---
title: "CFDataIncreaseLength(_:_:)"
framework: corefoundation
role: symbol
role_heading: Function
path: "corefoundation/cfdataincreaselength(_:_:)"
---

# CFDataIncreaseLength(_:_:)

Increases the length of a CFMutableData object’s internal byte buffer, zero-filling the extension to the buffer.

## Declaration

```swift
func CFDataIncreaseLength(_ theData: CFMutableData!, _ extraLength: CFIndex)
```

## Parameters

- `theData`: A CFMutableData object. If you pass an immutable CFData object, the behavior is not defined.
- `extraLength`: The number of bytes by which to increase the byte buffer.

## Discussion

Discussion This function increases the length of a CFMutableData object’s underlying byte buffer to a new size, initializing the new bytes to 0.

## See Also

### Modifying a Mutable Data Object

- [CFDataAppendBytes(_:_:_:)](corefoundation/cfdataappendbytes(_:_:_:).md)
- [CFDataDeleteBytes(_:_:)](corefoundation/cfdatadeletebytes(_:_:).md)
- [CFDataReplaceBytes(_:_:_:_:)](corefoundation/cfdatareplacebytes(_:_:_:_:).md)
- [CFDataSetLength(_:_:)](corefoundation/cfdatasetlength(_:_:).md)