Trait FamStruct

Source

pub unsafe trait FamStruct {
    type Entry: PartialEq + Copy;

    // Required methods
    fn len(&self) -> usize;
    fn set_len(&mut self, len: usize);
    fn max_len() -> usize;
    fn as_slice(&self) -> &[Self::Entry];
    fn as_mut_slice(&mut self) -> &mut [Self::Entry];
}

Expand description

Trait for accessing properties of C defined FAM structures.

§Safety

This is unsafe due to the number of constraints that aren’t checked:

the implementer should be a POD
the implementor should contain a flexible array member of elements of type Entry
Entry should be a POD

Violating these may cause problems.

§Example

use vmm_sys_util::fam::*;

#[repr(C)]
#[derive(Default)]
pub struct __IncompleteArrayField<T>(::std::marker::PhantomData<T>, [T; 0]);
impl<T> __IncompleteArrayField<T> {
    #[inline]
    pub fn new() -> Self {
        __IncompleteArrayField(::std::marker::PhantomData, [])
    }
    #[inline]
    pub unsafe fn as_ptr(&self) -> *const T {
        ::std::mem::transmute(self)
    }
    #[inline]
    pub unsafe fn as_mut_ptr(&mut self) -> *mut T {
        ::std::mem::transmute(self)
    }
    #[inline]
    pub unsafe fn as_slice(&self, len: usize) -> &[T] {
        ::std::slice::from_raw_parts(self.as_ptr(), len)
    }
    #[inline]
    pub unsafe fn as_mut_slice(&mut self, len: usize) -> &mut [T] {
        ::std::slice::from_raw_parts_mut(self.as_mut_ptr(), len)
    }
}

#[repr(C)]
#[derive(Default)]
struct MockFamStruct {
    pub len: u32,
    pub padding: u32,
    pub entries: __IncompleteArrayField<u32>,
}

unsafe impl FamStruct for MockFamStruct {
    type Entry = u32;

    fn len(&self) -> usize {
        self.len as usize
    }

    fn set_len(&mut self, len: usize) {
        self.len = len as u32
    }

    fn max_len() -> usize {
        100
    }

    fn as_slice(&self) -> &[u32] {
        let len = self.len();
        unsafe { self.entries.as_slice(len) }
    }

    fn as_mut_slice(&mut self) -> &mut [u32] {
        let len = self.len();
        unsafe { self.entries.as_mut_slice(len) }
    }
}

type MockFamStructWrapper = FamStructWrapper<MockFamStruct>;