Foreign Function Interface | How to use FFI in Flutter | How to use native code in flutter ?

FFI stands for Foreign Function Interface, and it is a way to call functions that are written in other programming languages from within Dart code in Flutter. This can be useful when you want to use functionality from a native library or when you want to write performance-critical code in a language like C or C++.

Here is a simple example of how to use FFI in Flutter:

• First, you need to create a Dart class that represents the foreign function interface. This class will contain the functions that you want to call from the native library. For example:

//dart Program

import 'dart:ffi'; // Import the FFI library

typedef NativeAdd = Int32 Function(Int32, Int32); // Define the signature of the native function
typedef DartAdd = int Function(int, int); // Define the signature of the Dart function

class MathLibrary {
  final DynamicLibrary _library; // Store a reference to the native library

  MathLibrary()
      : _library = Platform.isAndroid
            ? DynamicLibrary.open("libmath.so") // Load the native library
            : DynamicLibrary.process();

  int add(int a, int b) {
    final nativeAdd =
        _library.lookupFunction<NativeAdd, DartAdd>("add"); // Look up the function in the library
    return nativeAdd(a, b); // Call the function and return the result
  }
}

In this example, we define a MathLibrary class that loads a native library and provides a add function that calls a native function with the same name.

• Next, you need to write the native library that implements the functions you want to call from Dart. Here’s an example of a simple math.c file that exports a add function:
• In this example, we define a add function that takes two integers and returns their sum.

//C Program
#include <stdint.h>

int32_t add(int32_t a, int32_t b) {
  return a + b;
}

• Finally, you need to build the native library and make it accessible to your Dart code. The exact process for building the library depends on your platform and development environment. Once you have built the library, you can use the MathLibrary class to call the add function:

//C Program
void main() {
  final math = MathLibrary();
  final result = math.add(1, 2);
  print("1 + 2 = $result");
}

In this example, we create a MathLibrary instance and call its add function with two arguments. The function returns the sum of the arguments, which we then print to the console.

This is just a simple example, but FFI can be used to call any function from a native library, including functions that take complex data types as arguments or return values. However, it’s important to be careful when using FFI, as it can introduce security risks and compatibility issues if not used correctly.