Summary - dart:ffi

Combine DynamicLibrary and lookupFunction to call C.

Summary - dart:ffi

Calling a C function combines two steps: load the library with DynamicLibrary.open, and bind the function to Dart with lookupFunction. Define the signatures with two typedefs (Native and Dart).

final lib = DynamicLibrary.open('libmath.so');
final topla = lib.lookupFunction<NativeTopla, DartTopla>('topla');
print(topla(2, 3));

Exercise Call the abs function

First define the typedefs NativeAbs = Int32 Function(Int32) and DartAbs = int Function(int). In main, get lib with DynamicLibrary.process(), look up the 'abs' symbol with lookupFunction, and print the result of abs(-5).

Show example solution

import 'dart:ffi';

typedef NativeAbs = Int32 Function(Int32);
typedef DartAbs = int Function(int);

void main() {
  final lib = DynamicLibrary.process();
  final abs = lib.lookupFunction<NativeAbs, DartAbs>('abs');
  print(abs(-5));
}

Test yourself

Which two ffi tools combine to call a C function?
- setState and build
- DynamicLibrary and lookupFunction
- Widget and BuildContext
- Navigator and Route
Show answer

DynamicLibrary and lookupFunction — DynamicLibrary loads the C library, lookupFunction converts the symbol to a Dart function; together they let you call the C function.
Call the topla function
```
print(____(2, 3));
```
Show answer
```
print(topla(2, 3));
```
dart:ffi summary matches

dart:ffi

FFI framework
DynamicLibrary

Library object
lookupFunction

Symbol binding
typedef

Signature definition

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