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# field-offset: safe pointer-to-member functionality
This crate implements an `offset_of!(...)` macro which safely encapsulates
a pointer-to-member.
Example:
```rust
struct Foo {
x: u32,
y: f64
}
let foo_y = offset_of!(Foo => y);
let mut a = Foo { x: 1, y: 2.0 };
*foo_y.apply_mut(&mut a) = 3.0;
assert!(a.y == 3.0);
```
The macro returns an instance of `FieldOffset<T, U>`, which represents a
pointer to a field of type `U` within a containing type, `T`.
The `FieldOffset` type implements `Add`. Applying the resulting field offset
is equivalent to applying the first field offset, then applying the second
field offset.
The macro also supports accessing nested fields:
```rust
let bar_foo_y = offset_of!(Bar => foo: Foo => y);
```
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