#![allow(dead_code)]
/* This file is almost identical to the aligned_memory.rs file in the
   spiral-rs crate.  The name is modified from AlignedMemory to
   AlignedMemoryMT, and there is one (unsafe!) change to the API:

    pub unsafe fn as_mut_ptr(&mut self) -> *mut u64

   has changed to:

    pub unsafe fn as_mut_ptr(&self) -> *mut u64

   The reason for this change is explicitly to allow multiple threads to
   *write* into the memory pool concurrently, with the caveat that the
   threads *must not* try to write into the same memory location.  In
   Spiral, each polynomial created from the database ends up scattered
   into noncontiguous words of memory, but any one word still only comes
   from one polynomial.  So with this change, different threads can read
   different parts of the database to produce different polynomials, and
   write those polynomials into the same memory pool (but *not* the same
   memory locations) at the same time.
*/

use std::{
    alloc::{alloc_zeroed, dealloc, Layout},
    mem::size_of,
    ops::{Index, IndexMut},
    slice::{from_raw_parts, from_raw_parts_mut},
};

const ALIGN_SIMD: usize = 64; // enough to support AVX-512
pub type AlignedMemoryMT64 = AlignedMemoryMT<ALIGN_SIMD>;

pub struct AlignedMemoryMT<const ALIGN: usize> {
    p: *mut u64,
    sz_u64: usize,
    layout: Layout,
}

impl<const ALIGN: usize> AlignedMemoryMT<{ ALIGN }> {
    pub fn new(sz_u64: usize) -> Self {
        let sz_bytes = sz_u64 * size_of::<u64>();
        let layout = Layout::from_size_align(sz_bytes, ALIGN).unwrap();

        let ptr;
        unsafe {
            ptr = alloc_zeroed(layout);
        }

        Self {
            p: ptr as *mut u64,
            sz_u64,
            layout,
        }
    }

    // pub fn from(data: &[u8]) -> Self {
    //     let sz_u64 = (data.len() + size_of::<u64>() - 1) / size_of::<u64>();
    //     let mut out = Self::new(sz_u64);
    //     let out_slice = out.as_mut_slice();
    //     let mut i = 0;
    //     for chunk in data.chunks(size_of::<u64>()) {
    //         out_slice[i] = u64::from_ne_bytes(chunk);
    //         i += 1;
    //     }
    //     out
    // }

    pub fn as_slice(&self) -> &[u64] {
        unsafe { from_raw_parts(self.p, self.sz_u64) }
    }

    pub fn as_mut_slice(&mut self) -> &mut [u64] {
        unsafe { from_raw_parts_mut(self.p, self.sz_u64) }
    }

    pub unsafe fn as_ptr(&self) -> *const u64 {
        self.p
    }

    pub unsafe fn as_mut_ptr(&self) -> *mut u64 {
        self.p
    }

    pub fn len(&self) -> usize {
        self.sz_u64
    }
}

unsafe impl<const ALIGN: usize> Send for AlignedMemoryMT<{ ALIGN }> {}
unsafe impl<const ALIGN: usize> Sync for AlignedMemoryMT<{ ALIGN }> {}

impl<const ALIGN: usize> Drop for AlignedMemoryMT<{ ALIGN }> {
    fn drop(&mut self) {
        unsafe {
            dealloc(self.p as *mut u8, self.layout);
        }
    }
}

impl<const ALIGN: usize> Index<usize> for AlignedMemoryMT<{ ALIGN }> {
    type Output = u64;

    fn index(&self, index: usize) -> &Self::Output {
        &self.as_slice()[index]
    }
}

impl<const ALIGN: usize> IndexMut<usize> for AlignedMemoryMT<{ ALIGN }> {
    fn index_mut(&mut self, index: usize) -> &mut Self::Output {
        &mut self.as_mut_slice()[index]
    }
}

impl<const ALIGN: usize> Clone for AlignedMemoryMT<{ ALIGN }> {
    fn clone(&self) -> Self {
        let mut out = Self::new(self.sz_u64);
        out.as_mut_slice().copy_from_slice(self.as_slice());
        out
    }
}