# read(_:maxLength:) Reads up to a given number of bytes into a given buffer. ``` func read(_ buffer: UnsafeMutablePointer, maxLength len: Int) -> Int ``` ## Parameters `buffer` A data buffer. The buffer must be large enough to contain the number of bytes specified by `len`. `len` The maximum number of bytes to read. ## Return Value A number indicating the outcome of the operation: ## Discussion - A positive number indicates the number of bytes read. - `0` indicates that the end of the buffer was reached. - `-1` means that the operation failed; more information about the error can be obtained with [`streamError`](/documentation/Foundation/Stream/streamError). --- 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)