Function bitvec::ptr::copy_nonoverlapping

source · 
pub unsafe fn copy_nonoverlapping<T1, T2, O1, O2>(
    src: BitPtr<Const, T1, O1>,
    dst: BitPtr<Mut, T2, O2>,
    count: usize
)where
    O1: BitOrder,
    O2: BitOrder,
    T1: BitStore,
    T2: BitStore,
Expand description

Bit-wise memcpy

This copies bits from a region beginning at src into a region beginning at dst, each extending upwards in the address space for count bits.

The two regions may not overlap.

Original

ptr::copy_nonoverlapping

Overlap Definition

The two regions may be in the same provenance as long as they have no common bits. bitvec only defines the possibility of overlap when the O1 and O2 bit-ordering parameters are the same; if they are different, then it considers the regions to not overlap, and does not attempt to detect real-memory collisions.

Safety

In addition to the bit-ordering constraints, this inherits the restrictions of the original ptr::copy_nonoverlapping:

  • src must be valid to read the next count bits out of memory.
  • dst must be valid to write into the next count bits.
  • Both src and dst must satisfy BitPtr’s non-null, well-aligned, requirements.

Behavior

This reads and writes each bit individually. It is incapable of optimizing its behavior to perform batched memory accesses that have better awareness of the underlying memory.

The BitSlice::copy_from_bitslice method is able to perform this optimization, and tolerates overlap. You should always prefer to use BitSlice if you are sensitive to performance.

Examples

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

let start = 0b1011u8;
let mut end = 0u16;

let src = BitPtr::<_, _, Lsb0>::from_ref(&start);
let dst = BitPtr::<_, _, Msb0>::from_mut(&mut end);

unsafe {
  bv_ptr::copy_nonoverlapping(src, dst, 4);
}
assert_eq!(end, 0b1101_0000_0000_0000);