HSDPA and driver implementation

2026-03-09 20:51:51 +09:00 · 2025-08-17 01:09:42 +09:00
parent e6fc6ed070
commit 1d3d3bd246
8 changed files with 886 additions and 24 deletions
--- a/assets/disk0/tvdos/HSDPADRV.SYS
+++ b/assets/disk0/tvdos/HSDPADRV.SYS
@@ -0,0 +1,271 @@
+///////////////////////////////////////////////////////////////////////////////
+// High Speed Disk Peripheral Adapter (HSDPA) Driver for TVDOS
+// This driver treats each disk from HSDPA as a single large file
+// Created by Claude on 2025-08-16
+///////////////////////////////////////////////////////////////////////////////
+
+// Add TAPE device names to reserved names
+files.reservedNames.push("TAPE0", "TAPE1", "TAPE2", "TAPE3")
+
+// HSDPA peripheral addresses for slot 4
+// MMIO area (for registers): -524289 to -655360 (backwards!)
+// Memory Space area (for buffer): -4194305 to -5242880 (backwards!)
+const HSDPA_SLOT4_MMIO_START = -524289  // MMIO area start
+const HSDPA_REG_DISK1_STATUS = HSDPA_SLOT4_MMIO_START - 0
+const HSDPA_REG_DISK2_STATUS = HSDPA_SLOT4_MMIO_START - 3
+const HSDPA_REG_DISK3_STATUS = HSDPA_SLOT4_MMIO_START - 6
+const HSDPA_REG_DISK4_STATUS = HSDPA_SLOT4_MMIO_START - 9
+const HSDPA_REG_DISK_CONTROL = HSDPA_SLOT4_MMIO_START - 12
+const HSDPA_REG_ACTIVE_DISK = HSDPA_SLOT4_MMIO_START - 20
+const HSDPA_REG_SEQ_IO_CONTROL = HSDPA_SLOT4_MMIO_START - 256
+const HSDPA_REG_SEQ_IO_OPCODE = HSDPA_SLOT4_MMIO_START - 258
+const HSDPA_REG_SEQ_IO_ARG1 = HSDPA_SLOT4_MMIO_START - 259
+const HSDPA_REG_SEQ_IO_ARG2 = HSDPA_SLOT4_MMIO_START - 262
+
+// Sequential I/O opcodes
+const HSDPA_OPCODE_NOP = 0x00
+const HSDPA_OPCODE_SKIP = 0x01
+const HSDPA_OPCODE_READ = 0x02
+const HSDPA_OPCODE_WRITE = 0x03
+const HSDPA_OPCODE_REWIND = 0xF0
+const HSDPA_OPCODE_TERMINATE = 0xFF
+
+// Helper functions for HSDPA MMIO access
+const hsdpa = {}
+
+hsdpa.setActiveDisk = (diskNumber) => {
+    sys.poke(HSDPA_REG_ACTIVE_DISK, diskNumber) // 1-based
+}
+
+hsdpa.getActiveDisk = () => {
+    return sys.peek(HSDPA_REG_ACTIVE_DISK)
+}
+
+hsdpa.enableSequentialIO = () => {
+    sys.poke(HSDPA_REG_SEQ_IO_CONTROL, 0x01)
+}
+
+hsdpa.disableSequentialIO = () => {
+    sys.poke(HSDPA_REG_SEQ_IO_CONTROL, 0x00)
+}
+
+hsdpa.rewind = () => {
+    sys.poke(HSDPA_REG_SEQ_IO_OPCODE, HSDPA_OPCODE_REWIND)
+}
+
+hsdpa.skip = (bytes) => {
+    // Write arg1 (3 bytes, little endian) - using backwards addressing
+    sys.poke(HSDPA_REG_SEQ_IO_ARG1, bytes & 0xFF)        // LSB
+    sys.poke(HSDPA_REG_SEQ_IO_ARG1 - 1, (bytes >> 8) & 0xFF)   // MSB
+    sys.poke(HSDPA_REG_SEQ_IO_ARG1 - 2, (bytes >> 16) & 0xFF)  // MSB2
+    // Execute skip operation
+    sys.poke(HSDPA_REG_SEQ_IO_OPCODE, HSDPA_OPCODE_SKIP)
+}
+
+hsdpa.readToMemory = (bytes, vmMemoryPointer) => {
+    serial.println(`HSDPA: readToMemory(${bytes}, ${vmMemoryPointer})`)
+    // Write arg1 (bytes to read) - using backwards addressing
+    sys.poke(HSDPA_REG_SEQ_IO_ARG1, bytes & 0xFF)        // LSB
+    sys.poke(HSDPA_REG_SEQ_IO_ARG1 - 1, (bytes >> 8) & 0xFF)   // MSB  
+    sys.poke(HSDPA_REG_SEQ_IO_ARG1 - 2, (bytes >> 16) & 0xFF)  // MSB2
+    // Write arg2 (VM memory pointer) - using backwards addressing
+    sys.poke(HSDPA_REG_SEQ_IO_ARG2, vmMemoryPointer & 0xFF)           // LSB
+    sys.poke(HSDPA_REG_SEQ_IO_ARG2 - 1, (vmMemoryPointer >> 8) & 0xFF)  // MSB
+    sys.poke(HSDPA_REG_SEQ_IO_ARG2 - 2, (vmMemoryPointer >> 16) & 0xFF) // MSB2
+    // Execute read operation
+    serial.println(`HSDPA: Executing read opcode...`)
+    sys.poke(HSDPA_REG_SEQ_IO_OPCODE, HSDPA_OPCODE_READ)
+    serial.println(`HSDPA: Read opcode executed`)
+}
+
+hsdpa.writeFromMemory = (bytes, vmMemoryPointer) => {
+    // Write arg1 (bytes to write) - using backwards addressing
+    sys.poke(HSDPA_REG_SEQ_IO_ARG1, bytes & 0xFF)        // LSB
+    sys.poke(HSDPA_REG_SEQ_IO_ARG1 - 1, (bytes >> 8) & 0xFF)   // MSB
+    sys.poke(HSDPA_REG_SEQ_IO_ARG1 - 2, (bytes >> 16) & 0xFF)  // MSB2
+    // Write arg2 (VM memory pointer) - using backwards addressing
+    sys.poke(HSDPA_REG_SEQ_IO_ARG2, vmMemoryPointer & 0xFF)           // LSB
+    sys.poke(HSDPA_REG_SEQ_IO_ARG2 - 1, (vmMemoryPointer >> 8) & 0xFF)  // MSB
+    sys.poke(HSDPA_REG_SEQ_IO_ARG2 - 2, (vmMemoryPointer >> 16) & 0xFF) // MSB2
+    // Execute write operation
+    sys.poke(HSDPA_REG_SEQ_IO_OPCODE, HSDPA_OPCODE_WRITE)
+}
+
+hsdpa.terminate = () => {
+    sys.poke(HSDPA_REG_SEQ_IO_OPCODE, HSDPA_OPCODE_TERMINATE)
+}
+
+// Helper to get disk number from device name (TAPE0 -> 1, TAPE1 -> 2, etc.)
+hsdpa.getHsdpaDiskNumber = (deviceName) => {
+    if (deviceName.startsWith("TAPE")) {
+        let diskIndex = parseInt(deviceName.substring(4))
+        return diskIndex + 1 // HSDPA uses 1-based disk numbers
+    }
+    return 0
+}
+
+// State tracking for open files
+hsdpa.openFiles = {}
+
+// Create TAPE device drivers
+for (let tapeIndex = 0; tapeIndex < 4; tapeIndex++) {
+    let deviceName = `DEVTAPE${tapeIndex}`
+    
+    _TVDOS.DRV.FS[deviceName] = {}
+    
+    let driver = _TVDOS.DRV.FS[deviceName]
+    
+    // Get file size - for HSDPA tapes, we don't know the size ahead of time
+    // So we return a very large number to indicate it's available
+    driver.getFileLen = (fd) => {
+        return 0x7FFFFFFF // Return max positive 32-bit integer
+    }
+    
+    // Sequential read from tape
+    driver.pread = (fd, ptr, count, offset) => {
+        let diskNumber = hsdpa.getHsdpaDiskNumber(fd._driverID.substring(3)) // Remove "DEV" prefix
+        
+        // Set active disk
+        hsdpa.setActiveDisk(diskNumber)
+        hsdpa.enableSequentialIO()
+        
+        try {
+            // If offset specified, rewind and skip to position
+            if (offset && offset > 0) {
+                hsdpa.rewind()
+                hsdpa.skip(offset)
+            }
+            
+            // Read data to VM memory
+            hsdpa.readToMemory(count, ptr)
+        } catch (e) {
+            console.error("HSDPA read error:", e)
+            // Fill with zeros on error
+            for (let i = 0; i < count; i++) {
+                sys.poke(ptr + i, 0)
+            }
+        }
+    }
+    
+    // Binary read - reads entire file into byte array
+    driver.bread = (fd) => {
+        let diskNumber = hsdpa.getHsdpaDiskNumber(fd._driverID.substring(3))
+        
+        // For simplicity, read a reasonable chunk size
+        let chunkSize = 65536 // 64KB
+        let tempPtr = sys.malloc(chunkSize)
+        
+        try {
+            hsdpa.setActiveDisk(diskNumber)
+            hsdpa.enableSequentialIO()
+            hsdpa.rewind()
+            hsdpa.readToMemory(chunkSize, tempPtr)
+            
+            // Copy to JavaScript array
+            let result = new Int8Array(chunkSize)
+            for (let i = 0; i < chunkSize; i++) {
+                result[i] = sys.peek(tempPtr + i)
+            }
+            
+            return result
+        } finally {
+            sys.free(tempPtr)
+        }
+    }
+    
+    // String read - reads file as string
+    driver.sread = (fd) => {
+        let bytes = driver.bread(fd)
+        let result = ""
+        for (let i = 0; i < bytes.length && bytes[i] !== 0; i++) {
+            result += String.fromCharCode(bytes[i] & 0xFF)
+        }
+        return result
+    }
+    
+    // Write operations (not supported for tape devices)
+    driver.pwrite = (fd, ptr, count, offset) => {
+        throw Error("Write operations not supported on HSDPA tape devices")
+    }
+    
+    driver.bwrite = (fd, bytes) => {
+        throw Error("Write operations not supported on HSDPA tape devices")
+    }
+    
+    driver.swrite = (fd, string) => {
+        throw Error("Write operations not supported on HSDPA tape devices")
+    }
+    
+    driver.pappend = (fd, ptr, count) => {
+        throw Error("Append operations not supported on HSDPA tape devices")
+    }
+    
+    driver.bappend = (fd, bytes) => {
+        throw Error("Append operations not supported on HSDPA tape devices")
+    }
+    
+    driver.sappend = (fd, string) => {
+        throw Error("Append operations not supported on HSDPA tape devices")
+    }
+    
+    // File operations
+    driver.flush = (fd) => {
+        // No-op for read-only tape
+    }
+    
+    driver.close = (fd) => {
+        let diskNumber = hsdpa.getHsdpaDiskNumber(fd._driverID.substring(3))
+        hsdpa.setActiveDisk(diskNumber)
+        hsdpa.terminate()
+        hsdpa.disableSequentialIO()
+        
+        // Remove from open files tracking
+        delete hsdpa.openFiles[fd._driverID]
+    }
+    
+    // Directory operations (tapes are single files, not directories)
+    driver.isDirectory = (fd) => {
+        return false
+    }
+    
+    driver.listFiles = (fd) => {
+        return undefined // Not a directory
+    }
+    
+    // File management operations (not supported)
+    driver.touch = (fd) => {
+        throw Error("Touch operation not supported on HSDPA tape devices")
+    }
+    
+    driver.mkDir = (fd) => {
+        throw Error("Directory creation not supported on HSDPA tape devices")
+    }
+    
+    driver.mkFile = (fd) => {
+        throw Error("File creation not supported on HSDPA tape devices")
+    }
+    
+    driver.remove = (fd) => {
+        throw Error("File removal not supported on HSDPA tape devices")
+    }
+    
+    // Check if tape exists (always true if disk is attached)
+    driver.exists = (fd) => {
+        let diskNumber = hsdpa.getHsdpaDiskNumber(fd._driverID.substring(3))
+        
+        // Try to set active disk and check if it responds
+        try {
+            hsdpa.setActiveDisk(diskNumber)
+            // If we can read the active disk register back, the disk exists
+            return hsdpa.getActiveDisk() === diskNumber
+        } catch (e) {
+            return false
+        }
+    }
+    
+    // Freeze the driver object
+    Object.freeze(driver)
+}
+
+// Print initialization message
+serial.println("HSDPA Driver loaded: TAPE0-TAPE3 devices available at $:/TAPE0/, $:/TAPE1/, $:/TAPE2/, $:/TAPE3/")
--- a/assets/disk0/tvdos/TVDOS.SYS
+++ b/assets/disk0/tvdos/TVDOS.SYS
@@ -1388,7 +1388,7 @@ Object.freeze(unicode);
 ///////////////////////////////////////////////////////////////////////////////

 // patch con to use VTs
-con.move = function(y, x) {
+/*con.move = function(y, x) {
    let activeVT = _TVDOS.ACTIVE_VT || 0 // 0 is physical terminal
    let vt = _TVDOS.VT_CONTEXTS[activeVT]

@@ -1400,7 +1400,7 @@ con.getyx = function() {
    let vt = _TVDOS.VT_CONTEXTS[activeVT]

    return vt.getCursorYX()
-};
+};*/

 ///////////////////////////////////////////////////////////////////////////////

@@ -1516,6 +1516,16 @@ var execApp = (cmdsrc, args, appname) => {

 ///////////////////////////////////////////////////////////////////////////////

+// Load HSDPA driver
+try {
+    let hsdpadrvFile = files.open("A:/tvdos/HSDPADRV.SYS")
+    if (hsdpadrvFile.exists) {
+        eval(hsdpadrvFile.sread())
+    }
+} catch (e) {
+    serial.println("Warning: Could not load HSDPA driver: " + e.message)
+}
+
 // Boot script
 serial.println(`TVDOS.SYS initialised on VM ${sys.getVmId()}, running boot script...`);

--- a/assets/disk0/tvdos/bin/playmov.js
+++ b/assets/disk0/tvdos/bin/playmov.js
@@ -17,24 +17,40 @@ graphics.clearPixels(255)
 graphics.clearPixels2(240)


-let seqread = require("seqread")
-seqread.prepare(fullFilePath.full)
+let seqreadserial = require("seqread")
+let seqreadtape = require("seqreadtape")
+let seqread = undefined
+let fullFilePathStr = fullFilePath.full
+
+// select seqread driver to use
+if (fullFilePathStr.startsWith('$:/TAPE') || fullFilePathStr.startsWith('$:\\TAPE')) {
+    seqread = seqreadtape
+    seqread.seek(0)
+}
+else {
+    seqread = seqreadserial
+}
+
+seqread.prepare(fullFilePathStr)



 let magic = seqread.readBytes(8)
 let magicMatching = true

+let actualMagic = []
+
 // check if magic number matches
 MAGIC.forEach((b,i) => {
    let testb = sys.peek(magic + i) & 255 // for some reason this must be located here
+    actualMagic.push(testb)
    if (testb != b) {
        magicMatching = false
    }
 })
 sys.free(magic)
 if (!magicMatching) {
-    println("Not a movie file (MAGIC mismatch)")
+    println("Not a movie file (MAGIC mismatch) -- got " + actualMagic.join())
    return 1
 }

--- a/assets/disk0/tvdos/include/seqreadtape.mjs
+++ b/assets/disk0/tvdos/include/seqreadtape.mjs
@@ -0,0 +1,263 @@
+// Sequential reader for HSDPA TAPE devices
+// Unlike seqread.mjs which is limited to 4096 bytes per read due to serial communication,
+// this module can read larger chunks efficiently from HSDPA devices.
+
+let readCount = 0
+let currentTapeDevice = undefined
+let fileDescriptor = undefined
+let fileHeader = new Uint8Array(65536) // Much larger header buffer than serial version
+
+// HSDPA peripheral addresses for slot 4
+// MMIO area (for registers): -524289 to -655360 (backwards!)
+const HSDPA_SLOT4_MMIO_START = -524289  // MMIO area start
+const HSDPA_REG_ACTIVE_DISK = HSDPA_SLOT4_MMIO_START - 20
+const HSDPA_REG_SEQ_IO_CONTROL = HSDPA_SLOT4_MMIO_START - 256
+const HSDPA_REG_SEQ_IO_OPCODE = HSDPA_SLOT4_MMIO_START - 258
+const HSDPA_REG_SEQ_IO_ARG1 = HSDPA_SLOT4_MMIO_START - 259
+const HSDPA_REG_SEQ_IO_ARG2 = HSDPA_SLOT4_MMIO_START - 262
+
+// Sequential I/O opcodes
+const HSDPA_OPCODE_NOP = 0x00
+const HSDPA_OPCODE_SKIP = 0x01
+const HSDPA_OPCODE_READ = 0x02
+const HSDPA_OPCODE_WRITE = 0x03
+const HSDPA_OPCODE_REWIND = 0xF0
+const HSDPA_OPCODE_TERMINATE = 0xFF
+
+// Helper functions for HSDPA MMIO access
+function hsdpaSetActiveDisk(diskNumber) {
+    sys.poke(HSDPA_REG_ACTIVE_DISK, diskNumber) // 1-based
+}
+
+function hsdpaEnableSequentialIO() {
+    sys.poke(HSDPA_REG_SEQ_IO_CONTROL, 0x01)
+}
+
+function hsdpaDisableSequentialIO() {
+    sys.poke(HSDPA_REG_SEQ_IO_CONTROL, 0x00)
+}
+
+function hsdpaRewind() {
+    sys.poke(HSDPA_REG_SEQ_IO_OPCODE, HSDPA_OPCODE_REWIND)
+}
+
+function hsdpaSkip(bytes) {
+    // Write arg1 (3 bytes, little endian) - using backwards addressing
+    sys.poke(HSDPA_REG_SEQ_IO_ARG1, bytes & 0xFF)        // LSB
+    sys.poke(HSDPA_REG_SEQ_IO_ARG1 - 1, (bytes >> 8) & 0xFF)   // MSB
+    sys.poke(HSDPA_REG_SEQ_IO_ARG1 - 2, (bytes >> 16) & 0xFF)  // MSB2
+    // Execute skip operation
+    sys.poke(HSDPA_REG_SEQ_IO_OPCODE, HSDPA_OPCODE_SKIP)
+}
+
+function hsdpaReadToMemory(bytes, vmMemoryPointer) {
+    // Write arg1 (bytes to read) - using backwards addressing
+    sys.poke(HSDPA_REG_SEQ_IO_ARG1, bytes & 0xFF)        // LSB
+    sys.poke(HSDPA_REG_SEQ_IO_ARG1 - 1, (bytes >> 8) & 0xFF)   // MSB
+    sys.poke(HSDPA_REG_SEQ_IO_ARG1 - 2, (bytes >> 16) & 0xFF)  // MSB2
+    // Write arg2 (VM memory pointer) - using backwards addressing
+    sys.poke(HSDPA_REG_SEQ_IO_ARG2, vmMemoryPointer & 0xFF)           // LSB
+    sys.poke(HSDPA_REG_SEQ_IO_ARG2 - 1, (vmMemoryPointer >> 8) & 0xFF)  // MSB
+    sys.poke(HSDPA_REG_SEQ_IO_ARG2 - 2, (vmMemoryPointer >> 16) & 0xFF) // MSB2
+    // Execute read operation
+    sys.poke(HSDPA_REG_SEQ_IO_OPCODE, HSDPA_OPCODE_READ)
+}
+
+function hsdpaTerminate() {
+    sys.poke(HSDPA_REG_SEQ_IO_OPCODE, HSDPA_OPCODE_TERMINATE)
+}
+
+function prepare(fullPath) {
+    // Parse tape device path like "$:/TAPE0/"
+    if (!fullPath.startsWith("$:/TAPE") && !fullPath.startsWith("$:\\TAPE")) {
+        throw Error("seqreadtape: Expected TAPE device path like $:\\TAPE0, got '" + fullPath + "'")
+    }
+    
+    readCount = 0
+    
+    // Extract tape number from path (TAPE0 -> 0, TAPE1 -> 1, etc.)
+    let tapeMatch = fullPath.match(/\$:[/\\]TAPE([0-9]+)/)
+    if (!tapeMatch) {
+        throw Error("seqreadtape: Invalid TAPE device path format: " + fullPath)
+    }
+    
+    let tapeNumber = parseInt(tapeMatch[1])
+    if (tapeNumber < 0 || tapeNumber > 3) {
+        throw Error("seqreadtape: TAPE device number must be 0-3, got " + tapeNumber)
+    }
+    
+    currentTapeDevice = tapeNumber
+    
+    try {
+        // Open the tape device using TVDOS file system
+        fileDescriptor = files.open(fullPath)
+        if (!fileDescriptor.exists) {
+            throw Error(`seqreadtape: TAPE device ${tapeNumber} not available or no file attached`)
+        }
+        
+        // Initialize HSDPA for sequential reading
+        hsdpaSetActiveDisk(tapeNumber + 1) // HSDPA uses 1-based disk numbers
+        hsdpaEnableSequentialIO()
+        hsdpaRewind()
+        
+        // Read file header (much larger than serial version)
+        let headerPtr = sys.malloc(fileHeader.length)
+        try {
+            hsdpaReadToMemory(fileHeader.length, headerPtr)
+            
+            // Copy header to our buffer
+            for (let i = 0; i < fileHeader.length; i++) {
+                fileHeader[i] = sys.peek(headerPtr + i) & 0xFF
+            }
+        } finally {
+            sys.free(headerPtr)
+        }
+        
+        // Reset position for actual reading
+        hsdpaRewind()
+        readCount = 0
+        
+        return 0
+        
+    } catch (e) {
+        throw Error("seqreadtape: Failed to prepare TAPE device: " + e.message)
+    }
+}
+
+function readBytes(length, ptrToDecode) {
+    if (length <= 0) return
+    
+    let ptr = (ptrToDecode === undefined) ? sys.malloc(length) : ptrToDecode
+    
+    try {
+        // Skip to current read position if needed
+        if (readCount > 0) {
+            hsdpaRewind()
+            if (readCount > 0) {
+                hsdpaSkip(readCount)
+            }
+        }
+        
+        // Read directly using HSDPA - no 4096 byte limitation!
+        hsdpaReadToMemory(length, ptr)
+        
+        readCount += length
+        
+        return ptr
+        
+    } catch (e) {
+        if (ptrToDecode === undefined) {
+            sys.free(ptr)
+        }
+        throw Error("seqreadtape: Failed to read bytes: " + e.message)
+    }
+}
+
+function readInt() {
+    let b = readBytes(4)
+    let i = (sys.peek(b) & 0xFF) | 
+            ((sys.peek(b+1) & 0xFF) << 8) | 
+            ((sys.peek(b+2) & 0xFF) << 16) | 
+            ((sys.peek(b+3) & 0xFF) << 24)
+    sys.free(b)
+    return i
+}
+
+function readShort() {
+    let b = readBytes(2)
+    let i = (sys.peek(b) & 0xFF) | ((sys.peek(b+1) & 0xFF) << 8)
+    sys.free(b)
+    return i
+}
+
+function readOneByte() {
+    let b = readBytes(1)
+    let i = sys.peek(b) & 0xFF
+    sys.free(b)
+    return i
+}
+
+function readFourCC() {
+    let b = readBytes(4)
+    let a = [sys.peek(b) & 0xFF, sys.peek(b+1) & 0xFF, sys.peek(b+2) & 0xFF, sys.peek(b+3) & 0xFF]
+    sys.free(b)
+    let s = String.fromCharCode.apply(null, a)
+    if (s.length != 4) {
+        throw Error(`seqreadtape: FourCC is not 4 characters long (${s}; ${a.map(it=>"0x"+it.toString(16).padStart(2,'0')).join()})`)
+    }
+    return s
+}
+
+function readString(length) {
+    let b = readBytes(length)
+    let s = ""
+    for (let k = 0; k < length; k++) {
+        s += String.fromCharCode(sys.peek(b + k) & 0xFF)
+    }
+    sys.free(b)
+    return s
+}
+
+function skip(n) {
+    if (n <= 0) return
+    
+    // For HSDPA, we can skip efficiently without reading
+    hsdpaSkip(n)
+    readCount += n
+}
+
+function getReadCount() {
+    return readCount
+}
+
+function close() {
+    if (fileDescriptor) {
+        try {
+            hsdpaTerminate()
+            hsdpaDisableSequentialIO()
+            fileDescriptor.close()
+        } catch (e) {
+            // Ignore close errors
+        }
+        fileDescriptor = undefined
+        currentTapeDevice = undefined
+        readCount = 0
+    }
+}
+
+function getCurrentTapeDevice() {
+    return currentTapeDevice
+}
+
+function isReady() {
+    return fileDescriptor !== undefined && currentTapeDevice !== undefined
+}
+
+function seek(position) {
+    // Seek to absolute position
+    hsdpaRewind()
+    if (position > 0) {
+        hsdpaSkip(position)
+    }
+    readCount = position
+}
+
+function rewind() { seek(0) }
+
+exports = {
+    fileHeader, 
+    prepare, 
+    readBytes, 
+    readInt, 
+    readShort, 
+    readFourCC, 
+    readOneByte, 
+    readString, 
+    skip, 
+    getReadCount,
+    close,
+    getCurrentTapeDevice,
+    isReady,
+    // Enhanced functions
+    seek
+}