> ## Documentation Index
> Fetch the complete documentation index at: https://docs.arkffi.hmbill.cn/llms.txt
> Use this file to discover all available pages before exploring further.

# Function Pointers

> Working with raw C function pointers via CFunction

Some C APIs expect function pointers as arguments. arkffi provides `CFunction` to wrap them.

## Obtaining a Pointer

```typescript theme={null}
const handle = ffi.load('libffi_target.so');
const ptr = ffi.getSymbolPtr(handle, 'add');
// ptr is the memory address of the C function
```

## Creating a CFunction Wrapper

```typescript theme={null}
import { CFunction, FFIType } from 'arkffi';

const add = CFunction({
  args: [FFIType.double, FFIType.double],
  returns: FFIType.double,
  ptr: ptr,
});

add(2.0, 3.0); // → 5.0
add.close();
```

## Lifecycle

Always close wrappers when done:

```typescript theme={null}
const fn = CFunction({ ... });
fn();
fn.close();
```

## Passing to C APIs

```typescript theme={null}
// C: void sort(int* arr, int (*cmp)(int, int));
const cmp = CFunction({ args: ['i', 'i'], returns: 'i', ptr: cmpPtr });
ffi.callMixed(handle, 'sort', 'ip', 'v', [arrPtr, cmp.ptr], []);
```

## Using JSCallback Instead

For TypeScript-to-C callbacks, use `JSCallback`:

```typescript theme={null}
const cmp = new JSCallback(
  (a: number, b: number): number => a - b,
  { args: [FFIType.int32, FFIType.int32], returns: FFIType.int32 },
);

ffi.callMixed(handle, 'sort', 'ip', 'v', [arrPtr, cmp.ptr], []);
cmp.close();
```