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How to read partially a Data object

The recent change in Swift 4 provides the simple way to initialize a byte array with your Data object. The result gets you an [UInt8] with the whole data stored into it. 

let array = [UInt8](data)

I can't find the solution to load the same Data object only partially using an offset and a length. Is it possible without slicing the whole array or should I switch to InputStream?

Solution

  • You can slice a Data object with a subscript.

    For example, you just want the 3rd to 5th index in the data, you would use

    data[3..<6]

    In your case, you would do

    let array = [UInt8](data[lowerIndex..<upperIndex])

    where lowerIndex and upperIndex are the indexes.