new save format wip (no branching on this commit)

src/net/torvald/terrarum/tvda/DiskSkimmer.kt

@@ -23,7 +23,7 @@ class DiskSkimmer(
         val diskFile: File,
         val charset: Charset = Charset.defaultCharset(),
         noInit: Boolean = false
-) {
+): SimpleFileSystem {
 
     /*
 
@@ -250,6 +250,8 @@ removefile:
         }
     }
 
+    override fun getFile(id: EntryID) = requestFile(id)?.contents as? EntryFile
+
     /**
      * Try to find a file with given path (which uses '/' as a separator). Is search is failed for whatever reason,
      * `null` is returned.

src/net/torvald/terrarum/tvda/SimpleFileSystem.kt

@@ -0,0 +1,8 @@
+package net.torvald.terrarum.tvda
+
+/**
+ * Created by minjaesong on 2021-10-07.
+ */
+interface SimpleFileSystem {
+    fun getFile(id: EntryID): EntryFile?
+}

src/net/torvald/terrarum/tvda/VirtualDisk.kt

@@ -124,7 +124,7 @@ class VirtualDisk(
         /** capacity of 0 makes the disk read-only */
         var capacity: Long,
         var diskName: ByteArray = ByteArray(NAME_LENGTH)
-) {
+): SimpleFileSystem {
     var extraInfoBytes = ByteArray(16)
     val entries = HashMap<EntryID, DiskEntry>()
     var isReadOnly: Boolean
@@ -143,6 +143,8 @@ class VirtualDisk(
         extraInfoBytes = footer.toByteArray()
     }
 
+    override fun getFile(id: EntryID) = try { VDUtil.getAsNormalFile(this, id) } catch (e: NullPointerException) { null }
+
     private fun serializeEntriesOnly(): ByteArray64 {
         val buffer = ByteArray64()
         entries.forEach {