# CFReadStreamGetBuffer(_:_:_:) Returns a pointer to a stream’s internal buffer of unread data, if possible. ``` func CFReadStreamGetBuffer(_ stream: CFReadStream!, _ maxBytesToRead: CFIndex, _ numBytesRead: UnsafeMutablePointer!) -> UnsafePointer! ``` ## Parameters `stream` The stream to examine. `maxBytesToRead` The maximum number of bytes to read. If greater than `0`, `maxBytesToRead` limits the number of bytes read; if `0` or less, all available bytes are read. `numBytesRead` On return, contains the length of returned buffer. If `stream` is not open or has encountered an error, `numBytesRead` is set to `-1`. ## Return Value A pointer to the internal buffer of unread data for `stream`, if possible; `NULL` otherwise. The buffer is good only until the next stream operation called on the stream. You should neither change the contents of the returned buffer nor attempt to deallocate the buffer; it is still owned by the stream. The bytes returned in the buffer are considered read from the stream. ## 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)