Enum wasmtime_environ::VMGcKind

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#[repr(u32)]
pub enum VMGcKind { ExternRef = 1_073_741_824, ExternOfAnyRef = 1_610_612_736, AnyRef = 2_147_483_648, AnyOfExternRef = 2_415_919_104, EqRef = 2_684_354_560, ArrayRef = 2_751_463_424, StructRef = 2_818_572_288, }
Expand description

The kind of an object in a GC heap.

Note that this type is accessed from Wasm JIT code.

VMGcKind is a bitset where to test if a is a subtype of an “abstract-ish” type b, we can simply use a single bitwise-and operation:

a <: b   iff   a & b == b

For example, because VMGcKind::AnyRef has the high bit set, every kind representing some subtype of anyref also has its high bit set.

We say “abstract-ish” type because in addition to the abstract heap types (other than i31) we also have variants for externrefs that have been converted into an anyref via extern.convert_any and externrefs that have been converted into an anyref via any.convert_extern. Note that in the latter case, because any.convert_extern $foo produces a value that is not an instance of eqref, VMGcKind::AnyOfExternRef & VMGcKind::EqRef != VMGcKind::EqRef.

Furthermore, this type only uses the highest 6 bits of its u32 representation, allowing the lower 26 bytes to be bitpacked with other stuff as users see fit.

Variants§

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ExternRef = 1_073_741_824

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ExternOfAnyRef = 1_610_612_736

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AnyRef = 2_147_483_648

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AnyOfExternRef = 2_415_919_104

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EqRef = 2_684_354_560

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ArrayRef = 2_751_463_424

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StructRef = 2_818_572_288

Implementations§

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impl VMGcKind

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pub const MASK: u32 = 4_227_858_432u32

Mask this value with a u32 to get just the bits that VMGcKind uses.

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pub const UNUSED_MASK: u32 = 67_108_863u32

Mask this value with a u32 that potentially contains a VMGcKind to get the bits that VMGcKind doesn’t use.

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pub fn value_fits_in_unused_bits(value: u32) -> bool

Does the given value fit in the unused bits of a VMGcKind?

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pub fn from_high_bits_of_u32(val: u32) -> VMGcKind

Convert the given value into a VMGcKind by masking off the unused bottom bits.

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pub fn matches(self, other: Self) -> bool

Does this kind match the other kind?

That is, is this kind a subtype of the other kind?

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pub fn as_u32(self) -> u32

Get this VMGcKind as a raw u32.

Trait Implementations§

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impl Clone for VMGcKind

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fn clone(&self) -> VMGcKind

Returns a copy of the value. Read more
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fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl Debug for VMGcKind

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fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more
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impl PartialEq for VMGcKind

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fn eq(&self, other: &VMGcKind) -> bool

Tests for self and other values to be equal, and is used by ==.
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fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
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impl Copy for VMGcKind

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impl Eq for VMGcKind

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impl StructuralPartialEq for VMGcKind

Auto Trait Implementations§

Blanket Implementations§

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impl<T> Any for T
where T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> CloneToUninit for T
where T: Clone,

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unsafe fn clone_to_uninit(&self, dst: *mut T)

🔬This is a nightly-only experimental API. (clone_to_uninit)
Performs copy-assignment from self to dst. Read more
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impl<Q, K> Equivalent<K> for Q
where Q: Eq + ?Sized, K: Borrow<Q> + ?Sized,

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fn equivalent(&self, key: &K) -> bool

Compare self to key and return true if they are equal.
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impl<Q, K> Equivalent<K> for Q
where Q: Eq + ?Sized, K: Borrow<Q> + ?Sized,

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fn equivalent(&self, key: &K) -> bool

Checks if this value is equivalent to the given key. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into<U> for T
where U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<T> ToOwned for T
where T: Clone,

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type Owned = T

The resulting type after obtaining ownership.
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fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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impl<T, U> TryFrom<U> for T
where U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.