Function sparse_mmap::try_compare_exchange

pub unsafe fn try_compare_exchange<T: AsBytes + FromBytes>(
    dest: *mut T,
    current: T,
    new: T,
) -> Result<Result<T, T>, MemoryError>

Atomically swaps the value at dest with new when *dest is current, using a sequentially-consistent memory ordering.

Returns Ok(Ok(new)) if the swap was successful, Ok(Err(*dest)) if the swap failed, or Err(MemoryError::AccessViolation) if the swap could not be attempted due to an access violation.

Panics if the size is not 1, 2, 4, or 8 bytes.

Safety

This routine is safe to use if the memory pointed to by dest is being concurrently mutated.

WARNING: This routine should only be used when you know that dest is valid, reserved addresses but you do not know if they are mapped with the appropriate protection. For example, this routine is useful if dest is a sparse mapping where some pages are mapped with PAGE_NOACCESS/PROT_NONE, and some are mapped with PAGE_READWRITE/PROT_WRITE.