Add SharedArrayBuffer support

README.md

@@ -68,13 +68,14 @@ Alternatively, there's a browser bundle with a `Flatbush` global variable:
 
 ## API
 
-#### `new Flatbush(numItems[, nodeSize, ArrayType])`
+#### `new Flatbush(numItems[, nodeSize, ArrayType, useSharedArrayBuffer])`
 
 Creates a Flatbush index that will hold a given number of items (`numItems`). Additionally accepts:
 
 - `nodeSize`: size of the tree node (`16` by default); experiment with different values for best performance (increasing this value makes indexing faster and queries slower, and vise versa).
 - `ArrayType`: the array type used for coordinates storage (`Float64Array` by default);
 other types may be faster in certain cases (e.g. `Int32Array` when your data is integer).
+- `useSharedArrayBuffer`: set `true` if you prefer to use a `SharedArrayBuffer` in place of `ArrayBuffer` (`false` by default). This kind of data structure can be shared between threads.
 
 #### `index.add(minX, minY, maxX, maxY)`
 
@@ -114,9 +115,9 @@ Also accepts a `filterFn` similar to `index.search`.
 
 #### `Flatbush.from(data)`
 
-Recreates a Flatbush index from raw `ArrayBuffer` data
+Recreates a Flatbush index from raw `ArrayBuffer` or `SharedArrayBuffer` data
 (that's exposed as `index.data` on a previously indexed Flatbush instance).
-Very useful for transferring indices between threads or storing them in a file.
+Very useful for transferring or sharing indices between threads or storing them in a file.
 
 ### Properties
 

index.js

@@ -1,4 +1,4 @@
-
+/* global SharedArrayBuffer */
 import FlatQueue from 'flatqueue';
 
 const ARRAY_TYPES = [
@@ -11,8 +11,8 @@ const VERSION = 3; // serialized format version
 export default class Flatbush {
 
     static from(data) {
-        if (!(data instanceof ArrayBuffer)) {
-            throw new Error('Data must be an instance of ArrayBuffer.');
+        if (!(data instanceof ArrayBuffer) && SharedArrayBuffer && !(data instanceof SharedArrayBuffer)) {
+            throw new Error('Data must be an instance of ArrayBuffer or SharedArrayBuffer.');
         }
         const [magic, versionAndType] = new Uint8Array(data, 0, 2);
         if (magic !== 0xfb) {
@@ -24,12 +24,13 @@ export default class Flatbush {
         const [nodeSize] = new Uint16Array(data, 2, 1);
         const [numItems] = new Uint32Array(data, 4, 1);
 
-        return new Flatbush(numItems, nodeSize, ARRAY_TYPES[versionAndType & 0x0f], data);
+        return new Flatbush(numItems, nodeSize, ARRAY_TYPES[versionAndType & 0x0f], undefined, data);
     }
 
-    constructor(numItems, nodeSize = 16, ArrayType = Float64Array, data) {
+    constructor(numItems, nodeSize = 16, ArrayType = Float64Array, useSharedArrayBuffer = false, data) {
         if (numItems === undefined) throw new Error('Missing required argument: numItems.');
-        if (isNaN(numItems) || numItems <= 0) throw new Error(`Unpexpected numItems value: ${numItems}.`);
+        if (isNaN(numItems) || numItems <= 0) throw new Error(`Unexpected numItems value: ${numItems}.`);
+        if (useSharedArrayBuffer && !SharedArrayBuffer) throw new Error('SharedArrayBuffer not available in your runtime.');
 
         this.numItems = +numItems;
         this.nodeSize = Math.min(Math.max(+nodeSize, 2), 65535);
@@ -46,6 +47,7 @@ export default class Flatbush {
         } while (n !== 1);
 
         this.ArrayType = ArrayType || Float64Array;
+        this.ArrayBufferType = useSharedArrayBuffer ? SharedArrayBuffer : ArrayBuffer;
         this.IndexArrayType = numNodes < 16384 ? Uint16Array : Uint32Array;
 
         const arrayTypeIndex = ARRAY_TYPES.indexOf(this.ArrayType);
@@ -55,7 +57,7 @@ export default class Flatbush {
             throw new Error(`Unexpected typed array class: ${ArrayType}.`);
         }
 
-        if (data && (data instanceof ArrayBuffer)) {
+        if (data && ((data instanceof ArrayBuffer) || (SharedArrayBuffer && data instanceof SharedArrayBuffer))) {
             this.data = data;
             this._boxes = new this.ArrayType(this.data, 8, numNodes * 4);
             this._indices = new this.IndexArrayType(this.data, 8 + nodesByteSize, numNodes);
@@ -67,7 +69,7 @@ export default class Flatbush {
             this.maxY = this._boxes[this._pos - 1];
 
         } else {
-            this.data = new ArrayBuffer(8 + nodesByteSize + numNodes * this.IndexArrayType.BYTES_PER_ELEMENT);
+            this.data = new this.ArrayBufferType(8 + nodesByteSize + numNodes * this.IndexArrayType.BYTES_PER_ELEMENT);
             this._boxes = new this.ArrayType(this.data, 8, numNodes * 4);
             this._indices = new this.IndexArrayType(this.data, 8 + nodesByteSize, numNodes);
             this._pos = 0;