Macro map_field

macro_rules! map_field {
    ($volatile:ident.$place:ident) => { ... };
}

Provides safe field projection for volatile pointers referencing structs.

Examples

Accessing a struct field:

use volatile::{VolatilePtr, map_field};
use core::ptr::NonNull;

struct Example { field_1: u32, field_2: u8, }
let mut value = Example { field_1: 15, field_2: 255 };
let mut volatile = unsafe { VolatilePtr::new((&mut value).into()) };

// construct a volatile reference to a field
let field_2 = map_field!(volatile.field_2);
assert_eq!(field_2.read(), 255);

Creating VolatilePtrs to unaligned field in packed structs is not allowed:

use volatile::{VolatilePtr, map_field};
use core::ptr::NonNull;

#[repr(packed)]
struct Example { field_1: u8, field_2: usize, }
let mut value = Example { field_1: 15, field_2: 255 };
let mut volatile = unsafe { VolatilePtr::new((&mut value).into()) };

// Constructing a volatile reference to an unaligned field doesn't compile.
let field_2 = map_field!(volatile.field_2);