dart:ffi

Learn C interop with dart:ffi.

dart:ffi

dart:ffi is Dart's library for communicating with C libraries. FFI (Foreign Function Interface) lets Dart code call C functions. It is imported with import 'dart:ffi';.

FFI is useful for performance-critical operations or for reusing existing C libraries. Dart supports FFI on native platforms (Flutter native, CLI); not on the web. With dart:ffi, a DynamicLibrary is loaded and functions are bound with lookupFunction.

FFI limits

dart:ffi works only on native platforms; it is not supported on the web. To load a C library, use DynamicLibrary.open('libmylib.so') (Linux), .dylib (macOS), or .dll (Windows).

FFI provides Pointer, Struct, and Union types to share data between Dart and C. These types give direct memory access; use them carefully. Incorrect use can corrupt memory.

Exercise An FfiBinding class

Add import 'dart:ffi'; to import the FFI library. Define an FfiBinding class with final String name; final String dartType; FfiBinding(this.name, this.dartType); field and constructor. Add a String describe() => '$name: $dartType'; method. In main create final b = FfiBinding('add', 'int Function(int, int)');; print with print(b.describe());.

Show example solution

import 'dart:ffi';

class FfiBinding {
  final String name;
  final String dartType;
  FfiBinding(this.name, this.dartType);
  String describe() => '$name: $dartType';
}

void main() {
  final b = FfiBinding('add', 'int Function(int, int)');
  print(b.describe());
}

Test yourself

What does dart:ffi provide?
- Web rendering
- Communication with C libraries
- Garbage collection
- UI widgets
Show answer

Communication with C libraries — dart:ffi is Dart's C interop library.

dart:ffi import

import '____';

void main() {
  print('ffi loaded');
}

Show answer

import 'dart:ffi';

void main() {
  print('ffi loaded');
}

Match the FFI parts

dart:ffi

C interop library
DynamicLibrary

C library loader
lookupFunction

Function binder
Pointer

Memory address

Next lesson: DynamicLibrary

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