don't unnecessarily lock for pointer derefs
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parent
d581440210
commit
4bb748246c
66
src/main.rs
66
src/main.rs
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@ -9,20 +9,51 @@ use std::sync::Mutex;
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use lazy_static::lazy_static;
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#[repr(C, align(65536))]
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lazy_static! {
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static ref POOL: Pool = Pool::default();
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}
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struct Pool {
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data: [u8; 65536],
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inner: Mutex<PoolInner>,
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base_ptr: usize,
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}
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impl Default for Pool {
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fn default() -> Self {
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let inner = Mutex::new(PoolInner { data: [0; 0x10000], begin: 0, end: 0, last_position: 0 });
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let base_ptr = inner.lock().unwrap().data.as_ptr() as usize;
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Pool {
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inner,
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base_ptr,
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}
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}
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}
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impl Pool {
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fn alloc(&self, layout: Layout) -> u16 {
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self.inner.lock().unwrap().alloc(layout)
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}
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fn dealloc(&self, sptr: u16) {
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self.inner.lock().unwrap().dealloc(sptr)
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}
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}
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impl std::fmt::Debug for Pool {
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fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
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self.inner.lock().unwrap().fmt(f)
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}
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}
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#[repr(C, align(0x10000))]
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struct PoolInner {
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data: [u8; 0x10000],
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begin: usize,
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end: usize,
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last_position: usize,
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}
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lazy_static! {
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static ref POOL: Mutex<Pool> = Mutex::new(Pool { data: [0; 65536], begin: 0, end: 0, last_position: 0 });
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}
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// halfassed bump allocator just to prove a point.
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impl Pool {
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impl PoolInner {
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fn alloc(&mut self, layout: Layout) -> u16 {
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let size = layout.size();
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let align = layout.align();
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@ -78,10 +109,11 @@ impl Pool {
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}
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}
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impl std::fmt::Debug for Pool {
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impl std::fmt::Debug for PoolInner {
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fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
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write!(
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f, "Pool {{ data: [_; 65536], begin: {}, end: {}, last_position: {} }}",
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f, "Pool {{ data: [_; {}], begin: {}, end: {}, last_position: {} }}",
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self.data.len(),
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self.begin,
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self.end,
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self.last_position,
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@ -93,20 +125,20 @@ pub struct ShortPointer<T>(u16, PhantomData<T>);
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impl<T> Drop for ShortPointer<T> {
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fn drop(&mut self) {
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POOL.lock().unwrap().dealloc(self.0)
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POOL.dealloc(self.0)
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}
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}
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impl<T> ShortPointer<T> {
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fn deref_inner(&self) -> &mut T {
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unsafe {
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((((POOL.lock().unwrap().data.as_mut_ptr()) as usize) + (self.0 as usize)) as *mut T).as_mut().unwrap()
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((POOL.base_ptr + (self.0 as usize)) as *mut T).as_mut().unwrap()
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}
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}
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pub fn new(obj: T) -> Self {
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let layout = Layout::for_value(&obj);
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let mut sptr = Self(POOL.lock().unwrap().alloc(layout), PhantomData::default());
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let mut sptr = Self(POOL.alloc(layout), PhantomData::default());
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let uninitialized = core::mem::replace(sptr.deref_mut(), obj);
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core::mem::forget(uninitialized);
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sptr
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@ -129,16 +161,16 @@ impl<T> DerefMut for ShortPointer<T> {
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#[allow(unused_must_use)] // dbg! statements
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fn main() {
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dbg!(POOL.lock().unwrap());
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dbg!(&*POOL);
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{
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let foo = ShortPointer::new([1, 2, 3, 4, 5]);
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dbg!(POOL.lock().unwrap());
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dbg!(&*POOL);
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{
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let bar = ShortPointer::new(0x900dCafeDa7e5_u64);
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dbg!(POOL.lock().unwrap());
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dbg!(&*POOL);
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println!("{} | {:?} | {:x}", size_of_val(&foo), *foo, *bar);
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}
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dbg!(POOL.lock().unwrap());
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dbg!(&*POOL);
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}
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dbg!(POOL.lock().unwrap());
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dbg!(&*POOL);
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}
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