test read cluster via COM

assets/disk0/tvdos/bin/defrag.js

@@ -0,0 +1,18 @@
+
+let drive = _G.shell.getCurrentDrive()
+let port = _TVDOS.DRV.FS.SERIAL._toPorts(drive)
+    com.sendMessage(port[0], "CLOSE")
+for (let i = 0; i < 20; i++) {
+    com.sendMessage(port[0], "READCLUST"+i)
+    let response = com.getStatusCode(port[0])
+    if (response < 0 || response >= 128) {
+        throw Error(`Reading cluster #${i} failed with `+response)
+    }
+    let bytes = com.pullMessage(port[0])
+    print(`#${i}\t`)
+    for (let k = 0; k < 16; k++) {
+        print(bytes.charCodeAt(k).toString(16).padStart(2, '0'))
+        print(' ')
+    }
+    println()
+}