Half way done with the generalized solution. Tests are green. And I am proud.

Signed-off-by: Adam Rocska <adam.rocska@adams.solutions>

Sources/MaxMindDBReader/ControlByte.swift

@@ -19,22 +19,27 @@ struct ControlByte {
       return nil
     }
 
+    let payloadSizeDefinition = firstByte & 0b0001_1111
+    if payloadSizeDefinition < 29 {
+      payloadSize = UInt32(payloadSizeDefinition)
+    } else {
+      let numberOfAdditionalBytesToRead = Int(payloadSizeDefinition & 0b0000_0011)
+      let lastIndexOfBytes              = bytes.index(before: bytes.endIndex)
       let sliceFrom                     = bytes.index(
         bytes.startIndex,
         offsetBy: isExtendedType ? 2 : 1,
-      limitedBy: bytes.endIndex
+        limitedBy: lastIndexOfBytes
-    ) ?? bytes.startIndex
+      ) ?? lastIndexOfBytes
-
+      let sliceTo                       = bytes.index(
-    let bytesAfterTypeSpecifyingBytes = bytes[sliceFrom...]
+        sliceFrom,
-
+        offsetBy: numberOfAdditionalBytesToRead,
-    let payloadSizeDefinition = firstByte & 0b0001_1111
+        limitedBy: lastIndexOfBytes
-    switch payloadSizeDefinition {
+      ) ?? lastIndexOfBytes
-      case _ where payloadSizeDefinition < 29:
+      let bytesAfterTypeSpecifyingBytes = bytes[sliceFrom...sliceTo]
-        payloadSize = UInt32(payloadSizeDefinition)
+      let payloadSizeWholeBytes: Data   = bytesAfterTypeSpecifyingBytes + Data(
-      case 29:
+        count: 4 - bytesAfterTypeSpecifyingBytes.count
-        payloadSize = 29 + UInt32(bytesAfterTypeSpecifyingBytes.first ?? 0)
+      )
-      default:
+      payloadSize = 29 + payloadSizeWholeBytes.withUnsafeBytes { $0.load(as: UInt32.self) }
-        return nil
     }
 
     self.type = type