1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520
mod forward_transition;
pub(crate) mod template;
#[cfg(test)]
mod tests;
use std::{collections::hash_map::RandomState, hash::Hash};
use bitflags::bitflags;
use boa_gc::{empty_trace, Finalize, Gc, Trace, WeakGc};
use indexmap::IndexMap;
use crate::{object::JsPrototype, property::PropertyKey, JsObject};
use self::forward_transition::ForwardTransition;
use super::{
property_table::PropertyTable, slot::SlotAttributes, ChangeTransition, ChangeTransitionAction,
Slot, UniqueShape,
};
/// Represent a [`SharedShape`] property transition.
#[derive(Debug, Finalize, Clone, PartialEq, Eq, Hash)]
pub(crate) struct TransitionKey {
pub(crate) property_key: PropertyKey,
pub(crate) attributes: SlotAttributes,
}
// SAFETY: Non of the member of this struct are garbage collected,
// so this should be fine.
unsafe impl Trace for TransitionKey {
empty_trace!();
}
const INSERT_PROPERTY_TRANSITION_TYPE: u8 = 0b0000_0000;
const CONFIGURE_PROPERTY_TRANSITION_TYPE: u8 = 0b0000_0001;
const PROTOTYPE_TRANSITION_TYPE: u8 = 0b0000_0010;
// Reserved for future use!
#[allow(unused)]
const RESEREVED_TRANSITION_TYPE: u8 = 0b0000_0011;
bitflags! {
/// Flags of a shape.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Finalize)]
pub struct ShapeFlags: u8 {
/// Represents the transition type of a [`SharedShape`].
const TRANSITION_TYPE = 0b0000_0011;
}
}
impl Default for ShapeFlags {
fn default() -> Self {
Self::empty()
}
}
impl ShapeFlags {
// NOTE: Remove type bits and set the new ones.
fn insert_property_transition_from(previous: Self) -> Self {
previous.difference(Self::TRANSITION_TYPE)
| Self::from_bits_retain(INSERT_PROPERTY_TRANSITION_TYPE)
}
fn configure_property_transition_from(previous: Self) -> Self {
previous.difference(Self::TRANSITION_TYPE)
| Self::from_bits_retain(CONFIGURE_PROPERTY_TRANSITION_TYPE)
}
fn prototype_transition_from(previous: Self) -> Self {
previous.difference(Self::TRANSITION_TYPE)
| Self::from_bits_retain(PROTOTYPE_TRANSITION_TYPE)
}
const fn is_insert_transition_type(self) -> bool {
self.intersection(Self::TRANSITION_TYPE).bits() == INSERT_PROPERTY_TRANSITION_TYPE
}
const fn is_prototype_transition_type(self) -> bool {
self.intersection(Self::TRANSITION_TYPE).bits() == PROTOTYPE_TRANSITION_TYPE
}
}
// SAFETY: Non of the member of this struct are garbage collected,
// so this should be fine.
unsafe impl Trace for ShapeFlags {
empty_trace!();
}
/// The internal representation of a [`SharedShape`].
#[derive(Debug, Trace, Finalize)]
struct Inner {
/// See [`ForwardTransition`].
forward_transitions: ForwardTransition,
/// The count of how many properties this [`SharedShape`] holds.
property_count: u32,
/// Instance prototype `__proto__`.
prototype: JsPrototype,
// SAFETY: This is safe because nothing in [`PropertyTable`]
// needs tracing
#[unsafe_ignore_trace]
property_table: PropertyTable,
/// The previous shape in the transition chain.
///
/// [`None`] if it is the root shape.
previous: Option<SharedShape>,
/// How many transitions have happened from the root node.
transition_count: u16,
/// Flags about the shape.
flags: ShapeFlags,
}
/// Represents a shared object shape.
#[derive(Debug, Trace, Finalize, Clone)]
pub struct SharedShape {
inner: Gc<Inner>,
}
impl SharedShape {
fn property_table(&self) -> &PropertyTable {
&self.inner.property_table
}
/// Return the property count that this shape owns in the [`PropertyTable`].
fn property_count(&self) -> u32 {
self.inner.property_count
}
/// Return the index to the property in the the [`PropertyTable`].
fn property_index(&self) -> u32 {
self.inner.property_count.saturating_sub(1)
}
/// Getter for the transition count field.
#[must_use]
pub fn transition_count(&self) -> u16 {
self.inner.transition_count
}
/// Getter for the previous field.
#[must_use]
pub fn previous(&self) -> Option<&Self> {
self.inner.previous.as_ref()
}
/// Get the prototype of the shape.
#[must_use]
pub fn prototype(&self) -> JsPrototype {
self.inner.prototype.clone()
}
/// Get the property this [`SharedShape`] refers to.
pub(crate) fn property(&self) -> (PropertyKey, Slot) {
let inner = self.property_table().inner().borrow();
let (key, slot) = inner
.keys
.get(self.property_index() as usize)
.expect("There should be a property");
(key.clone(), *slot)
}
/// Get the flags of the shape.
fn flags(&self) -> ShapeFlags {
self.inner.flags
}
/// Getter for the [`ForwardTransition`] field.
fn forward_transitions(&self) -> &ForwardTransition {
&self.inner.forward_transitions
}
/// Check if the shape has the given prototype.
#[must_use]
pub fn has_prototype(&self, prototype: &JsObject) -> bool {
self.inner
.prototype
.as_ref()
.map_or(false, |this| this == prototype)
}
/// Create a new [`SharedShape`].
fn new(inner: Inner) -> Self {
Self {
inner: Gc::new(inner),
}
}
/// Create a root [`SharedShape`].
#[must_use]
pub(crate) fn root() -> Self {
Self::new(Inner {
forward_transitions: ForwardTransition::default(),
prototype: None,
property_count: 0,
property_table: PropertyTable::default(),
previous: None,
flags: ShapeFlags::default(),
transition_count: 0,
})
}
/// Create a [`SharedShape`] change prototype transition.
pub(crate) fn change_prototype_transition(&self, prototype: JsPrototype) -> Self {
if let Some(shape) = self.forward_transitions().get_prototype(&prototype) {
if let Some(inner) = shape.upgrade() {
return Self { inner };
}
self.forward_transitions().prune_prototype_transitions();
}
let new_inner_shape = Inner {
forward_transitions: ForwardTransition::default(),
prototype: prototype.clone(),
property_table: self.property_table().clone(),
property_count: self.property_count(),
previous: Some(self.clone()),
transition_count: self.transition_count() + 1,
flags: ShapeFlags::prototype_transition_from(self.flags()),
};
let new_shape = Self::new(new_inner_shape);
self.forward_transitions()
.insert_prototype(prototype, &new_shape.inner);
new_shape
}
/// Create a [`SharedShape`] insert property transition.
pub(crate) fn insert_property_transition(&self, key: TransitionKey) -> Self {
// Check if we have already created such a transition, if so use it!
if let Some(shape) = self.forward_transitions().get_property(&key) {
if let Some(inner) = shape.upgrade() {
return Self { inner };
}
self.forward_transitions().prune_property_transitions();
}
let property_table = self.property_table().add_property_deep_clone_if_needed(
key.property_key.clone(),
key.attributes,
self.property_count(),
);
let new_inner_shape = Inner {
prototype: self.prototype(),
forward_transitions: ForwardTransition::default(),
property_table,
property_count: self.property_count() + 1,
previous: Some(self.clone()),
transition_count: self.transition_count() + 1,
flags: ShapeFlags::insert_property_transition_from(self.flags()),
};
let new_shape = Self::new(new_inner_shape);
self.forward_transitions()
.insert_property(key, &new_shape.inner);
new_shape
}
/// Create a [`SharedShape`] change prototype transition, returning [`ChangeTransition`].
pub(crate) fn change_attributes_transition(
&self,
key: TransitionKey,
) -> ChangeTransition<Self> {
let slot = self.property_table().get_expect(&key.property_key);
// Check if we have already created such a transition, if so use it!
if let Some(shape) = self.forward_transitions().get_property(&key) {
if let Some(inner) = shape.upgrade() {
let action = if slot.attributes.width_match(key.attributes) {
ChangeTransitionAction::Nothing
} else if slot.attributes.is_accessor_descriptor() {
// Accessor property --> Data property
ChangeTransitionAction::Remove
} else {
// Data property --> Accessor property
ChangeTransitionAction::Insert
};
return ChangeTransition {
shape: Self { inner },
action,
};
}
self.forward_transitions().prune_property_transitions();
}
// The attribute change transitions, didn't change from accessor to data property or vice-versa.
if slot.attributes.width_match(key.attributes) {
let property_table = self.property_table().deep_clone_all();
property_table.set_attributes_at_index(&key.property_key, key.attributes);
let inner_shape = Inner {
forward_transitions: ForwardTransition::default(),
prototype: self.prototype(),
property_table,
property_count: self.property_count(),
previous: Some(self.clone()),
transition_count: self.transition_count() + 1,
flags: ShapeFlags::configure_property_transition_from(self.flags()),
};
let shape = Self::new(inner_shape);
self.forward_transitions()
.insert_property(key, &shape.inner);
return ChangeTransition {
shape,
action: ChangeTransitionAction::Nothing,
};
}
// Rollback before the property has added.
let (mut base, prototype, transitions) = self.rollback_before(&key.property_key);
// Apply prototype transition, if it was found.
if let Some(prototype) = prototype {
base = base.change_prototype_transition(prototype);
}
// Apply this property.
base = base.insert_property_transition(key);
// Apply previous properties.
for (property_key, attributes) in transitions.into_iter().rev() {
let transition = TransitionKey {
property_key,
attributes,
};
base = base.insert_property_transition(transition);
}
// Determine action to be performed on the storage.
let action = if slot.attributes.is_accessor_descriptor() {
// Accessor property --> Data property
ChangeTransitionAction::Remove
} else {
// Data property --> Accessor property
ChangeTransitionAction::Insert
};
ChangeTransition {
shape: base,
action,
}
}
/// Rollback to shape before the insertion of the [`PropertyKey`] that is provided.
///
/// This returns the shape before the insertion, if it sees a prototype transition it will return the lastest one,
/// ignoring any others, [`None`] otherwise. It also will return the property transitions ordered from
/// latest to oldest that it sees.
///
/// NOTE: In the transitions it does not include the property that we are rolling back.
///
/// NOTE: The prototype transitions if it sees a property insert and then later an attribute change it will condense
/// into one property insert transition with the new attribute in the change attribute transition,
/// in the same place that the property was inserted initially.
//
// For example with the following chain:
//
// INSERT(x) INSERT(y) INSERT(z)
// { } ------------> { x } ------------> { x, y } ------------> { x, y, z }
//
// Then we call rollback on `y`:
//
// INSERT(x) INSERT(y) INSERT(z)
// { } ------------> { x } ------------> { x, y } ------------> { x, y, z }
// ^
// \--- base (with array of transitions to be performed: INSERT(z),
// and protortype: None )
fn rollback_before(
&self,
key: &PropertyKey,
) -> (
Self,
Option<JsPrototype>,
IndexMap<PropertyKey, SlotAttributes>,
) {
let mut prototype = None;
let mut transitions: IndexMap<PropertyKey, SlotAttributes, RandomState> =
IndexMap::default();
let mut current = Some(self);
let base = loop {
let Some(current_shape) = current else {
unreachable!("The chain should have insert transition type!")
};
// We only take the latest prototype change it, if it exists.
if current_shape.flags().is_prototype_transition_type() {
if prototype.is_none() {
prototype = Some(current_shape.prototype().clone());
}
// Skip when it is a prototype transition.
current = current_shape.previous();
continue;
}
let (current_property_key, slot) = current_shape.property();
if current_shape.flags().is_insert_transition_type() && ¤t_property_key == key {
let base = if let Some(base) = current_shape.previous() {
base.clone()
} else {
// It's the root, because it doesn't have previous.
current_shape.clone()
};
break base;
}
// Do not add property that we are trying to delete.
// this can happen if a configure was called after inserting it into the shape
if ¤t_property_key != key {
// Only take the latest changes to a property. To try to build a smaller tree.
transitions
.entry(current_property_key)
.or_insert(slot.attributes);
}
current = current_shape.previous();
};
(base, prototype, transitions)
}
/// Remove a property from [`SharedShape`], returning the new [`SharedShape`].
pub(crate) fn remove_property_transition(&self, key: &PropertyKey) -> Self {
let (mut base, prototype, transitions) = self.rollback_before(key);
// Apply prototype transition, if it was found.
if let Some(prototype) = prototype {
base = base.change_prototype_transition(prototype);
}
for (property_key, attributes) in transitions.into_iter().rev() {
let transition = TransitionKey {
property_key,
attributes,
};
base = base.insert_property_transition(transition);
}
base
}
/// Do a property lookup, returns [`None`] if property not found.
pub(crate) fn lookup(&self, key: &PropertyKey) -> Option<Slot> {
let property_count = self.property_count();
if property_count == 0 {
return None;
}
let property_table_inner = self.property_table().inner().borrow();
if let Some((property_table_index, slot)) = property_table_inner.map.get(key) {
// Check if we are trying to access properties that belong to another shape.
if *property_table_index < self.property_count() {
return Some(*slot);
}
}
None
}
/// Gets all keys first strings then symbols in creation order.
pub(crate) fn keys(&self) -> Vec<PropertyKey> {
let property_table = self.property_table().inner().borrow();
property_table.keys_cloned_n(self.property_count())
}
/// Returns a new [`UniqueShape`] with the properties of the [`SharedShape`].
pub(crate) fn to_unique(&self) -> UniqueShape {
UniqueShape::new(
self.prototype(),
self.property_table()
.inner()
.borrow()
.clone_count(self.property_count()),
)
}
/// Return location in memory of the [`SharedShape`].
pub(crate) fn to_addr_usize(&self) -> usize {
let ptr: *const _ = self.inner.as_ref();
ptr as usize
}
}
/// Represents a weak reference to [`SharedShape`].
#[derive(Debug, Trace, Finalize, Clone, PartialEq)]
pub(crate) struct WeakSharedShape {
inner: WeakGc<Inner>,
}
impl WeakSharedShape {
/// Return location in memory of the [`WeakSharedShape`].
///
/// Returns `0` if the inner [`SharedShape`] has been freed.
#[inline]
#[must_use]
pub(crate) fn to_addr_usize(&self) -> usize {
self.inner.upgrade().map_or(0, |inner| {
let ptr: *const _ = inner.as_ref();
ptr as usize
})
}
/// Upgrade returns a [`SharedShape`] pointer for the internal value if the pointer is still live,
/// or [`None`] if the value was already garbage collected.
#[inline]
#[must_use]
pub(crate) fn upgrade(&self) -> Option<SharedShape> {
Some(SharedShape {
inner: self.inner.upgrade()?,
})
}
}
impl From<&SharedShape> for WeakSharedShape {
fn from(value: &SharedShape) -> Self {
WeakSharedShape {
inner: WeakGc::new(&value.inner),
}
}
}