121 lines
4.6 KiB
JavaScript
121 lines
4.6 KiB
JavaScript
'use strict';
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const v8Util = process.electronBinding('v8_util');
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const getOwnerKey = (webContents, contextId) => {
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return `${webContents.id}-${contextId}`;
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};
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class ObjectsRegistry {
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constructor() {
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this.nextId = 0;
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// Stores all objects by ref-counting.
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// (id) => {object, count}
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this.storage = {};
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// Stores the IDs + refCounts of objects referenced by WebContents.
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// (ownerKey) => { id: refCount }
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this.owners = {};
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}
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// Register a new object and return its assigned ID. If the object is already
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// registered then the already assigned ID would be returned.
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add(webContents, contextId, obj) {
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// Get or assign an ID to the object.
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const id = this.saveToStorage(obj);
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// Add object to the set of referenced objects.
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const ownerKey = getOwnerKey(webContents, contextId);
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let owner = this.owners[ownerKey];
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if (!owner) {
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owner = this.owners[ownerKey] = new Map();
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this.registerDeleteListener(webContents, contextId);
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}
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if (!owner.has(id)) {
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owner.set(id, 0);
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// Increase reference count if not referenced before.
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this.storage[id].count++;
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}
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owner.set(id, owner.get(id) + 1);
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return id;
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}
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// Get an object according to its ID.
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get(id) {
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const pointer = this.storage[id];
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if (pointer != null)
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return pointer.object;
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}
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// Dereference an object according to its ID.
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// Note that an object may be double-freed (cleared when page is reloaded, and
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// then garbage collected in old page).
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// rendererSideRefCount is the ref count that the renderer process reported
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// at time of GC if this is different to the number of references we sent to
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// the given owner then a GC occurred between a ref being sent and the value
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// being pulled out of the weak map.
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// In this case we decrement out ref count and do not delete the stored
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// object
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// For more details on why we do renderer side ref counting see
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// https://github.com/electron/electron/pull/17464
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remove(webContents, contextId, id, rendererSideRefCount) {
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const ownerKey = getOwnerKey(webContents, contextId);
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const owner = this.owners[ownerKey];
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if (owner && owner.has(id)) {
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const newRefCount = owner.get(id) - rendererSideRefCount;
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// Only completely remove if the number of references GCed in the
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// renderer is the same as the number of references we sent them
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if (newRefCount <= 0) {
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// Remove the reference in owner.
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owner.delete(id);
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// Dereference from the storage.
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this.dereference(id);
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}
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else {
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owner.set(id, newRefCount);
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}
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}
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}
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// Clear all references to objects refrenced by the WebContents.
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clear(webContents, contextId) {
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const ownerKey = getOwnerKey(webContents, contextId);
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const owner = this.owners[ownerKey];
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if (!owner)
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return;
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for (const id of owner.keys())
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this.dereference(id);
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delete this.owners[ownerKey];
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}
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// Private: Saves the object into storage and assigns an ID for it.
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saveToStorage(object) {
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let id = v8Util.getHiddenValue(object, 'atomId');
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if (!id) {
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id = ++this.nextId;
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this.storage[id] = {
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count: 0,
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object: object
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};
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v8Util.setHiddenValue(object, 'atomId', id);
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}
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return id;
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}
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// Private: Dereference the object from store.
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dereference(id) {
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const pointer = this.storage[id];
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if (pointer == null) {
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return;
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}
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pointer.count -= 1;
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if (pointer.count === 0) {
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v8Util.deleteHiddenValue(pointer.object, 'atomId');
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delete this.storage[id];
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}
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}
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// Private: Clear the storage when renderer process is destroyed.
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registerDeleteListener(webContents, contextId) {
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// contextId => ${processHostId}-${contextCount}
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const processHostId = contextId.split('-')[0];
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const listener = (event, deletedProcessHostId) => {
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if (deletedProcessHostId &&
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deletedProcessHostId.toString() === processHostId) {
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webContents.removeListener('render-view-deleted', listener);
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this.clear(webContents, contextId);
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}
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};
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webContents.on('render-view-deleted', listener);
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}
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}
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module.exports = new ObjectsRegistry();
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