# CFDataAppendBytes(_:_:_:) Appends the bytes from a byte buffer to the contents of a CFData object. ``` func CFDataAppendBytes(_ theData: CFMutableData!, _ bytes: UnsafePointer!, _ 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`. ## Discussion --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)