# ReadPackedLongDelta(long, in StreamCompressionModel)

> Reads an 8-byte signed long delta value from the data stream using a StreamCompressionModel.

## Definition

* **Type:** Method
* **Namespace:** [Unity.Collections](/engine/6000.7/script-reference/unity/collections.md)
* **Assembly:** UnityEngine.ManagedKernelModule

## ReadPackedLongDelta(long, StreamCompressionModel)

```csharp
public long ReadPackedLongDelta(long baseline, in StreamCompressionModel model)
```

### Parameters

**** (\[long]\(https\://learn.microsoft.com/dotnet/api/system.int64)): The previous 8-byte signed long value, used to compute the diff.**** (\[StreamCompressionModel]\(/engine/6000.7/script-reference/unity/collections/streamcompressionmodel)): [StreamCompressionModel](/engine/6000.7/script-reference/unity/collections/streamcompressionmodel.md) model for reading value in a packed manner.

### Returns

| Type                                                        | Description                                                                                                                                          |
| ----------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------- |
| [long](https://learn.microsoft.com/dotnet/api/system.int64) | An 8-byte signed long read from the current stream, or 0 if the end of the stream has been reached. If the data did not change, this also returns 0. |