⚡ Bolt: Zero-copy decoding for SharedArrayBuffer

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);

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);
 

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);

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);