NSInputStream+Read.swift

import Foundation

protocol EndianConvertible {
    typealias IntegerType

    init(bigEndian value: IntegerType)
    init(littleEndian value: IntegerType)

    var bigEndian: IntegerType { get }
    var littleEndian: IntegerType { get }

    var byteSwapped: IntegerType { get }
}

extension  Int16 : EndianConvertible {}
extension  Int32 : EndianConvertible {}
extension  Int64 : EndianConvertible {}
extension UInt16 : EndianConvertible {}
extension UInt32 : EndianConvertible {}
extension UInt64 : EndianConvertible {}

extension NSInputStream {

    func read<T : Integer>() -> T? {
        var buffer : T = 0

        let n = withUnsafePointer(&buffer) { (p) in
            self.read(UnsafePointer<UInt8>(p), maxLength: sizeof(T))
        }

        if n > 0 {
            assert(n == sizeof(T), "read length must be sizeof(T)")
            return buffer
        } else {
            return nil
        }
    }

    func readNetworkBytes<T : EndianConvertible where T.IntegerType : Integer>() -> T? {
        if let value : T.IntegerType = self.read() {
            return T(bigEndian: value)
        }

        return nil
    }

    func readNetworkBytes() -> UInt8? { return self.read() }

    func readNetworkBytes() -> Int8?  { return self.read() }
}