core: add Deno.core.dispatchByName (#6395)

This commit adds alternate dispatch method to core JS API.

"Deno.core.dispatchByName()" works like "Deno.core.dispatch()", 
but takes op name instead of op id as a first argument.

6 files changed, 27 insertions, 41 deletions

diff --git a/cli/js/globals.ts b/cli/js/globals.ts
index 09be63315..5746b224f 100644
--- a/cli/js/globals.ts
+++ b/cli/js/globals.ts
@@ -82,6 +82,11 @@ declare global {
       control: Uint8Array,
       ...zeroCopy: ArrayBufferView[]
     ): Uint8Array | null;
+    dispatchByName(
+      opName: string,
+      control: Uint8Array,
+      ...zeroCopy: ArrayBufferView[]
+    ): Uint8Array | null;
     setAsyncHandler(opId: number, cb: (msg: Uint8Array) => void): void;
     sharedQueue: {
       head(): number;
diff --git a/cli/js/ops/dispatch_json.ts b/cli/js/ops/dispatch_json.ts
index 6292c188a..6a91f6a4f 100644
--- a/cli/js/ops/dispatch_json.ts
+++ b/cli/js/ops/dispatch_json.ts
@@ -1,7 +1,6 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 import * as util from "../util.ts";
 import { core } from "../core.ts";
-import { OPS_CACHE } from "../runtime.ts";
 import { ErrorKind, getErrorClass } from "../errors.ts";
 
 // eslint-disable-next-line @typescript-eslint/no-explicit-any
@@ -61,12 +60,10 @@ export function sendSync(
   args: object = {},
   ...zeroCopy: Uint8Array[]
 ): Ok {
-  const opId = OPS_CACHE[opName];
-  util.log("sendSync", opName, opId);
+  util.log("sendSync", opName);
   const argsUi8 = encode(args);
-  const resUi8 = core.dispatch(opId, argsUi8, ...zeroCopy);
+  const resUi8 = core.dispatchByName(opName, argsUi8, ...zeroCopy);
   util.assert(resUi8 != null);
-
   const res = decode(resUi8);
   util.assert(res.promiseId == null);
   return unwrapResponse(res);
@@ -77,14 +74,12 @@ export async function sendAsync(
   args: object = {},
   ...zeroCopy: Uint8Array[]
 ): Promise<Ok> {
-  const opId = OPS_CACHE[opName];
-  util.log("sendAsync", opName, opId);
+  util.log("sendAsync", opName);
   const promiseId = nextPromiseId();
   args = Object.assign(args, { promiseId });
   const promise = util.createResolvable<Ok>();
-
   const argsUi8 = encode(args);
-  const buf = core.dispatch(opId, argsUi8, ...zeroCopy);
+  const buf = core.dispatchByName(opName, argsUi8, ...zeroCopy);
   if (buf) {
     // Sync result.
     const res = decode(buf);
diff --git a/cli/js/ops/dispatch_minimal.ts b/cli/js/ops/dispatch_minimal.ts
index 570463583..0d1dac44e 100644
--- a/cli/js/ops/dispatch_minimal.ts
+++ b/cli/js/ops/dispatch_minimal.ts
@@ -83,7 +83,7 @@ export function asyncMsgFromRust(ui8: Uint8Array): void {
 }
 
 export async function sendAsyncMinimal(
-  opId: number,
+  opName: string,
   arg: number,
   zeroCopy: Uint8Array
 ): Promise<number> {
@@ -92,7 +92,7 @@ export async function sendAsyncMinimal(
   scratch32[1] = arg;
   scratch32[2] = 0; // result
   const promise = util.createResolvable<RecordMinimal>();
-  const buf = core.dispatch(opId, scratchBytes, zeroCopy);
+  const buf = core.dispatchByName(opName, scratchBytes, zeroCopy);
   if (buf) {
     const record = recordFromBufMinimal(buf);
     // Sync result.
@@ -107,13 +107,13 @@ export async function sendAsyncMinimal(
 }
 
 export function sendSyncMinimal(
-  opId: number,
+  opName: string,
   arg: number,
   zeroCopy: Uint8Array
 ): number {
   scratch32[0] = 0; // promiseId 0 indicates sync
   scratch32[1] = arg;
-  const res = core.dispatch(opId, scratchBytes, zeroCopy)!;
+  const res = core.dispatchByName(opName, scratchBytes, zeroCopy)!;
   const resRecord = recordFromBufMinimal(res);
   return unwrapResponse(resRecord);
 }
diff --git a/cli/js/ops/io.ts b/cli/js/ops/io.ts
index b4ef837e0..cc3d1d170 100644
--- a/cli/js/ops/io.ts
+++ b/cli/js/ops/io.ts
@@ -1,22 +1,12 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 
 import { sendAsyncMinimal, sendSyncMinimal } from "./dispatch_minimal.ts";
-// TODO(bartlomieju): remove this import and maybe lazy-initialize
-// OPS_CACHE that belongs only to this module
-import { OPS_CACHE } from "../runtime.ts";
-
-// This is done because read/write are extremely performance sensitive.
-let OP_READ = -1;
-let OP_WRITE = -1;
 
 export function readSync(rid: number, buffer: Uint8Array): number | null {
   if (buffer.length == 0) {
     return 0;
   }
-  if (OP_READ < 0) {
-    OP_READ = OPS_CACHE["op_read"];
-  }
-  const nread = sendSyncMinimal(OP_READ, rid, buffer);
+  const nread = sendSyncMinimal("op_read", rid, buffer);
   if (nread < 0) {
     throw new Error("read error");
   } else if (nread == 0) {
@@ -33,10 +23,7 @@ export async function read(
   if (buffer.length == 0) {
     return 0;
   }
-  if (OP_READ < 0) {
-    OP_READ = OPS_CACHE["op_read"];
-  }
-  const nread = await sendAsyncMinimal(OP_READ, rid, buffer);
+  const nread = await sendAsyncMinimal("op_read", rid, buffer);
   if (nread < 0) {
     throw new Error("read error");
   } else if (nread == 0) {
@@ -47,10 +34,7 @@ export async function read(
 }
 
 export function writeSync(rid: number, data: Uint8Array): number {
-  if (OP_WRITE < 0) {
-    OP_WRITE = OPS_CACHE["op_write"];
-  }
-  const result = sendSyncMinimal(OP_WRITE, rid, data);
+  const result = sendSyncMinimal("op_write", rid, data);
   if (result < 0) {
     throw new Error("write error");
   } else {
@@ -59,10 +43,7 @@ export function writeSync(rid: number, data: Uint8Array): number {
 }
 
 export async function write(rid: number, data: Uint8Array): Promise<number> {
-  if (OP_WRITE < 0) {
-    OP_WRITE = OPS_CACHE["op_write"];
-  }
-  const result = await sendAsyncMinimal(OP_WRITE, rid, data);
+  const result = await sendAsyncMinimal("op_write", rid, data);
   if (result < 0) {
     throw new Error("write error");
   } else {
diff --git a/cli/js/runtime.ts b/cli/js/runtime.ts
index e16cee228..39d158f71 100644
--- a/cli/js/runtime.ts
+++ b/cli/js/runtime.ts
@@ -9,8 +9,6 @@ import { setPrepareStackTrace } from "./error_stack.ts";
 import { Start, opStart } from "./ops/runtime.ts";
 import { handleTimerMacrotask } from "./web/timers.ts";
 
-export let OPS_CACHE: { [name: string]: number };
-
 function getAsyncHandler(opName: string): (msg: Uint8Array) => void {
   switch (opName) {
     case "op_write":
@@ -24,8 +22,8 @@ function getAsyncHandler(opName: string): (msg: Uint8Array) => void {
 // TODO(bartlomieju): temporary solution, must be fixed when moving
 // dispatches to separate crates
 export function initOps(): void {
-  OPS_CACHE = core.ops();
-  for (const [name, opId] of Object.entries(OPS_CACHE)) {
+  const opsMap = core.ops();
+  for (const [name, opId] of Object.entries(opsMap)) {
     core.setAsyncHandler(opId, getAsyncHandler(name));
   }
   core.setMacrotaskCallback(handleTimerMacrotask);
diff --git a/core/core.js b/core/core.js
index 23cc325ab..b3c0ddc13 100644
--- a/core/core.js
+++ b/core/core.js
@@ -37,6 +37,7 @@ SharedQueue Binary Layout
   let asyncHandlers;
 
   let initialized = false;
+  let opsCache = {};
 
   function maybeInit() {
     if (!initialized) {
@@ -61,7 +62,8 @@ SharedQueue Binary Layout
     // op id 0 is a special value to retrieve the map of registered ops.
     const opsMapBytes = send(0, new Uint8Array([]));
     const opsMapJson = String.fromCharCode.apply(null, opsMapBytes);
-    return JSON.parse(opsMapJson);
+    opsCache = JSON.parse(opsMapJson);
+    return { ...opsCache };
   }
 
   function assert(cond) {
@@ -181,9 +183,14 @@ SharedQueue Binary Layout
     }
   }
 
+  function dispatch(opName, control, ...zeroCopy) {
+    return send(opsCache[opName], control, ...zeroCopy);
+  }
+
   Object.assign(window.Deno.core, {
     setAsyncHandler,
     dispatch: send,
+    dispatchByName: dispatch,
     ops,
     // sharedQueue is private but exposed for testing.
     sharedQueue: {