Code

use std::sync::atomic::{AtomicU64, Ordering::*};

/// Lock-free concurrent counter with overflow protection
pub struct AtomicAccumulator {
    state: AtomicU64,
    epoch: AtomicU64,
}

impl AtomicAccumulator {
    #[inline(always)]
    pub fn fetch_add_checked(&self, val: u64) -> Option<u64> {
        loop {
            let current = self.state.load(Acquire);
            let (new_val, overflow) = current.overflowing_add(val);
            if overflow {
                self.epoch.fetch_add(1, Release);
                return None;
            }
            if self.state.compare_exchange_weak(
                current, new_val, AcqRel, Relaxed
            ).is_ok() {
                return Some(new_val);
            }
        }
    }
}

package failover

import (
    "context"
    "sync/atomic"
    "time"
)

type CircuitBreaker struct {
    failures  atomic.Int64
    lastFail  atomic.Int64
    threshold int64
    timeout   time.Duration
}

func (cb *CircuitBreaker) Allow() bool {
    if cb.failures.Load() < cb.threshold {
        return true
    }
    if time.Now().UnixNano()-cb.lastFail.Load() > int64(cb.timeout) {
        cb.failures.Store(0)
        return true
    }
    return false
}

func (cb *CircuitBreaker) Execute(ctx context.Context, fn func() error) error {
    if !cb.Allow() {
        return ErrCircuitOpen
    }
    if err := fn(); err != nil {
        cb.failures.Add(1)
        cb.lastFail.Store(time.Now().UnixNano())
        return err
    }
    return nil
}

section .data
    align 64
    .sbox: times 256 db 0

section .text
global aes_key_schedule_128
global aes_encrypt_block

; ────────────────────────────────────────────────────
; AES-128 Key Schedule - Rijndael key expansion
; rdi = round_keys[11][16], rsi = key[16]
; ────────────────────────────────────────────────────
aes_key_schedule_128:
    push    rbx
    push    r12
    movdqu  xmm0, [rsi]
    movdqa  [rdi], xmm0
    
    mov     r12, 1
.expand:
    aeskeygenassist xmm1, xmm0, 0
    call    .key_combine
    movdqa  [rdi + r12*16], xmm0
    inc     r12
    cmp     r12, 10
    jle     .expand
    
    pop     r12
    pop     rbx
    ret

.key_combine:
    pshufd  xmm1, xmm1, 0xff
    vpslldq xmm2, xmm0, 4
    pxor    xmm0, xmm2
    vpslldq xmm2, xmm0, 4
    pxor    xmm0, xmm2
    vpslldq xmm2, xmm0, 4
    pxor    xmm0, xmm2
    pxor    xmm0, xmm1
    ret

; ────────────────────────────────────────────────────
; AES-128 ECB Encrypt - Single block
; rdi = out[16], rsi = in[16], rdx = round_keys
; ────────────────────────────────────────────────────
aes_encrypt_block:
    movdqu  xmm0, [rsi]
    pxor    xmm0, [rdx]
    
    aesenc  xmm0, [rdx + 16]
    aesenc  xmm0, [rdx + 32]
    aesenc  xmm0, [rdx + 48]
    aesenc  xmm0, [rdx + 64]
    aesenc  xmm0, [rdx + 80]
    aesenc  xmm0, [rdx + 96]
    aesenc  xmm0, [rdx + 112]
    aesenc  xmm0, [rdx + 128]
    aesenc  xmm0, [rdx + 144]
    aesenclast xmm0, [rdx + 160]
    
    movdqu  [rdi], xmm0
    ret