Prevent overruns in DL11

src/main/kotlin/com/thequux/mcpdp/peripheral/DL11.kt

@@ -11,6 +11,8 @@ import com.thequux.mcpdp.ext.bit.maskSet
 import java.io.InputStream
 import java.io.OutputStream
 import java.util.concurrent.Semaphore
+import java.util.concurrent.locks.Lock
+import java.util.concurrent.locks.LockSupport
 import kotlin.concurrent.thread
 
 
@@ -47,7 +49,7 @@ class DL11(private var istr: InputStream, private val ostr: OutputStream, val re
                 rcsr = rcsr bic 15
                 oldRcsr
             }
-            2 -> { rcsr = rcsr bic 7; rbuf }
+            2 -> { rcsr = rcsr bic 7; LockSupport.unpark(reader); rbuf }
             4 -> xcsr
             6 -> 0u
             else -> throw OddAddressError(addr)
@@ -88,10 +90,14 @@ class DL11(private var istr: InputStream, private val ostr: OutputStream, val re
         try {
             while (true) {
                 val data = istr.read()
+                // wait for rcsr to be read
+                while (synchronized(this) {(rcsr bit 7 || xcsr bit 2)}) {
+                    LockSupport.park()
+                }
+
                 synchronized(this) {
                     // receive if not in maintenance mode
-                    // TODO: block until receiver ready
+                    if (!(xcsr bit 2)) recvByte(data)
-                    if (!(xcsr bit 1)) recvByte(data)
                 }
                 if (data < 0) {
                     break
@@ -104,8 +110,7 @@ class DL11(private var istr: InputStream, private val ostr: OutputStream, val re
     override fun start() {
         super.start()
         reader = thread(block = this::readThread, isDaemon = false)
-
+        LockSupport.unpark(reader)
-//        reader?.interrupt()
     }
 
     override fun stop() {