From 2aa8685eb5728c7b09c01ea496a265d1c054be44 Mon Sep 17 00:00:00 2001
From: Mark Spanbroek <mark@spanbroek.net>
Date: Wed, 1 Dec 2021 11:40:12 +0100
Subject: [PATCH] Simplify decoding of tuples

---
 contractabi/decoding.nim           | 11 ++++-
 tests/contractabi/testDecoding.nim | 66 +++---------------------------
 2 files changed, 15 insertions(+), 62 deletions(-)

diff --git a/contractabi/decoding.nim b/contractabi/decoding.nim
index cdf1bd3..36fb237 100644
--- a/contractabi/decoding.nim
+++ b/contractabi/decoding.nim
@@ -84,7 +84,7 @@ func decode*(decoder: var AbiDecoder, T: type seq[byte]): T =
     let len = decoder.read(uint64).int
     decoder.read(len, padRight)
 
-func startTuple*(decoder: var AbiDecoder, dynamic: bool) =
+func startTuple(decoder: var AbiDecoder, dynamic: bool) =
   var start: int
   if decoder.currentTuple.dynamic and dynamic:
     start = decoder.readOffset()
@@ -92,12 +92,19 @@ func startTuple*(decoder: var AbiDecoder, dynamic: bool) =
     start = decoder.index
   decoder.stack.add(Tuple.init(start, dynamic))
 
-func finishTuple*(decoder: var AbiDecoder) =
+func finishTuple(decoder: var AbiDecoder) =
   doAssert decoder.stack.len > 1, "unable to finish a tuple that hasn't started"
   let tupl = decoder.stack.pop()
   if not tupl.dynamic:
     decoder.index = tupl.index
 
+func decode*(decoder: var AbiDecoder, T: type tuple): T =
+  const dynamic = AbiEncoder.isDynamic(typeof(result))
+  decoder.startTuple(dynamic)
+  for element in result.fields:
+    element = decoder.read(typeof(element))
+  decoder.finishTuple()
+
 func finish*(decoder: var AbiDecoder) =
   doAssert decoder.stack.len == 1, "not all tuples were finished"
   doAssert decoder.last == decoder.bytes.len, "unread trailing bytes found"
diff --git a/tests/contractabi/testDecoding.nim b/tests/contractabi/testDecoding.nim
index d6e44d3..23e1025 100644
--- a/tests/contractabi/testDecoding.nim
+++ b/tests/contractabi/testDecoding.nim
@@ -68,86 +68,32 @@ suite "ABI decoding":
     let b = @[1'u8, 2'u8, 3'u8]
     let c = 0xAABBCCDD'u32
     let d = @[4'u8, 5'u8, 6'u8]
-    let encoding = AbiEncoder.encode( (a, b, c, d) )
-
-    var decoder = AbiDecoder.init(encoding)
-    decoder.startTuple(dynamic=true)
-    check decoder.read(bool) == a
-    check decoder.read(seq[byte]) == b
-    check decoder.read(uint32) == c
-    check decoder.read(seq[byte]) == d
-    decoder.finishTuple()
-    decoder.finish()
+    checkDecode( (a, b, c, d) )
 
   test "decodes nested tuples":
     let a = true
     let b = @[1'u8, 2'u8, 3'u8]
     let c = 0xAABBCCDD'u32
     let d = @[4'u8, 5'u8, 6'u8]
-
-    let encoding = AbiEncoder.encode( (a, b, (c, d)) )
-    var decoder = AbiDecoder.init(encoding)
-    decoder.startTuple(dynamic=true)
-    check decoder.read(bool) == a
-    check decoder.read(seq[byte]) == b
-    decoder.startTuple(dynamic=true)
-    check decoder.read(uint32) == c
-    check decoder.read(seq[byte]) == d
-    decoder.finishTuple()
-    decoder.finishTuple()
-    decoder.finish()
+    checkDecode( (a, b, (c, d)) )
 
   test "reads elements after dynamic tuple":
     let a = @[1'u8, 2'u8, 3'u8]
     let b = 0xAABBCCDD'u32
-    let encoding = AbiEncoder.encode( ((a,), b) )
-
-    var decoder = AbiDecoder.init(encoding)
-    decoder.startTuple(dynamic=true)
-    decoder.startTuple(dynamic=true)
-    check decoder.read(seq[byte]) == a
-    decoder.finishTuple()
-    check decoder.read(uint32) == b
-    decoder.finishTuple()
-    decoder.finish()
+    checkDecode( ((a,), b) )
 
   test "reads elements after static tuple":
     let a = 0x123'u16
     let b = 0xAABBCCDD'u32
-    let encoding = AbiEncoder.encode( ((a,), b) )
-
-    var decoder = AbiDecoder.init(encoding)
-    decoder.startTuple(dynamic=false)
-    decoder.startTuple(dynamic=false)
-    check decoder.read(uint16) == a
-    decoder.finishTuple()
-    check decoder.read(uint32) == b
-    decoder.finishTuple()
-    decoder.finish()
+    checkDecode( ((a,), b) )
 
   test "reads static tuple inside dynamic tuple":
     let a = @[1'u8, 2'u8, 3'u8]
     let b = 0xAABBCCDD'u32
-    let encoding = AbiEncoder.encode( (a, (b,)) )
-
-    var decoder = AbiDecoder.init(encoding)
-    decoder.startTuple(dynamic=true)
-    check decoder.read(seq[byte]) == a
-    decoder.startTuple(dynamic=false)
-    check decoder.read(uint32) == b
-    decoder.finishTuple()
-    decoder.finishTuple()
-    decoder.finish()
+    checkDecode( (a, (b,)) )
 
   test "reads empty tuples":
-    let encoding = AbiEncoder.encode( ((),) )
-
-    var decoder = AbiDecoder.init(encoding)
-    decoder.startTuple(dynamic=false)
-    decoder.startTuple(dynamic=false)
-    decoder.finishTuple()
-    decoder.finishTuple()
-    decoder.finish()
+    checkDecode( ((),) )
 
   test "decodes sequences":
     checkDecode(@[seq[byte].example, seq[byte].example])