# sharedBufferPipe(capacity:) Creates a pair of streams and links them by a shared buffer. ``` static func sharedBufferPipe(capacity: Int) -> (output: ArchiveByteStream, input: ArchiveByteStream)? ``` ## Parameters `capacity` The size of the internal buffer allocation, in bytes. ## Return Value A new pair of [`ArchiveByteStream`](/documentation/AppleArchive/ArchiveByteStream) instances on success; `nil` otherwise. ## Discussion This function creates two [`ArchiveByteStream`](/documentation/AppleArchive/ArchiveByteStream) instances that provide one-way communication between two threads. One thread calls the sequential output stream `output`, and the other thread calls the sequential input stream `input`. The function blocks writing to `output` when the buffer is full, and blocks reading from `input` when the buffer is empty. If either thread calls [`cancel`](/documentation/AppleArchive/ArchiveHeader/EntryMessageStatus/cancel), the operation aborts both streams, and immediately calls return (without blocking) with an error. Closing `output`, indicates end-of-file (EOF) and writing additional bytes fails. After the operation reaches EOF and has read all data, the read function on `input` returns `0` to signal EOF. The operation destroys the underlying buffer after it closes both streams. --- 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)