Struct abi_stable::prefix_type::PrefixRef [−][src]
#[repr(transparent)]pub struct PrefixRef<P> { /* fields omitted */ }
Expand description
A reference to a prefix type.
This is the type that all *_Ref
pointer types generated by StableAbi
wrap.
Example
use abi_stable::{
prefix_type::{PrefixRef, PrefixTypeTrait, WithMetadata},
staticref, StableAbi,
};
fn main() {
// `Module_Ref`'s constructor can also be called at compile-time
asserts(Module_Ref(PREFIX_A));
asserts(Module_Ref(PREFIX_B));
}
fn asserts(module: Module_Ref) {
assert_eq!(module.first(), 5);
assert_eq!(module.second(), 8);
// If this Module_Ref had come from a previous version of the library without a
// `third` field it would return `None`.
assert_eq!(module.third(), Some(13));
}
#[repr(C)]
#[derive(StableAbi)]
#[sabi(kind(Prefix(prefix_ref = "Module_Ref", prefix_fields = "Module_Prefix")))]
struct Module {
first: usize,
// The `#[sabi(last_prefix_field)]` attribute here means that this is
// the last field in this struct that was defined in the
// first compatible version of the library,
// requiring new fields to always be added after it.
// Moving this attribute is a breaking change, it can only be done in a
// major version bump..
#[sabi(last_prefix_field)]
second: usize,
third: usize,
}
const MOD_VAL: Module = Module {
first: 5,
second: 8,
third: 13,
};
/////////////////////////////////////////
// First way to construct a PrefixRef
// This is a way that PrefixRef can be constructed in statics
const PREFIX_A: PrefixRef<Module_Prefix> = {
const S: &WithMetadata<Module> =
&WithMetadata::new(PrefixTypeTrait::METADATA, MOD_VAL);
S.static_as_prefix()
};
/////////////////////////////////////////
// Second way to construct a PrefixRef
// This is a way that PrefixRef can be constructed in associated constants,
struct WithAssoc;
impl WithAssoc {
// This macro declares a `StaticRef` pointing to the assigned `WithMetadata`.
staticref!(const MOD_WM: WithMetadata<Module> = {
WithMetadata::new(PrefixTypeTrait::METADATA, MOD_VAL)
});
}
const PREFIX_B: PrefixRef<Module_Prefix> = WithAssoc::MOD_WM.as_prefix();
/////////////////////////////////////////
Implementations
Constructs a PrefixRef
from a raw pointer.
Safety
The pointer must be a non-dangling pointer to a valid, initialized instance of T
,
and live for the rest of the program’s lifetime
(if called at compile-time it means live for the entire program).
T
must implement PrefixTypeTrait<Fields = P>
,
this is automatically true if this is called with
&WithMetadata::new(PrefixTypeTrait::METADATA, <value>)
.
Example
use abi_stable::{
for_examples::{Module, Module_Prefix, Module_Ref},
prefix_type::{PrefixRef, PrefixTypeTrait, WithMetadata},
rstr,
std_types::*,
};
const MOD_WM: &WithMetadata<Module> = {
&WithMetadata::new(
PrefixTypeTrait::METADATA,
Module {
first: RSome(3),
second: rstr!("hello"),
third: 8,
},
)
};
const PREFIX: PrefixRef<Module_Prefix> = unsafe { PrefixRef::from_raw(MOD_WM) };
const MODULE: Module_Ref = Module_Ref(PREFIX);
assert_eq!(MODULE.first(), RSome(3));
assert_eq!(MODULE.second().as_str(), "hello");
// The accessor returns an `Option` because the field comes after the prefix,
// and returning an Option is the default for those.
assert_eq!(MODULE.third(), Some(8));
Constructs a PrefixRef
from a StaticRef
.
Example
use abi_stable::{
for_examples::{Module, Module_Prefix, Module_Ref},
prefix_type::{PrefixRef, PrefixTypeTrait, WithMetadata},
rstr, staticref,
std_types::*,
};
struct Foo {}
impl Foo {
// This macro declares a `StaticRef` pointing to the assigned `WithMetadata`.
staticref! {const MOD_WM: WithMetadata<Module> =
WithMetadata::new(PrefixTypeTrait::METADATA, Module{
first: RNone,
second: rstr!("world"),
third: 13,
})
}
}
const PREFIX: PrefixRef<Module_Prefix> = PrefixRef::from_staticref(Foo::MOD_WM);
const MODULE: Module_Ref = Module_Ref(PREFIX);
assert_eq!(MODULE.first(), RNone);
assert_eq!(MODULE.second().as_str(), "world");
// The accessor returns an `Option` because the field comes after the prefix,
// and returning an Option is the default for those.
assert_eq!(MODULE.third(), Some(13));
Constructs a PrefixRef
from a static reference.
Example
use abi_stable::{
for_examples::{Module, Module_Prefix, Module_Ref},
prefix_type::{PrefixRef, PrefixTypeTrait, WithMetadata},
rstr,
std_types::*,
};
const MOD_WM: &WithMetadata<Module> = {
&WithMetadata::new(
PrefixTypeTrait::METADATA,
Module {
first: RNone,
second: rstr!("foo"),
third: 21,
},
)
};
const PREFIX: PrefixRef<Module_Prefix> = PrefixRef::from_ref(MOD_WM);
const MODULE: Module_Ref = Module_Ref(PREFIX);
assert_eq!(MODULE.first(), RNone);
assert_eq!(MODULE.second().as_str(), "foo");
// The accessor returns an `Option` because the field comes after the prefix,
// and returning an Option is the default for those.
assert_eq!(MODULE.third(), Some(21));
Gets the metadata about the prefix type, including available fields.
Example
use abi_stable::{
for_examples::{Module, Module_Prefix},
prefix_type::{PrefixRef, PrefixTypeTrait, WithMetadata},
std_types::*,
};
const MOD_WM: &WithMetadata<Module> = {
&WithMetadata::new(
PrefixTypeTrait::METADATA,
Module {
first: RNone,
second: RStr::empty(),
third: 0,
},
)
};
const PREFIX: PrefixRef<Module_Prefix> = PrefixRef::from_ref(MOD_WM);
let accessibility = PREFIX.metadata().field_accessibility();
assert!(accessibility.is_accessible(0)); // The `first` field
assert!(accessibility.is_accessible(1)); // The `second` field
assert!(accessibility.is_accessible(2)); // The `third` field
assert!(!accessibility.is_accessible(3)); // There's no field after `third`
Gets a reference to the pointed-to prefix.
Example
use abi_stable::{
for_examples::{Module, Module_Prefix},
prefix_type::{PrefixRef, PrefixTypeTrait, WithMetadata},
rstr,
std_types::*,
};
const MOD_WM: &WithMetadata<Module> = {
&WithMetadata::new(
PrefixTypeTrait::METADATA,
Module {
first: RNone,
second: rstr!("foo"),
third: 21,
},
)
};
const PREFIX_REF: PrefixRef<Module_Prefix> = PrefixRef::from_ref(MOD_WM);
let prefix: &Module_Prefix = PREFIX_REF.prefix();
assert_eq!(prefix.first, RNone);
assert_eq!(prefix.second.as_str(), "foo");
// The `third` field is not in the prefix, so it can't be accessed here.
// prefix.third;
Converts this PrefixRef into a raw pointer.
A const-callable version of to_raw_ptr
,
use to_raw_ptr
in non-const code instead of this.
to_raw_ptr
exists for efficiency-in-debug-build reasons.
Casts the pointed-to prefix to another type.
Safety
This function is intended for casting the PrefixRef<P>
to PrefixRef<U>
,
and then cast back to PrefixRef<P>
to use it again.
The prefix in the returned PrefixRef<U>
must only be accessed
when this PrefixRef
was originally cosntructed with a ẀithMetadata_<_, U>
.
access includes calling prefix
, and reading the value
field in the WithMetadata
that this points to.
Trait Implementations
type StaticEquivalent = PrefixRef<GetStaticEquivalent<P>>
type Target = WithMetadata_<P, P>
type Target = WithMetadata_<P, P>
The referent of the pointer, what it points to.
A marker type that can be used as a proof that the T
type parameter of
ImmutableRefTarget<T, U>
implements ImmutableRef<Target = U>
. Read more
Converts this pointer to a NonNull
.
Constructs this pointer from a NonNull
. Read more
Converts this pointer to a raw pointer.
type PrefixFields = P
type PrefixFields = P
A struct that contains all the fields of some other struct
up to the field annotated with
#[sabi(last_prefix_field)]
inclusive. Read more
A type used to prove that the This
type parameter in
PointsToPrefixFields<This, PF>
implements
PrefixRefTrait<PrefixFields = PF>
. Read more
Converts a PrefixRef
to Self
Converts Self
to a PrefixRef
type IsNonZeroType = True
type IsNonZeroType = True
Whether this type has a single invalid bit-pattern. Read more
The layout of the type provided by implementors.
const
-equivalents of the associated types.
Auto Trait Implementations
impl<P> RefUnwindSafe for PrefixRef<P> where
P: RefUnwindSafe,
impl<P> UnwindSafe for PrefixRef<P> where
P: RefUnwindSafe,
Blanket Implementations
Mutably borrows from an owned value. Read more
type ROwned = T
type ROwned = T
The owned type, stored in RCow::Owned
type ForSelf = WithMetadata_<T, T>
type ForSelf = WithMetadata_<T, T>
This is always WithMetadata_<Self, Self>
Compares the address of self
with the address of other
. Read more
Emulates the pipeline operator, allowing method syntax in more places. Read more
The same as piped
except that the function takes &Self
Useful for functions that take &Self
instead of Self
. Read more
The same as piped
, except that the function takes &mut Self
.
Useful for functions that take &mut Self
instead of Self
. Read more
Mutates self using a closure taking self by mutable reference, passing it along the method chain. Read more
Observes the value of self, passing it along unmodified. Useful in long method chains. Read more
Performs a conversion with Into
.
using the turbofish .into_::<_>()
syntax. Read more
Performs a reference to reference conversion with AsRef
,
using the turbofish .as_ref_::<_>()
syntax. Read more
Performs a mutable reference to mutable reference conversion with AsMut
,
using the turbofish .as_mut_::<_>()
syntax. Read more
unsafe fn transmute_element<T>(
self
) -> <Self as CanTransmuteElement<T>>::TransmutedPtr where
Self: CanTransmuteElement<T>,
unsafe fn transmute_element<T>(
self
) -> <Self as CanTransmuteElement<T>>::TransmutedPtr where
Self: CanTransmuteElement<T>,
Transmutes the element type of this pointer.. Read more
type Type = T
type Type = T
This is always Self
.
Converts a value back to the original type.
Converts a mutable reference back to the original type.
alloc
only.Converts a box back to the original type.
Converts a value back to the original type.
Converts a reference back to the original type.
Converts a mutable reference back to the original type.
alloc
only.Converts a box back to the original type.
alloc
only.Converts an Arc back to the original type.
alloc
only.Converts an Rc back to the original type.