# hun_offsetof

Provides C-like macros: offset_of and container_of

## 和memoffset crate的区别- Differences between crate memoffset and crate self
1. 基于指针操作，不占用栈空间，支持超大数据结构，无栈溢出风险
1. Pointer-based opertions do not occupy stack space, support super-large data structures, and avoid stack overflow risks.
2. 提供container_of操作
2. Provides the container_of operation.

基于指针的操作属于unsafe范围，如果使用声明宏方式，可能出现嵌套unsafe的编译告
警，而过程宏可以消除这类告警。
Pointer-based operations are unsafe, If the declaration macro mode is used, nested unsafe compilation warnings may be generated, which can be eliminated by procedure macro.

# interfaces

```rust
offset_of!(type, member) -> usize;
container_of!(&obj, type, member) -> &type;
container_of_mut!(&obj, type, member) -> &mut type;
```

# Examples

```rust

extern crate hun_offsetof as hun;

#[repr(C)]
struct Bar {
	key:	i32,
	value:	i32,
}

#[repr(C)]
struct Foo {
	key:	i32,
	value:	[Bar; 2],
}

assert_eq!(hun::offset_of!(Bar, value), 4);
assert_eq!(hun::offset_of!(Foo, value[1].key), 12);

let foo = Foo {
	key: 1,
	value: [ Bar { key: 2, value: 2}, Bar { key: 3, value: 3 }],
};
let value = &foo.value[1].value;

let obj = unsafe { hun::container_of!(value, Foo, value[1].value) };
assert_eq!(obj as *const _, &foo as *const _);
```