Function bitvec::slice::from_raw_parts_mut

source · [−]
pub unsafe fn from_raw_parts_mut<'a, T, O>(
    data: BitPtr<Mut, T, O>,
    len: usize
) -> Result<&'a mut BitSlice<T, O>, BitSpanError<T>> where
    O: BitOrder,
    T: 'a + BitStore, 
Expand description

Raw Bit-Slice Construction

This produces an &mut BitSlice<T, O> reference handle from a BitPtr<Mut, T, O> bit-pointer and a length.

Parameters

  1. data: a bit-pointer to the starting bit of the produced bit-slice. This should generally have been produced by BitSlice::as_mut_ptr, but you are able to construct these pointers directly if you wish.
  2. len: the number of bits, beginning at data, that the produced bit-slice includes. This value cannot depart an allocation area, or exceed BitSlice’s encoding limitations.

Returns

This returns a Result, because it can detect and gracefully fail if len is too large, or if data is ill-formed. This fails if it has an error while encoding the &mut BitSlice, and succeeds if it is able to produce a correctly encoded value.

Note that this is not able to detect semantic violations of the memory model. You are responsible for upholding memory safety.

Original

slice::from_raw_parts_mut

API Differences

This takes a BitPtr<Mut, T, O> instead of a hypothetical *mut Bit, because bitvec is not able to express raw Rust pointers to individual bits.

Additionally, it returns a Result rather than a direct bit-slice, because the given len argument may be invalid to encode into a &mut BitSlice reference.

Safety

This has the same memory safety requirements as the standard-library function:

  • data must be valid for reads and writes of at least len bits,
  • The bits that the produced bit-slice refers to must be wholly unreachable by any other part of the program for the duration of the lifetime 'a,

and additionally imposes some of its own:

Examples

use bitvec::{
  prelude::*,
  index::BitIdx,
  ptr::Mut,
  slice as bv_slice,
};

let mut elem = 0u16;
let addr = (&mut elem).into();
let head = BitIdx::new(1).unwrap();

let data: BitPtr<Mut, u16> = BitPtr::new(addr, head).unwrap();
let bits = unsafe { bv_slice::from_raw_parts_mut(data, 3) };
bits.unwrap()[1 ..].fill(true);

assert_eq!(elem, 12);