use core::mem::MaybeUninit;

/// Unpoisons `buf` if MSAN support is enabled.

///

/// Most backends do not need to unpoison their output. Rust language- and

/// library- provided functionality unpoisons automatically. Similarly, libc

/// either natively supports MSAN and/or MSAN hooks libc-provided functions

/// to unpoison outputs on success. Only when all of these things are

/// bypassed do we need to do it ourselves.

///

/// The call to unpoison should be done as close to the write as possible.

/// For example, if the backend partially fills the output buffer in chunks,

/// each chunk should be unpoisoned individually. This way, the correctness of

/// the chunking logic can be validated (in part) using MSAN.

pub unsafe fn unpoison(buf: &mut [MaybeUninit<u8>]) {

    cfg_if! {

        if #[cfg(getrandom_msan)] {

            unsafe extern "C" {

                fn __msan_unpoison(a: *mut core::ffi::c_void, size: usize);

            }

            let a = buf.as_mut_ptr().cast();

            let size = buf.len();

            unsafe { __msan_unpoison(a, size) };

        } else {

            let _ = buf;

        }

    }

}