In Swift 3, you cannot init an UnsafePointer using an UnsafeRawPointer.You can use assumingMemoryBound(to:) to convert an UnsafeRawPointer into an UnsafePointer. Like this:

var ptr = data.bytes.assumingMemoryBound(to: UInt8.self)

Use debugDescription or distance(to:) to compare two pointer.

while(ptr.debugDescription < endPtr.debugDescription)

or

while(ptr.distance(to:endPtr) > 0)

ios - UnsafePointer initializer in Swift 3 - Stack Overflow