src: add internal binding for constructing SharedArrayBuffers

Author: Renegade334

lib/eslint.config_partial.mjs

@@ -225,10 +225,10 @@ export default [
           message: 'Use `const { ShadowRealm } = globalThis;` instead of the global.',
         },
         // SharedArrayBuffer is not available in primordials because it can be
-        // disabled with --no-harmony-sharedarraybuffer CLI flag.
+        // disabled with --enable-sharedarraybuffer-per-context CLI flag.
         {
           name: 'SharedArrayBuffer',
-          message: 'Use `const { SharedArrayBuffer } = globalThis;` instead of the global.',
+          message: "Use `const { constructSharedArrayBuffer } = require('internal/util');` instead of the global.",
         },
         {
           name: 'TextDecoder',

lib/internal/util.js

@@ -59,6 +59,7 @@ const {
 } = require('internal/errors');
 const { signals } = internalBinding('constants').os;
 const {
+  constructSharedArrayBuffer,
   guessHandleType: _guessHandleType,
   defineLazyProperties,
   privateSymbols: {
@@ -954,6 +955,7 @@ module.exports = {
   assertTypeScript,
   assignFunctionName,
   cachedResult,
+  constructSharedArrayBuffer,
   convertToValidSignal,
   createClassWrapper,
   decorateErrorStack,

src/node_util.cc

@@ -10,6 +10,7 @@ namespace util {
 
 using v8::ALL_PROPERTIES;
 using v8::Array;
+using v8::ArrayBuffer;
 using v8::ArrayBufferView;
 using v8::BigInt;
 using v8::Boolean;
@@ -34,6 +35,7 @@ using v8::ONLY_WRITABLE;
 using v8::Promise;
 using v8::PropertyFilter;
 using v8::Proxy;
+using v8::SharedArrayBuffer;
 using v8::SKIP_STRINGS;
 using v8::SKIP_SYMBOLS;
 using v8::StackFrame;
@@ -438,6 +440,30 @@ static void DefineLazyProperties(const FunctionCallbackInfo<Value>& args) {
   }
 }
 
+void ConstructSharedArrayBuffer(const FunctionCallbackInfo<Value>& args) {
+  Environment* env = Environment::GetCurrent(args);
+  int64_t length;
+  // Note: IntegerValue() clamps its output, so excessively large input values
+  // will not overflow
+  if (!args[0]->IntegerValue(env->context()).To(&length)) {
+    return;
+  }
+  if (length < 0 ||
+      static_cast<unsigned>(length) > ArrayBuffer::kMaxByteLength) {
+    env->ThrowRangeError("Invalid array buffer length");
+    return;
+  }
+  Local<SharedArrayBuffer> sab;
+  if (!SharedArrayBuffer::MaybeNew(env->isolate(), static_cast<size_t>(length))
+           .ToLocal(&sab)) {
+    // Note: SharedArrayBuffer::MaybeNew doesn't schedule an exception if it
+    // fails
+    env->ThrowRangeError("Array buffer allocation failed");
+    return;
+  }
+  args.GetReturnValue().Set(sab);
+}
+
 void RegisterExternalReferences(ExternalReferenceRegistry* registry) {
   registry->Register(GetPromiseDetails);
   registry->Register(GetProxyDetails);
@@ -455,6 +481,7 @@ void RegisterExternalReferences(ExternalReferenceRegistry* registry) {
   registry->Register(IsInsideNodeModules);
   registry->Register(DefineLazyProperties);
   registry->Register(DefineLazyPropertiesGetter);
+  registry->Register(ConstructSharedArrayBuffer);
 }
 
 void Initialize(Local<Object> target,
@@ -554,9 +581,12 @@ void Initialize(Local<Object> target,
   SetMethodNoSideEffect(context, target, "getCallSites", GetCallSites);
   SetMethod(context, target, "sleep", Sleep);
   SetMethod(context, target, "parseEnv", ParseEnv);
-
   SetMethod(
       context, target, "arrayBufferViewHasBuffer", ArrayBufferViewHasBuffer);
+  SetMethod(context,
+            target,
+            "constructSharedArrayBuffer",
+            ConstructSharedArrayBuffer);
 
   Local<String> should_abort_on_uncaught_toggle =
       FIXED_ONE_BYTE_STRING(env->isolate(), "shouldAbortOnUncaughtToggle");

test/parallel/test-internal-util-construct-sab.js

@@ -0,0 +1,18 @@
+// Flags: --enable-sharedarraybuffer-per-context --expose-internals
+'use strict';
+
+require('../common');
+const assert = require('assert');
+const { isSharedArrayBuffer } = require('util/types');
+const { constructSharedArrayBuffer } = require('internal/util');
+
+// We're testing that we can construct a SAB even when the global is not exposed.
+assert.strictEqual(typeof SharedArrayBuffer, 'undefined');
+
+for (const length of [undefined, 0, 1, 2 ** 32]) {
+  assert(isSharedArrayBuffer(constructSharedArrayBuffer(length)));
+}
+
+for (const length of [-1, Number.MAX_SAFE_INTEGER + 1, 2 ** 64]) {
+  assert.throws(() => constructSharedArrayBuffer(length), RangeError);
+}

typings/internalBinding/util.d.ts

@@ -46,6 +46,7 @@ export interface UtilBinding {
   parseEnv(content: string): Record<string, string>;
   styleText(format: Array<string> | string, text: string): string;
   isInsideNodeModules(frameLimit: number, defaultValue: unknown): boolean;
+  constructSharedArrayBuffer(length?: number): SharedArrayBuffer;
 
   constants: {
     kPending: 0;