Quelle intern.rs Sprache: unbekannt

/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */

//! The interning module provides a generic data structure
//! interning container. It is similar in concept to a
//! traditional string interning container, but it is
//! specialized to the WR thread model.
//!
//! There is an Interner structure, that lives in the
//! scene builder thread, and a DataStore structure
//! that lives in the frame builder thread.
//!
//! Hashing, interning and handle creation is done by
//! the interner structure during scene building.
//!
//! Delta changes for the interner are pushed during
//! a transaction to the frame builder. The frame builder
//! is then able to access the content of the interned
//! handles quickly, via array indexing.
//!
//! Epoch tracking ensures that the garbage collection
//! step which the interner uses to remove items is
//! only invoked on items that the frame builder thread
//! is no longer referencing.
//!
//! Items in the data store are stored in a traditional
//! free-list structure, for content access and memory
//! usage efficiency.
//!
//! The epoch is incremented each time a scene is
//! built. The most recently used scene epoch is
//! stored inside each handle. This is then used for
//! cache invalidation.

use crate::internal_types::FastHashMap;
use malloc_size_of::MallocSizeOf;
use std::fmt::Debug;
use std::hash::Hash;
use std::marker::PhantomData;
use std::{ops, u64};
use crate::util::VecHelper;
use crate::profiler::TransactionProfile;
use peek_poke::PeekPoke;

#[cfg_attr(feature = "capture", derive(Serialize))]
#[cfg_attr(feature = "replay", derive(Deserialize))]
#[derive(Debug, Copy, Clone, Hash, MallocSizeOf, PartialEq, Eq)]
struct Epoch(u32);

/// A list of updates to be applied to the data store,
/// provided by the interning structure.
#[cfg_attr(feature = "capture", derive(Serialize))]
#[cfg_attr(feature = "replay", derive(Deserialize))]
#[derive(MallocSizeOf)]
pub struct UpdateList<S> {
 /// Items to insert.
 pub insertions: Vec<Insertion<S>>,

 /// Items to remove.
 pub removals: Vec<Removal>,
}

#[cfg_attr(feature = "capture", derive(Serialize))]
#[cfg_attr(feature = "replay", derive(Deserialize))]
#[derive(MallocSizeOf)]
pub struct Insertion<S> {
 pub index: usize,
 pub uid: ItemUid,
 pub value: S,
}

#[cfg_attr(feature = "capture", derive(Serialize))]
#[cfg_attr(feature = "replay", derive(Deserialize))]
#[derive(MallocSizeOf)]
pub struct Removal {
 pub index: usize,
 pub uid: ItemUid,
}

impl<S> UpdateList<S> {
 fn new() -> UpdateList<S> {
 UpdateList {
 insertions: Vec::new(),
 removals: Vec::new(),
 }
 }

 fn take_and_preallocate(&mut self) -> UpdateList<S> {
 UpdateList {
 insertions: self.insertions.take_and_preallocate(),
 removals: self.removals.take_and_preallocate(),
 }
 }
}

/// A globally, unique identifier
#[cfg_attr(feature = "capture", derive(Serialize))]
#[cfg_attr(feature = "replay", derive(Deserialize))]
#[derive(Debug, Copy, Clone, Eq, Hash, MallocSizeOf, PartialEq, PeekPoke, Default)]
pub struct ItemUid {
 uid: u64,
}

impl ItemUid {
 // Intended for debug usage only
 pub fn get_uid(&self) -> u64 {
 self.uid
 }
}

#[cfg_attr(feature = "capture", derive(Serialize))]
#[cfg_attr(feature = "replay", derive(Deserialize))]
#[derive(Debug, Hash, MallocSizeOf, PartialEq, Eq)]
pub struct Handle {
 index: u32,
 epoch: Epoch,
 _marker: PhantomData,
}

impl Clone for Handle {
 fn clone(&self) -> Self {
 Handle {
 index: self.index,
 epoch: self.epoch,
 _marker: self._marker,
 }
 }
}

impl Copy for Handle {}

impl Handle {
 pub fn uid(&self) -> ItemUid {
 ItemUid {
 // The index in the freelist + the epoch it was interned generates a stable
 // unique id for an interned element.
 uid: ((self.index as u64) << 32) | self.epoch.0 as u64
 }
 }

 pub const INVALID: Self = Handle { index: !0, epoch: Epoch(!0), _marker: PhantomData };
}

pub trait InternDebug {
 fn on_interned(&self, _uid: ItemUid) {}
}

/// The data store lives in the frame builder thread. It
/// contains a free-list of items for fast access.
#[cfg_attr(feature = "capture", derive(Serialize))]
#[cfg_attr(feature = "replay", derive(Deserialize))]
#[derive(MallocSizeOf)]
pub struct DataStore<I: Internable> {
 items: Vec<Option<I::StoreData>>,
}

impl<I: Internable> Default for DataStore {
 fn default() -> Self {
 DataStore {
 items: Vec::new(),
 }
 }
}

impl<I: Internable> DataStore {
 /// Apply any updates from the scene builder thread to
 /// this data store.
 pub fn apply_updates(
 &mut self,
 update_list: UpdateList<I::Key>,
 profile: &mut TransactionProfile,
 ) {
 for insertion in update_list.insertions {
 self.items
 .entry(insertion.index)
 .set(Some(insertion.value.into()));
 }

 for removal in update_list.removals {
 self.items[removal.index] = None;
 }

 profile.set(I::PROFILE_COUNTER, self.items.len());
 }
}

/// Retrieve an item from the store via handle
impl<I: Internable> ops::Index<Handle> for DataStore {
 type Output = I::StoreData;
 fn index(&self, handle: Handle) -> &I::StoreData {
 self.items[handle.index as usize].as_ref().expect("Bad datastore lookup")
 }
}

/// Retrieve a mutable item from the store via handle
/// Retrieve an item from the store via handle
impl<I: Internable> ops::IndexMut<Handle> for DataStore {
 fn index_mut(&mut self, handle: Handle) -> &mut I::StoreData {
 self.items[handle.index as usize].as_mut().expect("Bad datastore lookup")
 }
}

#[cfg_attr(feature = "capture", derive(Serialize))]
#[cfg_attr(feature = "replay", derive(Deserialize))]
#[derive(MallocSizeOf)]
struct ItemDetails {
 /// Frame that this element was first interned
 interned_epoch: Epoch,
 /// Last frame this element was referenced (used to GC intern items)
 last_used_epoch: Epoch,
 /// Index into the freelist this item is located
 index: usize,
 /// Type marker for create_handle method
 _marker: PhantomData,
}

impl ItemDetails {
 /// Construct a stable handle value from the item details
 fn create_handle(&self) -> Handle {
 Handle {
 index: self.index as u32,
 epoch: self.interned_epoch,
 _marker: PhantomData,
 }
 }
}

/// The main interning data structure. This lives in the
/// scene builder thread, and handles hashing and interning
/// unique data structures. It also manages a free-list for
/// the items in the data store, which is synchronized via
/// an update list of additions / removals.
#[cfg_attr(feature = "capture", derive(Serialize))]
#[cfg_attr(feature = "replay", derive(Deserialize))]
#[derive(MallocSizeOf)]
pub struct Interner<I: Internable> {
 /// Uniquely map an interning key to a handle
 map: FastHashMap<I::Key, ItemDetails>,
 /// List of free slots in the data store for re-use.
 free_list: Vec<usize>,
 /// Pending list of updates that need to be applied.
 update_list: UpdateList<I::Key>,
 /// The current epoch for the interner.
 current_epoch: Epoch,
 /// The information associated with each interned
 /// item that can be accessed by the interner.
 local_data: Vec<I::InternData>,
}

impl<I: Internable> Default for Interner {
 fn default() -> Self {
 Interner {
 map: FastHashMap::default(),
 free_list: Vec::new(),
 update_list: UpdateList::new(),
 current_epoch: Epoch(1),
 local_data: Vec::new(),
 }
 }
}

impl<I: Internable> Interner {
 /// Intern a data structure, and return a handle to
 /// that data. The handle can then be stored in the
 /// frame builder, and safely accessed via the data
 /// store that lives in the frame builder thread.
 /// The provided closure is invoked to build the
 /// local data about an interned structure if the
 /// key isn't already interned.
 pub fn intern<F>(
 &mut self,
 data: &I::Key,
 fun: F,
 ) -> Handle where F: FnOnce() -> I::InternData {
 // Use get_mut rather than entry here to avoid
 // cloning the (sometimes large) key in the common
 // case, where the data already exists in the interner.
 if let Some(details) = self.map.get_mut(data) {
 // Update the last referenced frame for this element
 details.last_used_epoch = self.current_epoch;
 // Return a stable handle value for dependency checking
 return details.create_handle();
 }

 // We need to intern a new data item. First, find out
 // if there is a spare slot in the free-list that we
 // can use. Otherwise, append to the end of the list.
 let index = match self.free_list.pop() {
 Some(index) => index,
 None => self.local_data.len(),
 };

 // Generate a handle for access via the data store.
 let handle = Handle {
 index: index as u32,
 epoch: self.current_epoch,
 _marker: PhantomData,
 };

 let uid = handle.uid();

 // Add a pending update to insert the new data.
 self.update_list.insertions.push(Insertion {
 index,
 uid,
 value: data.clone(),
 });

 #[cfg(debug_assertions)]
 data.on_interned(uid);

 // Store this handle so the next time it is
 // interned, it gets re-used.
 self.map.insert(data.clone(), ItemDetails {
 interned_epoch: self.current_epoch,
 last_used_epoch: self.current_epoch,
 index,
 _marker: PhantomData,
 });

 // Create the local data for this item that is
 // being interned.
 self.local_data.entry(index).set(fun());

 handle
 }

 /// Retrieve the pending list of updates for an interner
 /// that need to be applied to the data store. Also run
 /// a GC step that removes old entries.
 pub fn end_frame_and_get_pending_updates(&mut self) -> UpdateList<I::Key> {
 let mut update_list = self.update_list.take_and_preallocate();

 let free_list = &mut self.free_list;
 let current_epoch = self.current_epoch.0;

 // First, run a GC step. Walk through the handles, and
 // if we find any that haven't been used for some time,
 // remove them. If this ever shows up in profiles, we
 // can make the GC step partial (scan only part of the
 // map each frame). It also might make sense in the
 // future to adjust how long items remain in the cache
 // based on the current size of the list.
 self.map.retain(|_, details| {
 if details.last_used_epoch.0 + 10 < current_epoch {
 // To expire an item:
 // - Add index to the free-list for re-use.
 // - Add an update to the data store to invalidate this slot.
 // - Remove from the hash map.
 free_list.push(details.index);
 update_list.removals.push(Removal {
 index: details.index,
 uid: details.create_handle().uid(),
 });
 return false;
 }

 true
 });

 // Begin the next epoch
 self.current_epoch = Epoch(self.current_epoch.0 + 1);

 update_list
 }
}

/// Retrieve the local data for an item from the interner via handle
impl<I: Internable> ops::Index<Handle> for Interner {
 type Output = I::InternData;
 fn index(&self, handle: Handle) -> &I::InternData {
 &self.local_data[handle.index as usize]
 }
}

/// Meta-macro to enumerate the various interner identifiers and types.
///
/// IMPORTANT: Keep this synchronized with the list in mozilla-central located at
/// gfx/webrender_bindings/webrender_ffi.h
///
/// Note that this could be a lot less verbose if concat_idents! were stable. :-(
#[macro_export]
macro_rules! enumerate_interners {
 ($macro_name: ident) => {
 $macro_name! {
 clip: ClipIntern,
 prim: PrimitiveKeyKind,
 normal_border: NormalBorderPrim,
 image_border: ImageBorder,
 image: Image,
 yuv_image: YuvImage,
 line_decoration: LineDecoration,
 linear_grad: LinearGradient,
 radial_grad: RadialGradient,
 conic_grad: ConicGradient,
 picture: Picture,
 text_run: TextRun,
 filter_data: FilterDataIntern,
 backdrop_capture: BackdropCapture,
 backdrop_render: BackdropRender,
 polygon: PolygonIntern,
 box_shadow: BoxShadow,
 }
 }
}

macro_rules! declare_interning_memory_report {
 ( $( $name:ident: $ty:ident, )+ ) => {
 ///
 #[repr(C)]
 #[derive(AddAssign, Clone, Debug, Default)]
 pub struct InternerSubReport {
 $(
 ///
 pub $name: usize,
 )+
 }
 }
}

enumerate_interners!(declare_interning_memory_report);

/// Memory report for interning-related data structures.
/// cbindgen:derive-eq=false
/// cbindgen:derive-ostream=false
#[repr(C)]
#[derive(Clone, Debug, Default)]
pub struct InterningMemoryReport {
 ///
 pub interners: InternerSubReport,
 ///
 pub data_stores: InternerSubReport,
}

impl ::std::ops::AddAssign for InterningMemoryReport {
 fn add_assign(&mut self, other: InterningMemoryReport) {
 self.interners += other.interners;
 self.data_stores += other.data_stores;
 }
}

// The trick to make trait bounds configurable by features.
mod dummy {
 #[cfg(not(feature = "capture"))]
 pub trait Serialize {}
 #[cfg(not(feature = "capture"))]
 impl<T> Serialize for T {}
 #[cfg(not(feature = "replay"))]
 pub trait Deserialize<'a> {}
 #[cfg(not(feature = "replay"))]
 impl<'a, T> Deserialize<'a> for T {}
}
#[cfg(feature = "capture")]
use serde::Serialize as InternSerialize;
#[cfg(not(feature = "capture"))]
use self::dummy::Serialize as InternSerialize;
#[cfg(feature = "replay")]
use serde::Deserialize as InternDeserialize;
#[cfg(not(feature = "replay"))]
use self::dummy::Deserialize as InternDeserialize;

/// Implement `Internable` for a type that wants to participate in interning.
pub trait Internable: MallocSizeOf {
 type Key: Eq + Hash + Clone + Debug + MallocSizeOf + InternDebug + InternSerialize + for<'a> InternDeserialize<'a>;
 type StoreData: From<Self::Key> + MallocSizeOf + InternSerialize + for<'a> InternDeserialize<'a>;
 type InternData: MallocSizeOf + InternSerialize + for<'a> InternDeserialize<'a>;

 // Profile counter indices, see the list in profiler.rs
 const PROFILE_COUNTER: usize;
}

Quelle intern.rs Sprache: unbekannt

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