Struct holochain_state::query::prelude::Arc 1.0.0[−][src]
pub struct Arc<T> where
T: ?Sized, { /* fields omitted */ }
Expand description
A thread-safe reference-counting pointer. ‘Arc’ stands for ‘Atomically Reference Counted’.
The type Arc<T>
provides shared ownership of a value of type T
,
allocated in the heap. Invoking clone
on Arc
produces
a new Arc
instance, which points to the same allocation on the heap as the
source Arc
, while increasing a reference count. When the last Arc
pointer to a given allocation is destroyed, the value stored in that allocation (often
referred to as “inner value”) is also dropped.
Shared references in Rust disallow mutation by default, and Arc
is no
exception: you cannot generally obtain a mutable reference to something
inside an Arc
. If you need to mutate through an Arc
, use
Mutex
, RwLock
, or one of the Atomic
types.
Thread Safety
Unlike Rc<T>
, Arc<T>
uses atomic operations for its reference
counting. This means that it is thread-safe. The disadvantage is that
atomic operations are more expensive than ordinary memory accesses. If you
are not sharing reference-counted allocations between threads, consider using
Rc<T>
for lower overhead. Rc<T>
is a safe default, because the
compiler will catch any attempt to send an Rc<T>
between threads.
However, a library might choose Arc<T>
in order to give library consumers
more flexibility.
Arc<T>
will implement Send
and Sync
as long as the T
implements
Send
and Sync
. Why can’t you put a non-thread-safe type T
in an
Arc<T>
to make it thread-safe? This may be a bit counter-intuitive at
first: after all, isn’t the point of Arc<T>
thread safety? The key is
this: Arc<T>
makes it thread safe to have multiple ownership of the same
data, but it doesn’t add thread safety to its data. Consider
Arc<RefCell<T>>
. RefCell<T>
isn’t Sync
, and if Arc<T>
was always
Send
, Arc<RefCell<T>>
would be as well. But then we’d have a problem:
RefCell<T>
is not thread safe; it keeps track of the borrowing count using
non-atomic operations.
In the end, this means that you may need to pair Arc<T>
with some sort of
std::sync
type, usually Mutex<T>
.
Breaking cycles with Weak
The downgrade
method can be used to create a non-owning
Weak
pointer. A Weak
pointer can be upgrade
d
to an Arc
, but this will return None
if the value stored in the allocation has
already been dropped. In other words, Weak
pointers do not keep the value
inside the allocation alive; however, they do keep the allocation
(the backing store for the value) alive.
A cycle between Arc
pointers will never be deallocated. For this reason,
Weak
is used to break cycles. For example, a tree could have
strong Arc
pointers from parent nodes to children, and Weak
pointers from children back to their parents.
Cloning references
Creating a new reference from an existing reference-counted pointer is done using the
Clone
trait implemented for Arc<T>
and Weak<T>
.
use std::sync::Arc;
let foo = Arc::new(vec![1.0, 2.0, 3.0]);
// The two syntaxes below are equivalent.
let a = foo.clone();
let b = Arc::clone(&foo);
// a, b, and foo are all Arcs that point to the same memory location
Deref
behavior
Arc<T>
automatically dereferences to T
(via the Deref
trait),
so you can call T
’s methods on a value of type Arc<T>
. To avoid name
clashes with T
’s methods, the methods of Arc<T>
itself are associated
functions, called using fully qualified syntax:
use std::sync::Arc;
let my_arc = Arc::new(());
let my_weak = Arc::downgrade(&my_arc);
Arc<T>
’s implementations of traits like Clone
may also be called using
fully qualified syntax. Some people prefer to use fully qualified syntax,
while others prefer using method-call syntax.
use std::sync::Arc;
let arc = Arc::new(());
// Method-call syntax
let arc2 = arc.clone();
// Fully qualified syntax
let arc3 = Arc::clone(&arc);
Weak<T>
does not auto-dereference to T
, because the inner value may have
already been dropped.
Examples
Sharing some immutable data between threads:
use std::sync::Arc;
use std::thread;
let five = Arc::new(5);
for _ in 0..10 {
let five = Arc::clone(&five);
thread::spawn(move || {
println!("{:?}", five);
});
}
Sharing a mutable AtomicUsize
:
use std::sync::Arc;
use std::sync::atomic::{AtomicUsize, Ordering};
use std::thread;
let val = Arc::new(AtomicUsize::new(5));
for _ in 0..10 {
let val = Arc::clone(&val);
thread::spawn(move || {
let v = val.fetch_add(1, Ordering::SeqCst);
println!("{:?}", v);
});
}
See the rc
documentation for more examples of reference
counting in general.
Implementations
🔬 This is a nightly-only experimental API. (arc_new_cyclic
)
arc_new_cyclic
)Constructs a new Arc<T>
using a weak reference to itself. Attempting
to upgrade the weak reference before this function returns will result
in a None
value. However, the weak reference may be cloned freely and
stored for use at a later time.
Examples
#![feature(arc_new_cyclic)]
#![allow(dead_code)]
use std::sync::{Arc, Weak};
struct Foo {
me: Weak<Foo>,
}
let foo = Arc::new_cyclic(|me| Foo {
me: me.clone(),
});
🔬 This is a nightly-only experimental API. (new_uninit
)
new_uninit
)Constructs a new Arc
with uninitialized contents.
Examples
#![feature(new_uninit)]
#![feature(get_mut_unchecked)]
use std::sync::Arc;
let mut five = Arc::<u32>::new_uninit();
let five = unsafe {
// Deferred initialization:
Arc::get_mut_unchecked(&mut five).as_mut_ptr().write(5);
five.assume_init()
};
assert_eq!(*five, 5)
🔬 This is a nightly-only experimental API. (new_uninit
)
new_uninit
)Constructs a new Arc
with uninitialized contents, with the memory
being filled with 0
bytes.
See MaybeUninit::zeroed
for examples of correct and incorrect usage
of this method.
Examples
#![feature(new_uninit)]
use std::sync::Arc;
let zero = Arc::<u32>::new_zeroed();
let zero = unsafe { zero.assume_init() };
assert_eq!(*zero, 0)
Constructs a new Pin<Arc<T>>
. If T
does not implement Unpin
, then
data
will be pinned in memory and unable to be moved.
🔬 This is a nightly-only experimental API. (allocator_api
)
allocator_api
)Constructs a new Pin<Arc<T>>
, return an error if allocation fails.
🔬 This is a nightly-only experimental API. (allocator_api
)
allocator_api
)Constructs a new Arc<T>
, returning an error if allocation fails.
Examples
#![feature(allocator_api)]
use std::sync::Arc;
let five = Arc::try_new(5)?;
🔬 This is a nightly-only experimental API. (allocator_api
)
allocator_api
)Constructs a new Arc
with uninitialized contents, returning an error
if allocation fails.
Examples
#![feature(new_uninit, allocator_api)]
#![feature(get_mut_unchecked)]
use std::sync::Arc;
let mut five = Arc::<u32>::try_new_uninit()?;
let five = unsafe {
// Deferred initialization:
Arc::get_mut_unchecked(&mut five).as_mut_ptr().write(5);
five.assume_init()
};
assert_eq!(*five, 5);
🔬 This is a nightly-only experimental API. (allocator_api
)
allocator_api
)Constructs a new Arc
with uninitialized contents, with the memory
being filled with 0
bytes, returning an error if allocation fails.
See MaybeUninit::zeroed
for examples of correct and incorrect usage
of this method.
Examples
#![feature(new_uninit, allocator_api)]
use std::sync::Arc;
let zero = Arc::<u32>::try_new_zeroed()?;
let zero = unsafe { zero.assume_init() };
assert_eq!(*zero, 0);
Returns the inner value, if the Arc
has exactly one strong reference.
Otherwise, an Err
is returned with the same Arc
that was
passed in.
This will succeed even if there are outstanding weak references.
Examples
use std::sync::Arc;
let x = Arc::new(3);
assert_eq!(Arc::try_unwrap(x), Ok(3));
let x = Arc::new(4);
let _y = Arc::clone(&x);
assert_eq!(*Arc::try_unwrap(x).unwrap_err(), 4);
🔬 This is a nightly-only experimental API. (new_uninit
)
new_uninit
)Constructs a new atomically reference-counted slice with uninitialized contents.
Examples
#![feature(new_uninit)]
#![feature(get_mut_unchecked)]
use std::sync::Arc;
let mut values = Arc::<[u32]>::new_uninit_slice(3);
let values = unsafe {
// Deferred initialization:
Arc::get_mut_unchecked(&mut values)[0].as_mut_ptr().write(1);
Arc::get_mut_unchecked(&mut values)[1].as_mut_ptr().write(2);
Arc::get_mut_unchecked(&mut values)[2].as_mut_ptr().write(3);
values.assume_init()
};
assert_eq!(*values, [1, 2, 3])
🔬 This is a nightly-only experimental API. (new_uninit
)
new_uninit
)Constructs a new atomically reference-counted slice with uninitialized contents, with the memory being
filled with 0
bytes.
See MaybeUninit::zeroed
for examples of correct and
incorrect usage of this method.
Examples
#![feature(new_uninit)]
use std::sync::Arc;
let values = Arc::<[u32]>::new_zeroed_slice(3);
let values = unsafe { values.assume_init() };
assert_eq!(*values, [0, 0, 0])
🔬 This is a nightly-only experimental API. (new_uninit
)
new_uninit
)Converts to Arc<T>
.
Safety
As with MaybeUninit::assume_init
,
it is up to the caller to guarantee that the inner value
really is in an initialized state.
Calling this when the content is not yet fully initialized
causes immediate undefined behavior.
Examples
#![feature(new_uninit)]
#![feature(get_mut_unchecked)]
use std::sync::Arc;
let mut five = Arc::<u32>::new_uninit();
let five = unsafe {
// Deferred initialization:
Arc::get_mut_unchecked(&mut five).as_mut_ptr().write(5);
five.assume_init()
};
assert_eq!(*five, 5)
🔬 This is a nightly-only experimental API. (new_uninit
)
new_uninit
)Converts to Arc<[T]>
.
Safety
As with MaybeUninit::assume_init
,
it is up to the caller to guarantee that the inner value
really is in an initialized state.
Calling this when the content is not yet fully initialized
causes immediate undefined behavior.
Examples
#![feature(new_uninit)]
#![feature(get_mut_unchecked)]
use std::sync::Arc;
let mut values = Arc::<[u32]>::new_uninit_slice(3);
let values = unsafe {
// Deferred initialization:
Arc::get_mut_unchecked(&mut values)[0].as_mut_ptr().write(1);
Arc::get_mut_unchecked(&mut values)[1].as_mut_ptr().write(2);
Arc::get_mut_unchecked(&mut values)[2].as_mut_ptr().write(3);
values.assume_init()
};
assert_eq!(*values, [1, 2, 3])
Consumes the Arc
, returning the wrapped pointer.
To avoid a memory leak the pointer must be converted back to an Arc
using
Arc::from_raw
.
Examples
use std::sync::Arc;
let x = Arc::new("hello".to_owned());
let x_ptr = Arc::into_raw(x);
assert_eq!(unsafe { &*x_ptr }, "hello");
Provides a raw pointer to the data.
The counts are not affected in any way and the Arc
is not consumed. The pointer is valid for
as long as there are strong counts in the Arc
.
Examples
use std::sync::Arc;
let x = Arc::new("hello".to_owned());
let y = Arc::clone(&x);
let x_ptr = Arc::as_ptr(&x);
assert_eq!(x_ptr, Arc::as_ptr(&y));
assert_eq!(unsafe { &*x_ptr }, "hello");
Constructs an Arc<T>
from a raw pointer.
The raw pointer must have been previously returned by a call to
Arc<U>::into_raw
where U
must have the same size and
alignment as T
. This is trivially true if U
is T
.
Note that if U
is not T
but has the same size and alignment, this is
basically like transmuting references of different types. See
mem::transmute
for more information on what
restrictions apply in this case.
The user of from_raw
has to make sure a specific value of T
is only
dropped once.
This function is unsafe because improper use may lead to memory unsafety,
even if the returned Arc<T>
is never accessed.
Examples
use std::sync::Arc;
let x = Arc::new("hello".to_owned());
let x_ptr = Arc::into_raw(x);
unsafe {
// Convert back to an `Arc` to prevent leak.
let x = Arc::from_raw(x_ptr);
assert_eq!(&*x, "hello");
// Further calls to `Arc::from_raw(x_ptr)` would be memory-unsafe.
}
// The memory was freed when `x` went out of scope above, so `x_ptr` is now dangling!
Gets the number of Weak
pointers to this allocation.
Safety
This method by itself is safe, but using it correctly requires extra care. Another thread can change the weak count at any time, including potentially between calling this method and acting on the result.
Examples
use std::sync::Arc;
let five = Arc::new(5);
let _weak_five = Arc::downgrade(&five);
// This assertion is deterministic because we haven't shared
// the `Arc` or `Weak` between threads.
assert_eq!(1, Arc::weak_count(&five));
Gets the number of strong (Arc
) pointers to this allocation.
Safety
This method by itself is safe, but using it correctly requires extra care. Another thread can change the strong count at any time, including potentially between calling this method and acting on the result.
Examples
use std::sync::Arc;
let five = Arc::new(5);
let _also_five = Arc::clone(&five);
// This assertion is deterministic because we haven't shared
// the `Arc` between threads.
assert_eq!(2, Arc::strong_count(&five));
Increments the strong reference count on the Arc<T>
associated with the
provided pointer by one.
Safety
The pointer must have been obtained through Arc::into_raw
, and the
associated Arc
instance must be valid (i.e. the strong count must be at
least 1) for the duration of this method.
Examples
use std::sync::Arc;
let five = Arc::new(5);
unsafe {
let ptr = Arc::into_raw(five);
Arc::increment_strong_count(ptr);
// This assertion is deterministic because we haven't shared
// the `Arc` between threads.
let five = Arc::from_raw(ptr);
assert_eq!(2, Arc::strong_count(&five));
}
Decrements the strong reference count on the Arc<T>
associated with the
provided pointer by one.
Safety
The pointer must have been obtained through Arc::into_raw
, and the
associated Arc
instance must be valid (i.e. the strong count must be at
least 1) when invoking this method. This method can be used to release the final
Arc
and backing storage, but should not be called after the final Arc
has been
released.
Examples
use std::sync::Arc;
let five = Arc::new(5);
unsafe {
let ptr = Arc::into_raw(five);
Arc::increment_strong_count(ptr);
// Those assertions are deterministic because we haven't shared
// the `Arc` between threads.
let five = Arc::from_raw(ptr);
assert_eq!(2, Arc::strong_count(&five));
Arc::decrement_strong_count(ptr);
assert_eq!(1, Arc::strong_count(&five));
}
Makes a mutable reference into the given Arc
.
If there are other Arc
pointers to the same allocation, then make_mut
will
clone
the inner value to a new allocation to ensure unique ownership. This is also
referred to as clone-on-write.
However, if there are no other Arc
pointers to this allocation, but some Weak
pointers, then the Weak
pointers will be disassociated and the inner value will not
be cloned.
See also get_mut
, which will fail rather than cloning the inner value
or diassociating Weak
pointers.
Examples
use std::sync::Arc;
let mut data = Arc::new(5);
*Arc::make_mut(&mut data) += 1; // Won't clone anything
let mut other_data = Arc::clone(&data); // Won't clone inner data
*Arc::make_mut(&mut data) += 1; // Clones inner data
*Arc::make_mut(&mut data) += 1; // Won't clone anything
*Arc::make_mut(&mut other_data) *= 2; // Won't clone anything
// Now `data` and `other_data` point to different allocations.
assert_eq!(*data, 8);
assert_eq!(*other_data, 12);
Weak
pointers will be disassociated:
use std::sync::Arc;
let mut data = Arc::new(75);
let weak = Arc::downgrade(&data);
assert!(75 == *data);
assert!(75 == *weak.upgrade().unwrap());
*Arc::make_mut(&mut data) += 1;
assert!(76 == *data);
assert!(weak.upgrade().is_none());
Returns a mutable reference into the given Arc
, if there are
no other Arc
or Weak
pointers to the same allocation.
Returns None
otherwise, because it is not safe to
mutate a shared value.
See also make_mut
, which will clone
the inner value when there are other Arc
pointers.
Examples
use std::sync::Arc;
let mut x = Arc::new(3);
*Arc::get_mut(&mut x).unwrap() = 4;
assert_eq!(*x, 4);
let _y = Arc::clone(&x);
assert!(Arc::get_mut(&mut x).is_none());
🔬 This is a nightly-only experimental API. (get_mut_unchecked
)
get_mut_unchecked
)Returns a mutable reference into the given Arc
,
without any check.
See also get_mut
, which is safe and does appropriate checks.
Safety
Any other Arc
or Weak
pointers to the same allocation must not be dereferenced
for the duration of the returned borrow.
This is trivially the case if no such pointers exist,
for example immediately after Arc::new
.
Examples
#![feature(get_mut_unchecked)]
use std::sync::Arc;
let mut x = Arc::new(String::new());
unsafe {
Arc::get_mut_unchecked(&mut x).push_str("foo")
}
assert_eq!(*x, "foo");
Attempt to downcast the Arc<dyn Any + Send + Sync>
to a concrete type.
Examples
use std::any::Any;
use std::sync::Arc;
fn print_if_string(value: Arc<dyn Any + Send + Sync>) {
if let Ok(string) = value.downcast::<String>() {
println!("String ({}): {}", string.len(), string);
}
}
let my_string = "Hello World".to_string();
print_if_string(Arc::new(my_string));
print_if_string(Arc::new(0i8));
Trait Implementations
impl<'a, A> Arbitrary<'a> for Arc<A> where
A: Arbitrary<'a>,
impl<'a, A> Arbitrary<'a> for Arc<A> where
A: Arbitrary<'a>,
Generate an arbitrary value of Self
from the given unstructured data. Read more
Get a size hint for how many bytes out of an Unstructured
this type
needs to construct itself. Read more
fn arbitrary_take_rest(u: Unstructured<'a>) -> Result<Self, Error>
fn arbitrary_take_rest(u: Unstructured<'a>) -> Result<Self, Error>
Generate an arbitrary value of Self
from the entirety of the given unstructured data. Read more
pub fn read_lock(&self) -> ReadGuard<'_>
pub fn read_lock(&self) -> ReadGuard<'_>
Obtain read access to the underlying buffer.
impl ClientConfig<TlsSession> for Arc<ClientConfig>
impl ClientConfig<TlsSession> for Arc<ClientConfig>
pub fn start_session(
&self,
server_name: &str,
params: &TransportParameters
) -> Result<TlsSession, ConnectError>
pub fn start_session(
&self,
server_name: &str,
params: &TransportParameters
) -> Result<TlsSession, ConnectError>
Start a client session with this configuration
impl ControllerFactory for Arc<NewRenoConfig>
impl ControllerFactory for Arc<NewRenoConfig>
This impl requires the "rc"
Cargo feature of Serde.
Deserializing a data structure containing Arc
will not attempt to
deduplicate Arc
references to the same data. Every deserialized Arc
will end up with a strong count of 1.
pub fn deserialize<D>(
deserializer: D
) -> Result<Arc<T>, <D as Deserializer<'de>>::Error> where
D: Deserializer<'de>,
pub fn deserialize<D>(
deserializer: D
) -> Result<Arc<T>, <D as Deserializer<'de>>::Error> where
D: Deserializer<'de>,
Deserialize this value from the given Serde deserializer. Read more
Drops the Arc
.
This will decrement the strong reference count. If the strong reference
count reaches zero then the only other references (if any) are
Weak
, so we drop
the inner value.
Examples
use std::sync::Arc;
struct Foo;
impl Drop for Foo {
fn drop(&mut self) {
println!("dropped!");
}
}
let foo = Arc::new(Foo);
let foo2 = Arc::clone(&foo);
drop(foo); // Doesn't print anything
drop(foo2); // Prints "dropped!"
use the Display impl or to_string()
replaced by Error::source, which can support downcasting
The lower-level source of this error, if any. Read more
Returns true
if this layer is interested in a span or event with the
given Metadata
in the current Context
, similarly to
Subscriber::enabled
. Read more
Returns an optional hint of the highest verbosity level that
this Filter
will enable. Read more
Takes each element in the Iterator
and collects it into an Arc<[T]>
.
Performance characteristics
The general case
In the general case, collecting into Arc<[T]>
is done by first
collecting into a Vec<T>
. That is, when writing the following:
let evens: Arc<[u8]> = (0..10).filter(|&x| x % 2 == 0).collect();
this behaves as if we wrote:
let evens: Arc<[u8]> = (0..10).filter(|&x| x % 2 == 0)
.collect::<Vec<_>>() // The first set of allocations happens here.
.into(); // A second allocation for `Arc<[T]>` happens here.
This will allocate as many times as needed for constructing the Vec<T>
and then it will allocate once for turning the Vec<T>
into the Arc<[T]>
.
Iterators of known length
When your Iterator
implements TrustedLen
and is of an exact size,
a single allocation will be made for the Arc<[T]>
. For example:
let evens: Arc<[u8]> = (0..10).collect(); // Just a single allocation happens here.
pub fn column_result(value: ValueRef<'_>) -> Result<Arc<str>, FromSqlError>
pub fn column_result(value: ValueRef<'_>) -> Result<Arc<str>, FromSqlError>
Converts SQLite value into Rust value.
impl<'a, T> IntoErased<'a> for Arc<T> where
T: 'a,
impl<'a, T> IntoErased<'a> for Arc<T> where
T: 'a,
pub fn into_erased(self) -> <Arc<T> as IntoErased<'a>>::Erased
pub fn into_erased(self) -> <Arc<T> as IntoErased<'a>>::Erased
Perform the type erasure.
Performs late initialization when attaching a Layer
to a
Subscriber
. Read more
Notifies this layer that a new span was constructed with the given
Attributes
and Id
. Read more
Registers a new callsite with this layer, returning whether or not
the layer is interested in being notified about the callsite, similarly
to Subscriber::register_callsite
. Read more
Returns true
if this layer is interested in a span or event with the
given metadata
in the current Context
, similarly to
Subscriber::enabled
. Read more
Notifies this layer that a span with the given Id
recorded the given
values
. Read more
Notifies this layer that a span with the ID span
recorded that it
follows from the span with the ID follows
. Read more
Notifies this layer that an event has occurred.
Notifies this layer that a span with the given ID was entered.
Notifies this layer that the span with the given ID was exited.
Notifies this layer that the span with the given ID has been closed.
Notifies this layer that a span ID has been cloned, and that the subscriber returned a different ID. Read more
Composes this layer around the given Layer
, returning a Layered
struct implementing Layer
. Read more
Composes this Layer
with the given Subscriber
, returning a
Layered
struct that implements Subscriber
. Read more
Performs late initialization when attaching a Layer
to a
Subscriber
. Read more
Notifies this layer that a new span was constructed with the given
Attributes
and Id
. Read more
Registers a new callsite with this layer, returning whether or not
the layer is interested in being notified about the callsite, similarly
to Subscriber::register_callsite
. Read more
Returns true
if this layer is interested in a span or event with the
given metadata
in the current Context
, similarly to
Subscriber::enabled
. Read more
Notifies this layer that a span with the given Id
recorded the given
values
. Read more
Notifies this layer that a span with the ID span
recorded that it
follows from the span with the ID follows
. Read more
Notifies this layer that an event has occurred.
Notifies this layer that a span with the given ID was entered.
Notifies this layer that the span with the given ID was exited.
Notifies this layer that the span with the given ID has been closed.
Notifies this layer that a span ID has been cloned, and that the subscriber returned a different ID. Read more
Composes this layer around the given Layer
, returning a Layered
struct implementing Layer
. Read more
Composes this Layer
with the given Subscriber
, returning a
Layered
struct that implements Subscriber
. Read more
pub fn spawn_local_obj(
&self,
future: LocalFutureObj<'static, ()>
) -> Result<(), SpawnError>
pub fn spawn_local_obj(
&self,
future: LocalFutureObj<'static, ()>
) -> Result<(), SpawnError>
Spawns a future that will be run to completion. Read more
pub fn status_local(&self) -> Result<(), SpawnError>
pub fn status_local(&self) -> Result<(), SpawnError>
Determines whether the executor is able to spawn new tasks. Read more
The concrete io::Write
implementation returned by make_writer
. Read more
Comparison for two Arc
s.
The two are compared by calling cmp()
on their inner values.
Examples
use std::sync::Arc;
use std::cmp::Ordering;
let five = Arc::new(5);
assert_eq!(Ordering::Less, five.cmp(&Arc::new(6)));
Compares and returns the maximum of two values. Read more
Compares and returns the minimum of two values. Read more
Equality for two Arc
s.
Two Arc
s are equal if their inner values are equal, even if they are
stored in different allocation.
If T
also implements Eq
(implying reflexivity of equality),
two Arc
s that point to the same allocation are always equal.
Examples
use std::sync::Arc;
let five = Arc::new(5);
assert!(five == Arc::new(5));
Inequality for two Arc
s.
Two Arc
s are unequal if their inner values are unequal.
If T
also implements Eq
(implying reflexivity of equality),
two Arc
s that point to the same value are never unequal.
Examples
use std::sync::Arc;
let five = Arc::new(5);
assert!(five != Arc::new(6));
Partial comparison for two Arc
s.
The two are compared by calling partial_cmp()
on their inner values.
Examples
use std::sync::Arc;
use std::cmp::Ordering;
let five = Arc::new(5);
assert_eq!(Some(Ordering::Less), five.partial_cmp(&Arc::new(6)));
Less-than comparison for two Arc
s.
The two are compared by calling <
on their inner values.
Examples
use std::sync::Arc;
let five = Arc::new(5);
assert!(five < Arc::new(6));
‘Less than or equal to’ comparison for two Arc
s.
The two are compared by calling <=
on their inner values.
Examples
use std::sync::Arc;
let five = Arc::new(5);
assert!(five <= Arc::new(5));
Greater-than comparison for two Arc
s.
The two are compared by calling >
on their inner values.
Examples
use std::sync::Arc;
let five = Arc::new(5);
assert!(five > Arc::new(4));
This impl requires the "rc"
Cargo feature of Serde.
Serializing a data structure containing Arc
will serialize a copy of
the contents of the Arc
each time the Arc
is referenced within the
data structure. Serialization will not attempt to deduplicate these
repeated data.
pub fn serialize<S>(
&self,
serializer: S
) -> Result<<S as Serializer>::Ok, <S as Serializer>::Error> where
S: Serializer,
pub fn serialize<S>(
&self,
serializer: S
) -> Result<<S as Serializer>::Ok, <S as Serializer>::Error> where
S: Serializer,
Serialize this value into the given Serde serializer. Read more
impl ServerConfig<TlsSession> for Arc<ServerConfig>
impl ServerConfig<TlsSession> for Arc<ServerConfig>
pub fn start_session(&self, params: &TransportParameters) -> TlsSession
pub fn start_session(&self, params: &TransportParameters) -> TlsSession
Start a server session with this configuration
Registers a new callsite with this subscriber, returning whether or not the subscriber is interested in being notified about the callsite. Read more
Returns the highest verbosity level that this Subscriber
will
enable, or None
, if the subscriber does not implement level-based
filtering or chooses not to implement this method. Read more
Record a set of values on a span. Read more
Adds an indication that span
follows from the span with the id
follows
. Read more
Returns a type representing this subscriber’s view of the current span. Read more
Auto Trait Implementations
impl<T: ?Sized> RefUnwindSafe for Arc<T> where
T: RefUnwindSafe,
Blanket Implementations
fn type_id_compat(&self) -> TypeId
fn type_id_compat(&self) -> TypeId
TODO: once 1.33.0 is the minimum supported compiler version, remove Any::type_id_compat and use StdAny::type_id instead. https://github.com/rust-lang/rust/issues/27745 Read more
Mutably borrows from an owned value. Read more
Compare self to key
and return true
if they are equal.
fn with_context(self, otel_cx: Context) -> WithContext<Self>
fn with_context(self, otel_cx: Context) -> WithContext<Self>
fn with_current_context(self) -> WithContext<Self>
fn with_current_context(self) -> WithContext<Self>
Instruments this type with the provided Span
, returning an
Instrumented
wrapper. Read more
impl<Sp> LocalSpawnExt for Sp where
Sp: LocalSpawn + ?Sized,
impl<Sp> LocalSpawnExt for Sp where
Sp: LocalSpawn + ?Sized,
Wraps self
and returns a MakeWriter
that will only write output
for events at or below the provided verbosity Level
. For instance,
Level::TRACE
is considered to be _more verbosethan
Level::INFO`. Read more
Wraps self
and returns a MakeWriter
that will only write output
for events at or above the provided verbosity Level
. Read more
Wraps self
with a predicate that takes a span or event’s Metadata
and returns a bool
. The returned MakeWriter
’s
MakeWriter::make_writer_for
method will check the predicate to
determine if a writer should be produced for a given span or event. Read more
Combines self
with another type implementing MakeWriter
, returning
a new MakeWriter
that produces writers that write to both
outputs. Read more
fn or_else<W, B>(self, other: B) -> OrElse<Self, B> where
Self: MakeWriter<Writer = EitherWriter<W, Sink>>,
B: MakeWriter,
W: Write,
fn or_else<W, B>(self, other: B) -> OrElse<Self, B> where
Self: MakeWriter<Writer = EitherWriter<W, Sink>>,
B: MakeWriter,
W: Write,
Combines self
with another type implementing MakeWriter
, returning
a new MakeWriter
that calls other
’s make_writer
if self
’s
make_writer
returns OptionalWriter::none
. Read more
impl<Sp> SpawnExt for Sp where
Sp: Spawn + ?Sized,
impl<Sp> SpawnExt for Sp where
Sp: Spawn + ?Sized,
Sets self
as the default subscriber in the current scope, returning a
guard that will unset it when dropped. Read more
Attempts to set self
as the global default subscriber in the current
scope, returning an error if one is already set. Read more
Attempts to set self
as the global default subscriber in the current
scope, panicking if this fails. Read more
pub fn vzip(self) -> V
Attaches the provided Subscriber
to this type, returning a
WithDispatch
wrapper. Read more
Attaches the current default Subscriber
to this type, returning a
WithDispatch
wrapper. Read more
Attaches the provided Subscriber
to this type, returning a
WithDispatch
wrapper. Read more
Attaches the current default Subscriber
to this type, returning a
WithDispatch
wrapper. Read more