1 files changed, 73 insertions, 0 deletions
diff --git a/extensions/web/02_structured_clone.js b/extensions/web/02_structured_clone.js
new file mode 100644
index 000000000..2170095d9
--- /dev/null
+++ b/extensions/web/02_structured_clone.js
@@ -0,0 +1,73 @@
+// Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
+
+// @ts-check
+/// <reference path="../../core/lib.deno_core.d.ts" />
+/// <reference path="../web/internal.d.ts" />
+/// <reference path="../web/lib.deno_web.d.ts" />
+
+"use strict";
+
+((window) => {
+  const core = window.Deno.core;
+
+  const objectCloneMemo = new WeakMap();
+
+  function cloneArrayBuffer(
+    srcBuffer,
+    srcByteOffset,
+    srcLength,
+    _cloneConstructor,
+  ) {
+    // this function fudges the return type but SharedArrayBuffer is disabled for a while anyway
+    return srcBuffer.slice(
+      srcByteOffset,
+      srcByteOffset + srcLength,
+    );
+  }
+
+  /** Clone a value in a similar way to structured cloning.  It is similar to a
+* StructureDeserialize(StructuredSerialize(...)). */
+  function structuredClone(value) {
+    // Performance optimization for buffers, otherwise
+    // `serialize/deserialize` will allocate new buffer.
+    if (value instanceof ArrayBuffer) {
+      const cloned = cloneArrayBuffer(
+        value,
+        0,
+        value.byteLength,
+        ArrayBuffer,
+      );
+      objectCloneMemo.set(value, cloned);
+      return cloned;
+    }
+    if (ArrayBuffer.isView(value)) {
+      const clonedBuffer = structuredClone(value.buffer);
+      // Use DataViewConstructor type purely for type-checking, can be a
+      // DataView or TypedArray.  They use the same constructor signature,
+      // only DataView has a length in bytes and TypedArrays use a length in
+      // terms of elements, so we adjust for that.
+      let length;
+      if (value instanceof DataView) {
+        length = value.byteLength;
+      } else {
+        length = value.length;
+      }
+      return new (value.constructor)(
+        clonedBuffer,
+        value.byteOffset,
+        length,
+      );
+    }
+
+    try {
+      return core.deserialize(core.serialize(value));
+    } catch (e) {
+      if (e instanceof TypeError) {
+        throw new DOMException("Uncloneable value", "DataCloneError");
+      }
+      throw e;
+    }
+  }
+
+  window.__bootstrap.structuredClone = structuredClone;
+})(globalThis);