| # Single-Bit Unaligned Write |
| |
| This writes a bit into `dst` directly. It uses compiler intrinsics to tolerate |
| an unaligned `T` address. However, because `BitPtr` has a type invariant that |
| addresses are always well-aligned (and non-null), this has no benefit or |
| purpose. |
| |
| ## Original |
| |
| [`ptr::write_unaligned](core::ptr::write_unaligned) |
| |
| ## Safety |
| |
| - `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 |
| |
| ```rust |
| 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_unaligned(ptr.add(2), true); } |
| assert_eq!(data, 4); |
| ``` |
