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#![feature(allocator_api, maybe_uninit)]

extern crate libc;
extern crate time;

use libc::c_void;
use std::alloc::{Alloc, AllocErr, GlobalAlloc, Layout, System};
use std::fs::File;
use std::mem;
use std::os::unix::io::AsRawFd;
use std::process;
use std::ptr::{null_mut, NonNull};
use std::sync::atomic::{AtomicBool, Ordering};

static mut TRACE_FD: i32 = -1;
static TRACE_ACTIVATE: AtomicBool = AtomicBool::new(false);

pub struct Allocator {}

impl Allocator {
    pub fn new() -> Allocator {
        Allocator {}
    }

    pub fn initialize(f: &File) {
        unsafe {
            TRACE_FD = f.as_raw_fd();
        }
    }

    pub fn write_to_stdout() {
        unsafe {
            TRACE_FD = 0;
        }
    }

    pub fn write_to_stderr() {
        unsafe {
            TRACE_FD = 1;
        }
    }

    pub fn activate() {
        TRACE_ACTIVATE.store(true, Ordering::Relaxed);
    }

    pub fn deactivate() {
        TRACE_ACTIVATE.store(false, Ordering::Relaxed);
    }
}

fn to_hex(i: u8) -> u8 {
    if i > 15 {
        process::exit(42);
    }

    if i < 10 {
        48 + i
    } else {
        (i - 10) + 65
    }
}

enum Action {
    Allocating,
    Deallocating,
}

unsafe fn print_size(address: usize, size: usize, action: Action) {
    if TRACE_FD != -1 && TRACE_ACTIVATE.load(Ordering::Relaxed) {
        let mut buf: [u8; 100] = mem::MaybeUninit::uninit().assume_init();
        let psz = mem::size_of::<usize>();
        let shr = (psz as u32) * 8 - 8;

        let mut index = 0;
        let mut counter = 8;

        let c = time::precise_time_ns() as usize;

        loop {
            if counter == 0 {
                break;
            }

            let current = ((c.overflowing_shl(64 - 8 * counter as u32).0)
                .overflowing_shr(shr)
                .0) as u8;
            buf[index] = to_hex(current >> 4);
            buf[index + 1] = to_hex((current << 4) >> 4);

            counter -= 1;
            index += 2;
        }

        buf[index] = b' ';

        index += 1;

        match action {
            Action::Allocating => buf[index] = b'A',
            Action::Deallocating => buf[index] = b'D',
        };

        buf[index + 1] = b' ';

        index += 2;
        counter = 8;

        let c = address;

        loop {
            if counter == 0 {
                break;
            }

            let current = ((c.overflowing_shl(64 - 8 * counter as u32).0)
                .overflowing_shr(shr)
                .0) as u8;

            buf[index] = to_hex(current >> 4);
            buf[index + 1] = to_hex((current << 4) >> 4);

            counter -= 1;
            index += 2;
        }

        buf[index] = b' ';

        index += 1;
        counter = 8;

        loop {
            if counter == 0 {
                break;
            }

            let current = ((size.overflowing_shl(64 - 8 * counter as u32).0)
                .overflowing_shr(shr)
                .0) as u8;

            buf[index] = to_hex(current >> 4);
            buf[index + 1] = to_hex((current << 4) >> 4);

            counter -= 1;
            index += 2;
        }
        buf[index] = b'\n';

        libc::write(TRACE_FD, buf.as_ptr() as *const c_void, index + 1);
    }
}

unsafe impl<'a> Alloc for &'a Allocator {
    unsafe fn alloc(&mut self, layout: Layout) -> Result<NonNull<u8>, AllocErr> {
        let size = layout.size();
        let res = System.alloc(layout);

        print_size(res as usize, size, Action::Allocating);

        Ok(NonNull::new(res).unwrap())
    }

    unsafe fn dealloc(&mut self, ptr: std::ptr::NonNull<u8>, layout: Layout) {
        let ptr = ptr.as_ptr();

        print_size(ptr as usize, layout.size(), Action::Deallocating);

        System.dealloc(ptr, layout)
    }
}

unsafe impl GlobalAlloc for Allocator {
    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
        let size = layout.size();
        let ptr = System.alloc(layout);

        print_size(ptr as usize, size, Action::Allocating);

        ptr
    }

    unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) {
        print_size(ptr as usize, layout.size(), Action::Deallocating);

        System.dealloc(ptr, layout)
    }
}