work on optimizing web implementation
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Evan Almloff committed
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@@ -11,8 +11,13 @@
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//! The logic for this was borrowed from <https://docs.rs/stack_dst/0.6.1/stack_dst/>. Unfortunately, this crate does not
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//! support non-static closures, so we've implemented the core logic of `ValueA` in this module.
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use smallbox::{
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smallbox,
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space::{S1, S16, S4, S8},
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SmallBox,
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};
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use crate::{innerlude::VNode, ScopeState};
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use std::mem;
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/// A concrete type provider for closures that build [`VNode`] structures.
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///
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@@ -24,14 +29,7 @@ use std::mem;
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/// LazyNodes::new(|f| f.element("div", [], [], [] None))
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/// ```
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pub struct LazyNodes<'a, 'b> {
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inner: StackNodeStorage<'a, 'b>,
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}
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type StackHeapSize = [usize; 16];
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enum StackNodeStorage<'a, 'b> {
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Stack(LazyStack),
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Heap(Box<dyn FnMut(Option<&'a ScopeState>) -> Option<VNode<'a>> + 'b>),
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inner: SmallBox<dyn FnMut(&'a ScopeState) -> VNode<'a> + 'b, S16>,
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}
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impl<'a, 'b> LazyNodes<'a, 'b> {
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@@ -44,114 +42,11 @@ impl<'a, 'b> LazyNodes<'a, 'b> {
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// there's no way to call FnOnce without a box, so we need to store it in a slot and use static dispatch
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let mut slot = Some(val);
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let val = move |fac: Option<&'a ScopeState>| {
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fac.map(
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slot.take()
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.expect("LazyNodes closure to be called only once"),
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)
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};
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// miri does not know how to work with mucking directly into bytes
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// just use a heap allocated type when miri is running
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if cfg!(miri) {
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Self {
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inner: StackNodeStorage::Heap(Box::new(val)),
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}
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} else {
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unsafe { LazyNodes::new_inner(val) }
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}
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}
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/// Create a new [`LazyNodes`] closure, but force it onto the heap.
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pub fn new_boxed<F>(inner: F) -> Self
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where
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F: FnOnce(&'a ScopeState) -> VNode<'a> + 'b,
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{
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// there's no way to call FnOnce without a box, so we need to store it in a slot and use static dispatch
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let mut slot = Some(inner);
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Self {
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inner: StackNodeStorage::Heap(Box::new(move |fac: Option<&'a ScopeState>| {
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fac.map(
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slot.take()
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.expect("LazyNodes closure to be called only once"),
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)
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})),
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}
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}
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unsafe fn new_inner<F>(val: F) -> Self
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where
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F: FnMut(Option<&'a ScopeState>) -> Option<VNode<'a>> + 'b,
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{
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let mut ptr: *const _ = &val as &dyn FnMut(Option<&'a ScopeState>) -> Option<VNode<'a>>;
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assert_eq!(
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ptr as *const u8, &val as *const _ as *const u8,
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"MISUSE: Closure returned different pointer"
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);
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assert_eq!(
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std::mem::size_of_val(&*ptr),
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std::mem::size_of::<F>(),
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"MISUSE: Closure returned a subset pointer"
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);
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let words = ptr_as_slice(&mut ptr);
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assert!(
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words[0] == &val as *const _ as usize,
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"BUG: Pointer layout is not (data_ptr, info...)"
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);
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// - Ensure that Self is aligned same as data requires
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assert!(
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std::mem::align_of::<F>() <= std::mem::align_of::<Self>(),
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"TODO: Enforce alignment >{} (requires {})",
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std::mem::align_of::<Self>(),
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std::mem::align_of::<F>()
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);
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let info = &words[1..];
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let data = words[0] as *mut ();
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let size = mem::size_of::<F>();
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let stored_size = info.len() * mem::size_of::<usize>() + size;
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let max_size = mem::size_of::<StackHeapSize>();
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if stored_size > max_size {
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Self {
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inner: StackNodeStorage::Heap(Box::new(val)),
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}
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} else {
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let mut buf: StackHeapSize = StackHeapSize::default();
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assert!(info.len() + round_to_words(size) <= buf.as_ref().len());
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// Place pointer information at the end of the region
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// - Allows the data to be at the start for alignment purposes
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{
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let info_ofs = buf.as_ref().len() - info.len();
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let info_dst = &mut buf.as_mut()[info_ofs..];
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for (d, v) in Iterator::zip(info_dst.iter_mut(), info.iter()) {
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*d = *v;
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}
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}
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let src_ptr = data as *const u8;
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let dataptr = buf.as_mut_ptr().cast::<u8>();
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for i in 0..size {
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*dataptr.add(i) = *src_ptr.add(i);
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}
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std::mem::forget(val);
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Self {
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inner: StackNodeStorage::Stack(LazyStack {
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_align: [],
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buf,
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dropped: false,
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}),
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}
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inner: smallbox!(move |f| {
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let val = slot.take().expect("cannot call LazyNodes twice");
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val(f)
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}),
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}
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}
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@@ -163,88 +58,10 @@ impl<'a, 'b> LazyNodes<'a, 'b> {
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/// let node = f.call(cac);
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/// ```
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#[must_use]
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pub fn call(self, f: &'a ScopeState) -> VNode<'a> {
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match self.inner {
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StackNodeStorage::Heap(mut lazy) => {
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lazy(Some(f)).expect("Closure should not be called twice")
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}
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StackNodeStorage::Stack(mut stack) => stack.call(f),
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pub fn call(mut self, f: &'a ScopeState) -> VNode<'a> {
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if self.inner.is_heap() {
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panic!();
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}
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(self.inner)(f)
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}
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}
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struct LazyStack {
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_align: [u64; 0],
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buf: StackHeapSize,
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dropped: bool,
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}
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impl LazyStack {
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fn call<'a>(&mut self, f: &'a ScopeState) -> VNode<'a> {
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let LazyStack { buf, .. } = self;
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let data = buf.as_ref();
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let info_size =
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mem::size_of::<*mut dyn FnMut(Option<&'a ScopeState>) -> Option<VNode<'a>>>()
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/ mem::size_of::<usize>()
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- 1;
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let info_ofs = data.len() - info_size;
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let g: *mut dyn FnMut(Option<&'a ScopeState>) -> Option<VNode<'a>> =
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unsafe { make_fat_ptr(data[..].as_ptr() as usize, &data[info_ofs..]) };
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self.dropped = true;
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let clos = unsafe { &mut *g };
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clos(Some(f)).unwrap()
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}
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}
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impl Drop for LazyStack {
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fn drop(&mut self) {
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if !self.dropped {
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let LazyStack { buf, .. } = self;
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let data = buf.as_ref();
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let info_size =
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mem::size_of::<*mut dyn FnMut(Option<&ScopeState>) -> Option<VNode<'_>>>()
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/ mem::size_of::<usize>()
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- 1;
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let info_ofs = data.len() - info_size;
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let g: *mut dyn FnMut(Option<&ScopeState>) -> Option<VNode<'_>> =
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unsafe { make_fat_ptr(data[..].as_ptr() as usize, &data[info_ofs..]) };
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self.dropped = true;
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let clos = unsafe { &mut *g };
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clos(None);
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}
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}
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}
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/// Obtain mutable access to a pointer's words
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fn ptr_as_slice<T>(ptr: &mut T) -> &mut [usize] {
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assert!(mem::size_of::<T>() % mem::size_of::<usize>() == 0);
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let words = mem::size_of::<T>() / mem::size_of::<usize>();
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// SAFE: Points to valid memory (a raw pointer)
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unsafe { core::slice::from_raw_parts_mut(ptr as *mut _ as *mut usize, words) }
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}
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/// Re-construct a fat pointer
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unsafe fn make_fat_ptr<T: ?Sized>(data_ptr: usize, meta_vals: &[usize]) -> *mut T {
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let mut rv = mem::MaybeUninit::<*mut T>::uninit();
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{
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let s = ptr_as_slice(&mut rv);
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s[0] = data_ptr;
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s[1..].copy_from_slice(meta_vals);
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}
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let rv = rv.assume_init();
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assert_eq!(rv as *const (), data_ptr as *const ());
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rv
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}
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fn round_to_words(len: usize) -> usize {
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(len + mem::size_of::<usize>() - 1) / mem::size_of::<usize>()
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}
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