deno/ext/web/02_structured_clone.js

// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.

// @ts-check
/// <reference path="../../core/lib.deno_core.d.ts" />
/// <reference path="../../core/internal.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 { DOMException } = window.__bootstrap.domException;
  const {
    ArrayBuffer,
    ArrayBufferPrototype,
    ArrayBufferPrototypeGetByteLength,
    ArrayBufferPrototypeSlice,
    ArrayBufferIsView,
    DataView,
    DataViewPrototypeGetBuffer,
    DataViewPrototypeGetByteLength,
    DataViewPrototypeGetByteOffset,
    ObjectPrototypeIsPrototypeOf,
    TypedArrayPrototypeGetBuffer,
    TypedArrayPrototypeGetByteOffset,
    TypedArrayPrototypeGetLength,
    TypedArrayPrototypeGetSymbolToStringTag,
    TypeErrorPrototype,
    WeakMap,
    WeakMapPrototypeSet,
    Int8Array,
    Int16Array,
    Int32Array,
    BigInt64Array,
    Uint8Array,
    Uint8ClampedArray,
    Uint16Array,
    Uint32Array,
    BigUint64Array,
    Float32Array,
    Float64Array,
  } = window.__bootstrap.primordials;

  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 ArrayBufferPrototypeSlice(
      srcBuffer,
      srcByteOffset,
      srcByteOffset + srcLength,
    );
  }

  // TODO(petamoriken): Resizable ArrayBuffer support in the future
  /** 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 (ObjectPrototypeIsPrototypeOf(ArrayBufferPrototype, value)) {
      const cloned = cloneArrayBuffer(
        value,
        0,
        ArrayBufferPrototypeGetByteLength(value),
        ArrayBuffer,
      );
      WeakMapPrototypeSet(objectCloneMemo, value, cloned);
      return cloned;
    }

    if (ArrayBufferIsView(value)) {
      const tag = TypedArrayPrototypeGetSymbolToStringTag(value);
      // DataView
      if (tag === undefined) {
        return new DataView(
          structuredClone(DataViewPrototypeGetBuffer(value)),
          DataViewPrototypeGetByteOffset(value),
          DataViewPrototypeGetByteLength(value),
        );
      }
      // TypedArray
      let Constructor;
      switch (tag) {
        case "Int8Array":
          Constructor = Int8Array;
          break;
        case "Int16Array":
          Constructor = Int16Array;
          break;
        case "Int32Array":
          Constructor = Int32Array;
          break;
        case "BigInt64Array":
          Constructor = BigInt64Array;
          break;
        case "Uint8Array":
          Constructor = Uint8Array;
          break;
        case "Uint8ClampedArray":
          Constructor = Uint8ClampedArray;
          break;
        case "Uint16Array":
          Constructor = Uint16Array;
          break;
        case "Uint32Array":
          Constructor = Uint32Array;
          break;
        case "BigUint64Array":
          Constructor = BigUint64Array;
          break;
        case "Float32Array":
          Constructor = Float32Array;
          break;
        case "Float64Array":
          Constructor = Float64Array;
          break;
      }
      return new Constructor(
        structuredClone(TypedArrayPrototypeGetBuffer(value)),
        TypedArrayPrototypeGetByteOffset(value),
        TypedArrayPrototypeGetLength(value),
      );
    }

    try {
      return core.deserialize(core.serialize(value));
    } catch (e) {
      if (ObjectPrototypeIsPrototypeOf(TypeErrorPrototype, e)) {
        throw new DOMException(e.message, "DataCloneError");
      }
      throw e;
    }
  }

  window.__bootstrap.structuredClone = structuredClone;
})(globalThis);