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use std::alloc::{Layout, System};
use std::sync::atomic::{AtomicUsize, Ordering};
use std::time::Instant;

use pagetable::PageTable;

#[global_allocator]
static ALLOCATOR: Alloc = Alloc;

static ALLOCATED: AtomicUsize = AtomicUsize::new(0);
static FREED: AtomicUsize = AtomicUsize::new(0);
static RESIDENT: AtomicUsize = AtomicUsize::new(0);

fn allocated() -> usize {
    ALLOCATED.swap(0, Ordering::Relaxed)
}

fn freed() -> usize {
    FREED.swap(0, Ordering::Relaxed)
}

fn resident() -> usize {
    RESIDENT.load(Ordering::Relaxed)
}

#[derive(Default, Debug, Clone, Copy)]
struct Alloc;

unsafe impl std::alloc::GlobalAlloc for Alloc {
    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
        let ret = System.alloc(layout);
        assert_ne!(ret, std::ptr::null_mut());
        ALLOCATED.fetch_add(layout.size(), Ordering::Relaxed);
        RESIDENT.fetch_add(layout.size(), Ordering::Relaxed);
        std::ptr::write_bytes(ret, 0xa1, layout.size());
        ret
    }

    unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) {
        std::ptr::write_bytes(ptr, 0xde, layout.size());
        FREED.fetch_add(layout.size(), Ordering::Relaxed);
        RESIDENT.fetch_sub(layout.size(), Ordering::Relaxed);
        System.dealloc(ptr, layout)
    }
}

fn main() {
    let before = Instant::now();
    let pt = PageTable::<AtomicUsize>::default();

    for i in 0_u64..(1 << 33) {
        pt.get(i);
    }

    dbg!(before.elapsed());

    dbg!(allocated());
    dbg!(freed());
    dbg!(resident());

    drop(pt);
    println!("after drop:");
    dbg!(before.elapsed());

    dbg!(allocated());
    dbg!(freed());
    dbg!(resident());
}