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