Fix packet read/writing because it was completely broken before, oops...

src/modernnet/io.nim

@@ -78,24 +78,19 @@ func readVar*[R: int32 | int64](data: openArray[byte]): Result[tuple[num: R, byt
 
 
 func readRawPacket*(data: openArray[byte]): Result[tuple[packet: RawPacket, bytesRead: int], int] =
-  var pos = 0
   let id = data.readVar[:int32]()
 
   if not id.isOk:
-    return typeof(result)(isOk: false, err: id.err - data.len)
+    return typeof(result)(isOk: false, err: id.err)
 
-  pos += id.ok.bytesRead
-
-  let
-    idPos = pos
-    length = data.readVar[:int32]()
+  let length = data[id.ok.bytesRead..^1].readVar[:int32]()
 
   if not length.isOk:
-    return typeof(result)(isOk: false, err: length.err - data.len)
+    return typeof(result)(isOk: false, err: length.err)
 
-  pos += length.ok.bytesRead
+  let lenPos = id.ok.bytesRead + length.ok.bytesRead
 
-  if data.len < (pos + length.ok.num):
-    return typeof(result)(isOk: false, err: (pos + length.ok.num) - data.len)
+  if data.len - lenPos < length.ok.num:
+    return typeof(result)(isOk: false, err: lenPos + length.ok.num - data.len)
 
-  return typeof(result)(isOk: true, ok: (RawPacket(id: id.ok.num, buf: newBuffer(data[idPos..<(pos + length.ok.num)])), pos + length.ok.num))
+  return typeof(result)(isOk: true, ok: (RawPacket(id: id.ok.num, buf: newBuffer(data[lenPos..<(lenPos + length.ok.num)])), lenPos + length.ok.num))

tests/test1.nim

@@ -115,25 +115,32 @@ test "IO read/write test":
   # Commence tests~
   var b: seq[byte] # Pretend this is a buffered socket
 
-  var res = readRawPacket(b)
-
-  var i = 0
+  var
+    res = readRawPacket(b)
+    counter = 0
 
   while not res.isOk:
-    i += 1
+    for i in 0..<res.err: b.add(buffer.readNum[:byte]())
 
-    if i in [1, 2]:
+    inc counter
+
+    if counter < 3:
+      # Check if variable length numbers are read correctly
       check res.err == 1
-    elif i == 3:
-      check res.err == 8
     else:
-      echo "[ERROR] Unimplemented test case where `i` was " & $i & '.'
-      fail
+      # Check if the length was also read correctly.
+      check res.err == 8
 
-    b = buffer.buf[0..<(b.len + res.err)]
     res = readRawPacket(b)
 
+  # Check packet ID
   check res.ok.packet.id == 0x27
-  check res.ok.packet.buf.readVarNum[:int32]() == 8
-  check res.ok.packet.buf.readNum[:int64]() == 23142
+
+  # Use parsed buffer
+  buffer = res.ok.packet.buf
+
+  # Length should be omitted in parsed buffer.
+  check buffer.readNum[:int64]() == 23142
+
+  # Check if the total bytes read was also correct
   check res.ok.bytesRead == 10