Some convenient Swift extension methods for reading raw or binary data in NSInputStream

NSInputStreamHelper.swift

// Convenience extension for reading from NSInputStream from swift
// Useful for reading binary data in chunks using arbitary structs 

extension NSInputStream {
    func readByteArray(len: Int) -> [UInt8] {
        var readBuffer = Array<UInt8>(count:len, repeatedValue: 0)
        let numberOfBytesRead = self.read(&readBuffer, maxLength: readBuffer.count)
        assert(numberOfBytesRead == len)
        return readBuffer
    }
    
    func readNSData(len: Int) -> NSData {
        return NSData(bytes: readByteArray(len), length: len)
    }
    
    func readCharsAsString(len: Int) -> String {
        return String(data: readNSData(len), encoding: NSUTF8StringEncoding)!
    }
    
    func readType<T>(_: T.Type) -> T {
        let buffer = readByteArray(sizeof(T))
        return UnsafePointer<T>(buffer).memory
    }
}

// Example 
struct RGBA {
    var r,g,b,a: UInt8
}

func generateRandomData(count:Int) -> NSData
{
    var array = Array<UInt8>(count: count, repeatedValue: 0)
    arc4random_buf(&array, Int(count))
    return NSData(bytes: array, length: count)
}

let randomData = generateRandomData(256)

func getRGBAFromBinaryData(data: NSData) -> [RGBA] {
    var myStructArray: [RGBA] = []
    
    let stream = NSInputStream(data: randomData)
    stream.open(); defer { stream.close() } // defer closes handle on scope exit
    
    while stream.hasBytesAvailable {
        myStructArray.append(stream.readStruct(RGBA))
    }
    
    return myStructArray
}

let structuredData = getRGBAFromBinaryData(randomData)
//[{r 127, g 78, b 133, a 51}, {r 79, g 26, b 20, a 189}, {r 25, g 124, b 6, a 130}, {r 252, g 244, b 128, a 227}, ...]