GeezerVison

Let's say we were defining a platform object Person, which had associated with it two pieces of associated data:

• a name value, which is a string; and

• a best friend value, which is either another Person instance or null.

We could then define Person instances to be serializable objects by annotating the Person interface with the [Serializable] extended attribute, and defining the following accompanying algorithms:

To restrict a Record record to the same agent cluster, set record.[[AgentCluster]] to the surrounding agent's agent cluster.

2.7.4 StructuredSerializeInternal ( value, forStorage [ , memory ] )

The StructuredSerializeInternal abstract operation takes as input a JavaScript value value and serializes it to a realm-independent form, represented here as a Record. This serialized form has all the information necessary to later deserialize into a new JavaScript value in a different realm.

This process can throw an exception, for example when trying to serialize un-serializable objects.

1. If memory was not supplied, let memory be an empty map.

   The purpose of the memory map is to avoid serializing objects twice. This ends up preserving cycles and the identity of duplicate objects in graphs.

2. If memory[value] exists, then return memory[value].

3. Let deep be false.

4. Let sameAgentCluster be false.

5. If value is undefined, null, a Boolean, a Number, a BigInt, or a String, then return { [[Type]]: "primitive", [[Value]]: value }.

6. If value is a Symbol, then throw a "DataCloneError" DOMException.

7. Let serialized be an uninitialized value.

8. If value has a [[BooleanData]] internal slot, then set serialized to { [[Type]]: "Boolean", [[BooleanData]]: value.[[BooleanData]] }.

9. Otherwise, if value has a [[NumberData]] internal slot, then set serialized to { [[Type]]: "Number", [[NumberData]]: value.[[NumberData]] }.

10. Otherwise, if value has a [[BigIntData]] internal slot, then set serialized to { [[Type]]: "BigInt", [[BigIntData]]: value.[[BigIntData]] }.

11. Otherwise, if value has a [[StringData]] internal slot, then set serialized to { [[Type]]: "String", [[StringData]]: value.[[StringData]] }.

12. Otherwise, if value has a [[DateValue]] internal slot, then set serialized to { [[Type]]: "Date", [[DateValue]]: value.[[DateValue]] }.

13. Otherwise, if value has a [[RegExpMatcher]] internal slot, then set serialized to { [[Type]]: "RegExp", [[RegExpMatcher]]: value.[[RegExpMatcher]], [[OriginalSource]]: value.[[OriginalSource]], [[OriginalFlags]]: value.[[OriginalFlags]] }.

14. Otherwise, if value has an [[ArrayBufferData]] internal slot:

    1. If IsSharedArrayBuffer(value) is true:

       1. If the current settings object's cross-origin isolated capability is false, then throw a "DataCloneError" DOMException.

          This check is only needed when serializing (and not when deserializing) as the cross-origin isolated capability cannot change over time and a SharedArrayBuffer cannot leave an agent cluster.

       2. If value has an [[ArrayBufferMaxByteLength]] internal slot, then set serialized to { [[Type]]: "GrowableSharedArrayBuffer", [[ArrayBufferData]]: value.[[ArrayBufferData]], [[ArrayBufferByteLengthData]]: value.[[ArrayBufferByteLengthData]], [[ArrayBufferMaxByteLength]]: value.[[ArrayBufferMaxByteLength]] }.

       3. Otherwise, set serialized to { [[Type]]: "SharedArrayBuffer", [[ArrayBufferData]]: value.[[ArrayBufferData]], [[ArrayBufferByteLength]]: value.[[ArrayBufferByteLength]] }.

       4. Set sameAgentCluster to true.

    2. Otherwise:

       1. If IsDetachedBuffer(value) is true, then throw a "DataCloneError" DOMException.

       2. Let size be value.[[ArrayBufferByteLength]].

       3. Let dataCopy be ? CreateByteDataBlock(size).

          This can throw a RangeError exception upon allocation failure.

       4. Perform CopyDataBlockBytes(dataCopy, 0, value.[[ArrayBufferData]], 0, size).

       5. If value has an [[ArrayBufferMaxByteLength]] internal slot, then set serialized to { [[Type]]: "ResizableArrayBuffer", [[ArrayBufferData]]: dataCopy, [[ArrayBufferByteLength]]: size, [[ArrayBufferMaxByteLength]]: value.[[ArrayBufferMaxByteLength]] }.

       6. Otherwise, set serialized to { [[Type]]: "ArrayBuffer", [[ArrayBufferData]]: dataCopy, [[ArrayBufferByteLength]]: size }.

15. Otherwise, if value has a [[ViewedArrayBuffer]] internal slot:

    1. If IsArrayBufferViewOutOfBounds(value) is true, then throw a "DataCloneError" DOMException.

    2. Let buffer be the value of value's [[ViewedArrayBuffer]] internal slot.

    3. Let bufferSerialized be ? StructuredSerializeInternal(buffer, forStorage, memory).

    4. Assert: bufferSerialized.[[Type]] is "ArrayBuffer", "ResizableArrayBuffer", "SharedArrayBuffer", or "GrowableSharedArrayBuffer".

    5. If value has a [[DataView]] internal slot, then set serialized to { [[Type]]: "ArrayBufferView", [[Constructor]]: "DataView", [[ArrayBufferSerialized]]: bufferSerialized, [[ByteLength]]: value.[[ByteLength]], [[ByteOffset]]: value.[[ByteOffset]] }.

    6. Otherwise:

       1. Assert: value has a [[TypedArrayName]] internal slot.

       2. Set serialized to { [[Type]]: "ArrayBufferView", [[Constructor]]: value.[[TypedArrayName]], [[ArrayBufferSerialized]]: bufferSerialized, [[ByteLength]]: value.[[ByteLength]], [[ByteOffset]]: value.[[ByteOffset]], [[ArrayLength]]: value.[[ArrayLength]] }.

16. Otherwise, if value has a [[MapData]] internal slot:

    1. Set serialized to { [[Type]]: "Map", [[MapData]]: a new empty List }.

    2. Set deep to true.

17. Otherwise, if value has a [[SetData]] internal slot:

    1. Set serialized to { [[Type]]: "Set", [[SetData]]: a new empty List }.

    2. Set deep to true.

18. Otherwise, if value has an [[ErrorData]] internal slot and value is not a platform object:

    1. Let name be ? Get(value, "name").

    2. If name is not one of "Error", "EvalError", "RangeError", "ReferenceError", "SyntaxError", "TypeError", or "URIError", then set name to "Error".

    3. Let valueMessageDesc be ? value.[[GetOwnProperty]]("message").

    4. Let message be undefined if IsDataDescriptor(valueMessageDesc) is false, and ? ToString(valueMessageDesc.[[Value]]) otherwise.

    5. Let stack be an implementation-defined string that represents value.[[Stack]]. [JSERRORSTACKACCESSOR] [JSERRORSTACKS]

    6. Set serialized to { [[Type]]: "Error", [[Name]]: name, [[Message]]: message, [[Stack]]: stack }.

    7. User agents should attach a serialized representation of any interesting accompanying data which are not yet specified to serialized.

19. Otherwise, if value is an Array exotic object:

    1. Let valueLenDescriptor be ? OrdinaryGetOwnProperty(value, "length").

    2. Let valueLen be valueLenDescriptor.[[Value]].

    3. Set serialized to { [[Type]]: "Array", [[Length]]: valueLen, [[Properties]]: a new empty List }.

    4. Set deep to true.

20. Otherwise, if value is a platform object that is a serializable object:

    1. If value has a [[Detached]] internal slot whose value is true, then throw a "DataCloneError" DOMException.

    2. Let typeString be the identifier of the primary interface of value.

    3. Set serialized to { [[Type]]: typeString }.

    4. If value's primary interface is decorated with [SameAgentCluster], then set sameAgentCluster to true.

    5. Set deep to true.

21. Otherwise, if value is a platform object, then throw a "DataCloneError" DOMException.

22. Otherwise, if IsCallable(value) is true, then throw a "DataCloneError" DOMException.

23. Otherwise, if value has any internal slot other than [[Prototype]], [[Extensible]], or [[PrivateElements]], then throw a "DataCloneError" DOMException.

    For instance, a [[PromiseState]] or [[WeakMapData]] internal slot.

24. Otherwise, if value is an exotic object and value is not the %Object.prototype% intrinsic object associated with any realm, then throw a "DataCloneError" DOMException.

    For instance, a proxy object.

25. Otherwise:

    1. Set serialized to { [[Type]]: "Object", [[Properties]]: a new empty List }.

    2. Set deep to true.

    %Object.prototype% will end up being handled via this step and subsequent steps. The end result is that its exoticness is ignored, and after deserialization the result will be an empty object (not an immutable prototype exotic object).

26. If sameAgentCluster is true, then restrict serialized to the same agent cluster; otherwise, set serialized.[[AgentCluster]] to null.

27. Set memory[value] to serialized.

28. If deep is true:

    1. If value has a [[MapData]] internal slot:

       1. Let copiedList be a new empty List.

       2. For each Record { [[Key]], [[Value]] } entry of value.[[MapData]]:

          1. Let copiedEntry be a new Record { [[Key]]: entry.[[Key]], [[Value]]: entry.[[Value]] }.

          2. If copiedEntry.[[Key]] is not the special value empty, append copiedEntry to copiedList.

       3. For each Record { [[Key]], [[Value]] } entry of copiedList:

          1. Let serializedKey be ? StructuredSerializeInternal(entry.[[Key]], forStorage, memory).

          2. Let serializedValue be ? StructuredSerializeInternal(entry.[[Value]], forStorage, memory).

          3. Append { [[Key]]: serializedKey, [[Value]]: serializedValue } to serialized.[[MapData]].

    2. Otherwise, if value has a [[SetData]] internal slot:

       1. Let copiedList be a new empty List.

       2. For each entry of value.[[SetData]]:

          1. If entry is not the special value empty, append entry to copiedList.

       3. For each entry of copiedList:

          1. Let serializedEntry be ? StructuredSerializeInternal(entry, forStorage, memory).

          2. Append serializedEntry to serialized.[[SetData]].

    3. Otherwise, if value is a platform object that is a serializable object, then perform the serialization steps for value's primary interface, given value, serialized, and forStorage.

       The serialization steps may need to perform a sub-serialization. This is an operation which takes as input a value subValue, and returns StructuredSerializeInternal(subValue, forStorage, memory). (In other words, a sub-serialization is a specialization of StructuredSerializeInternal to be consistent within this invocation.)

    4. Otherwise, for each key in ! EnumerableOwnProperties(value, key):

       1. If ! HasOwnProperty(value, key) is true:

          1. Let inputValue be ? value.[[Get]](key, value).

          2. Let outputValue be ? StructuredSerializeInternal(inputValue, forStorage, memory).

          3. Append { [[Key]]: key, [[Value]]: outputValue } to serialized.[[Properties]].

29. If forStorage is true and serialized.[[AgentCluster]] is not null, then throw a "DataCloneError" DOMException.

    This happens after the serialization steps have run, as they can restrict serialized to the same agent cluster too.

30. Return serialized.

It's important to realize that the Records produced by StructuredSerializeInternal might contain "pointers" to other records that create circular references. For example, when we pass the following JavaScript object into StructuredSerializeInternal:

const o = {};
o.myself = o;

it produces the following result:

{
  [[Type]]: "Object",
  [[Properties]]: «
    {
      [[Key]]: "myself",
      [[Value]]: <a pointer to this whole structure>
    }
  »
}

2.7.5 StructuredSerialize ( value )

1. Return ? StructuredSerializeInternal(value, false).

2.7.6 StructuredSerializeForStorage ( value )

1. Return ? StructuredSerializeInternal(value, true).

2.7.7 StructuredDeserialize ( serialized, targetRealm [ , memory ] )

The StructuredDeserialize abstract operation takes as input a Record serialized, which was previously produced by StructuredSerialize or StructuredSerializeForStorage, and deserializes it into a new JavaScript value, created in targetRealm.

This process can throw an exception, for example when trying to allocate memory for the new objects (especially ArrayBuffer objects).

1. If memory was not supplied, let memory be an empty map.

   The purpose of the memory map is to avoid deserializing objects twice. This ends up preserving cycles and the identity of duplicate objects in graphs.

2. If memory[serialized] exists, then return memory[serialized].

3. If serialized.[[Type]] is "primitive", then return serialized.[[Value]].

4. If serialized.[[AgentCluster]] is not null and targetRealm's corresponding agent cluster is not serialized.[[AgentCluster]], then throw a "DataCloneError" DOMException.

5. Let deep be false.

6. Let value be an uninitialized value.

7. If serialized.[[Type]] is "Boolean", then set value to a new Boolean object in targetRealm whose [[BooleanData]] internal slot value is serialized.[[BooleanData]].

8. Otherwise, if serialized.[[Type]] is "Number", then set value to a new Number object in targetRealm whose [[NumberData]] internal slot value is serialized.[[NumberData]].

9. Otherwise, if serialized.[[Type]] is "BigInt", then set value to a new BigInt object in targetRealm whose [[BigIntData]] internal slot value is serialized.[[BigIntData]].

10. Otherwise, if serialized.[[Type]] is "String", then set value to a new String object in targetRealm whose [[StringData]] internal slot value is serialized.[[StringData]].

11. Otherwise, if serialized.[[Type]] is "Date", then set value to a new Date object in targetRealm whose [[DateValue]] internal slot value is serialized.[[DateValue]].

12. Otherwise, if serialized.[[Type]] is "RegExp", then set value to a new RegExp object in targetRealm whose [[RegExpMatcher]] internal slot value is serialized.[[RegExpMatcher]], whose [[OriginalSource]] internal slot value is serialized.[[OriginalSource]], and whose [[OriginalFlags]] internal slot value is serialized.[[OriginalFlags]].

13. Otherwise, if serialized.[[Type]] is "SharedArrayBuffer", then set value to a new SharedArrayBuffer object in targetRealm whose [[ArrayBufferData]] internal slot value is serialized.[[ArrayBufferData]] and whose [[ArrayBufferByteLength]] internal slot value is serialized.[[ArrayBufferByteLength]].

14. Otherwise, if serialized.[[Type]] is "GrowableSharedArrayBuffer", then set value to a new SharedArrayBuffer object in targetRealm whose [[ArrayBufferData]] internal slot value is serialized.[[ArrayBufferData]], whose [[ArrayBufferByteLengthData]] internal slot value is serialized.[[ArrayBufferByteLengthData]], and whose [[ArrayBufferMaxByteLength]] internal slot value is serialized.[[ArrayBufferMaxByteLength]].

15. Otherwise, if serialized.[[Type]] is "ArrayBuffer", then set value to a new ArrayBuffer object in targetRealm whose [[ArrayBufferData]] internal slot value is serialized.[[ArrayBufferData]], and whose [[ArrayBufferByteLength]] internal slot value is serialized.[[ArrayBufferByteLength]].

    If this throws an exception, catch it, and then throw a "DataCloneError" DOMException.

    This step might throw an exception if there is not enough memory available to create such an ArrayBuffer object.

16. Otherwise, if serialized.[[Type]] is "ResizableArrayBuffer", then set value to a new ArrayBuffer object in targetRealm whose [[ArrayBufferData]] internal slot value is serialized.[[ArrayBufferData]], whose [[ArrayBufferByteLength]] internal slot value is serialized.[[ArrayBufferByteLength]], and whose [[ArrayBufferMaxByteLength]] internal slot value is serialized.[[ArrayBufferMaxByteLength]].

    If this throws an exception, catch it, and then throw a "DataCloneError" DOMException.

    This step might throw an exception if there is not enough memory available to create such an ArrayBuffer object.

17. Otherwise, if serialized.[[Type]] is "ArrayBufferView":

    1. Let deserializedArrayBuffer be ? StructuredDeserialize(serialized.[[ArrayBufferSerialized]], targetRealm, memory).

    2. If serialized.[[Constructor]] is "DataView", then set value to a new DataView object in targetRealm whose [[ViewedArrayBuffer]] internal slot value is deserializedArrayBuffer, whose [[ByteLength]] internal slot value is serialized.[[ByteLength]], and whose [[ByteOffset]] internal slot value is serialized.[[ByteOffset]].

    3. Otherwise, set value to a new typed array object in targetRealm, using the constructor given by serialized.[[Constructor]], whose [[ViewedArrayBuffer]] internal slot value is deserializedArrayBuffer, whose [[TypedArrayName]] internal slot value is serialized.[[Constructor]], whose [[ByteLength]] internal slot value is serialized.[[ByteLength]], whose [[ByteOffset]] internal slot value is serialized.[[ByteOffset]], and whose [[ArrayLength]] internal slot value is serialized.[[ArrayLength]].

18. Otherwise, if serialized.[[Type]] is "Map":

    1. Set value to a new Map object in targetRealm whose [[MapData]] internal slot value is a new empty List.

    2. Set deep to true.

19. Otherwise, if serialized.[[Type]] is "Set":

    1. Set value to a new Set object in targetRealm whose [[SetData]] internal slot value is a new empty List.

    2. Set deep to true.

20. Otherwise, if serialized.[[Type]] is "Array":

    1. Let outputProto be targetRealm.[[Intrinsics]].[[%Array.prototype%]].

    2. Set value to ! ArrayCreate(serialized.[[Length]], outputProto).

    3. Set deep to true.

21. Otherwise, if serialized.[[Type]] is "Object":

    1. Set value to a new Object in targetRealm.

    2. Set deep to true.

22. Otherwise, if serialized.[[Type]] is "Error":

    1. Let prototype be %Error.prototype%.

    2. If serialized.[[Name]] is "EvalError", then set prototype to %EvalError.prototype%.

    3. If serialized.[[Name]] is "RangeError", then set prototype to %RangeError.prototype%.

    4. If serialized.[[Name]] is "ReferenceError", then set prototype to %ReferenceError.prototype%.

    5. If serialized.[[Name]] is "SyntaxError", then set prototype to %SyntaxError.prototype%.

    6. If serialized.[[Name]] is "TypeError", then set prototype to %TypeError.prototype%.

    7. If serialized.[[Name]] is "URIError", then set prototype to %URIError.prototype%.

    8. Let message be serialized.[[Message]].

    9. Set value to OrdinaryObjectCreate(prototype, « [[ErrorData]], [[Stack]] »).

    10. Let messageDesc be PropertyDescriptor { [[Value]]: message, [[Writable]]: true, [[Enumerable]]: false, [[Configurable]]: true }.

    11. If message is not undefined, then perform ! OrdinaryDefineOwnProperty(value, "message", messageDesc).

    12. Set value.[[Stack]] to serialized.[[Stack]].

    13. Any interesting accompanying data attached to serialized should be deserialized and attached to value.

23. Otherwise:

    1. Let interfaceName be serialized.[[Type]].

    2. If the interface identified by interfaceName is not exposed in targetRealm, then throw a "DataCloneError" DOMException.

    3. Set value to a new instance of the interface identified by interfaceName, created in targetRealm.

    4. Set deep to true.

24. Set memory[serialized] to value.

25. If deep is true:

    1. If serialized.[[Type]] is "Map":

       1. For each Record { [[Key]], [[Value]] } entry of serialized.[[MapData]]:

          1. Let deserializedKey be ? StructuredDeserialize(entry.[[Key]], targetRealm, memory).

          2. Let deserializedValue be ? StructuredDeserialize(entry.[[Value]], targetRealm, memory).

          3. Append { [[Key]]: deserializedKey, [[Value]]: deserializedValue } to value.[[MapData]].

    2. Otherwise, if serialized.[[Type]] is "Set":

       1. For each entry of serialized.[[SetData]]:

          1. Let deserializedEntry be ? StructuredDeserialize(entry, targetRealm, memory).

          2. Append deserializedEntry to value.[[SetData]].

    3. Otherwise, if serialized.[[Type]] is "Array" or "Object":

       1. For each Record { [[Key]], [[Value]] } entry of serialized.[[Properties]]:

          1. Let deserializedValue be ? StructuredDeserialize(entry.[[Value]], targetRealm, memory).

          2. Let result be ! CreateDataProperty(value, entry.[[Key]], deserializedValue).

          3. Assert: result is true.

    4. Otherwise:

       1. Perform the appropriate deserialization steps for the interface identified by serialized.[[Type]], given serialized, value, and targetRealm.

          The deserialization steps may need to perform a sub-deserialization. This is an operation which takes as input a previously-serialized Record subSerialized, and returns StructuredDeserialize(subSerialized, targetRealm, memory). (In other words, a sub-deserialization is a specialization of StructuredDeserialize to be consistent within this invocation.)

26. Return value.

2.7.8 StructuredSerializeWithTransfer ( value, transferList )

1. Let memory be an empty map.

   In addition to how it is used normally by StructuredSerializeInternal, in this algorithm memory is also used to ensure that StructuredSerializeInternal ignores items in transferList, and let us do our own handling instead.

2. For each transferable of transferList:

   1. If transferable has neither an [[ArrayBufferData]] internal slot nor a [[Detached]] internal slot, then throw a "DataCloneError" DOMException.

   2. If transferable has an [[ArrayBufferData]] internal slot and IsSharedArrayBuffer(transferable) is true, then throw a "DataCloneError" DOMException.

   3. If memory[transferable] exists, then throw a "DataCloneError" DOMException.

   4. Set memory[transferable] to { [[Type]]: an uninitialized value, [[AgentCluster]]: null }.

      transferable is not transferred yet as transferring has side effects and StructuredSerializeInternal needs to be able to throw first.

3. Let serialized be ? StructuredSerializeInternal(value, false, memory).

4. Let transferDataHolders be a new empty List.

5. For each transferable of transferList:

   1. If transferable has an [[ArrayBufferData]] internal slot and IsDetachedBuffer(transferable) is true, then throw a "DataCloneError" DOMException.

   2. If transferable has a [[Detached]] internal slot and transferable.[[Detached]] is true, then throw a "DataCloneError" DOMException.

   3. Let dataHolder be memory[transferable].

   4. If transferable has an [[ArrayBufferData]] internal slot:

      1. If transferable has an [[ArrayBufferMaxByteLength]] internal slot:

         1. Set dataHolder.[[Type]] to "ResizableArrayBuffer".

         2. Set dataHolder.[[ArrayBufferData]] to transferable.[[ArrayBufferData]].

         3. Set dataHolder.[[ArrayBufferByteLength]] to transferable.[[ArrayBufferByteLength]].

         4. Set dataHolder.[[ArrayBufferMaxByteLength]] to transferable.[[ArrayBufferMaxByteLength]].

      2. Otherwise:

         1. Set dataHolder.[[Type]] to "ArrayBuffer".

         2. Set dataHolder.[[ArrayBufferData]] to transferable.[[ArrayBufferData]].

         3. Set dataHolder.[[ArrayBufferByteLength]] to transferable.[[ArrayBufferByteLength]].

      3. Perform ? DetachArrayBuffer(transferable).

         Specifications can use the [[ArrayBufferDetachKey]] internal slot to prevent ArrayBuffers from being detached. This is used in WebAssembly JavaScript Interface, for example. [WASMJS]

   5. Otherwise:

      1. Assert: transferable is a platform object that is a transferable object.

      2. Let interfaceName be the identifier of the primary interface of transferable.

      3. Set dataHolder.[[Type]] to interfaceName.

      4. If transferable's primary interface is decorated with [SameAgentCluster], then restrict dataHolder to the same agent cluster.

      5. Perform the appropriate transfer steps for the interface identified by interfaceName, given transferable and dataHolder.

      6. Set transferable.[[Detached]] to true.

   6. Append dataHolder to transferDataHolders.

6. Let result be { [[Serialized]]: serialized, [[TransferDataHolders]]: transferDataHolders, [[InterfaceNames]]: an empty ordered set, [[AgentCluster]]: null }.

7. For each object → record of memory:

   1. If object is a platform object, then append record.[[Type]] to result.[[InterfaceNames]].

   2. If record.[[AgentCluster]] is not null, then restrict result to the same agent cluster.

8. Return result.

2.7.9 StructuredDeserializeWithTransfer ( serializeWithTransferResult, targetRealm )

1. Let memory be an empty map.

   Analogous to StructuredSerializeWithTransfer, in addition to how it is used normally by StructuredDeserialize, in this algorithm memory is also used to ensure that StructuredDeserialize ignores items in serializeWithTransferResult.[[TransferDataHolders]], and let us do our own handling instead.

2. If serializeWithTransferResult.[[AgentCluster]] is not null and targetRealm's corresponding agent cluster is not serializeWithTransferResult.[[AgentCluster]], then throw a "DataCloneError" DOMException.

3. For each interfaceName of serializeWithTransferResult.[[InterfaceNames]]:

   1. If the interface identified by interfaceName is not exposed in targetRealm, then throw a "DataCloneError" DOMException.

4. Let transferredValues be a new empty List.

5. For each transferDataHolder of serializeWithTransferResult.[[TransferDataHolders]]:

   1. Let value be an uninitialized value.

   2. If transferDataHolder.[[Type]] is "ArrayBuffer", then set value to a new ArrayBuffer object in targetRealm whose [[ArrayBufferData]] internal slot value is transferDataHolder.[[ArrayBufferData]], and whose [[ArrayBufferByteLength]] internal slot value is transferDataHolder.[[ArrayBufferByteLength]].

      In cases where the original memory occupied by [[ArrayBufferData]] is accessible during the deserialization, this step is unlikely to throw an exception, as no new memory needs to be allocated: the memory occupied by [[ArrayBufferData]] is instead just getting transferred into the new ArrayBuffer. This could be true, for example, when both the source and target realms are in the same process.

   3. Otherwise, if transferDataHolder.[[Type]] is "ResizableArrayBuffer", then set value to a new ArrayBuffer object in targetRealm whose [[ArrayBufferData]] internal slot value is transferDataHolder.[[ArrayBufferData]], whose [[ArrayBufferByteLength]] internal slot value is transferDataHolder.[[ArrayBufferByteLength]], and whose [[ArrayBufferMaxByteLength]] internal slot value is transferDataHolder.[[ArrayBufferMaxByteLength]].

      For the same reason as the previous step, this step is also unlikely to throw an exception.

   4. Otherwise:

      1. Let interfaceName be transferDataHolder.[[Type]].

      2. Set value to a new instance of the interface identified by interfaceName, created in targetRealm.

      3. Perform the appropriate transfer-receiving steps for the interface identified by interfaceName given transferDataHolder and value.

   5. Set memory[transferDataHolder] to value.

   6. Append value to transferredValues.

6. Let deserialized be ? StructuredDeserialize(serializeWithTransferResult.[[Serialized]], targetRealm, memory).

7. Return { [[Deserialized]]: deserialized, [[TransferredValues]]: transferredValues }.

The structuredClone(value, options) method steps are:

1. Let serialized be ? StructuredSerializeWithTransfer(value, options["transfer"]).

2. Let deserializeRecord be ? StructuredDeserializeWithTransfer(serialized, this's relevant realm).

3. Return deserializeRecord.[[Deserialized]].