fix(NODE-5577): improve ObjectId serialization by around 10%

src/parser/serializer.ts

@@ -257,14 +257,18 @@ function serializeObjectId(buffer: Uint8Array, key: string, value: ObjectId, ind
  buffer[index++] = 0;
 
  // Write the objectId into the shared buffer
- if (isUint8Array(value.id)) {
- buffer.set(value.id.subarray(0, 12), index);
+ const idValue = value.id;
+
+ if (isUint8Array(idValue)) {
+ for (let i = 0; i < 12; i++) {
+ buffer[index++] = idValue[i];
+ }
  } else {
  throw new BSONError('object [' + JSON.stringify(value) + '] is not a valid ObjectId');
  }
 
  // Adjust index
- return index + 12;
+ return index;
 }
 
 function serializeBuffer(buffer: Uint8Array, key: string, value: Uint8Array, index: number) {

test/bench/src/index.ts

@@ -1,4 +1,5 @@
 import { getStringDeserializationSuite } from './suites/string_deserialization';
+import { getObjectIdSerializationSuite } from './suites/objectid_serialization';
 import { type PerfSendData } from './util';
 import { writeFile } from 'fs';
 import { cpus, totalmem } from 'os';
@@ -17,7 +18,7 @@ console.log(
  ].join('\n')
 );
 
-for (const suite of [getStringDeserializationSuite()]) {
+for (const suite of [getStringDeserializationSuite(), getObjectIdSerializationSuite()]) {
  suite.run();
  results.push(suite.results);
 }

test/bench/src/suites/objectid_serialization.ts

@@ -0,0 +1,24 @@
+import { Suite } from '../suite';
+import * as BSON from '../../../../';
+
+export function getObjectIdSerializationSuite(): Suite {
+ const suite = new Suite('objectid serialization');
+ const data = {
+ docs: Array.from({ length: 1_000 }, () => new BSON.ObjectId())
+ };
+
+ suite.task({
+ name: 'ObjectId serialization',
+ data,
+ fn: objectIds => {
+ BSON.serialize(objectIds);
+ },
+ iterations: 10_000,
+ resultUnit: 'megabytes_per_second',
+ transform: (runtimeMS: number) => {
+ return BSON.calculateObjectSize(data) / 1024 ** 2 / (runtimeMS / 1000);
+ }
+ });
+
+ return suite;
+}