#809 Fix more PR suggestions, especially a potential integer overflow (Thanks @coderabbitai).

Author: yruslan

cobol-parser/src/main/scala/za/co/absa/cobrix/cobol/reader/VarLenNestedReader.scala

@@ -217,10 +217,7 @@ class VarLenNestedReader[T: ClassTag](copybookContents: Seq[String],
 
   private def getSplitSizeMB(isCompressed: Boolean): Option[Int] = {
     if (isCompressed) {
-      readerProperties.inputSplitSizeCompressedMB match {
-        case Some(size) => readerProperties.inputSplitSizeCompressedMB
-        case None => Some(1024)
-      }
+      readerProperties.inputSplitSizeCompressedMB.orElse(Some(1024))
     } else {
       if (readerProperties.inputSplitSizeMB.isDefined) {
         readerProperties.inputSplitSizeMB

spark-cobol/src/main/scala/za/co/absa/cobrix/spark/cobol/source/streaming/BufferedFSDataInputStream.scala

@@ -38,7 +38,7 @@ class BufferedFSDataInputStream(filePath: Path, hadoopConfig: Configuration, sta
   private val buffer = new Array[Byte](bufferSizeInBytes)
   private var bufferPos = 0
   private var bufferContainBytes = 0
-  private var bytesRead = 0
+  private var bytesRead = 0L
 
   @throws[IOException]
   def close(): Unit = {
@@ -67,7 +67,7 @@ class BufferedFSDataInputStream(filePath: Path, hadoopConfig: Configuration, sta
       if (bufferPos < bufferContainBytes) {
         val bytesLeft = bufferContainBytes - bufferPos
         System.arraycopy(buffer, bufferPos, b, off, bytesLeft)
-        lengthLeft -= bufferContainBytes - bufferPos
+        lengthLeft -= bytesLeft
         offsetLeft += bytesLeft
       }
       bufferPos = 0