95 lines
2.7 KiB
Rust
95 lines
2.7 KiB
Rust
use crate::{ExternRef, ExternalReferenceType};
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use alloc::boxed::Box;
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use core::cell::Cell;
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use core::mem::forget;
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struct TemporaryData<T> {
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use_count: Cell<usize>,
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is_deleted: bool,
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value: T,
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}
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pub struct Temporary<T> {
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value: *mut TemporaryData<T>,
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}
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static mut TEMPORARIES: alloc::collections::BTreeMap<u32, *const u8> =
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alloc::collections::BTreeMap::new();
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impl<T> Temporary<T>
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where
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T: ExternalReferenceType,
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T: Clone,
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{
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#[inline]
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pub fn from_reference(reference: ExternRef<T>) -> Self {
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let temporaries = unsafe { &mut TEMPORARIES };
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let existing = temporaries.get(&reference.get_internal_index());
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unsafe {
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if let Some(v) = existing {
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let rc = (*v as *mut TemporaryData<T>).as_mut().unwrap();
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if !rc.is_deleted {
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*rc.use_count.get_mut() += 1;
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return Self {
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value: rc as *mut TemporaryData<T>,
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};
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}
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}
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}
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let value = reference.get_value().unwrap();
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let mut reference_counter = TemporaryData {
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use_count: Cell::new(1),
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is_deleted: false,
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value,
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};
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let ptr = &mut reference_counter as *mut TemporaryData<T>;
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forget(reference_counter);
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temporaries.insert(reference.get_internal_index(), ptr as *const u8);
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Self { value: ptr }
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}
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#[inline]
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pub fn value(&self) -> T {
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unsafe { self.value.as_ref().unwrap().value.clone() }
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}
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#[inline]
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pub fn value_ref(&self) -> &T {
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unsafe { &self.value.as_ref().unwrap().value }
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}
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pub(crate) fn mark_as_deleted(reference: ExternRef<T>) {
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let temporaries = unsafe { &mut TEMPORARIES };
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let existing = temporaries.get(&reference.get_internal_index());
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unsafe {
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if let Some(v) = existing {
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crate::utils::print_raw(b"Dropping temporary");
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let rc = (*v as *mut TemporaryData<T>).as_mut().unwrap();
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rc.is_deleted = true;
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if rc.use_count.get() == 0 {
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drop(Box::from(*v as *mut TemporaryData<T>))
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}
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temporaries.remove(&reference.get_internal_index());
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}
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}
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}
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}
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impl<T> Clone for Temporary<T> {
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fn clone(&self) -> Self {
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*unsafe { self.value.as_mut() }.unwrap().use_count.get_mut() += 1;
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Self { value: self.value }
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}
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}
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impl<T> Drop for Temporary<T> {
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fn drop(&mut self) {
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let data = unsafe { self.value.as_mut() }.unwrap();
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let v = data.use_count.get_mut();
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*v -= 1;
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if *v == 0 && data.is_deleted {
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drop(Box::from(self.value))
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}
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}
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}
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