Simple Example

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

int gcd(int a, int b) {
    while (b != 0) { int t = b; b = a % b; a = t; }
    return a;
}

long long factorial(int n) {
    long long r = 1;
    for (int i = 2; i <= n; i++) r *= i;
    return r;
}

double compute(int mode, double value, const char* name) {
    if (strcmp(name, "square") == 0) return value * value;
    if (strcmp(name, "half") == 0)   return value / 2.0;
    return value;
}

const char* getVersion(void) { return "1.0.0"; }

import ffi from 'liblibrary.so';
import { dlopen, FFIType, CString, CFunction, JSCallback } from 'arkffi';

const LIB = 'libffi_target.so';

// ── dlopen ──
const lib = dlopen(LIB, {
  add:        { args: [FFIType.double, FFIType.double],  returns: FFIType.double },
  gcd:        { args: [FFIType.int32,  FFIType.int32],   returns: FFIType.int32 },
  factorial:  { args: [FFIType.int32],                    returns: FFIType.int64 },
  compute:    { args: [FFIType.int32, FFIType.double, FFIType.CString], returns: FFIType.double },
  getVersion: { args: [],                                  returns: FFIType.int64 },
});

const sum = lib.symbols.add(2.0, 3.0);              // 5.0
const g   = lib.symbols.gcd(12, 18);                 // 6
const sq  = lib.symbols.compute(0, 4.0, 'square');  // 16.0
const ptr = lib.symbols.getVersion();
new CString(ptr).toString();                         // "1.0.0"

// ── CFunction ──
const addPtr = ffi.getSymbolPtr(handle, 'add');
const addFn  = CFunction({
  args: [FFIType.double, FFIType.double],
  returns: FFIType.double, ptr: addPtr,
});
addFn(7.0, 8.0);                                    // 15.0
addFn.close();

// ── JSCallback ──
const cb = new JSCallback(
  (a: number, b: number): number => a + b,
  { args: [FFIType.int32, FFIType.int32], returns: FFIType.int32 },
);
cb.call(100, 200);                                   // 300
cb.close();

// ── Raw bridge ──
const h = ffi.load(LIB);
ffi.defineFunction(h, 'divide', 'dd', 'd');
ffi.callBySig(h, 'divide', [10.0, 3.0], []);
ffi.close(h);

lib.close();

# Build test HAP
hvigorw --mode module -p module=library@ohosTest genOnDeviceTestHap

# Install and run
hdc install library/build/default/outputs/ohosTest/library-ohosTest-signed.hap
hdc shell aa test -b <bundleName> -m library_test -s unittest OpenHarmonyTestRunner