rearrage_stuff

node_modules/sync-message-port/dist/lib/index.js

@@ -0,0 +1,174 @@
+"use strict";
+// Copyright 2021 Google LLC. Use of this source code is governed by an
+// MIT-style license that can be found in the LICENSE file or at
+// https://opensource.org/licenses/MIT.
+Object.defineProperty(exports, "__esModule", { value: true });
+exports.SyncMessagePort = exports.TimeoutException = void 0;
+const assert_1 = require("assert");
+const events_1 = require("events");
+const worker_threads_1 = require("worker_threads");
+/**
+ * An enum of possible states for the shared buffer that two `SyncMessagePort`s
+ * use to communicate.
+ */
+var BufferState;
+(function (BufferState) {
+    /**
+     * The initial state. When an endpoint is ready to receive messages, it'll set
+     * the buffer to this state so that it can use `Atomics.wait()` to be notified
+     * when it switches to `MessageSent`.
+     */
+    BufferState[BufferState["AwaitingMessage"] = 0] = "AwaitingMessage";
+    /**
+     * The state indicating that a message has been sent. Whenever an endpoint
+     * sends a message, it'll set the buffer to this state so that the other
+     * endpoint's `Atomics.wait()` call terminates.
+     */
+    BufferState[BufferState["MessageSent"] = 1] = "MessageSent";
+    /**
+     * The bitmask indicating that the channel has been closed. This is masked on
+     * top of AwaitingMessage and MessageSent state. It never transitions to any
+     * other states once closed.
+     */
+    BufferState[BufferState["Closed"] = 2] = "Closed";
+})(BufferState || (BufferState = {}));
+/**
+ * An exception thrown by {@link SyncMessagePort.receiveMessage} if a message
+ * isn't received within {@link ReceivedMessageOptions.timeout} milliseconds.
+ */
+class TimeoutException extends Error {
+    constructor(message) {
+        super(message);
+    }
+}
+exports.TimeoutException = TimeoutException;
+/**
+ * A communication port that can receive messages synchronously from another
+ * `SyncMessagePort`.
+ *
+ * This also emits the same asynchronous events as `MessagePort`.
+ */
+class SyncMessagePort extends events_1.EventEmitter {
+    port;
+    /** Creates a channel whose ports can be passed to `new SyncMessagePort()`. */
+    static createChannel() {
+        const channel = new worker_threads_1.MessageChannel();
+        // Four bytes is the minimum necessary to use `Atomics.wait()`.
+        const buffer = new SharedArrayBuffer(4);
+        // Queue up messages on each port so the caller doesn't have to explicitly
+        // pass the buffer around along with them.
+        channel.port1.postMessage(buffer);
+        channel.port2.postMessage(buffer);
+        return channel;
+    }
+    /**
+     * An Int32 view of the shared buffer.
+     *
+     * Each port sets this to `BufferState.AwaitingMessage` before checking for
+     * new messages in `receiveMessage()`, and each port sets it to
+     * `BufferState.MessageSent` after sending a new message. It's set to
+     * `BufferState.Closed` when the channel is closed.
+     */
+    buffer;
+    /**
+     * Creates a new message port. The `port` must be created by
+     * `SyncMessagePort.createChannel()` and must connect to a port passed to
+     * another `SyncMessagePort` in another worker.
+     */
+    constructor(port) {
+        super();
+        this.port = port;
+        const buffer = (0, worker_threads_1.receiveMessageOnPort)(this.port)?.message;
+        if (!buffer) {
+            throw new Error('new SyncMessagePort() must be passed a port from ' +
+                'SyncMessagePort.createChannel().');
+        }
+        this.buffer = new Int32Array(buffer);
+        this.on('newListener', (event, listener) => {
+            this.port.on(event, listener);
+        });
+        this.on('removeListener', (event, listener) => this.port.removeListener(event, listener));
+    }
+    /** See `MessagePort.postMesage()`. */
+    postMessage(value, transferList) {
+        this.port.postMessage(value, transferList);
+        // If the other port is waiting for a new message, notify it that the
+        // message is ready. Use `Atomics.compareExchange` so that we don't
+        // overwrite the "closed" state.
+        if (Atomics.compareExchange(this.buffer, 0, BufferState.AwaitingMessage, BufferState.MessageSent) === BufferState.AwaitingMessage) {
+            Atomics.notify(this.buffer, 0);
+        }
+    }
+    /**
+     * Returns the message sent by the other port, if one is available. This *does
+     * not* block, and will return `undefined` immediately if no message is
+     * available. In order to distinguish between a message with value `undefined`
+     * and no message, a message is return in an object with a `message` field.
+     *
+     * This may not be called while this has a listener for the `'message'` event.
+     * It does *not* throw an error if the port is closed when this is called;
+     * instead, it just returns `undefined`.
+     */
+    receiveMessageIfAvailable() {
+        if (this.listenerCount('message')) {
+            throw new Error('SyncMessageChannel.receiveMessageIfAvailable() may not be called ' +
+                'while there are message listeners.');
+        }
+        return (0, worker_threads_1.receiveMessageOnPort)(this.port);
+    }
+    /**
+     * Blocks and returns the next message sent by the other port.
+     *
+     * This may not be called while this has a listener for the `'message'` event.
+     * Throws an error if the channel is closed, including if it closes while this
+     * is waiting for a message, unless {@link ReceiveMessageOptions.closedValue}
+     * is passed.
+     */
+    receiveMessage(options) {
+        if (this.listenerCount('message')) {
+            throw new Error('SyncMessageChannel.receiveMessage() may not be called while there ' +
+                'are message listeners.');
+        }
+        // Set the "new message" indicator to zero before we check for new messages.
+        // That way if the other port sets it to 1 between the call to
+        // `receiveMessageOnPort` and the call to `Atomics.wait()`, we won't
+        // overwrite it. Use `Atomics.compareExchange` so that we don't overwrite
+        // the "closed" state.
+        const previousState = Atomics.compareExchange(this.buffer, 0, BufferState.MessageSent, BufferState.AwaitingMessage);
+        if (previousState === BufferState.Closed) {
+            if (options && 'closedValue' in options)
+                return options.closedValue;
+            throw new Error("The SyncMessagePort's channel is closed.");
+        }
+        let message = (0, worker_threads_1.receiveMessageOnPort)(this.port);
+        if (message)
+            return message.message;
+        // If there's no new message, wait for the other port to flip the "new
+        // message" indicator to 1. If it's been set to 1 since we stored 0, this
+        // will terminate immediately.
+        const result = Atomics.wait(this.buffer, 0, BufferState.AwaitingMessage, options?.timeout);
+        message = (0, worker_threads_1.receiveMessageOnPort)(this.port);
+        if (message)
+            return message.message;
+        if (result === 'timed-out') {
+            if ('timeoutValue' in options)
+                return options.timeoutValue;
+            throw new TimeoutException('SyncMessagePort.receiveMessage() timed out.');
+        }
+        // Update the state to 0b10 after the last message is consumed.
+        const oldState = Atomics.and(this.buffer, 0, BufferState.Closed);
+        // Assert the old state was either 0b10 or 0b11.
+        assert_1.strict.equal(oldState & BufferState.Closed, BufferState.Closed);
+        if (options && 'closedValue' in options)
+            return options.closedValue;
+        throw new Error("The SyncMessagePort's channel is closed.");
+    }
+    /** See `MessagePort.close()`. */
+    close() {
+        Atomics.or(this.buffer, 0, BufferState.Closed);
+        Atomics.notify(this.buffer, 0);
+        this.port.close();
+    }
+}
+exports.SyncMessagePort = SyncMessagePort;
+//# sourceMappingURL=index.js.map