From a0fad53523f15df10aa0c814c979c374afe1c590 Mon Sep 17 00:00:00 2001
From: Mark Spanbroek <mark@spanbroek.net>
Date: Thu, 9 Dec 2021 10:38:34 +0100
Subject: [PATCH] Support decoding of signed integers

---
 contractabi/decoding.nim           | 19 ++++++++++++++++++-
 contractabi/encoding.nim           |  2 +-
 tests/contractabi/examples.nim     |  8 ++++----
 tests/contractabi/testDecoding.nim |  8 ++++++++
 4 files changed, 31 insertions(+), 6 deletions(-)

diff --git a/contractabi/decoding.nim b/contractabi/decoding.nim
index 09c8d55..4227da2 100644
--- a/contractabi/decoding.nim
+++ b/contractabi/decoding.nim
@@ -62,7 +62,7 @@ func skipPadding(decoder: var AbiDecoder, amount: int): ?!void =
   let index = decoder.index
   ?decoder.advance(amount)
   for i in index..<index+amount:
-    if decoder.bytes[i] != 0:
+    if decoder.bytes[i] notin [0x00'u8, 0xFF'u8]:
       return failure "invalid padding found"
   success()
 
@@ -79,6 +79,23 @@ func read(decoder: var AbiDecoder, amount: int, padding=padLeft): ?!seq[byte] =
 func decode(decoder: var AbiDecoder, T: type UInt): ?!T =
   success T.fromBytesBE(?decoder.read(sizeof(T)))
 
+template unsigned(T: type SomeSignedInt): type SomeUnsignedInt =
+  when T is int8: uint8
+  elif T is int16: uint16
+  elif T is int32: uint32
+  elif T is int64: uint64
+  else: {.error "unsupported signed integer type".}
+
+func decode(decoder: var AbiDecoder, T: type SomeSignedInt): ?!T =
+  let bytes = ?decoder.read(sizeof(T))
+  let unsigned = T.unsigned.fromBytesBE(bytes)
+  let signed = cast[T](unsigned)
+  success signed
+
+func decode[bits](decoder: var AbiDecoder, T: type StInt[bits]): ?!T =
+  let unsigned = ?decoder.read(StUint[bits])
+  success cast[T](unsigned)
+
 template basetype(Range: type range): untyped =
   when Range isnot SomeUnsignedInt: {.error: "only uint ranges supported".}
   elif sizeof(Range) == sizeof(uint8): uint8
diff --git a/contractabi/encoding.nim b/contractabi/encoding.nim
index 0297771..823f386 100644
--- a/contractabi/encoding.nim
+++ b/contractabi/encoding.nim
@@ -89,7 +89,7 @@ func encode[bits](encoder: var AbiEncoder, value: StInt[bits]) =
   encoder.padleft(bytes, padding)
 
 func encode(encoder: var AbiEncoder, value: SomeSignedInt) =
-  encoder.write(value.i256)
+  encoder.write(value.to(StInt[64]))
 
 func encode(encoder: var AbiEncoder, value: bool) =
   encoder.encode(if value: 1'u8 else: 0'u8)
diff --git a/tests/contractabi/examples.nim b/tests/contractabi/examples.nim
index 4003628..7d9a745 100644
--- a/tests/contractabi/examples.nim
+++ b/tests/contractabi/examples.nim
@@ -18,8 +18,8 @@ proc example*[T](_: type seq[T], len = 0..5): seq[T] =
   let chosenlen = rand(len)
   newSeqWith(chosenlen, T.example)
 
-proc example*(_: type UInt256): UInt256 =
-  UInt256.fromBytes(array[32, byte].example)
+proc example*(T: type StUint): T =
+  T.fromBytes(array[sizeof(T), byte].example)
 
-proc example*(_: type UInt128): UInt128 =
-  UInt128.fromBytes(array[16, byte].example)
+proc example*(T: type StInt): T =
+  cast[T](StUint[T.bits].example)
diff --git a/tests/contractabi/testDecoding.nim b/tests/contractabi/testDecoding.nim
index 916479f..3f4a848 100644
--- a/tests/contractabi/testDecoding.nim
+++ b/tests/contractabi/testDecoding.nim
@@ -20,6 +20,12 @@ suite "ABI decoding":
     checkDecode(uint32)
     checkDecode(uint64)
 
+  test "decodes int8, int16, int32, int64":
+    checkDecode(int8)
+    checkDecode(int16)
+    checkDecode(int32)
+    checkDecode(int64)
+
   test "fails to decode when reading past end":
     var encoded = AbiEncoder.encode(uint8.example)
     encoded.delete(encoded.len-1)
@@ -75,6 +81,8 @@ suite "ABI decoding":
   test "decodes stints":
     checkDecode(UInt128)
     checkDecode(UInt256)
+    checkDecode(Int128)
+    checkDecode(Int256)
 
   test "decodes byte arrays":
     checkDecode([1'u8, 2'u8, 3'u8])