Allow defining custom segment fill

src/main/scala/millfork/Platform.scala

@@ -34,6 +34,7 @@ class Platform(
                 val generateBbcMicroInfFile: Boolean,
                 val generateGameBoyChecksums: Boolean,
                 val bankNumbers: Map[String, Int],
+                val bankFill: Map[String, Int],
                 val defaultCodeBank: String,
                 val ramInitialValuesBank: Option[String],
                 val outputLabelsFormat: DebugOutputFormat,
@@ -169,6 +170,10 @@ object Platform {
       case "" => 0
       case x => parseNumber(x)
     })).toMap
+    val bankFills = banks.map(b => b -> (as.get(classOf[String], s"segment_${b}_fill", "00") match {
+      case "" => 0
+      case x => parseNumber(x)
+    })).toMap
 
     // TODO: validate stuff
     banks.foreach(b => {
@@ -274,6 +279,7 @@ object Platform {
       generateBbcMicroInfFile,
       generateGameBoyChecksums,
       bankNumbers,
+      bankFills,
       defaultCodeBank,
       ramInitialValuesBank,
       debugOutputFormat,

src/main/scala/millfork/output/AbstractAssembler.scala

@@ -33,7 +33,7 @@ abstract class AbstractAssembler[T <: AbstractCode](private val program: Program
   var initializedVariablesSize: Int = 0
   protected val log: Logger = rootEnv.log
 
-  val mem = new CompiledMemory(platform.bankNumbers.toList, platform.isBigEndian)
+  val mem = new CompiledMemory(platform.bankNumbers.toList, platform.bankFill, platform.isBigEndian)
   val labelMap: mutable.Map[String, (Int, Int)] = mutable.Map()
   private val bytesToWriteLater = mutable.ListBuffer[(String, Int, Constant)]()
   private val wordsToWriteLater = mutable.ListBuffer[(String, Int, Constant)]()

src/main/scala/millfork/output/CompiledMemory.scala

@@ -5,12 +5,21 @@ import scala.collection.mutable
 /**
   * @author Karol Stasiak
   */
-class CompiledMemory(bankNames: List[(String, Int)], bigEndian: Boolean) {
+class CompiledMemory(bankNames: List[(String, Int)], bankFills: Map[String, Int], bigEndian: Boolean) {
   var programName = "MILLFORK"
-  val banks: mutable.Map[String, MemoryBank] = mutable.Map(bankNames.map(p => p._1 -> new MemoryBank(p._2, bigEndian)): _*)
+  val banks: mutable.Map[String, MemoryBank] = mutable.Map(bankNames.map{p =>
+    val bank = new MemoryBank(p._2, bigEndian)
+    bank.fill(bankFills.getOrElse(p._1, 0))
+    p._1 -> bank
+  }: _*)
 }
 
 class MemoryBank(val index: Int, val isBigEndian: Boolean) {
+
+  def fill(value: Int): Unit = {
+    output.indices.foreach(i => output(i) = value.toByte)
+  }
+
   def readByte(addr: Int): Int = output(addr) & 0xff
 
   def readWord(addr: Int): Int =

src/test/scala/millfork/test/emu/EmuPlatform.scala

@@ -36,6 +36,7 @@ object EmuPlatform {
     false,
     false,
     Map("default" -> 0, "second" -> 2, "third" -> 3),
+    Map("default" -> 0, "second" -> 0, "third" -> 0),
     "default",
     None,
     ViceDebugOutputFormat,