check AbiEncoder.encode(-1.i256) == 0xFF'u8.repeat(32)
     check AbiEncoder.encode(-1.i128) == 0xFF'u8.repeat(32)
 
+  test "encodes addresses":
+    let address = Address.example
+    check AbiEncoder.encode(address) == 12.zeroes & @(address.toArray)
+
   test "encodes byte arrays":
     let bytes3 = [1'u8, 2'u8, 3'u8]
     check AbiEncoder.encode(bytes3) == @bytes3 & 29.zeroes

tests/testAll.nim

@@ -1,3 +1,4 @@
+import ./contractabi/testAddress
 import ./contractabi/testEncoding
 import ./contractabi/testDecoding
 import ./contractabi/testCustomTypes