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value.rs
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value.rs
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use crate::{Chunk, ChunkStorage, Ident};
use std::rc::Rc;
use std::marker::PhantomData;
/// A single value stored in a chunk
pub struct Value<V> {
chunk: Chunk,
_marker: PhantomData<*mut V>,
}
impl<V> Value<V> {
/// Load the value in the chunk with the given identifier, or create it using a default value
pub fn load_or_default(ident: Ident, default: V, storage: Rc<dyn ChunkStorage>) -> Value<V> {
let (mut chunk, created_new) = storage.load_or_create_chunk(ident, ::std::mem::size_of::<V>());
if created_new {
unsafe {
::std::ptr::write(chunk.as_mut_ptr() as *mut V, default);
}
}
Value {
chunk,
_marker: PhantomData,
}
}
}
impl<V> ::std::ops::Deref for Value<V> {
type Target = V;
fn deref(&self) -> &V {
unsafe { (self.chunk.as_ptr() as *const V).as_ref().unwrap() }
}
}
impl<V> ::std::ops::DerefMut for Value<V> {
fn deref_mut(&mut self) -> &mut V {
unsafe { (self.chunk.as_mut_ptr() as *mut V).as_mut().unwrap() }
}
}
impl<V> Drop for Value<V> {
fn drop(&mut self) {
unsafe {
::std::ptr::drop_in_place(self.chunk.as_mut_ptr());
};
}
}