A memory leak, could my problem be with pointers [swift] - ios

Question

iOS 12.x Swift 5
I am using sockets to talk to another box and I wrote this code which I think makes sense. but I wanted to check with an expert. I ask cause I think I have some sort of memory leak with this app. And I suspect pointers, as you do. I am watching the memory it uses slowly increase as I am running it.
func sendMessage(message: String) {
let data = message.data(using: String.Encoding.utf8, allowLossyConversion: false)!
let dataMutablePointer = UnsafeMutablePointer<UInt8>.allocate(capacity: data.count)
//Copies the bytes to the Mutable Pointer
dataMutablePointer.initialize(to: 0)
data.copyBytes(to: dataMutablePointer, count: data.count)
//Cast to regular UnsafePointer
let dataPointer = UnsafePointer<UInt8>(dataMutablePointer)
//Your stream
outputStream.write(dataPointer, maxLength: data.count)
defer {
dataMutablePointer.deinitialize(count: data.count)
}
}
Does this code look sane? Could it be the source of my memory leak? Do I need to deinitalize this pointer?

Answer 1

Could it be the source of my memory leak?
Yes, surely.
Do I need to deinitalize this pointer?
As commented by bscothern, you need to deinitalize the pointer if the Pointee is non-trivial type. But in case of UInt8, it is not mandatory.
But you need to deallocate the pointer eventually.
Your code would be something like this:
func sendMessage(message: String) {
let data = message.data(using: String.Encoding.utf8, allowLossyConversion: false)!
let dataMutablePointer = UnsafeMutablePointer<UInt8>.allocate(capacity: data.count)
defer {
dataMutablePointer.deallocate()
}
//Copies the bytes to the Mutable Pointer
dataMutablePointer.initialize(to: 0)
defer {
//This is not required, but you can put `deinitialize` here if you prefer
dataMutablePointer.deinitialize(count: data.count)
}
data.copyBytes(to: dataMutablePointer, count: data.count)
//Cast to regular UnsafePointer
let dataPointer = UnsafePointer<UInt8>(dataMutablePointer)
//Your stream
outputStream.write(dataPointer, maxLength: data.count)
}
defer defers the execution of its block until the end of the enclosing block, so dataMutablePointer.deallocate() will be executed after outputStream.write(dataPointer, maxLength: data.count) is finished.
But I would write something equivalent without copying data:
func sendMessage(message: String) {
let data = message.data(using: String.Encoding.utf8, allowLossyConversion: false)!
data.withUnsafeBytes {bytes in
let dataPointer = bytes.baseAddress!.assumingMemoryBound(to: UInt8.self)
//Your stream
outputStream.write(dataPointer, maxLength: data.count)
}
}
Or, more simply:
func sendMessage(message: String) {
//Your stream
outputStream.write(message, maxLength: message.utf8.count)
}