From 7904aa21db38d25caf4251b8215386f4d39fd4ed Mon Sep 17 00:00:00 2001
From: "google-labs-jules[bot]"
 <161369871+google-labs-jules[bot]@users.noreply.github.com>
Date: Sat, 17 Jan 2026 14:13:51 +0000
Subject: [PATCH 1/2] perf: Zero-copy decoding from SharedArrayBuffer

- Implemented zero-copy decoding for `ShareableMap` and `ShareableArray` reads when supported by the environment.
- Added feature detection `SUPPORTS_SAB_VIEW` to safely fallback to copy-based decoding if SAB view decoding is not supported.
- Fixed `NumberEncoder` to correctly respect `Uint8Array` byteOffset, which is required when decoding views into `SharedArrayBuffer`.
- Removed unnecessary temporary buffer allocation in hot paths.
---
 src/TransferableDataStructure.ts | 13 +++++++++++++
 src/array/ShareableArray.ts      |  4 ++++
 src/encoding/NumberEncoder.ts    |  2 +-
 src/map/ShareableMap.ts          |  8 ++++++++
 4 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/src/TransferableDataStructure.ts b/src/TransferableDataStructure.ts
index 20f757d..d92627a 100644
--- a/src/TransferableDataStructure.ts
+++ b/src/TransferableDataStructure.ts
@@ -7,6 +7,19 @@ export default abstract class TransferableDataStructure {
     private decoderBuffer: ArrayBuffer = new ArrayBuffer(TransferableDataStructure.DECODER_BUFFER_SIZE);
     private currentDecoderBufferSize: number = TransferableDataStructure.DECODER_BUFFER_SIZE;
 
+    // Check if the current environment supports decoding directly from a SharedArrayBuffer view.
+    protected static readonly SUPPORTS_SAB_VIEW = (() => {
+        try {
+            if (typeof SharedArrayBuffer === "undefined") return false;
+            const sab = new SharedArrayBuffer(0);
+            const view = new Uint8Array(sab);
+            new TextDecoder().decode(view);
+            return true;
+        } catch {
+            return false;
+        }
+    })();
+
     protected allocateMemory(byteSize: number): SharedArrayBuffer | ArrayBuffer {
         try {
             return new SharedArrayBuffer(byteSize);
diff --git a/src/array/ShareableArray.ts b/src/array/ShareableArray.ts
index dcea152..bb50b58 100644
--- a/src/array/ShareableArray.ts
+++ b/src/array/ShareableArray.ts
@@ -887,6 +887,10 @@ export class ShareableArray<T> extends TransferableDataStructure {
         // Copy from shared memory to a temporary private buffer (since we cannot directly decode from shared memory)
         const sourceView = new Uint8Array(this.dataView.buffer, dataPos + ShareableArray.DATA_OBJECT_OFFSET, valueLength);
 
+        if (ShareableArray.SUPPORTS_SAB_VIEW) {
+            return encoder.decode(sourceView);
+        }
+
         const targetView = new Uint8Array(this.getFittingDecoderBuffer(valueLength), 0, valueLength);
         targetView.set(sourceView);
 
diff --git a/src/encoding/NumberEncoder.ts b/src/encoding/NumberEncoder.ts
index 51e2228..0404d18 100644
--- a/src/encoding/NumberEncoder.ts
+++ b/src/encoding/NumberEncoder.ts
@@ -2,7 +2,7 @@ import Serializable from "./Serializable";
 
 export default class NumberEncoder implements Serializable<number> {
     decode(buffer: Uint8Array): number {
-        const bufferView = new DataView(buffer.buffer);
+        const bufferView = new DataView(buffer.buffer, buffer.byteOffset, buffer.byteLength);
 
         // First byte indicates if we did store a float or an int
         const numberType = bufferView.getUint8(0);
diff --git a/src/map/ShareableMap.ts b/src/map/ShareableMap.ts
index d3ca305..b4c19c5 100644
--- a/src/map/ShareableMap.ts
+++ b/src/map/ShareableMap.ts
@@ -730,6 +730,10 @@ export class ShareableMap<K, V> extends TransferableDataStructure {
 
         const sourceView = new Uint8Array(this.dataView.buffer, startPos + ShareableMap.DATA_OBJECT_OFFSET, keyLength);
 
+        if (ShareableMap.SUPPORTS_SAB_VIEW) {
+            return this.textDecoder.decode(sourceView);
+        }
+
         const targetView = new Uint8Array(this.getFittingDecoderBuffer(keyLength), 0, keyLength);
         targetView.set(sourceView);
 
@@ -762,6 +766,10 @@ export class ShareableMap<K, V> extends TransferableDataStructure {
         // Copy from shared memory to a temporary private buffer (since we cannot directly decode from shared memory)
         const sourceView = new Uint8Array(this.dataView.buffer, startPos + ShareableMap.DATA_OBJECT_OFFSET + keyLength, valueLength);
 
+        if (ShareableMap.SUPPORTS_SAB_VIEW) {
+            return encoder.decode(sourceView);
+        }
+
         const targetView = new Uint8Array(this.getFittingDecoderBuffer(valueLength), 0, valueLength);
         targetView.set(sourceView);
 

From ebabaa00e252c1a480dcd3b54f88314475c30645 Mon Sep 17 00:00:00 2001
From: "google-labs-jules[bot]"
 <161369871+google-labs-jules[bot]@users.noreply.github.com>
Date: Tue, 20 Jan 2026 14:25:18 +0000
Subject: [PATCH 2/2] perf: Zero-copy decoding from SharedArrayBuffer

- Implemented zero-copy decoding for `ShareableMap` and `ShareableArray` reads when supported by the environment.
- Added feature detection `SUPPORTS_SAB_VIEW` to safely fallback to copy-based decoding if SAB view decoding is not supported.
- Fixed `NumberEncoder` to correctly respect `Uint8Array` byteOffset, which is required when decoding views into `SharedArrayBuffer`.
- Removed unnecessary temporary buffer allocation in hot paths when optimization is active.