---
title: "CFDataAppendBytes(_:_:_:)"
framework: corefoundation
role: symbol
role_heading: Function
path: "corefoundation/cfdataappendbytes(_:_:_:)"
---

# CFDataAppendBytes(_:_:_:)

Appends the bytes from a byte buffer to the contents of a CFData object.

## Declaration

```swift
func CFDataAppendBytes(_ theData: CFMutableData!, _ bytes: UnsafePointer<UInt8>!, _ length: CFIndex)
```

## Parameters

- `theData`: A CFMutableData object. If you pass an immutable CFData object, the behavior is not defined.
- `bytes`: A pointer to the buffer of bytes to be added to theData.
- `length`: The number of bytes in the byte buffer bytes.

## See Also

### Modifying a Mutable Data Object

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