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Passing big arrays efficiently between Flutter (dart) and its FFI (C/C++)?

We are developing a "image editor" app using Flutter. Thus, we need to (1) show images on the UI, and (2) manipulate images using some algorithms in C/C++.

Flutter does have a FFI between dart and c/c++, but I do not know how to pass big arrays like images (e.g. can be megabytes) efficiently?

Thanks very much!

Solution

  • After experiments, now I have some code (in the production code!) passing around array of 20MB size between C and Dart. It only takes several milliseconds (just a rough estimation, but surely it does not take seconds).

    Thus, my answer to my question is: Just do it. Memory copies seems to be quite cheap, and do not worry about it :)

    EDIT in 2022:

    Flutter does have have "zero copy" array transfer when going from native to Flutter side, via DartCObject. See the "ZeroCopyBuffer" feature in my library https://github.com/fzyzcjy/flutter_rust_bridge for an example of usage.