Add signal handlers (#3757)

1 files changed, 148 insertions, 0 deletions

diff --git a/cli/js/signals.ts b/cli/js/signals.ts
new file mode 100644
index 000000000..02d52bc2f
--- /dev/null
+++ b/cli/js/signals.ts
@@ -0,0 +1,148 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+import { Signal } from "./process.ts";
+import * as dispatch from "./dispatch.ts";
+import { sendSync, sendAsync } from "./dispatch_json.ts";
+import { build } from "./build.ts";
+
+/**
+ * Returns the stream of the given signal number. You can use it as an async
+ * iterator.
+ *
+ *     for await (const _ of Deno.signal(Deno.Signal.SIGTERM)) {
+ *       console.log("got SIGTERM!");
+ *     }
+ *
+ * You can also use it as a promise. In this case you can only receive the
+ * first one.
+ *
+ *     await Deno.signal(Deno.Signal.SIGTERM);
+ *     console.log("SIGTERM received!")
+ *
+ * If you want to stop receiving the signals, you can use .dispose() method
+ * of the signal stream object.
+ *
+ *     const sig = Deno.signal(Deno.Signal.SIGTERM);
+ *     setTimeout(() => { sig.dispose(); }, 5000);
+ *     for await (const _ of sig) {
+ *       console.log("SIGTERM!")
+ *     }
+ *
+ * The above for-await loop exits after 5 seconds when sig.dispose() is called.
+ */
+export function signal(signo: number): SignalStream {
+  if (build.os === "win") {
+    throw new Error("not implemented!");
+  }
+  return new SignalStream(signo);
+}
+
+export const signals = {
+  /** Returns the stream of SIGALRM signals.
+   * This method is the shorthand for Deno.signal(Deno.Signal.SIGALRM). */
+  alarm(): SignalStream {
+    return signal(Signal.SIGALRM);
+  },
+  /** Returns the stream of SIGCHLD signals.
+   * This method is the shorthand for Deno.signal(Deno.Signal.SIGCHLD). */
+  child(): SignalStream {
+    return signal(Signal.SIGCHLD);
+  },
+  /** Returns the stream of SIGHUP signals.
+   * This method is the shorthand for Deno.signal(Deno.Signal.SIGHUP). */
+  hungup(): SignalStream {
+    return signal(Signal.SIGHUP);
+  },
+  /** Returns the stream of SIGINT signals.
+   * This method is the shorthand for Deno.signal(Deno.Signal.SIGINT). */
+  interrupt(): SignalStream {
+    return signal(Signal.SIGINT);
+  },
+  /** Returns the stream of SIGIO signals.
+   * This method is the shorthand for Deno.signal(Deno.Signal.SIGIO). */
+  io(): SignalStream {
+    return signal(Signal.SIGIO);
+  },
+  /** Returns the stream of SIGPIPE signals.
+   * This method is the shorthand for Deno.signal(Deno.Signal.SIGPIPE). */
+  pipe(): SignalStream {
+    return signal(Signal.SIGPIPE);
+  },
+  /** Returns the stream of SIGQUIT signals.
+   * This method is the shorthand for Deno.signal(Deno.Signal.SIGQUIT). */
+  quit(): SignalStream {
+    return signal(Signal.SIGQUIT);
+  },
+  /** Returns the stream of SIGTERM signals.
+   * This method is the shorthand for Deno.signal(Deno.Signal.SIGTERM). */
+  terminate(): SignalStream {
+    return signal(Signal.SIGTERM);
+  },
+  /** Returns the stream of SIGUSR1 signals.
+   * This method is the shorthand for Deno.signal(Deno.Signal.SIGUSR1). */
+  userDefined1(): SignalStream {
+    return signal(Signal.SIGUSR1);
+  },
+  /** Returns the stream of SIGUSR2 signals.
+   * This method is the shorthand for Deno.signal(Deno.Signal.SIGUSR2). */
+  userDefined2(): SignalStream {
+    return signal(Signal.SIGUSR2);
+  },
+  /** Returns the stream of SIGWINCH signals.
+   * This method is the shorthand for Deno.signal(Deno.Signal.SIGWINCH). */
+  windowChange(): SignalStream {
+    return signal(Signal.SIGWINCH);
+  }
+};
+
+/** SignalStream represents the stream of signals, implements both
+ * AsyncIterator and PromiseLike */
+export class SignalStream implements AsyncIterator<void>, PromiseLike<void> {
+  private rid: number;
+  /** The promise of polling the signal,
+   * resolves with false when it receives signal,
+   * Resolves with true when the signal stream is disposed. */
+  private pollingPromise: Promise<boolean> = Promise.resolve(false);
+  /** The flag, which is true when the stream is disposed. */
+  private disposed = false;
+  constructor(signo: number) {
+    this.rid = sendSync(dispatch.OP_SIGNAL_BIND, { signo }).rid;
+    this.loop();
+  }
+
+  private async pollSignal(): Promise<boolean> {
+    return (
+      await sendAsync(dispatch.OP_SIGNAL_POLL, {
+        rid: this.rid
+      })
+    ).done;
+  }
+
+  private async loop(): Promise<void> {
+    do {
+      this.pollingPromise = this.pollSignal();
+    } while (!(await this.pollingPromise) && !this.disposed);
+  }
+
+  then<T, S>(
+    f: (v: void) => T | Promise<T>,
+    g?: (v: Error) => S | Promise<S>
+  ): Promise<T | S> {
+    return this.pollingPromise.then((_): void => {}).then(f, g);
+  }
+
+  async next(): Promise<IteratorResult<void>> {
+    return { done: await this.pollingPromise, value: undefined };
+  }
+
+  [Symbol.asyncIterator](): AsyncIterator<void> {
+    return this;
+  }
+
+  dispose(): void {
+    if (this.disposed) {
+      throw new Error("The stream has already been disposed.");
+    }
+    this.disposed = true;
+    sendSync(dispatch.OP_SIGNAL_UNBIND, { rid: this.rid });
+  }
+}