Function bitvec::ptr::write

source · 
pub unsafe fn write<T, O>(dst: BitPtr<Mut, T, O>, value: bool)where
    T: BitStore,
    O: BitOrder,
Expand description

Single-Bit Write

This writes a bit into dst directly.

Original

ptr::write

Safety

Because this performs a dereference of memory, it inherits the original ptr::write’s requirements:

  • dst must be valid to write
  • dst must be properly aligned. This is an invariant of the BitPtr type as well as of the memory access.

Additionally, dst must point to an initialized value of T. Integers cannot be initialized one bit at a time.

Behavior

This is required to perform a read/modify/write cycle on the memory location. LLVM may or may not emit a bit-write instruction on targets that have them in the ISA, but this is not specified in any way.

Examples

use bitvec::prelude::*;
use bitvec::ptr as bv_ptr;

let mut data = 0u8;
let ptr = BitPtr::<_, _, Lsb0>::from_mut(&mut data);
unsafe { bv_ptr::write(ptr.add(2), true); }
assert_eq!(data, 4);