# withCompressionStream(using:writingTo:blockSize:flags:threadCount:_:) Calls the given closure with a compression sequential output stream. ``` static func withCompressionStream(using compressionAlgorithm: ArchiveCompression, writingTo compressedStream: ArchiveByteStream, blockSize: Int = (1<<20), flags: ArchiveFlags = [], threadCount: Int = 0, _ body: (ArchiveByteStream) throws -> E) throws -> E ``` ## Parameters `compressionAlgorithm` The compression algorithm. `compressedStream` An output stream that receives compressed data, the operation only calls write methods. `blockSize` The compression block size, in bytes. `flags` Flags that control the behavior of the operation. `threadCount` The number of worker threads that the operation uses, set to `0` for default. `body` A closure with the archive byte stream passed as a parameter. ## Return Value The result of the closure. --- 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)