> ## 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.

# FFIType

> C 函數定義中的類型常量

`FFIType` 提供函數定義中使用的類型常量。

## 常量表

| 常量                                                       | 編碼  | ArkTS 類型     | C 類型                         |
| -------------------------------------------------------- | --- | ------------ | ---------------------------- |
| `FFIType.char` / `int8_t` / `i8`                         | `c` | `number`     | `char` / `int8_t`            |
| `FFIType.uint8_t` / `u8`                                 | `i` | `number`     | `uint8_t`                    |
| `FFIType.int16_t` / `i16`                                | `i` | `number`     | `int16_t`                    |
| `FFIType.uint16_t` / `u16`                               | `i` | `number`     | `uint16_t`                   |
| `FFIType.int32` / `i32` / `int` / `uint32_t` / `u32`     | `i` | `number`     | `int32_t`                    |
| `FFIType.int64` / `i64` / `int64_t` / `uint64_t` / `u64` | `l` | `number`     | `int64_t` / `uint64_t`       |
| `FFIType.double` / `f64`                                 | `d` | `number`     | `double`                     |
| `FFIType.float` / `f32`                                  | `f` | `number`     | `float`                      |
| `FFIType.bool`                                           | `b` | `number`     | `bool`                       |
| `FFIType.CString`                                        | `s` | `string`     | `const char*`                |
| `FFIType.ptr` / `pointer` / `function` / `buffer`        | `p` | `number`     | `void*`                      |
| `FFIType.callback`                                       | `k` | `JSCallback` | `int32_t (*)(int32_t)`（函數指針） |
| `FFIType.usize`                                          | `l` | `number`     | `size_t` / `uintptr_t`       |

## 用法

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

const def = {
  args: [FFIType.int32, FFIType.double, FFIType.CString],
  returns: FFIType.double,
};

// 也可使用字符串字面量（等價的簡寫形式）
// args: ['i', 'd', 's']
// returns: 'd'
```

## ARM64 寄存器映射

| C 類型                           | ArkTS 類型 | 寄存器       |
| ------------------------------ | -------- | --------- |
| `int32_t`, `bool`, `char`      | `number` | x0-x7     |
| `int64_t`, `uint64_t`, `void*` | `number` | x0-x7     |
| `float`, `double`              | `number` | v0-v7     |
| `const char*`                  | `string` | x0-x7（指針） |