# decodeBytes(withReturnedLength:) Decodes a buffer of data whose types are unspecified. ``` func decodeBytes(withReturnedLength lengthp: UnsafeMutablePointer) -> UnsafeMutableRawPointer? ``` ## Discussion `NSCoder`‘s implementation invokes [`decodeValue(ofObjCType:at:)`](/documentation/Foundation/NSCoder/decodeValue(ofObjCType:at:)) to decode the data as a series of bytes, which this method then places into a buffer and returns. The buffer’s length is returned by reference in `numBytes`. If you need the bytes beyond the scope of the current `@autoreleasepool` block, you must copy them. This method matches an [`encodeBytes(_:length:)`](/documentation/Foundation/NSCoder/encodeBytes(_:length:)) message used during encoding. ## See Also [`encodeArray(ofObjCType:count:at:)`](/documentation/Foundation/NSCoder/encodeArray(ofObjCType:count:at:)) Encodes an array of the given Objective-C type, provided the number of items and a pointer. --- 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)