REWIND command for serial device

assets/disk0/tvdos/include/seqread.mjs

@@ -155,4 +155,35 @@ function getReadCount() {
     return readCount
 }
 
-exports = {fileHeader, prepare, readBytes, readInt, readShort, readFourCC, readOneByte, readString, skip, getReadCount}
+function rewind() {
+    // Send REWIND command to reset stream position
+    com.sendMessage(port, "REWIND")
+    let statusCode = com.getStatusCode(port)
+    if (statusCode != 0) {
+        throw Error("REWIND failed with "+statusCode)
+    }
+    readCount = 0
+}
+
+function seek(position) {
+    if (position < 0) {
+        throw Error("seek: position must be non-negative")
+    }
+
+    let relPos = position - readCount
+
+    if (relPos == 0) {
+        return  // Already at target position
+    } else if (relPos < 0) {
+        // Seeking backward - must rewind and skip forward
+        rewind()
+        if (position > 0) {
+            skip(position)
+        }
+    } else {
+        // Seeking forward - skip the difference
+        skip(relPos)
+    }
+}
+
+exports = {fileHeader, prepare, readBytes, readInt, readShort, readFourCC, readOneByte, readString, skip, getReadCount, seek, rewind}

serialdev.txt

@@ -104,6 +104,13 @@ Description: reads one block of file. Any subsequent read attempts will return n
              than a single block, rest of the bytes will be filled with zero, and size-of-the-block (see terranmon.txt)
              will be set accordingly.
 
+    REWIND
+
+Description: resets the read position to the beginning of the file for the currently open file. This allows seeking
+             backwards in streaming read mode without closing and reopening the file. Only applicable for files opened
+             with OPENR. If no file is open or the file is not in read mode, returns error status code 135
+             (NO_FILE_OPENED).
+
     CLOSE
 
 Description: closes any file that is open.

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

@@ -395,6 +395,27 @@ class TestDiskDrive(private val vm: VM, private val driveNum: Int, theRootPath:
                 fileOpenMode = -1
                 statusCode.set(STATE_CODE_STANDBY)
             }
+            else if (inputString.startsWith("REWIND")) {
+                // Rewind the stream to beginning for seeking
+                if (readStreamActive && file.isFile) {
+                    try {
+                        closeReadStream()
+                        // Reopen the file at position 0
+                        readInputStream = FileInputStream(file)
+                        readStreamActive = true
+                        readFileSize = file.length()
+                        blockSendCount = 0
+                        statusCode.set(STATE_CODE_STANDBY)
+                    }
+                    catch (e: IOException) {
+                        closeReadStream()
+                        statusCode.set(STATE_CODE_SYSTEM_IO_ERROR)
+                    }
+                }
+                else {
+                    statusCode.set(STATE_CODE_NO_FILE_OPENED)
+                }
+            }
             else if (inputString.startsWith("READ")) {
                 //readModeLength = inputString.substring(4 until inputString.length).toInt()