# copyBytes(to:) Copies the bytes of data from the type into a typed memory buffer. ``` @discardableResult func copyBytes(to ptr: UnsafeMutableBufferPointer) -> Int ``` ## Parameters `ptr` A typed pointer to the buffer you want to copy the bytes into. ## Return Value The number of bytes copied. ## Discussion The following example copies the bytes from a typed memory buffer into the provided typed memory buffer: ```swift let source: [UInt8] = [0, 1, 2] var dest: [UInt8] = [0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF] dest.withUnsafeMutableBufferPointer { typedMemBuffer in let count = source.copyBytes(to: typedMemBuffer) // count == 3 } // dest = [0x00, 0x01, 0x02, 0xFF, 0xFF, 0xFF] ``` --- 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)