From 81311704756fc3a49a8813791e611ea801e283b9 Mon Sep 17 00:00:00 2001
From: Mark Spanbroek <mark@spanbroek.net>
Date: Wed, 8 Dec 2021 17:27:54 +0100
Subject: [PATCH] Support encoding of signed integers

---
 contractabi/encoding.nim           | 20 ++++++++++++++------
 tests/contractabi/testEncoding.nim | 17 ++++++++++++++++-
 2 files changed, 30 insertions(+), 7 deletions(-)

diff --git a/contractabi/encoding.nim b/contractabi/encoding.nim
index d1579db..0297771 100644
--- a/contractabi/encoding.nim
+++ b/contractabi/encoding.nim
@@ -67,22 +67,30 @@ func encode(encoder: var AbiEncoder, tupl: Tuple) =
 func finishTuple(encoder: var AbiEncoder) =
   encoder.encode(encoder.stack.pop())
 
-func pad(encoder: var AbiEncoder, len: int) =
+func pad(encoder: var AbiEncoder, len: int, padding=0'u8) =
   let padlen = (32 - len mod 32) mod 32
   for _ in 0..<padlen:
-    encoder.append([0'u8])
+    encoder.append([padding])
 
-func padleft(encoder: var AbiEncoder, bytes: openArray[byte]) =
-  encoder.pad(bytes.len)
+func padleft(encoder: var AbiEncoder, bytes: openArray[byte], padding=0'u8) =
+  encoder.pad(bytes.len, padding)
   encoder.append(bytes)
 
-func padright(encoder: var AbiEncoder, bytes: openArray[byte]) =
+func padright(encoder: var AbiEncoder, bytes: openArray[byte], padding=0'u8) =
   encoder.append(bytes)
-  encoder.pad(bytes.len)
+  encoder.pad(bytes.len, padding)
 
 func encode(encoder: var AbiEncoder, value: SomeUnsignedInt | StUint) =
   encoder.padleft(value.toBytesBE)
 
+func encode[bits](encoder: var AbiEncoder, value: StInt[bits]) =
+  let bytes = value.stuint(bits).toBytesBE
+  let padding = if value.isNegative: 0xFF'u8 else: 0x00'u8
+  encoder.padleft(bytes, padding)
+
+func encode(encoder: var AbiEncoder, value: SomeSignedInt) =
+  encoder.write(value.i256)
+
 func encode(encoder: var AbiEncoder, value: bool) =
   encoder.encode(if value: 1'u8 else: 0'u8)
 
diff --git a/tests/contractabi/testEncoding.nim b/tests/contractabi/testEncoding.nim
index daeafdf..809f855 100644
--- a/tests/contractabi/testEncoding.nim
+++ b/tests/contractabi/testEncoding.nim
@@ -1,5 +1,6 @@
 
 import std/unittest
+import std/sequtils
 import pkg/stint
 import pkg/stew/byteutils
 import contractabi
@@ -27,6 +28,16 @@ suite "ABI encoding":
       0x11'u8 & 0x22'u8 & 0x33'u8 & 0x44'u8 &
       0x55'u8 & 0x66'u8 & 0x77'u8 & 0x88'u8
 
+  test "encodes int8, 16, 32, 64":
+    check AbiEncoder.encode(1'i8) == 31.zeroes & 0x01'u8
+    check AbiEncoder.encode(-1'i8) == 0xFF'u8.repeat(32)
+    check AbiEncoder.encode(1'i16) == 31.zeroes & 0x01'u8
+    check AbiEncoder.encode(-1'i16) == 0xFF'u8.repeat(32)
+    check AbiEncoder.encode(1'i32) == 31.zeroes & 0x01'u8
+    check AbiEncoder.encode(-1'i32) == 0xFF'u8.repeat(32)
+    check AbiEncoder.encode(1'i64) == 31.zeroes & 0x01'u8
+    check AbiEncoder.encode(-1'i64) == 0xFF'u8.repeat(32)
+
   test "encodes ranges":
     type SomeRange = range[0x0000'u16..0xAAAA'u16]
     check AbiEncoder.encode(SomeRange(0x1122)) == 30.zeroes & 0x11'u8 & 0x22'u8
@@ -40,9 +51,13 @@ suite "ABI encoding":
 
   test "encodes stints":
     let uint256 = UInt256.example
-    check AbiEncoder.encode(uint256) == @(uint256.toBytesBE)
     let uint128 = UInt128.example
+    check AbiEncoder.encode(uint256) == @(uint256.toBytesBE)
     check AbiEncoder.encode(uint128) == 16.zeroes & @(uint128.toBytesBE)
+    check AbiEncoder.encode(1.i256) == 31.zeroes & 0x01'u8
+    check AbiEncoder.encode(1.i128) == 31.zeroes & 0x01'u8
+    check AbiEncoder.encode(-1.i256) == 0xFF'u8.repeat(32)
+    check AbiEncoder.encode(-1.i128) == 0xFF'u8.repeat(32)
 
   test "encodes byte arrays":
     let bytes3 = [1'u8, 2'u8, 3'u8]