CODEWITHSUNDEEP
c++objective-cswiftallocationunsafe-pointers
Senocico Stelian
Senocico Stelian

Reputation: 1697

iOS UnsafePointer memory deallocation

I am interfacing with a hardware device that runs C++ code and sends live data almost 10 times per second to the iOS device.

I have a Swift method like this:

func m16b_to_mE0(_ pointer: UnsafePointer<m16bytes_t>) -> UnsafePointer<metrics_E0>? {
     return UnsafeRawPointer(pointer).bindMemory(to: metrics_E0.self, capacity: MemoryLayout<metrics_E0>.size)
}

Where m16bytes_t is

typedef uint8_t m16bytes_t[16];

And metrics_E0 is

struct metrics_E0 {
    uint8_t   tag;
    uint8_t   hr;
    uint16_t  c_speed;
    uint16_t  c_max_speed;
    uint16_t  c_met_power;
    uint16_t  c_speed_intensity;
    uint16_t  c_hr_exertion;
    uint8_t   hr_avg;
    u3bytes_t c_acc_met_power; //typedef uint8_t u3bytes_t[3];
};

The above m16b_to_mE0 method is called almost 10 times per second, for about two hours, more or less.

My question is: is it required to deallocate / deinitialize memory for each UnsafeRawPointer after bindMemory to metrics_E0? If yes, how?

What happens if I don't take care to manually deallocate / deinitialize the UnsafePointer type from the memory?

Upvotes: 0

Views: 253

Answers (1)

Cristik
Cristik

Reputation: 32879

bindMemory doesn't change the ownership of the allocated memory, it's goal is to allow you to peak at the contents of the memory. Unless specified in the documentation of the C++ library that you need to manually release the received pointer, then you should not need to worry about this.

You can do some memory profiling if you want to be sure, and to monitor the memory usage of your application. Or, if you have access to the C++ code, you could set a breakpoint on the m16b_to_mE0 function and go through the stacktrace until you reach the C++ zone, and check what happens later with the pointer that was sent to your method.

Note that releasing the memory of that buffer might require some library dedicated functions for deallocations, instead of the standard ones, however this should be specified in the library documentation.

Upvotes: 1

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