servo_base/
id.rs

1/* This Source Code Form is subject to the terms of the Mozilla Public
2 * License, v. 2.0. If a copy of the MPL was not distributed with this
3 * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
4
5//! Namespaces and ids shared by many crates in Servo.
6
7#![allow(clippy::new_without_default)]
8
9use std::cell::Cell;
10use std::fmt;
11use std::marker::PhantomData;
12use std::num::NonZeroU32;
13use std::sync::atomic::{AtomicU32, Ordering};
14use std::sync::{Arc, LazyLock};
15
16use accesskit::{TreeId, Uuid};
17use malloc_size_of::MallocSizeOfOps;
18use malloc_size_of_derive::MallocSizeOf;
19use parking_lot::Mutex;
20use regex::Regex;
21use serde::{Deserialize, Serialize};
22use webrender_api::{
23    ExternalScrollId, FontInstanceKey, FontKey, IdNamespace, ImageKey,
24    PipelineId as WebRenderPipelineId, SpatialTreeItemKey,
25};
26
27use crate::generic_channel::{self, GenericReceiver, GenericSender};
28
29/// Asserts the size of a type at compile time.
30macro_rules! size_of_test {
31    ($t: ty, $expected_size: expr) => {
32        const _: () = assert!(std::mem::size_of::<$t>() == $expected_size);
33    };
34}
35
36/// A type that implements this trait is expected to be used as part of
37/// the [NamespaceIndex] type.
38pub trait Indexable {
39    /// The string prefix to display when debug printing an instance of
40    /// this type.
41    const DISPLAY_PREFIX: &'static str;
42}
43
44#[derive(Clone, Copy, Debug, Deserialize, Eq, Hash, Ord, PartialEq, PartialOrd, Serialize)]
45/// A non-zero index, associated with a particular type.
46pub struct Index<T>(pub NonZeroU32, pub PhantomData<T>);
47
48#[derive(Debug)]
49/// An attempt to create a new [Index] value failed because the index value
50/// was zero.
51pub struct ZeroIndex;
52
53impl<T> Index<T> {
54    /// Creates a new instance of [Index] with the given value.
55    /// Returns an error if the value is zero.
56    pub fn new(value: u32) -> Result<Index<T>, ZeroIndex> {
57        Ok(Index(NonZeroU32::new(value).ok_or(ZeroIndex)?, PhantomData))
58    }
59}
60
61impl<T> malloc_size_of::MallocSizeOf for Index<T> {
62    fn size_of(&self, _ops: &mut MallocSizeOfOps) -> usize {
63        0
64    }
65}
66
67#[derive(
68    Clone, Copy, Deserialize, Eq, Hash, MallocSizeOf, Ord, PartialEq, PartialOrd, Serialize,
69)]
70/// A pipeline-namespaced index associated with a particular type.
71pub struct NamespaceIndex<T> {
72    pub namespace_id: PipelineNamespaceId,
73    pub index: Index<T>,
74}
75
76impl<T> fmt::Debug for NamespaceIndex<T> {
77    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
78        let PipelineNamespaceId(namespace_id) = self.namespace_id;
79        let Index(index, _) = self.index;
80        write!(fmt, "({},{})", namespace_id, index.get())
81    }
82}
83
84impl<T: Indexable> fmt::Display for NamespaceIndex<T> {
85    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
86        write!(fmt, "{}{:?}", T::DISPLAY_PREFIX, self)
87    }
88}
89
90macro_rules! namespace_id {
91    ($id_name:ident, $index_name:ident, $display_prefix:literal) => {
92        #[derive(
93            Clone,
94            Copy,
95            Debug,
96            Deserialize,
97            Eq,
98            Hash,
99            Ord,
100            PartialEq,
101            PartialOrd,
102            Serialize,
103            MallocSizeOf,
104        )]
105        pub struct $index_name;
106        impl Indexable for $index_name {
107            const DISPLAY_PREFIX: &'static str = $display_prefix;
108        }
109        pub type $id_name = NamespaceIndex<$index_name>;
110        impl $id_name {
111            pub fn new() -> $id_name {
112                PIPELINE_NAMESPACE.with(|tls| {
113                    let mut namespace = tls.get().expect("No namespace set for this thread!");
114                    let next_id = namespace.next_namespace_index();
115                    tls.set(Some(namespace));
116                    next_id
117                })
118            }
119        }
120    };
121}
122
123#[derive(Debug, Deserialize, Serialize)]
124/// Request a pipeline-namespace id from the constellation.
125pub struct PipelineNamespaceRequest(pub GenericSender<PipelineNamespaceId>);
126
127/// A per-process installer of pipeline-namespaces.
128pub struct PipelineNamespaceInstaller {
129    request_sender: Option<GenericSender<PipelineNamespaceRequest>>,
130    namespace_sender: GenericSender<PipelineNamespaceId>,
131    namespace_receiver: GenericReceiver<PipelineNamespaceId>,
132}
133
134impl Default for PipelineNamespaceInstaller {
135    fn default() -> Self {
136        let (namespace_sender, namespace_receiver) =
137            generic_channel::channel().expect("PipelineNamespaceInstaller channel failure");
138        Self {
139            request_sender: None,
140            namespace_sender,
141            namespace_receiver,
142        }
143    }
144}
145
146impl PipelineNamespaceInstaller {
147    /// Provide a request sender to send requests to the constellation.
148    pub fn set_sender(&mut self, sender: GenericSender<PipelineNamespaceRequest>) {
149        self.request_sender = Some(sender);
150    }
151
152    /// Install a namespace, requesting a new Id from the constellation.
153    pub fn install_namespace(&self) {
154        match self.request_sender.as_ref() {
155            Some(sender) => {
156                let _ = sender.send(PipelineNamespaceRequest(self.namespace_sender.clone()));
157                let namespace_id = self
158                    .namespace_receiver
159                    .recv()
160                    .expect("The constellation to make a pipeline namespace id available");
161                PipelineNamespace::install(namespace_id);
162            },
163            None => unreachable!("PipelineNamespaceInstaller should have a request_sender setup"),
164        }
165    }
166}
167
168/// A per-process unique pipeline-namespace-installer.
169/// Accessible via PipelineNamespace.
170///
171/// Use PipelineNamespace::set_installer_sender to initiate with a sender to the constellation,
172/// when a new process has been created.
173///
174/// Use PipelineNamespace::fetch_install to install a unique pipeline-namespace from the calling thread.
175static PIPELINE_NAMESPACE_INSTALLER: LazyLock<Arc<Mutex<PipelineNamespaceInstaller>>> =
176    LazyLock::new(|| Arc::new(Mutex::new(PipelineNamespaceInstaller::default())));
177
178/// Each pipeline ID needs to be unique. However, it also needs to be possible to
179/// generate the pipeline ID from an iframe element (this simplifies a lot of other
180/// code that makes use of pipeline IDs).
181///
182/// To achieve this, each pipeline index belongs to a particular namespace. There is
183/// a namespace for the constellation thread, and also one for every script thread.
184///
185/// A namespace can be installed for any other thread in a process
186/// where an pipeline-installer has been initialized.
187///
188/// This allows pipeline IDs to be generated by any of those threads without conflicting
189/// with pipeline IDs created by other script threads or the constellation. The
190/// constellation is the only code that is responsible for creating new *namespaces*.
191/// This ensures that namespaces are always unique, even when using multi-process mode.
192///
193/// It may help conceptually to think of the namespace ID as an identifier for the
194/// thread that created this pipeline ID - however this is really an implementation
195/// detail so shouldn't be relied upon in code logic. It's best to think of the
196/// pipeline ID as a simple unique identifier that doesn't convey any more information.
197#[derive(Clone, Copy)]
198pub struct PipelineNamespace {
199    id: PipelineNamespaceId,
200    index: u32,
201}
202
203impl PipelineNamespace {
204    /// Install a namespace for a given Id.
205    pub fn install(namespace_id: PipelineNamespaceId) {
206        PIPELINE_NAMESPACE.with(|tls| {
207            assert!(tls.get().is_none());
208            tls.set(Some(PipelineNamespace {
209                id: namespace_id,
210                index: 0,
211            }));
212        });
213    }
214
215    /// Setup the pipeline-namespace-installer, by providing it with a sender to the constellation.
216    /// Idempotent in single-process mode.
217    pub fn set_installer_sender(sender: GenericSender<PipelineNamespaceRequest>) {
218        PIPELINE_NAMESPACE_INSTALLER.lock().set_sender(sender);
219    }
220
221    /// Install a namespace in the current thread, without requiring having a namespace Id ready.
222    /// Panics if called more than once per thread.
223    pub fn auto_install() {
224        // Note that holding the lock for the duration of the call is irrelevant to performance,
225        // since a thread would have to block on the ipc-response from the constellation,
226        // with the constellation already acting as a global lock on namespace ids,
227        // and only being able to handle one request at a time.
228        //
229        // Hence, any other thread attempting to concurrently install a namespace
230        // would have to wait for the current call to finish, regardless of the lock held here.
231        PIPELINE_NAMESPACE_INSTALLER.lock().install_namespace();
232    }
233
234    fn next_index(&mut self) -> NonZeroU32 {
235        self.index += 1;
236        NonZeroU32::new(self.index).expect("pipeline id index wrapped!")
237    }
238
239    fn next_namespace_index<T>(&mut self) -> NamespaceIndex<T> {
240        NamespaceIndex {
241            namespace_id: self.id,
242            index: Index(self.next_index(), PhantomData),
243        }
244    }
245}
246
247thread_local!(pub static PIPELINE_NAMESPACE: Cell<Option<PipelineNamespace>> = const { Cell::new(None) });
248
249#[derive(
250    Clone, Copy, Debug, Deserialize, Eq, Hash, MallocSizeOf, Ord, PartialEq, PartialOrd, Serialize,
251)]
252pub struct PipelineNamespaceId(pub u32);
253
254pub const EMBEDDER_PIPELINE_NAMESPACE_ID: PipelineNamespaceId = PipelineNamespaceId(0);
255pub const CONSTELLATION_PIPELINE_NAMESPACE_ID: PipelineNamespaceId = PipelineNamespaceId(1);
256/// The next available [`PipelineNamespaceId`] for the allocation in the constellation. Starting from 2,
257/// since we reserved namespace 0 for the embedder, and 1 for the constellation.
258pub const FIRST_CONTENT_PIPELINE_NAMESPACE_ID: PipelineNamespaceId = PipelineNamespaceId(2);
259
260namespace_id! {PipelineId, PipelineIndex, "Pipeline"}
261
262size_of_test!(PipelineId, 8);
263size_of_test!(Option<PipelineId>, 8);
264
265impl PipelineId {
266    pub fn root_scroll_id(&self) -> webrender_api::ExternalScrollId {
267        ExternalScrollId(0, self.into())
268    }
269}
270
271impl From<PipelineId> for TreeId {
272    /// Return the AccessKit [`TreeId`] for this [`PipelineId`], assuming it represents a document.
273    ///
274    /// This is a pure function of the namespace id and index values, allowing us to graft pipelines
275    /// into `WebView`s (or other pipelines) without IPC, but it also means you can’t have multiple
276    /// instances of [`Servo`] in a single application, because the tree ids would conflict.
277    ///
278    /// [`Servo`]: https://doc.servo.org/servo/struct.Servo.html
279    fn from(pipeline_id: PipelineId) -> TreeId {
280        const PIPELINE_IDS: Uuid = Uuid::from_u128(0x429419c0_3277_47eb_8d31_7573b97621ee);
281        let with_namespace_id =
282            Uuid::new_v5(&PIPELINE_IDS, &pipeline_id.namespace_id.0.to_be_bytes());
283        let with_index = Uuid::new_v5(&with_namespace_id, &pipeline_id.index.0.get().to_be_bytes());
284        TreeId(with_index)
285    }
286}
287
288impl From<PipelineId> for u64 {
289    fn from(pipeline_id: PipelineId) -> Self {
290        ((pipeline_id.namespace_id.0 as u64) << 32) + pipeline_id.index.0.get() as u64
291    }
292}
293
294#[cfg(test)]
295#[test]
296fn test_pipeline_id_to_accesskit_tree_id() {
297    let namespace_id = PipelineNamespaceId(1);
298    let index = Index::new(1).expect("Guaranteed by argument");
299    let pipeline_id = PipelineId {
300        namespace_id,
301        index,
302    };
303    assert_eq!(
304        TreeId::from(pipeline_id),
305        TreeId(Uuid::from_u128(0x879211fb_8799_5492_9a31_95a35c05a192))
306    );
307}
308
309impl From<WebRenderPipelineId> for PipelineId {
310    #[expect(unsafe_code)]
311    fn from(pipeline: WebRenderPipelineId) -> Self {
312        let WebRenderPipelineId(namespace_id, index) = pipeline;
313        unsafe {
314            PipelineId {
315                namespace_id: PipelineNamespaceId(namespace_id),
316                index: Index(NonZeroU32::new_unchecked(index), PhantomData),
317            }
318        }
319    }
320}
321
322impl From<PipelineId> for WebRenderPipelineId {
323    fn from(value: PipelineId) -> Self {
324        let PipelineNamespaceId(namespace_id) = value.namespace_id;
325        let Index(index, _) = value.index;
326        WebRenderPipelineId(namespace_id, index.get())
327    }
328}
329
330impl From<&PipelineId> for WebRenderPipelineId {
331    fn from(value: &PipelineId) -> Self {
332        (*value).into()
333    }
334}
335
336namespace_id! {BrowsingContextId, BrowsingContextIndex, "BrowsingContext"}
337
338size_of_test!(BrowsingContextId, 8);
339size_of_test!(Option<BrowsingContextId>, 8);
340
341#[derive(Clone, Copy, Debug, Default, Eq, Hash, PartialEq)]
342pub struct BrowsingContextGroupId(pub u32);
343impl fmt::Display for BrowsingContextGroupId {
344    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
345        write!(f, "BrowsingContextGroup{:?}", self)
346    }
347}
348
349impl BrowsingContextId {
350    pub fn from_string(str: &str) -> Option<BrowsingContextId> {
351        let re = Regex::new(r"^BrowsingContext\((\d+),(\d+)\)$").ok()?;
352        let caps = re.captures(str)?;
353        let namespace_id = caps.get(1)?.as_str().parse::<u32>().ok()?;
354        let index = caps.get(2)?.as_str().parse::<u32>().ok()?;
355
356        let result = BrowsingContextId {
357            namespace_id: PipelineNamespaceId(namespace_id),
358            index: Index::new(index).ok()?,
359        };
360        assert_eq!(result.to_string(), str.to_string());
361        Some(result)
362    }
363}
364
365#[derive(
366    Clone, Copy, Debug, Deserialize, Eq, Hash, MallocSizeOf, Ord, PartialEq, PartialOrd, Serialize,
367)]
368pub struct WebViewId(PainterId, BrowsingContextId);
369
370size_of_test!(WebViewId, 12);
371size_of_test!(Option<WebViewId>, 12);
372
373impl fmt::Display for WebViewId {
374    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
375        write!(f, "{}, TopLevel{}", self.0, self.1)
376    }
377}
378
379impl From<WebViewId> for SpatialTreeItemKey {
380    fn from(webview_id: WebViewId) -> Self {
381        Self::new(webview_id.1.index.0.get() as u64, 0)
382    }
383}
384
385impl WebViewId {
386    pub fn new(painter_id: PainterId) -> WebViewId {
387        WebViewId(painter_id, BrowsingContextId::new())
388    }
389
390    pub fn mock_for_testing(browsing_context_id: BrowsingContextId) -> WebViewId {
391        WebViewId(TEST_PAINTER_ID, browsing_context_id)
392    }
393}
394
395impl From<WebViewId> for BrowsingContextId {
396    fn from(id: WebViewId) -> BrowsingContextId {
397        id.1
398    }
399}
400
401impl From<WebViewId> for PainterId {
402    fn from(id: WebViewId) -> PainterId {
403        id.0
404    }
405}
406
407impl PartialEq<WebViewId> for BrowsingContextId {
408    fn eq(&self, rhs: &WebViewId) -> bool {
409        self.eq(&rhs.1)
410    }
411}
412
413impl PartialEq<BrowsingContextId> for WebViewId {
414    fn eq(&self, rhs: &BrowsingContextId) -> bool {
415        self.1.eq(rhs)
416    }
417}
418
419namespace_id! {MessagePortId, MessagePortIndex, "MessagePort"}
420
421namespace_id! {MessagePortRouterId, MessagePortRouterIndex, "MessagePortRouter"}
422
423namespace_id! {BroadcastChannelRouterId, BroadcastChannelRouterIndex, "BroadcastChannelRouter"}
424
425namespace_id! {ServiceWorkerId, ServiceWorkerIndex, "ServiceWorker"}
426
427namespace_id! {ServiceWorkerRegistrationId, ServiceWorkerRegistrationIndex, "ServiceWorkerRegistration"}
428
429namespace_id! {BlobId, BlobIndex, "Blob"}
430
431namespace_id! {FileId, FileIndex, "File"}
432
433namespace_id! {FileListId, FileListIndex, "FileList"}
434
435namespace_id! {DomPointId, DomPointIndex, "DomPoint"}
436
437namespace_id! {DomRectId, DomRectIndex, "DomRect"}
438
439namespace_id! {DomQuadId, DomQuadIndex, "DomQuad"}
440
441namespace_id! {DomMatrixId, DomMatrixIndex, "DomMatrix"}
442
443namespace_id! {DomExceptionId, DomExceptionIndex, "DomException"}
444
445namespace_id! {QuotaExceededErrorId, QuotaExceededErrorIndex, "QuotaExceededError"}
446
447namespace_id! {HistoryStateId, HistoryStateIndex, "HistoryState"}
448
449namespace_id! {ImageBitmapId, ImageBitmapIndex, "ImageBitmap"}
450
451namespace_id! {OffscreenCanvasId, OffscreenCanvasIndex, "OffscreenCanvas"}
452
453namespace_id! {CookieStoreId, CookieStoreIndex, "CookieStore"}
454
455namespace_id! {ImageDataId, ImageDataIndex, "ImageData"}
456
457// We provide ids just for unit testing.
458pub const TEST_NAMESPACE: PipelineNamespaceId = PipelineNamespaceId(1234);
459pub const TEST_PIPELINE_INDEX: Index<PipelineIndex> =
460    Index(NonZeroU32::new(5678).unwrap(), PhantomData);
461pub const TEST_PIPELINE_ID: PipelineId = PipelineId {
462    namespace_id: TEST_NAMESPACE,
463    index: TEST_PIPELINE_INDEX,
464};
465pub const TEST_BROWSING_CONTEXT_INDEX: Index<BrowsingContextIndex> =
466    Index(NonZeroU32::new(8765).unwrap(), PhantomData);
467pub const TEST_BROWSING_CONTEXT_ID: BrowsingContextId = BrowsingContextId {
468    namespace_id: TEST_NAMESPACE,
469    index: TEST_BROWSING_CONTEXT_INDEX,
470};
471
472pub const TEST_PAINTER_ID: PainterId = PainterId(9999);
473pub const TEST_WEBVIEW_ID: WebViewId = WebViewId(TEST_PAINTER_ID, TEST_BROWSING_CONTEXT_ID);
474pub const TEST_SCRIPT_EVENT_LOOP_ID: ScriptEventLoopId = ScriptEventLoopId(1234);
475
476/// An id for a ScrollTreeNode in the ScrollTree. This contains both the index
477/// to the node in the tree's array of nodes as well as the corresponding SpatialId
478/// for the SpatialNode in the WebRender display list.
479#[derive(Clone, Copy, Debug, Default, Deserialize, MallocSizeOf, PartialEq, Serialize)]
480pub struct ScrollTreeNodeId {
481    /// The index of this scroll tree node in the tree's array of nodes.
482    pub index: usize,
483}
484
485static PAINTER_ID: AtomicU32 = AtomicU32::new(1);
486
487#[derive(
488    Clone, Copy, Debug, PartialEq, PartialOrd, Ord, Hash, Eq, Serialize, Deserialize, MallocSizeOf,
489)]
490pub struct PainterId(u32);
491
492impl fmt::Display for PainterId {
493    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
494        write!(f, "PainterId: {}", self.0)
495    }
496}
497
498impl PainterId {
499    pub fn next() -> Self {
500        Self(PAINTER_ID.fetch_add(1, Ordering::Relaxed))
501    }
502}
503
504impl From<PainterId> for IdNamespace {
505    fn from(painter_id: PainterId) -> Self {
506        IdNamespace(painter_id.0)
507    }
508}
509
510impl From<IdNamespace> for PainterId {
511    fn from(id_namespace: IdNamespace) -> Self {
512        PainterId(id_namespace.0)
513    }
514}
515
516impl From<FontKey> for PainterId {
517    fn from(font_key: FontKey) -> Self {
518        font_key.0.into()
519    }
520}
521
522impl From<FontInstanceKey> for PainterId {
523    fn from(font_instance_key: FontInstanceKey) -> Self {
524        font_instance_key.0.into()
525    }
526}
527
528impl From<ImageKey> for PainterId {
529    fn from(image_key: ImageKey) -> Self {
530        image_key.0.into()
531    }
532}
533
534static SCRIPT_EVENT_LOOP_ID: AtomicU32 = AtomicU32::new(1);
535thread_local!(pub static INSTALLED_SCRIPT_EVENT_LOOP_ID: Cell<Option<ScriptEventLoopId>> =
536    const { Cell::new(None) });
537
538#[derive(
539    Clone, Copy, Debug, PartialEq, PartialOrd, Ord, Hash, Eq, Serialize, Deserialize, MallocSizeOf,
540)]
541pub struct ScriptEventLoopId(u32);
542
543impl ScriptEventLoopId {
544    pub fn new() -> Self {
545        Self(SCRIPT_EVENT_LOOP_ID.fetch_add(1, Ordering::Relaxed))
546    }
547
548    /// Each script and layout thread should have the [`ScriptEventLoopId`] installed,
549    /// since it is used by crash reporting.
550    pub fn install(id: Self) {
551        INSTALLED_SCRIPT_EVENT_LOOP_ID.with(|tls| tls.set(Some(id)))
552    }
553
554    pub fn installed() -> Option<Self> {
555        INSTALLED_SCRIPT_EVENT_LOOP_ID.with(|tls| tls.get())
556    }
557}
558
559impl fmt::Display for ScriptEventLoopId {
560    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
561        write!(f, "{}", self.0)
562    }
563}
servo_base/id.rs

servo_base/
id.rs
