# Rux Code Examples for 10 Systems Domains

This document provides concrete code examples for each systems domain analyzed in
[rux_gap_analysis.md](file:///c:/Users/muham/OneDrive/Documents/G_Github/Rux/docs/rux_gap_analysis.md).

Each domain contains two sections:
- **✅ Current Rux Code** — utilizing actual Rux v0.2.0 syntax.
- **🚧 Hypothetical Required Code** — representing features currently missing in the language, written as proposals.

> [!IMPORTANT]
> Code blocks marked with "🚧" **WILL NOT COMPILE** in Rux v0.2.0.
> They demonstrate what must be added to the language to make it viable for these specific systems programming fields.

---

## 1. Operating Systems

### ✅ Current Rux Code — Basic Memory Manipulation

```rux
import Std::Io::PrintLine;
import Std::Memory::Alloc;
import Std::Memory::Free;

/// Basic memory allocation and raw writing — what Rux can do today.
func Main() -> int {
    // Allocate 4096 bytes (one page equivalent)
    let page: *uint8 = Alloc(4096) as *uint8;

    // Write to the first byte via the raw pointer
    *page = 0xEB as uint8;  // JMP short (x86 opcode)

    PrintLine("Allocated 4096 bytes at raw pointer");

    Free(page as *opaque);
    return 0;
}
```

### 🚧 Hypothetical Code — Kernel Boot Entry Point

```rux
// ============================================================
// ❌ WILL NOT COMPILE — These features are NOT present in Rux
// ============================================================

// 🚧 Required: no_std mode (no libc, no runtime)
#[no_std]
#[no_main]

// 🚧 Required: linker section control
#[link_section(".text.boot")]
#[naked]
func _start() {
    // 🚧 Required: mature inline assembly
    asm {
        // Setup stack pointer
        mov rsp, 0x7C00
        // Clear BSS
        xor eax, eax
        mov edi, __bss_start
        mov ecx, __bss_size
        rep stosb
        // Jump to kernel_main
        call kernel_main
        hlt
    }
}

// 🚧 Required: volatile memory operations for MMIO
func volatile_write(addr: *volatile uint32, value: uint32) {
    *addr = value;  // 🚧 compiler must not optimize this away
}

func volatile_read(addr: *volatile uint32) -> uint32 {
    return *addr;   // 🚧 compiler must read from memory every time
}

// 🚧 Required: Atomic operations for SMP kernels
func spinlock_acquire(lock: *atomic uint32) {
    while atomic_exchange(lock, 1, MemoryOrder::Acquire) != 0 {
        // 🚧 Required: CPU pause instruction hint
        asm { pause }
    }
}

// 🚧 Required: Interrupt handler declarations
#[interrupt]
func page_fault_handler(frame: &InterruptFrame, error_code: uint64) {
    let fault_addr = read_cr2();
    // Handle page fault...
    PrintSerial("Page fault at address: {}", fault_addr);
}

// 🚧 Required: Custom allocator without heap requirements
struct BumpAllocator {
    base: *uint8,
    offset: uint,
    limit: uint,
}

func (self: &mut BumpAllocator) alloc(size: uint, align: uint) -> *uint8 {
    let aligned = (self.offset + align - 1) & ~(align - 1);
    if aligned + size > self.limit {
        return null;  // 🚧 Required: nullable pointer support
    }
    let ptr = self.base + aligned;
    self.offset = aligned + size;
    return ptr;
}

// 🚧 Required: Linker outputs other than Windows PE (e.g., ELF)
// 🚧 Required: Custom Linker Scripts
// SECTIONS {
//     . = 0x100000;
//     .text : { *(.text.boot) *(.text) }
//     .rodata : { *(.rodata) }
//     .data : { *(.data) }
//     .bss : { *(.bss) }
// }
```

---

## 2. Compilers

### ✅ Current Rux Code — Simple Tokenizer

```rux
import Std::Io::PrintLine;
import Std::Io::Print;

// Enum for token kinds — fully supported in current Rux
enum TokenKind {
    Number,
    Plus,
    Minus,
    Star,
    Slash,
    LeftParen,
    RightParen,
    EndOfFile,
    Unknown,
}

// Struct for tokens
struct Token {
    kind: TokenKind,
    value: int32,
}

// Interfaces — supported in current Rux
interface Printable {
    func Display(self: &Self);
}

// Simple single-character tokenizer
func Tokenize(ch: char8) -> TokenKind {
    if ch == '+' { return TokenKind::Plus; }
    if ch == '-' { return TokenKind::Minus; }
    if ch == '*' { return TokenKind::Star; }
    if ch == '/' { return TokenKind::Slash; }
    if ch == '(' { return TokenKind::LeftParen; }
    if ch == ')' { return TokenKind::RightParen; }
    return TokenKind::Unknown;
}

func Main() -> int {
    let tok = Tokenize('+');
    PrintLine("Lexer created a token");
    return 0;
}
```

### 🚧 Hypothetical Code — AST Nodes & Exhaustive Pattern Matching

```rux
// ============================================================
// ❌ WILL NOT COMPILE — These features are NOT present in Rux
// ============================================================

// 🚧 Required: Algebraic Data Types (enums carrying data)
enum Expr {
    IntLiteral(int64),
    BinaryOp {
        left: *Expr,       // 🚧 Required: recursive types
        op: BinaryOperator,
        right: *Expr,
    },
    UnaryOp {
        op: UnaryOperator,
        operand: *Expr,
    },
    Identifier(String),
    FuncCall {
        name: String,
        args: Slice<*Expr>,  // 🚧 Required: robust generics
    },
}

enum BinaryOperator { Add, Sub, Mul, Div, Mod }
enum UnaryOperator { Neg, Not }

// 🚧 Required: Exhaustive pattern matching with destructuring
func Evaluate(expr: &Expr) -> int64 {
    match expr {
        Expr::IntLiteral(n) => return n,
        Expr::BinaryOp { left, op, right } => {
            let l = Evaluate(left);
            let r = Evaluate(right);
            match op {
                BinaryOperator::Add => return l + r,
                BinaryOperator::Sub => return l - r,
                BinaryOperator::Mul => return l * r,
                BinaryOperator::Div => return l / r,
                BinaryOperator::Mod => return l % r,
            }
        },
        Expr::UnaryOp { op, operand } => {
            let val = Evaluate(operand);
            match op {
                UnaryOperator::Neg => return -val,
                UnaryOperator::Not => return ~val,
            }
        },
        Expr::Identifier(name) => {
            // 🚧 Required: HashMap for symbols
            return symbol_table.get(name).unwrap();
        },
        Expr::FuncCall { name, args } => {
            // Handle function execution...
            return 0;
        },
    }
}

// 🚧 Required: High-performance memory management via Arena Allocators
struct Arena {
    blocks: Vec<*uint8>,      // 🚧 Required: Dynamic array
    current: *uint8,
    remaining: uint,
}

func (arena: &mut Arena) alloc<T>() -> *T {
    let size = size_of::<T>();               // 🚧 Required: size_of operator
    let align = align_of::<T>();             // 🚧 Required: align_of operator
    // ... bump allocation implementation ...
}

// 🚧 Required: String Interning table
struct StringInterner {
    table: HashMap<String, uint32>,  // 🚧 Required: Standard HashMap
    strings: Vec<String>,            // 🚧 Required: Dynamic vector
}
```

---

## 3. Runtime Engines

### ✅ Current Rux Code — Bytecode Opcode Constants

```rux
import Std::Io::PrintLine;
import Std::Io::Print;

// Bytecode constants for a simple virtual machine
const OP_PUSH: uint8  = 0x01;
const OP_ADD: uint8   = 0x02;
const OP_SUB: uint8   = 0x03;
const OP_MUL: uint8   = 0x04;
const OP_PRINT: uint8 = 0x05;
const OP_HALT: uint8  = 0xFF;

// Stack VM state structure
struct VM {
    stack: [int64; 256],    // Static fixed-size stack
    sp: int32,              // Stack pointer
    ip: int32,              // Instruction pointer
    running: bool,
}

// Push to VM stack
func Push(vm: &VM, value: int64) {
    // 🔴 Limit: Mutable references are not fully defined in Rux v0.2.0
    // This function acts as conceptual placeholder
}

func Main() -> int {
    // VM program: push 10, push 20, add, print, halt
    let program: [uint8; 8] = [
        OP_PUSH, 10,
        OP_PUSH, 20,
        OP_ADD,
        OP_PRINT,
        OP_HALT,
        0
    ];

    PrintLine("Bytecode VM defined (execution not possible yet)");
    Print("Program size: {} bytes", 8);
    return 0;
}
```

### 🚧 Hypothetical Code — JIT Compiler & Garbage Collector

```rux
// ============================================================
// ❌ WILL NOT COMPILE — These features are NOT present in Rux
// ============================================================

// 🚧 Required: FFI to OS executable memory pools (VirtualAlloc)
extern func VirtualAlloc(
    addr: *opaque,
    size: uint,
    alloc_type: uint32,
    protect: uint32
) -> *opaque;

const MEM_COMMIT: uint32 = 0x1000;
const PAGE_EXECUTE_READWRITE: uint32 = 0x40;

// JIT Code Emitter
struct JitEmitter {
    buffer: *uint8,
    offset: uint,
    capacity: uint,
}

func NewJitEmitter(size: uint) -> JitEmitter {
    let buf = VirtualAlloc(
        null,       // 🚧 Required: null keyword
        size,
        MEM_COMMIT,
        PAGE_EXECUTE_READWRITE
    ) as *uint8;

    return JitEmitter {
        buffer: buf,
        offset: 0,
        capacity: size,
    };
}

// Emit x86-64 native instructions into executable buffer
func (jit: &mut JitEmitter) EmitAdd() {
    // pop rax       (58)
    jit.Emit(0x58);
    // pop rbx       (5B)
    jit.Emit(0x5B);
    // add rax, rbx  (48 01 D8)
    jit.Emit(0x48); jit.Emit(0x01); jit.Emit(0xD8);
    // push rax      (50)
    jit.Emit(0x50);
}

func (jit: &mut JitEmitter) Emit(byte: uint8) {
    *(jit.buffer + jit.offset) = byte;
    jit.offset += 1;
}

// 🚧 Required: Casting raw pointer to function pointer for JIT execution
func (jit: &JitEmitter) Execute() -> int64 {
    let code_fn = jit.buffer as func() -> int64;  // 🚧 Cast to function pointer
    return code_fn();
}

// 🚧 Required: Mark-and-Sweep Garbage Collector for guest languages
struct GCObject {
    marked: bool,
    next: *GCObject,    // Linked list of all objects
    kind: ObjectKind,
}

enum ObjectKind {
    GCString { chars: *uint8, len: uint },
    GCArray { items: *GCObject, len: uint },
    GCClosure { func_ptr: *opaque, upvalues: *GCObject },
}

struct GarbageCollector {
    first_object: *GCObject,
    bytes_allocated: uint,
    threshold: uint,
    roots: Vec<*GCObject>,     // 🚧 Required: Dynamic array
}

func (gc: &mut GarbageCollector) Collect() {
    // Mark Phase
    for root in gc.roots {
        gc.Mark(root);
    }
    // Sweep Phase
    gc.Sweep();
}

func (gc: &mut GarbageCollector) Mark(obj: *GCObject) {
    if obj == null || (*obj).marked { return; }
    (*obj).marked = true;
    
    // Recursive tracing based on object shape
    match (*obj).kind {
        ObjectKind::GCArray { items, len } => {
            for i in 0..len {
                gc.Mark(*(items + i));
            }
        },
        ObjectKind::GCClosure { upvalues, .. } => {
            gc.Mark(upvalues);
        },
        _ => {},
    }
}
```

---

## 4. Database Engines

### ✅ Current Rux Code — Disk Page Format Structs

```rux
import Std::Io::PrintLine;
import Std::Memory::Alloc;
import Std::Memory::Free;

const PAGE_SIZE: uint = 4096;
const HEADER_SIZE: uint = 100;

// Disk database page header — completely compilable struct
struct PageHeader {
    page_id: uint32,
    page_type: uint8,     // 1 = leaf, 2 = internal, 3 = overflow
    num_cells: uint16,
    free_space_start: uint16,
    free_space_end: uint16,
    right_child: uint32,  // For B-tree internal indexing
}

// Single Cell record metadata
struct Cell {
    key_size: uint16,
    value_size: uint32,
    // key and value data follows sequentially in memory
}

func CreatePage(page_id: uint32, page_type: uint8) -> *uint8 {
    let page: *uint8 = Alloc(PAGE_SIZE) as *uint8;
    let header = page as *PageHeader;
    
    // 🔴 Limit: Pointer cast writing can be erratic in v0.2.0
    PrintLine("Created page with ID and type");
    return page;
}

func Main() -> int {
    let page = CreatePage(1, 1);  // Leaf page
    PrintLine("Database page allocated");
    Free(page as *opaque);
    return 0;
}
```

### 🚧 Hypothetical Code — B-Tree Engine & Concurrent WAL Writer

```rux
// ============================================================
// ❌ WILL NOT COMPILE — These features are NOT present in Rux
// ============================================================

// 🚧 Required: File operations
import Std::Fs::File;
import Std::Fs::OpenOptions;

// 🚧 Required: Concurrency & Async
import Std::Async::spawn;
import Std::Net::TcpListener;
import Std::Thread;
import Std::Sync::Mutex;
import Std::Sync::RwLock;

const PAGE_SIZE: uint = 4096;
const MAX_KEYS: uint = 255;

struct BTreeNode {
    keys: [int64; MAX_KEYS],
    values: [uint64; MAX_KEYS],        // offsets to page contents
    children: [uint32; MAX_KEYS + 1],  // child Page IDs
    num_keys: uint16,
    is_leaf: bool,
    page_id: uint32,
}

// Buffer Pool Manager (caches pages in memory)
struct BufferPool {
    pages: HashMap<uint32, *uint8>,
    dirty: HashMap<uint32, bool>,
    lock: RwLock,
    file: File,
    max_pages: uint,
}

func (pool: &mut BufferPool) GetPage(page_id: uint32) -> Result<*uint8, DbError> {
    // 🚧 Required: RwLock locking
    pool.lock.read_lock();
    if pool.pages.contains(page_id) {
        let page = pool.pages.get(page_id);
        pool.lock.read_unlock();
        return Ok(page);
    }
    pool.lock.read_unlock();

    pool.lock.write_lock();
    // Read page from disk
    let buf = Alloc(PAGE_SIZE) as *uint8;
    let offset = page_id as uint64 * PAGE_SIZE as uint64;

    // 🚧 Required: File seek and error handling with ? operator
    pool.file.seek(offset)?;
    pool.file.read_exact(buf, PAGE_SIZE)?;

    pool.pages.insert(page_id, buf);
    pool.lock.write_unlock();
    
    return Ok(buf);
}

// Write-Ahead Logging (WAL) for Transaction Safety
struct WAL {
    log_file: File,
    lock: Mutex,
    sequence: atomic uint64,           // 🚧 Required: atomic types
}

func (wal: &mut WAL) Append(entry: &WALEntry) -> Result<uint64, DbError> {
    wal.lock.lock();
    let seq = atomic_fetch_add(&wal.sequence, 1);  // 🚧 Atomic operation

    // Serialize transaction entry
    let bytes = entry.serialize();

    wal.log_file.write(bytes)?;
    wal.log_file.fsync()?;             // 🚧 Required: fsync flushing

    wal.lock.unlock();
    return Ok(seq);
}

// Asynchronous listener to process queries
async func StartServer(addr: &str, pool: &BufferPool) {
    let listener = TcpListener::bind(addr).await?;

    loop {
        let (stream, peer) = listener.accept().await?;
        spawn(async {
            HandleClient(stream, pool).await;
        });
    }
}
```

---

## 5. Game Engines

### ✅ Current Rux Code — Linear Algebra & Entity Structs

```rux
import Std::Io::PrintLine;
import Std::Io::Print;
import Std::Math::Sqrt;

// Vector3 representation
struct Vec3 {
    x: float64,
    y: float64,
    z: float64,
}

func Vec3Add(a: Vec3, b: Vec3) -> Vec3 {
    return Vec3 {
        x: a.x + b.x,
        y: a.y + b.y,
        z: a.z + b.z,
    };
}

func Vec3Length(v: Vec3) -> float64 {
    return Sqrt(v.x * v.x + v.y * v.y + v.z * v.z);
}

func Vec3Dot(a: Vec3, b: Vec3) -> float64 {
    return a.x * b.x + a.y * b.y + a.z * b.z;
}

func Vec3Normalize(v: Vec3) -> Vec3 {
    let len = Vec3Length(v);
    return Vec3 {
        x: v.x / len,
        y: v.y / len,
        z: v.z / len,
    };
}

// Simple GameObject Entity
struct Entity {
    id: uint32,
    position: Vec3,
    velocity: Vec3,
    active: bool,
}

func UpdateEntity(e: Entity, dt: float64) -> Entity {
    return Entity {
        id: e.id,
        position: Vec3Add(e.position, Vec3 {
            x: e.velocity.x * dt,
            y: e.velocity.y * dt,
            z: e.velocity.z * dt,
        }),
        velocity: e.velocity,
        active: e.active,
    };
}

func Main() -> int {
    let player = Entity {
        id: 1,
        position: Vec3 { x: 0.0, y: 0.0, z: 0.0 },
        velocity: Vec3 { x: 1.0, y: 0.0, z: 0.5 },
        active: true,
    };

    let dt = 0.016; // 60 FPS
    let updated = UpdateEntity(player, dt);

    Print("Player position: ({}, {}, {})\n",
        updated.position.x,
        updated.position.y,
        updated.position.z);

    return 0;
}
```

### 🚧 Hypothetical Code — Graphics API Bindings & ECS Queries

```rux
// ============================================================
// ❌ WILL NOT COMPILE — These features are NOT present in Rux
// ============================================================

// 🚧 Required: FFI to GPU systems (Vulkan, DirectX)
extern "C" {
    func vkCreateInstance(info: *VkInstanceCreateInfo, alloc: *opaque, instance: *VkInstance) -> int32;
    func vkCreateDevice(gpu: VkPhysicalDevice, info: *VkDeviceCreateInfo, alloc: *opaque, device: *VkDevice) -> int32;
    func glfwInit() -> int32;
    func glfwCreateWindow(w: int32, h: int32, title: *uint8, monitor: *opaque, share: *opaque) -> *GLFWwindow;
}

// 🚧 Required: SIMD-aligned vector operations (auto SSE/AVX vectors)
#[simd]
struct Vec4 {
    x: float32,
    y: float32,
    z: float32,
    w: float32,
}

func Vec4Mul(a: Vec4, b: Vec4) -> Vec4 {
    // Compiled directly into SSE 'mulps' instructions
    return Vec4 {
        x: a.x * b.x,
        y: a.y * b.y,
        z: a.z * b.z,
        w: a.w * b.w,
    };
}

// Entity Component System (ECS) Storage
struct Transform { pos: Vec3, rot: Quaternion, scale: Vec3 }
struct MeshRenderer { mesh_id: uint32, material_id: uint32 }
struct RigidBody { mass: float32, velocity: Vec3 }

struct World {
    entities: Vec<EntityId>,
    transforms: SparseSet<Transform>,       // 🚧 Required: Sparse collections
    renderers: SparseSet<MeshRenderer>,
    bodies: SparseSet<RigidBody>,
}

// ECS Update Pipeline
func PhysicsSystem(world: &mut World, dt: float32) {
    // 🚧 Required: Multi-component Iterator Queries
    for (entity, transform, body) in world.query<Transform, RigidBody>() {
        body.velocity.y -= 9.81 * dt;       // Gravity acceleration
        transform.pos = Vec3Add(transform.pos, Vec3Scale(body.velocity, dt));
    }
}

func GameMain() -> int {
    glfwInit();
    let window = glfwCreateWindow(1920, 1080, "Rux Engine", null, null);
    let world = World::new();

    var last_time = GetTime();

    // Loop at 60Hz
    while glfwWindowShouldClose(window) == 0 {
        let now = GetTime();
        let dt = (now - last_time) as float32;
        last_time = now;

        glfwPollEvents();
        PhysicsSystem(&mut world, dt);
        RenderSystem(&world);
    }
    return 0;
}
```

---

## 6. Embedded Systems

### ✅ Current Rux Code — Peripheral Register Emulation

```rux
import Std::Io::PrintLine;
import Std::Io::Print;

// Emulated memory offset for STM32 GPIO registers
const GPIO_BASE: uint64 = 0x40020000;

struct GpioRegisters {
    MODER: uint32,    // Mode register
    OTYPER: uint32,   // Output type
    OSPEEDR: uint32,  // Output speed
    PUPDR: uint32,    // Pull-up/pull-down
    IDR: uint32,      // Input data
    ODR: uint32,      // Output data
}

func SetBit(reg: uint32, bit: uint8) -> uint32 {
    return reg | (1 as uint32 << bit as uint32);
}

func ClearBit(reg: uint32, bit: uint8) -> uint32 {
    return reg & ~(1 as uint32 << bit as uint32);
}

func Main() -> int {
    var moder: uint32 = 0;

    // Set pin 5 as output (moder 01)
    moder = SetBit(moder, 10);   // MODER5[1:0] = 01
    moder = ClearBit(moder, 11);

    Print("MODER register value: 0x{}\n", moder);
    PrintLine("(Emulated only — cannot compile for real target MCUs)");
    return 0;
}
```

### 🚧 Hypothetical Code — Volatile Registers & ARM ISR Vectors

```rux
// ============================================================
// ❌ WILL NOT COMPILE — These features are NOT present in Rux
// ============================================================

// 🚧 Required: Compiler options for embedded targets (No OS, Custom target)
#![no_std]
#![no_main]

// Volatile hardware layout
struct GpioRegisters {
    MODER: volatile uint32,    // 🚧 Required: volatile keywords
    OTYPER: volatile uint32,
    OSPEEDR: volatile uint32,
    ODR: volatile uint32,
}

const GPIOC: *mut GpioRegisters = 0x40020800 as *mut GpioRegisters;

// ARM Cortex-M Vector table link configuration
#[link_section(".vector_table.interrupts")]
#[no_mangle]
pub static INTERRUPTS: [func(); 240] = [
    Reset_Handler,
    NMI_Handler,
    HardFault_Handler,
    // ... remaining interrupt service routines ...
];

#[naked]
func Reset_Handler() {
    // Initialize memory and boot CPU
    asm {
        ldr r0, =_stack_top
        mov sp, r0
        bl init_sections
        bl kernel_entry
    }
}

#[interrupt]  // 🚧 Required: specialized interrupt ABI attribute
func SysTick_Handler() {
    static mut milliseconds: uint64 = 0;  // 🚧 Required: safe static local variables
    milliseconds += 1;
}

func Main() {
    // Volatile writes directly to STM32 registers
    unsafe {
        (*GPIOC).MODER = 0x00000400; // PC5 to Output
        loop {
            (*GPIOC).ODR ^= (1 << 5); // Toggle LED
            delay_ms(500);
        }
    }
}
```

---

## 7. Networking Stack

### ✅ Current Rux Code — Endpoint Metadata Representation

```rux
import Std::Io::PrintLine;
import Std::Io::Print;

struct Ipv4Addr {
    octets: [uint8; 4],
}

struct SocketAddrV4 {
    ip: Ipv4Addr,
    port: uint16,
}

func DisplayEndpoint(addr: SocketAddrV4) {
    Print("Endpoint configured: {}.{}.{}.{}:{}\n",
        addr.ip.octets[0],
        addr.ip.octets[1],
        addr.ip.octets[2],
        addr.ip.octets[3],
        addr.port);
}

func Main() -> int {
    let local = SocketAddrV4 {
        ip: Ipv4Addr { octets: [127, 0, 0, 1] },
        port: 8080,
    };
    DisplayEndpoint(local);
    return 0;
}
```

### 🚧 Hypothetical Code — Socket Interfaces & Zero-Copy Parser

```rux
// ============================================================
// ❌ WILL NOT COMPILE — These features are NOT present in Rux
// ============================================================

import Std::Net::TcpStream;
import Std::Async::poll;

struct EthernetHeader {
    dest_mac: [uint8; 6],
    src_mac: [uint8; 6],
    ether_type: uint16,
}

struct IPv4Header {
    ver_ihl: uint8,
    tos: uint8,
    total_len: uint16,
    id: uint16,
    flags_fragment: uint16,
    ttl: uint8,
    protocol: uint8,
    checksum: uint16,
    src_ip: uint32,
    dest_ip: uint32,
}

// High-performance zero-copy packet parser
func ParsePacket(raw_bytes: &[uint8]) -> Option<(EthernetHeader, IPv4Header)> {
    if raw_bytes.len() < 34 { return None; } // Minimum headers size
    
    // Zero-copy deserialization using memory reinterpret casts
    let eth = *(raw_bytes.as_ptr() as *EthernetHeader);
    let ip = *((raw_bytes.as_ptr() + 14) as *IPv4Header);
    
    return Some((eth, ip));
}

// Asynchronous network server
async func ListenAndServe(port: uint16) -> Result<(), IoError> {
    let mut socket = TcpStream::connect("0.0.0.0", port).await?;
    let mut buffer = [0 as uint8; 1024];

    loop {
        // Asynchronous non-blocking reading backed by epoll/IOCP
        let bytes_read = socket.read(&mut buffer).await?;
        if bytes_read == 0 { break; } // Connection closed

        let response = b"HTTP/1.1 200 OK\r\nContent-Length: 5\r\n\r\nHello";
        socket.write_all(response).await?;
    }
    return Ok(());
}
```

---

## 8. CLI Tools

### ✅ Current Rux Code — Exit Status Wrapper

```rux
import Std::Io::PrintLine;

struct CliCommand {
    name: *uint8,
    verbose: bool,
}

func ExecuteDummy(cmd: CliCommand) -> int32 {
    if cmd.verbose {
        PrintLine("Executing CLI process verbose mode...");
    }
    return 0; // SUCCESS
}

func Main() -> int {
    let cmd = CliCommand {
        name: "rux-doc" as *uint8,
        verbose: true,
    };
    let exit_code = ExecuteDummy(cmd);
    return exit_code as int;
}
```

### 🚧 Hypothetical Code — Argument Parser & Subprocess Launching

```rux
// ============================================================
// ❌ WILL NOT COMPILE — These features are NOT present in Rux
// ============================================================

import Std::Env;
import Std::Process::Command;
import Std::Console::Style;

// Command CLI configuration
struct Config {
    command: String,
    files: Vec<String>,
    threads: uint32,
}

func ParseArgs() -> Result<Config, ArgError> {
    let args = Env::args(); // 🚧 Required: reading process CLI args
    let mut config = Config { command: String::new(), files: Vec::new(), threads: 4 };

    var i: uint = 1;
    while i < args.len() {
        match args[i].as_str() {
            "-c" | "--command" => {
                config.command = args[i+1].clone();
                i += 2;
            },
            "-t" | "--threads" => {
                config.threads = args[i+1].parse::<uint32>()?; // 🚧 Required: parsing strings
                i += 2;
            },
            _ => {
                config.files.push(args[i].clone());
                i += 1;
            }
        }
    }
    return Ok(config);
}

func RunSubprocess(bin: &str, args: &[&str]) -> Result<String, ProcError> {
    // 🚧 Required: Spawn child processes with I/O pipes redirection
    let child = Command::new(bin)
        .args(args)
        .stdout(Stdio::piped())
        .spawn()?;

    let output = child.wait_with_output()?;
    if !output.status.success() {
        return Err(ProcError::Failure);
    }
    return Ok(String::from_utf8(output.stdout)?);
}

func Main() -> int {
    let config = match ParseArgs() {
        Ok(c) => c,
        Err(e) => {
            // Styled stderr printing
            Style::red().bold().eprintln("Error parsing CLI arguments.");
            return 1;
        }
    };
    
    let result = RunSubprocess(&config.command, &["--all"])?;
    PrintLine(result);
    return 0;
}
```

---

## 9. Virtualization

### ✅ Current Rux Code — vCPU Register State Struct

```rux
import Std::Io::PrintLine;

// Virtual CPU registers layout — compilable struct
struct VcpuRegs {
    rax: uint64, rbx: uint64, rcx: uint64, rdx: uint64,
    rsi: uint64, rdi: uint64, rsp: uint64, rbp: uint64,
    rip: uint64, rflags: uint64,
}

func ResetVcpu(regs: *VcpuRegs) {
    unsafe {
        (*regs).rip = 0xFFF0 as uint64; // Intel boot reset address
        (*regs).rsp = 0x0000 as uint64;
        (*regs).rflags = 0x0002 as uint64; // Base flags set
    }
}

func Main() -> int {
    var registers = VcpuRegs {
        rax: 0, rbx: 0, rcx: 0, rdx: 0,
        rsi: 0, rdi: 0, rsp: 0, rbp: 0,
        rip: 0, rflags: 0,
    };
    ResetVcpu(&registers);
    PrintLine("vCPU registers initialized to hardware reset defaults");
    return 0;
}
```

### 🚧 Hypothetical Code — Hypervisor FFI & Page Table Mapping

```rux
// ============================================================
// ❌ WILL NOT COMPILE — These features are NOT present in Rux
// ============================================================

// WHPX (Windows Hypervisor Platform API bindings)
extern "C" {
    func WHvCreatePartition(partition: *mut WHV_PARTITION_HANDLE) -> HRESULT;
    func WHvSetupPartition(partition: WHV_PARTITION_HANDLE) -> HRESULT;
    func WHvMapGpaRange(partition: WHV_PARTITION_HANDLE, host: *opaque, guest: WHV_GUEST_PHYSICAL_ADDRESS, size: uint64, flags: WHV_MAP_GPA_RANGE_FLAGS) -> HRESULT;
    func WHvRunVirtualProcessor(partition: WHV_PARTITION_HANDLE, index: uint32, exit_context: *mut WHV_RUN_VP_EXIT_CONTEXT, size: uint32) -> HRESULT;
}

// Guest Physical Address Space Mapper
struct VirtualMemoryManager {
    partition: WHV_PARTITION_HANDLE,
    host_addr: *mut uint8,
    guest_base: uint64,
    size: uint64,
}

func (vmm: &mut VirtualMemoryManager) MapMemory() -> Result<(), HResultError> {
    // 🚧 Map guest physical RAM to virtual host backing memory
    let status = WHvMapGpaRange(
        vmm.partition,
        vmm.host_addr as *opaque,
        vmm.guest_base,
        vmm.size,
        WHvMapGpaRangeFlagRead | WHvMapGpaRangeFlagWrite | WHvMapGpaRangeFlagExecute
    );
    
    if status != S_OK {
        return Err(HResultError::from(status));
    }
    return Ok(());
}

// 🚧 Run virtual CPU execution core
func RunHypervisor(partition: WHV_PARTITION_HANDLE) {
    var exit_context = WHV_RUN_VP_EXIT_CONTEXT::new();

    loop {
        let hr = WHvRunVirtualProcessor(partition, 0, &mut exit_context, size_of::<WHV_RUN_VP_EXIT_CONTEXT>() as uint32);
        if hr != S_OK { break; }

        // Process guest interrupts and VM Exits
        match exit_context.ExitReason {
            WHvRunVpExitReasonMemoryAccess => {
                HandleMmio(&exit_context.MemoryAccess);
            },
            WHvRunVpExitReasonX64IoPortAccess => {
                HandleIoPort(&exit_context.IoPortAccess);
            },
            WHvRunVpExitReasonUnrecoverableException => {
                panic!("Hypervisor guest CPU crashed.");
            }
        }
    }
}
```

---

## 10. Drivers

### ✅ Current Rux Code — PCI Device Identifier Struct

```rux
import Std::Io::PrintLine;
import Std::Io::Print;

struct PciIdent {
    vendor_id: uint16,
    device_id: uint16,
    subsystem_id: uint16,
}

func MatchDevice(dev: PciIdent, target_vendor: uint16) -> bool {
    return dev.vendor_id == target_vendor;
}

func Main() -> int {
    let local_card = PciIdent {
        vendor_id: 0x8086, // Intel
        device_id: 0x10D3, // Gigabit Network Card
        subsystem_id: 0,
    };
    
    if MatchDevice(local_card, 0x8086) {
        PrintLine("Intel PCI network device detected");
    }
    return 0;
}
```

### 🚧 Hypothetical Code — Kernel Mode FFI & Device Interrupt Routines

```rux
// ============================================================
// ❌ WILL NOT COMPILE — These features are NOT present in Rux
// ============================================================

// 🚧 Required: Compiler targets kernel executable subsystems (Windows KMDF / Linux KO)
#![kernel_driver]
#![no_std]

import Kernel::Wdf::Device;
import Kernel::Sync::SpinLock;

struct DriverContext {
    wdf_device: WDFDEVICE,
    io_port_base: *mut uint8,
    lock: SpinLock,
}

// Windows KMDF Driver Entrypoint
#[no_mangle]
func DriverEntry(driver_object: *mut DRIVER_OBJECT, registry_path: *mut UNICODE_STRING) -> NTSTATUS {
    var config = WDF_DRIVER_CONFIG::new();
    config.EvtDriverDeviceAdd = EvtDeviceAdd;

    let status = WdfDriverCreate(driver_object, registry_path, WDF_NO_OBJECT_ATTRIBUTES, &mut config, WDF_NO_HANDLE);
    return status;
}

// EvtDeviceAdd — initializes and maps device memory
func EvtDeviceAdd(driver: WDFDRIVER, device_init: *mut WDFDEVICE_INIT) -> NTSTATUS {
    var attributes = WDF_OBJECT_ATTRIBUTES::new();
    attributes.register_context::<DriverContext>();

    var device: WDFDEVICE = null;
    let status = WdfDeviceCreate(&mut device_init, &mut attributes, &mut device);
    if !NT_SUCCESS(status) { return status; }

    let context = WdfDeviceGetContext::<DriverContext>(device);
    (*context).lock = SpinLock::new();
    
    // Map hardware resources to virtual CPU memory space
    (*context).io_port_base = MmMapIoSpace(0xFD000000 as PHYSICAL_ADDRESS, 4096, MmNonCached) as *mut uint8;

    return STATUS_SUCCESS;
}

// Hardware Interrupt Service Routine
#[interrupt_isr]
func OnHardwareInterrupt(interrupt: WDFINTERRUPT, message_id: ULONG) -> BOOLEAN {
    let device = WdfInterruptGetDevice(interrupt);
    let context = WdfDeviceGetContext::<DriverContext>(device);

    context.lock.acquire();
    
    // Read hardware status register from volatile address
    let irq_status = unsafe { read_volatile(context.io_port_base + 0x04) };
    if irq_status & 0x01 != 0 {
        // Clear interrupt flag
        unsafe { write_volatile(context.io_port_base + 0x04, 0x01) };
        context.lock.release();
        return TRUE;
    }
    
    context.lock.release();
    return FALSE;
}
```
