distinguishing zero-byte write from full-block write

terranmon.txt

@@ -110,15 +110,17 @@ MMIO
 4080..4083 RO: 8-bit status code for connected device
 
 4084..4091 RO: Block transfer status
-    0b nnnnnnnn a000 mmmm
+    0b nnnnnnnn a00z mmmm
 
     n-read: size of the block from the other device, LSB (4096-full block size is zero)
     m-read: size of the block from the other device, MSB (4096-full block size is zero)
     a-read: if the other device hasNext (doYouHaveNext), false if device not present
+    z-read: set if the size is actually 0 instead of 4096
 
     n-write: size of the block I'm sending, LSB (4096-full block size is zero)
     m-write: size of the block I'm sending, MSB (4096-full block size is zero)
     a-write: if there's more to send (hasNext)
+    z-write: set if the size is actually 0 instead of 4096
 
 4092..4095 RW: Block transfer control for Port 1 through 4
     0b 00ms abcd

tsvm_core/src/net/torvald/tsvm/SerialHelper.kt

@@ -119,16 +119,18 @@ object SerialHelper {
     private fun setBlockTransferStatus(vm: VM, portNo: Int, blockSize: Int, moreToSend: Boolean = false) {
         vm.getIO().mmio_write(4084L + (portNo * 2), (blockSize and 255).toByte())
         vm.getIO().mmio_write(4085L + (portNo * 2),
-            ((blockSize ushr 8).and(15) or (moreToSend.toInt(7))).toByte()
+            ((blockSize ushr 8).and(15) or (moreToSend.toInt(7)) or (blockSize == 0).toInt(4)).toByte()
         )
     }
 
     private fun getBlockTransferStatus(vm: VM, portNo: Int): Pair<Int, Boolean> {
-        val bits = vm.getIO().mmio_read(4084L + (portNo * 2))!!.toUint() or
+        val lb = vm.getIO().mmio_read(4084L + (portNo * 2))!!.toUint()
-                (vm.getIO().mmio_read(4085L + (portNo * 2))!!.toUint() shl 8)
+        val hb = vm.getIO().mmio_read(4085L + (portNo * 2))!!.toUint()
+        val bits = lb or (hb shl 8)
         val rawcnt = bits.and(4095)
         val gotMore = bits.and(0x8000) != 0
-        return (if (rawcnt == 0) BLOCK_SIZE else rawcnt) to gotMore
+        val actuallyZero = (hb and 0x10 != 0)
+        return (if (rawcnt == 0 && !actuallyZero) BLOCK_SIZE else rawcnt) to gotMore
     }
 
     data class DeviceStatus(val code: Int, val message: String)

tsvm_core/src/net/torvald/tsvm/peripheral/IOSpace.kt

@@ -129,13 +129,13 @@ class IOSpace(val vm: VM) : PeriBase("io"), InputProcessor {
             4083L -> blockTransferPorts[3].getYourStatusCode().toByte()
 
             4084L -> (blockTransferPorts[0].yourBlockSize().toByte())
-            4085L -> (blockTransferPorts[0].doYouHaveNext().toInt(7) or blockTransferPorts[0].yourBlockSize().ushr(8).and(15)).toByte()
+            4085L -> (blockTransferPorts[0].doYouHaveNext().toInt(7) or (blockTransferPorts[0].yourBlockSize() == 0).toInt(4) or blockTransferPorts[0].yourBlockSize().ushr(8).and(15)).toByte()
             4086L -> (blockTransferPorts[1].yourBlockSize().toByte())
-            4087L -> (blockTransferPorts[1].doYouHaveNext().toInt(7) or blockTransferPorts[1].yourBlockSize().ushr(8).and(15)).toByte()
+            4087L -> (blockTransferPorts[1].doYouHaveNext().toInt(7) or (blockTransferPorts[1].yourBlockSize() == 0).toInt(4) or blockTransferPorts[1].yourBlockSize().ushr(8).and(15)).toByte()
             4088L -> (blockTransferPorts[2].yourBlockSize().toByte())
-            4089L -> (blockTransferPorts[2].doYouHaveNext().toInt(7) or blockTransferPorts[2].yourBlockSize().ushr(8).and(15)).toByte()
+            4089L -> (blockTransferPorts[2].doYouHaveNext().toInt(7) or (blockTransferPorts[2].yourBlockSize() == 0).toInt(4) or blockTransferPorts[2].yourBlockSize().ushr(8).and(15)).toByte()
             4090L -> (blockTransferPorts[3].yourBlockSize().toByte())
-            4091L -> (blockTransferPorts[3].doYouHaveNext().toInt(7) or blockTransferPorts[3].yourBlockSize().ushr(8).and(15)).toByte()
+            4091L -> (blockTransferPorts[3].doYouHaveNext().toInt(7) or (blockTransferPorts[3].yourBlockSize() == 0).toInt(4) or blockTransferPorts[3].yourBlockSize().ushr(8).and(15)).toByte()
 
             in 4092..4095 -> composeBlockTransferStatus(adi - 4092).toByte()
 
@@ -196,7 +196,7 @@ class IOSpace(val vm: VM) : PeriBase("io"), InputProcessor {
                 4085L -> {
                     blockTransferPorts[0].hasNext.set(byte < 0)
                     blockTransferPorts[0].blockSize.getAcquire().let {
-                        blockTransferPorts[0].blockSize.setRelease(it.and(0x00FF) or byte.toInt().and(15))
+                        blockTransferPorts[0].blockSize.setRelease(it.and(0x00FF) or byte.toInt().and(15) or (it == 0).toInt(4))
                     }
                 }
 
@@ -207,7 +207,7 @@ class IOSpace(val vm: VM) : PeriBase("io"), InputProcessor {
                 4087L -> {
                     blockTransferPorts[1].hasNext.set(byte < 0)
                     blockTransferPorts[1].blockSize.getAcquire().let {
-                        blockTransferPorts[1].blockSize.setRelease(it.and(0x00FF) or byte.toInt().and(15))
+                        blockTransferPorts[1].blockSize.setRelease(it.and(0x00FF) or byte.toInt().and(15) or (it == 0).toInt(4))
                     }
                 }
 
@@ -218,7 +218,7 @@ class IOSpace(val vm: VM) : PeriBase("io"), InputProcessor {
                 4089L -> {
                     blockTransferPorts[2].hasNext.set(byte < 0)
                     blockTransferPorts[2].blockSize.getAcquire().let {
-                        blockTransferPorts[2].blockSize.setRelease(it.and(0x00FF) or byte.toInt().and(15))
+                        blockTransferPorts[2].blockSize.setRelease(it.and(0x00FF) or byte.toInt().and(15) or (it == 0).toInt(4))
                     }
                 }
 
@@ -229,7 +229,7 @@ class IOSpace(val vm: VM) : PeriBase("io"), InputProcessor {
                 4091L -> {
                     blockTransferPorts[3].hasNext.set(byte < 0)
                     blockTransferPorts[3].blockSize.getAcquire().let {
-                        blockTransferPorts[3].blockSize.setRelease(it.and(0x00FF) or byte.toInt().and(15))
+                        blockTransferPorts[3].blockSize.setRelease(it.and(0x00FF) or byte.toInt().and(15) or (it == 0).toInt(4))
                     }
                 }
 

tsvm_core/src/net/torvald/tsvm/peripheral/TevdDiskDrive.kt

@@ -143,23 +143,38 @@ class TevdDiskDrive(private val vm: VM, private val driveNum: Int, theTevdPath:
             //println("[DiskDrive] writeout with inputdata length of ${inputData.size}")
             //println("[DiskDriveMsg] ${inputData.toString(Charsets.UTF_8)}")
 
+            println("[TevDiskDrive] write-payload (${inputData.size} bytes)")
+
+
             if (!fileOpen) throw InternalError("File is not open but the drive is in write mode")
 
-            System.arraycopy(inputData, 0, writeBuffer, writeBufferUsage, minOf(writeModeLength - writeBufferUsage, inputData.size, BLOCK_SIZE))
+            if (writeBuffer.isEmpty()) {
-            writeBufferUsage += inputData.size
-
-            if (writeBufferUsage >= writeModeLength) {
-                // commit to the disk
-                if (appendMode) {
-                    val filesize = file.length()
-                    file.pwrite(writeBuffer, 0, writeBuffer.size, filesize)
-                }
-                else if (writeMode)
-                    file.overwrite(writeBuffer)
-
                 writeMode = false
                 appendMode = false
             }
+            else {
+                System.arraycopy(
+                    inputData,
+                    0,
+                    writeBuffer,
+                    writeBufferUsage,
+                    minOf(writeModeLength - writeBufferUsage, inputData.size, BLOCK_SIZE)
+                )
+                writeBufferUsage += inputData.size
+
+                if (writeBufferUsage >= writeModeLength) {
+                    // commit to the disk
+                    if (appendMode) {
+                        val filesize = file.length()
+                        file.pwrite(writeBuffer, 0, writeBuffer.size, filesize)
+                    }
+                    else if (writeMode)
+                        file.overwrite(writeBuffer)
+
+                    writeMode = false
+                    appendMode = false
+                }
+            }
         }
         else if (fileOpenMode == 17) {
             if (!fileOpen) throw InternalError("Bootloader file is not open but the drive is in boot write mode")
@@ -175,7 +190,7 @@ class TevdDiskDrive(private val vm: VM, private val driveNum: Int, theTevdPath:
         else {
             val inputString = inputData.trimNull().toString(VM.CHARSET)
 
-//            println("[TevDiskDrive] $inputString")
+            println("[TevDiskDrive] $inputString")
 
             if (inputString.startsWith("DEVRST\u0017")) {
                 printdbg("Device Reset")
@@ -430,6 +445,7 @@ class TevdDiskDrive(private val vm: VM, private val driveNum: Int, theTevdPath:
                 }
             }
             else if (inputString.startsWith("WRITE")) {
+                writeModeLength = inputString.substring(5, inputString.length).toInt()
                 if (!fileOpen) {
                     statusCode.set(STATE_CODE_NO_FILE_OPENED)
                     return
@@ -440,7 +456,6 @@ class TevdDiskDrive(private val vm: VM, private val driveNum: Int, theTevdPath:
                 }
                 if (fileOpenMode == 1) { writeMode = true; appendMode = false }
                 else if (fileOpenMode == 2) { writeMode = false; appendMode = true }
-                writeModeLength = inputString.substring(5, inputString.length).toInt()
                 writeBuffer = ByteArray(writeModeLength)
                 writeBufferUsage = 0
                 statusCode.set(STATE_CODE_STANDBY)