libraries that are not supported by null sound safety in flutter

In Flutter, the Dart programming language is used for app development. However, you can also integrate C libraries into your Flutter project using the FFI (Foreign Function Interface) package.

When it comes to sound safety, it means that the libraries you use should not cause any null sound errors or issues. To ensure this, you need to carefully handle null values and ensure that they are not passed to the C libraries.

Here are the steps to use C libraries that are not supported by null sound safety in Flutter:

  1. Install the FFI package: To start using C libraries in Flutter, you need to include the FFI package in your project. You can do this by adding the following dependency to your pubspec.yaml file:
dependencies:
  ffi: ^1.1.2

After adding the dependency, run the command flutter pub get to install the package.

  1. Define the functions: In Dart, you need to define the functions that will be used to interact with the C libraries. This is done using the ffi package's native library. You can define the functions using the external keyword along with the native annotation. For example:
import 'dart:ffi';

typedef MyFunction = Int32 Function(Int32);
typedef MyFunctionDart = int Function(int);

@ffi.native
Int32 myFunction(Pointer<MyStruct> data);

Here, MyFunction and MyFunctionDart are typedefs representing the function signature, and myFunction is the actual function that will be used.

  1. Load the library: Next, you need to load the C library into your Flutter project. This is done using the DynamicLibrary class from the ffi package. You can load the library using the DynamicLibrary.open method. For example:
final myLibrary = DynamicLibrary.open('path/to/my/library.so');

Make sure to replace 'path/to/my/library.so' with the actual path to your C library.

  1. Bind the functions: After loading the library, you need to bind the functions defined in step 2 to the loaded library. This is done using the ffi package's NativeLibrary class. You can bind the functions using the lookupFunction method. For example:
final myFunction = myLibrary.lookupFunction<MyFunctionDart, MyFunction>('myFunction');

Here, MyFunctionDart is the typedef representing the Dart function, MyFunction is the typedef representing the C function, and 'myFunction' is the name of the C function.

  1. Use the functions: Finally, you can use the functions in your Flutter code. You can call the functions like any other Dart function. For example:
final result = myFunction(data);

Here, data is the data you want to pass to the C function, and result is the returned value from the C function.

By following these steps, you can integrate C libraries into your Flutter project and use them safely, avoiding null sound errors. Remember to handle null values properly to ensure the soundness of your code.