# InputFilter An encoder-decoder that reads input data from a stream. ``` class InputFilter where D : DataProtocol ``` ## Topics ### Initializers [`init(FilterOperation, using: Algorithm, bufferCapacity: Int, readingFrom: (Int) throws -> D?) throws`](/documentation/Compression/InputFilter/init(_:using:bufferCapacity:readingFrom:)) Creates an input filter that can be used to compress or decompress data. ### Instance Methods [`func readData(ofLength: Int) throws -> Data?`](/documentation/Compression/InputFilter/readData(ofLength:)) Reads processed data from the input filter. --- 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)