Rust allocator to debug allocations

counting_allocator.rs

use std::alloc::{System, GlobalAlloc};


static SYS_ALLOC: System = System;

struct CountingAlloc {
    bytes_allocated: AtomicIsize,
    bytes_used: AtomicIsize
}

#[global_allocator]
static COUNTING_ALLOC: CountingAlloc = CountingAlloc{bytes_allocated:AtomicIsize::new(0),bytes_used:AtomicIsize::new(0)};


impl Display for CountingAlloc {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "Allocated: {} Current Ram usage: {}", COUNTING_ALLOC.bytes_allocated.fetch_add(0, std::sync::atomic::Ordering::AcqRel), COUNTING_ALLOC.bytes_used.fetch_add(0, std::sync::atomic::Ordering::AcqRel))
    }
}

unsafe impl GlobalAlloc for CountingAlloc {
    unsafe fn alloc_zeroed(&self, layout: std::alloc::Layout) -> *mut u8 {
        let ptr = SYS_ALLOC.alloc_zeroed(layout);
        if ptr != std::ptr::null_mut() {
            self.bytes_allocated.fetch_add(layout.size() as isize, std::sync::atomic::Ordering::Relaxed);
            self.bytes_used.fetch_add(layout.size() as isize, std::sync::atomic::Ordering::Relaxed);            
        }
        ptr
    }

    unsafe fn realloc(&self, ptr: *mut u8, layout: std::alloc::Layout, new_size: usize) -> *mut u8 {
        let ptr = SYS_ALLOC.realloc(ptr, layout, new_size);
        if ptr != std::ptr::null_mut() {
            self.bytes_allocated.fetch_add( std::cmp::min(0, new_size as isize - (layout.size() as isize)), std::sync::atomic::Ordering::Relaxed);
            self.bytes_used.fetch_add(new_size as isize - (layout.size() as isize), std::sync::atomic::Ordering::Relaxed);
        } 
        ptr
    }

    unsafe fn alloc(&self, layout: std::alloc::Layout) -> *mut u8 {
        let ptr = SYS_ALLOC.alloc(layout);

        if ptr != std::ptr::null_mut() {
            self.bytes_allocated.fetch_add(layout.size() as isize, std::sync::atomic::Ordering::Relaxed);
            self.bytes_used.fetch_add(layout.size() as isize, std::sync::atomic::Ordering::Relaxed);
        }
        ptr
    }

    unsafe fn dealloc(&self, ptr: *mut u8, layout: std::alloc::Layout) {
        self.bytes_used.fetch_sub(layout.size() as isize, std::sync::atomic::Ordering::Relaxed);
        SYS_ALLOC.dealloc(ptr, layout)
    }
}


    // println!("{}", &COUNTING_ALLOC);
    // return Ok(());