struct Unique: Copy more from std and use for Rav1dPictureDataComponentInner::ptr to make it Send + Sync
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…he `Unique` from `CBox::from_c` to the API boundary.
…t is `Send + Sync`.
| @@ -189,7 +192,7 @@ impl Rav1dPictureDataComponentInner { | |||
| /// 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 { | |||
| let buf = AsBytes::as_bytes_mut(buf); | |||
| let ptr = NonNull::new(buf.as_mut_ptr()).unwrap(); | |||
| let ptr = Unique::from_ref_mut(buf).cast(); | |||
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How is this unique in the wrap_buf case? We're borrowing a reference to this data, right? So should we really use unique here?
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A &mut reference is always unique. So it can be &mut or owned. core::ptr::Unique impls From<&mut T> even.
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But once that constructor returns the borrow is over, unless there's a lifetime. So it's no longer unique? How do we ensure no where else has a pointer to the same thing?
| NonNull::new(self.as_strided_byte_mut_ptr().cast()) | ||
| let ptr = NonNull::new(self.as_strided_byte_mut_ptr()).unwrap(); | ||
| // SAFETY: The `ptr` originally comes from a `Unique` in `Rav1dPictureDataComponentInner::ptr`. | ||
| let ptr = unsafe { Unique::new(ptr) }; |
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Again, how is this unique? Can this method return a NonNull instead?
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Because self.as_strided_byte_mut_ptr() is derived from Rav1dPictureDataComponentInner::ptr, which is a Unique. I can say that more explicitly if that's clearer.
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Does that mean there's two Uniques pointing to the same data? The original and the one into the middle?
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e.g. can I just call this twice and get two Uniques? Doesn't that violate the invariants?
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Ugh, yeah, you're right.
Why does core::ptr::Unique: Copy + Clone then?
| @@ -0,0 +1,190 @@ | |||
| //! Largely copied from [`rust-lang/rust/library/core/src/ptr/unique.rs`](https://github.com/rust-lang/rust/blob/e35364a521372ce682e4bd4a5850d97ea33b0eab/library/core/src/ptr/unique.rs#L58). | |||
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Umm I don't know how to do that. What do I write?
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| //! Largely copied from [`rust-lang/rust/library/core/src/ptr/unique.rs`](https://github.com/rust-lang/rust/blob/e35364a521372ce682e4bd4a5850d97ea33b0eab/library/core/src/ptr/unique.rs#L58). | |
| //! Largely copied from [`rust-lang/rust/library/core/src/ptr/unique.rs`](https://github.com/rust-lang/rust/blob/e35364a521372ce682e4bd4a5850d97ea33b0eab/library/core/src/ptr/unique.rs#L58). | |
| //! | |
| //! Used under the MIT license <LICENSE-MIT> or <http://opensource.org/licenses/MIT>. | |
| //! Copyright is retained by the original Rust contributors. | |
| //! For full authorship information, see the Rust compiler version control history or | |
| //! https://thanks.rust-lang.org |
|
To follow up on the discussion of "should |
We may be able to replace
SendSyncNonNullwithUnique, but we can do that later. They have basically the same APIs, though slightly different safety invariants (uniqueness vs. thread-safe).