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fn Rav1dPictureDataComponent::wrap_buf: make unsafe to enforce buf outlives Self #1416

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fn Rav1dPictureDataComponent::wrap_buf: make unsafe to enforce buf outlives Self #1416

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22 changes: 17 additions & 5 deletions include/dav1d/picture.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -185,9 +185,15 @@ impl Rav1dPictureDataComponentInner {

/// # Safety
///
/// As opposed to [`Self::new`], this is safe because `buf` is a `&mut` and thus unique,
/// so it is sound to further subdivide it into disjoint `&mut`s.
pub fn wrap_buf<BD: BitDepth>(buf: &mut [BD::Pixel], stride: usize) -> Self {
/// `buf` must outlive the returned [`Self`].
///
/// As opposed to [`Self::new`], `buf` is a `&mut`, so it must be unique,
/// so it is sound to further subdivide it into disjoint `&mut`s as long as its lifetime lasts.
/// However, adding proper lifetimes is difficult
/// (see [#1317](https://github.com/memorysafety/rav1d/pull/1317)),
/// so instead we make this an `unsafe` precondition,
/// that `buf` must outlive the returned [`Self`].
pub unsafe fn wrap_buf<BD: BitDepth>(buf: &mut [BD::Pixel], stride: usize) -> Self {
let buf = AsBytes::as_bytes_mut(buf);
let ptr = NonNull::new(buf.as_mut_ptr()).unwrap();
assert!(ptr.cast::<AlignedPixelChunk>().is_aligned());
Expand Down Expand Up @@ -245,9 +251,15 @@ impl Strided for Rav1dPictureDataComponent {
}

impl Rav1dPictureDataComponent {
pub fn wrap_buf<BD: BitDepth>(buf: &mut [BD::Pixel], stride: usize) -> Self {
/// # Safety
///
/// `buf` must outlive the returned [`Self`].
///
/// See [`Rav1dPictureDataComponentInner::wrap_buf`] for more details.
pub unsafe fn wrap_buf<BD: BitDepth>(buf: &mut [BD::Pixel], stride: usize) -> Self {
Self(DisjointMut::new(
Rav1dPictureDataComponentInner::wrap_buf::<BD>(buf, stride),
// SAFETY: Delegated.
unsafe { Rav1dPictureDataComponentInner::wrap_buf::<BD>(buf, stride) },
))
}

Expand Down
49 changes: 33 additions & 16 deletions src/recon.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1779,7 +1779,8 @@ fn mc<BD: BitDepth>(
);
let stride = 192;
Rav1dPictureDataComponentOffset {
data: &Rav1dPictureDataComponent::wrap_buf::<BD>(emu_edge_buf, stride),
// SAFETY: Lifetime extension forces `buf` to outlive it.
data: &unsafe { Rav1dPictureDataComponent::wrap_buf::<BD>(emu_edge_buf, stride) },
offset: stride * (my != 0) as usize * 3 + (mx != 0) as usize * 3,
}
} else {
Expand Down Expand Up @@ -1852,7 +1853,8 @@ fn mc<BD: BitDepth>(
}
let stride = 320;
Rav1dPictureDataComponentOffset {
data: &Rav1dPictureDataComponent::wrap_buf::<BD>(emu_edge_buf, stride),
// SAFETY: Lifetime extension forces `buf` to outlive it.
data: &unsafe { Rav1dPictureDataComponent::wrap_buf::<BD>(emu_edge_buf, stride) },
offset: stride * 3 + 3,
}
} else {
Expand Down Expand Up @@ -1920,10 +1922,13 @@ fn obmc<BD: BitDepth>(
t.b,
MaybeTempPixels::NonTemp {
dst: Rav1dPictureDataComponentOffset {
data: &Rav1dPictureDataComponent::wrap_buf::<BD>(
lap,
ow4 as usize * h_mul as usize,
),
// SAFETY: Lifetime extension forces `buf` to outlive it.
data: &unsafe {
Rav1dPictureDataComponent::wrap_buf::<BD>(
lap,
ow4 as usize * h_mul as usize,
)
},
offset: 0,
},
},
Expand Down Expand Up @@ -1968,10 +1973,13 @@ fn obmc<BD: BitDepth>(
t.b,
MaybeTempPixels::NonTemp {
dst: Rav1dPictureDataComponentOffset {
data: &Rav1dPictureDataComponent::wrap_buf::<BD>(
lap,
ow4 as usize * h_mul as usize,
),
// SAFETY: Lifetime extension forces `buf` to outlive it.
data: &unsafe {
Rav1dPictureDataComponent::wrap_buf::<BD>(
lap,
ow4 as usize * h_mul as usize,
)
},
offset: 0,
},
},
Expand Down Expand Up @@ -2056,7 +2064,10 @@ fn warp_affine<BD: BitDepth>(
);
let stride = 32;
Rav1dPictureDataComponentOffset {
data: &Rav1dPictureDataComponent::wrap_buf::<BD>(emu_edge_buf, stride),
// SAFETY: Lifetime extension forces `buf` to outlive it.
data: &unsafe {
Rav1dPictureDataComponent::wrap_buf::<BD>(emu_edge_buf, stride)
},
offset: stride * 3 + 3,
}
} else {
Expand Down Expand Up @@ -3123,7 +3134,10 @@ pub(crate) fn rav1d_recon_b_inter<BD: BitDepth>(
let tmp = interintra_edge_pal.interintra.buf_mut::<BD>();
f.dsp.ipred.intra_pred[m as usize].call(
Rav1dPictureDataComponentOffset {
data: &Rav1dPictureDataComponent::wrap_buf::<BD>(tmp, 4 * bw4 as usize),
// SAFETY: Lifetime extension forces `buf` to outlive it.
data: &unsafe {
Rav1dPictureDataComponent::wrap_buf::<BD>(tmp, 4 * bw4 as usize)
},
offset: 0,
},
tl_edge_array,
Expand Down Expand Up @@ -3407,10 +3421,13 @@ pub(crate) fn rav1d_recon_b_inter<BD: BitDepth>(
let tmp = interintra_edge_pal.interintra.buf_mut::<BD>();
f.dsp.ipred.intra_pred[m as usize].call(
Rav1dPictureDataComponentOffset {
data: &Rav1dPictureDataComponent::wrap_buf::<BD>(
tmp,
4 * cbw4 as usize,
),
// SAFETY: Lifetime extension forces `buf` to outlive it.
data: &unsafe {
Rav1dPictureDataComponent::wrap_buf::<BD>(
tmp,
4 * cbw4 as usize,
)
},
offset: 0,
},
tl_edge_array,
Expand Down
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