91 lines
2.3 KiB
Rust
91 lines
2.3 KiB
Rust
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use std::marker::PhantomData;
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use crate::VirtualMachine;
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use easy_bitfield::*;
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/// Offset from allocation pointer to the actual object start.
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pub const OBJECT_REF_OFFSET: isize = 8;
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/// Object header behind object.
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pub const OBJECT_HEADER_OFFSET: isize = -OBJECT_REF_OFFSET;
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pub const HASHCODE_OFFSET: isize = -(OBJECT_REF_OFFSET + size_of::<usize>() as isize);
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pub type MetadataField = BitField<u64, usize, 0, 58, false>;
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pub type HashStateField = BitField<u64, HashState, { MetadataField::NEXT_BIT }, 2, false>;
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#[derive(Debug, Clone, Copy, PartialEq, Eq)]
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pub enum HashState {
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Unhashed,
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Hashed,
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HashedAndMoved,
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}
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impl FromBitfield<u64> for HashState {
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fn from_bitfield(value: u64) -> Self {
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match value {
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0 => Self::Unhashed,
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1 => Self::Hashed,
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2 => Self::HashedAndMoved,
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_ => unreachable!(),
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}
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}
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fn from_i64(value: i64) -> Self {
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match value {
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0 => Self::Unhashed,
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1 => Self::Hashed,
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2 => Self::HashedAndMoved,
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_ => unreachable!(),
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}
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}
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}
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impl ToBitfield<u64> for HashState {
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fn to_bitfield(self) -> u64 {
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match self {
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Self::Unhashed => 0,
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Self::Hashed => 1,
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Self::HashedAndMoved => 2,
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}
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}
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fn one() -> Self {
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Self::Hashed
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}
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fn zero() -> Self {
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Self::Unhashed
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}
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}
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pub struct HeapObjectHeader<VM: VirtualMachine> {
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pub metadata: AtomicBitfieldContainer<u64>,
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pub marker: PhantomData<VM>,
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}
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impl<VM: VirtualMachine> HeapObjectHeader<VM> {
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pub fn new(metadata: VM::Metadata) -> Self {
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Self {
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metadata: AtomicBitfieldContainer::new(metadata.to_bitfield()),
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marker: PhantomData,
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}
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}
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pub fn hash_state(&self) -> HashState {
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self.metadata.read::<HashStateField>()
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}
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pub fn set_hash_state(&self, state: HashState) {
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self.metadata.update_synchronized::<HashStateField>(state);
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}
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pub fn metadata(&self) -> VM::Metadata {
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VM::Metadata::from_bitfield(self.metadata.read::<MetadataField>() as _)
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}
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pub fn set_metadata(&self, metadata: VM::Metadata) {
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self.metadata.update_synchronized::<MetadataField>(metadata.to_bitfield() as _);
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}
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}
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