Trait tor_hsservice::internal_prelude::iter::FromIterator

pub trait FromIterator<A>: Sized {
    // Required method
    fn from_iter<T>(iter: T) -> Self
       where T: IntoIterator<Item = A>;
}

Conversion from an Iterator.

By implementing FromIterator for a type, you define how it will be created from an iterator. This is common for types which describe a collection of some kind.

If you want to create a collection from the contents of an iterator, the Iterator::collect() method is preferred. However, when you need to specify the container type, FromIterator::from_iter() can be more readable than using a turbofish (e.g. ::<Vec<_>>()). See the Iterator::collect() documentation for more examples of its use.

See also: IntoIterator.

Examples

Basic usage:

let five_fives = std::iter::repeat(5).take(5);

let v = Vec::from_iter(five_fives);

assert_eq!(v, vec![5, 5, 5, 5, 5]);

Using Iterator::collect() to implicitly use FromIterator:

let five_fives = std::iter::repeat(5).take(5);

let v: Vec<i32> = five_fives.collect();

assert_eq!(v, vec![5, 5, 5, 5, 5]);

Using FromIterator::from_iter() as a more readable alternative to Iterator::collect():

use std::collections::VecDeque;
let first = (0..10).collect::<VecDeque<i32>>();
let second = VecDeque::from_iter(0..10);

assert_eq!(first, second);

Implementing FromIterator for your type:

// A sample collection, that's just a wrapper over Vec<T>
#[derive(Debug)]
struct MyCollection(Vec<i32>);

// Let's give it some methods so we can create one and add things
// to it.
impl MyCollection {
    fn new() -> MyCollection {
        MyCollection(Vec::new())
    }

    fn add(&mut self, elem: i32) {
        self.0.push(elem);
    }
}

// and we'll implement FromIterator
impl FromIterator<i32> for MyCollection {
    fn from_iter<I: IntoIterator<Item=i32>>(iter: I) -> Self {
        let mut c = MyCollection::new();

        for i in iter {
            c.add(i);
        }

        c
    }
}

// Now we can make a new iterator...
let iter = (0..5).into_iter();

// ... and make a MyCollection out of it
let c = MyCollection::from_iter(iter);

assert_eq!(c.0, vec![0, 1, 2, 3, 4]);

// collect works too!

let iter = (0..5).into_iter();
let c: MyCollection = iter.collect();

assert_eq!(c.0, vec![0, 1, 2, 3, 4]);

Required Methods

fn from_iter<T>(iter: T) -> Self

where T: IntoIterator<Item = A>,

Creates a value from an iterator.

See the module-level documentation for more.

Examples

let five_fives = std::iter::repeat(5).take(5);

let v = Vec::from_iter(five_fives);

assert_eq!(v, vec![5, 5, 5, 5, 5]);

Object Safety

This trait is not object safe.

Implementors

impl FromIterator<(String, Value)> for serde_json::map::Map<String, Value>

impl FromIterator<(String, String)> for OptionsMap

impl FromIterator<(String, Value)> for Map<String, Value>

impl FromIterator<Error> for Option<Error>

impl FromIterator<char> for alloc::boxed::Box<str>

Available on non-no_global_oom_handling only.

impl FromIterator<char> for String

Available on non-no_global_oom_handling only.

impl FromIterator<u8> for Bytes

impl FromIterator<u8> for BytesMut

impl FromIterator<()> for ()

Collapses all unit items from an iterator into one.

This is more useful when combined with higher-level abstractions, like collecting to a Result<(), E> where you only care about errors:

use std::io::*;
let data = vec![1, 2, 3, 4, 5];
let res: Result<()> = data.iter()
    .map(|x| writeln!(stdout(), "{x}"))
    .collect();
assert!(res.is_ok());

impl FromIterator<String> for alloc::boxed::Box<str>

Available on non-no_global_oom_handling only.

impl FromIterator<String> for String

Available on non-no_global_oom_handling only.

impl FromIterator<OsString> for OsString

impl FromIterator<CipherCtxFlags> for CipherCtxFlags

impl FromIterator<CMSOptions> for CMSOptions

impl FromIterator<OcspFlag> for OcspFlag

impl FromIterator<Pkcs7Flags> for Pkcs7Flags

impl FromIterator<ExtensionContext> for ExtensionContext

impl FromIterator<ShutdownState> for ShutdownState

impl FromIterator<SslMode> for SslMode

impl FromIterator<SslOptions> for SslOptions

impl FromIterator<SslSessionCacheMode> for SslSessionCacheMode

impl FromIterator<SslVerifyMode> for SslVerifyMode

impl FromIterator<X509CheckFlags> for X509CheckFlags

impl FromIterator<X509VerifyFlags> for X509VerifyFlags

impl FromIterator<Access> for Access

impl FromIterator<Access> for Access

impl FromIterator<AtFlags> for AtFlags

impl FromIterator<AtFlags> for AtFlags

impl FromIterator<AuthCertKeyIds> for AuthCertRequest

impl FromIterator<BeginFlags> for BeginFlags

impl FromIterator<ControlModes> for ControlModes

impl FromIterator<CreateFlags> for CreateFlags

impl FromIterator<CreateFlags> for CreateFlags

impl FromIterator<CreateFlags> for CreateFlags

impl FromIterator<CreateFlags> for CreateFlags

impl FromIterator<DupFlags> for DupFlags

impl FromIterator<DupFlags> for DupFlags

impl FromIterator<EventFlags> for EventFlags

impl FromIterator<EventFlags> for EventFlags

impl FromIterator<EventfdFlags> for EventfdFlags

impl FromIterator<EventfdFlags> for EventfdFlags

impl FromIterator<FallocateFlags> for FallocateFlags

impl FromIterator<FallocateFlags> for FallocateFlags

impl FromIterator<FdFlags> for FdFlags

impl FromIterator<FdFlags> for FdFlags

impl FromIterator<FloatingPointEmulationControl> for FloatingPointEmulationControl

impl FromIterator<FloatingPointExceptionMode> for FloatingPointExceptionMode

impl FromIterator<IFlags> for IFlags

impl FromIterator<InputModes> for InputModes

impl FromIterator<Literal> for Seq

impl FromIterator<LocalModes> for LocalModes

impl FromIterator<MembarrierQuery> for MembarrierQuery

impl FromIterator<MemfdFlags> for MemfdFlags

impl FromIterator<MemfdFlags> for MemfdFlags

impl FromIterator<Mode> for Mode

impl FromIterator<Mode> for Mode

impl FromIterator<MountFlags> for MountFlags

impl FromIterator<MountFlags> for MountFlags

impl FromIterator<MountPropagationFlags> for MountPropagationFlags

impl FromIterator<MountPropagationFlags> for MountPropagationFlags

impl FromIterator<OFlags> for OFlags

impl FromIterator<OFlags> for OFlags

impl FromIterator<OutputModes> for OutputModes

impl FromIterator<PidfdFlags> for PidfdFlags

impl FromIterator<PidfdGetfdFlags> for PidfdGetfdFlags

impl FromIterator<PipeFlags> for PipeFlags

impl FromIterator<PipeFlags> for PipeFlags

impl FromIterator<PollFlags> for PollFlags

impl FromIterator<PollFlags> for PollFlags

impl FromIterator<ReadWriteFlags> for ReadWriteFlags

impl FromIterator<ReadWriteFlags> for ReadWriteFlags

impl FromIterator<RecvFlags> for RecvFlags

impl FromIterator<RelayFlags> for RelayFlags

impl FromIterator<RelayId> for RelayIdSet

impl FromIterator<RenameFlags> for RenameFlags

impl FromIterator<RenameFlags> for RenameFlags

impl FromIterator<ResolveFlags> for ResolveFlags

impl FromIterator<ResolveFlags> for ResolveFlags

impl FromIterator<SealFlags> for SealFlags

impl FromIterator<SealFlags> for SealFlags

impl FromIterator<SendFlags> for SendFlags

impl FromIterator<SockaddrXdpFlags> for SockaddrXdpFlags

impl FromIterator<SocketFlags> for SocketFlags

impl FromIterator<SpeculationFeatureControl> for SpeculationFeatureControl

impl FromIterator<SpeculationFeatureState> for SpeculationFeatureState

impl FromIterator<SpliceFlags> for SpliceFlags

impl FromIterator<SpliceFlags> for SpliceFlags

impl FromIterator<StatVfsMountFlags> for StatVfsMountFlags

impl FromIterator<StatVfsMountFlags> for StatVfsMountFlags

impl FromIterator<StatxFlags> for StatxFlags

impl FromIterator<StatxFlags> for StatxFlags

impl FromIterator<Table> for ArrayOfTables

impl FromIterator<TimerfdFlags> for TimerfdFlags

impl FromIterator<TimerfdTimerFlags> for TimerfdTimerFlags

impl FromIterator<TrustAnchor<'static>> for RootCertStore

impl FromIterator<UnalignedAccessControl> for UnalignedAccessControl

impl FromIterator<UnmountFlags> for UnmountFlags

impl FromIterator<UnmountFlags> for UnmountFlags

impl FromIterator<WaitOptions> for WaitOptions

impl FromIterator<WaitidOptions> for WaitidOptions

impl FromIterator<WatchFlags> for WatchFlags

impl FromIterator<WatchFlags> for WatchFlags

impl FromIterator<XattrFlags> for XattrFlags

impl FromIterator<XattrFlags> for XattrFlags

impl FromIterator<XdpDescOptions> for XdpDescOptions

impl FromIterator<XdpOptionsFlags> for XdpOptionsFlags

impl FromIterator<XdpRingFlags> for XdpRingFlags

impl FromIterator<XdpUmemRegFlags> for XdpUmemRegFlags

impl FromIterator<[u8; 20]> for RouterDescRequest

Available on crate feature routerdesc only.

impl FromIterator<[u8; 32]> for MicrodescRequest

impl<'a> FromIterator<&'a char> for alloc::boxed::Box<str>

Available on non-no_global_oom_handling only.

impl<'a> FromIterator<&'a char> for String

Available on non-no_global_oom_handling only.

impl<'a> FromIterator<&'a str> for alloc::boxed::Box<str>

Available on non-no_global_oom_handling only.

impl<'a> FromIterator<&'a str> for String

Available on non-no_global_oom_handling only.

impl<'a> FromIterator<&'a u8> for BytesMut

impl<'a> FromIterator<&'a OsStr> for OsString

impl<'a> FromIterator<Cow<'a, str>> for alloc::boxed::Box<str>

Available on non-no_global_oom_handling only.

impl<'a> FromIterator<Cow<'a, str>> for String

Available on non-no_global_oom_handling only.

impl<'a> FromIterator<Cow<'a, OsStr>> for OsString

impl<'a> FromIterator<char> for Cow<'a, str>

Available on non-no_global_oom_handling only.

impl<'a> FromIterator<String> for Cow<'a, str>

Available on non-no_global_oom_handling only.

impl<'a, 'b> FromIterator<&'b str> for Cow<'a, str>

Available on non-no_global_oom_handling only.

impl<'a, M, T1, T2, O1, O2> FromIterator<BitRef<'a, M, T2, O2>> for BitVec<T1, O1>

where M: Mutability, T1: BitStore, T2: BitStore, O1: BitOrder, O2: BitOrder,

Available on non-tarpaulin_include only.

Bit-Vector Collection from Proxy References

DO NOT use this. You clearly have a bit-slice. Use ::from_bitslice() instead!

Iterating over a bit-slice requires loading from memory and constructing a proxy reference for each bit. This is needlessly slow; the specialized method is able to avoid this per-bit cost and possibly even use batched operations.

impl<'a, T> FromIterator<T> for Cow<'a, [T]>

where T: Clone,

impl<'a, T, O> FromIterator<&'a bool> for BitVec<T, O>

where T: BitStore, O: BitOrder,

Available on non-tarpaulin_include only.

impl<'a, T, O> FromIterator<&'a T> for BitVec<T, O>

where T: BitStore, O: BitOrder,

Available on non-tarpaulin_include only.

impl<A> FromIterator<<A as Array>::Item> for ArrayVec<A>

where A: Array,

impl<A> FromIterator<<A as Array>::Item> for SmallVec<A>

where A: Array,

impl<A> FromIterator<<A as Array>::Item> for TinyVec<A>

where A: Array,

impl<A> FromIterator<Box<str, A>> for alloc::boxed::Box<str>

where A: Allocator,

Available on non-no_global_oom_handling only.

impl<A> FromIterator<Box<str, A>> for String

where A: Allocator,

Available on non-no_global_oom_handling only.

impl<A> FromIterator<A> for AsciiString

where A: AsRef<AsciiStr>,

impl<A, B, AE, BE> FromIterator<(AE, BE)> for (A, B)

where A: Default + Extend<AE>, B: Default + Extend<BE>,

This implementation turns an iterator of tuples into a tuple of types which implement Default and Extend.

This is similar to Iterator::unzip, but is also composable with other FromIterator implementations:

let string = "1,2,123,4";

let (numbers, lengths): (Vec<_>, Vec<_>) = string
    .split(',')
    .map(|s| s.parse().map(|n: u32| (n, s.len())))
    .collect::<Result<_, _>>()?;

assert_eq!(numbers, [1, 2, 123, 4]);
assert_eq!(lengths, [1, 1, 3, 1]);

impl<A, E, V> FromIterator<Result<A, E>> for Result<V, E>

where V: FromIterator<A>,

impl<A, V> FromIterator<Option<A>> for Option<V>

where V: FromIterator<A>,

impl<F> FromIterator<F> for JoinAll<F>

where F: Future,

impl<F> FromIterator<F> for TryJoinAll<F>

where F: TryFuture,

impl<Fut> FromIterator<Fut> for tor_hsservice::internal_prelude::future::SelectAll<Fut>

where Fut: Future + Unpin,

impl<Fut> FromIterator<Fut> for SelectOk<Fut>

where Fut: TryFuture + Unpin,

impl<Fut> FromIterator<Fut> for FuturesOrdered<Fut>

where Fut: Future,

impl<Fut> FromIterator<Fut> for FuturesUnordered<Fut>

impl<H> FromIterator<H> for ByRelayIds<H>

where H: HasRelayIds, RsaIdentity: Hash + Eq + Clone, Ed25519Identity: Hash + Eq + Clone,

impl<I> FromIterator<I> for alloc::boxed::Box<[I]>

Available on non-no_global_oom_handling only.

impl<I> FromIterator<I> for Box<[I]>

Available on non-no_global_oom_handling only.

impl<K, T> FromIterator<(K, T)> for NetParams<T>

where K: Into<String>,

impl<K, V> FromIterator<(Range<K>, V)> for RangeMap<K, V>

where K: Ord + Clone, V: Eq + Clone,

impl<K, V> FromIterator<(RangeInclusive<K>, V)> for RangeInclusiveMap<K, V>

where K: Ord + Clone + StepLite, V: Eq + Clone,

impl<K, V> FromIterator<(K, V)> for serde_json::value::Value

where K: Into<String>, V: Into<Value>,

impl<K, V> FromIterator<(K, V)> for BTreeMap<K, V>

where K: Ord,

impl<K, V> FromIterator<(K, V)> for InlineTable

where K: Into<Key>, V: Into<Value>,

impl<K, V> FromIterator<(K, V)> for Table

where K: Into<Key>, V: Into<Value>,

impl<K, V> FromIterator<(K, V)> for Value

where K: Into<Key>, V: Into<Value>,

impl<K, V> FromIterator<V> for alloc::boxed::Box<TiSlice<K, V>>

impl<K, V> FromIterator<V> for TiVec<K, V>

impl<K, V, S> FromIterator<(<K as WeakElement>::Strong, <V as WeakElement>::Strong)> for PtrWeakWeakHashMap<K, V, S>

where K: WeakElement, <K as WeakElement>::Strong: Deref, V: WeakElement, S: BuildHasher + Default,

impl<K, V, S> FromIterator<(<K as WeakElement>::Strong, <V as WeakElement>::Strong)> for WeakWeakHashMap<K, V, S>

where K: WeakKey, V: WeakElement, S: BuildHasher + Default,

impl<K, V, S> FromIterator<(<K as WeakElement>::Strong, V)> for PtrWeakKeyHashMap<K, V, S>

where K: WeakElement, <K as WeakElement>::Strong: Deref, S: BuildHasher + Default,

impl<K, V, S> FromIterator<(<K as WeakElement>::Strong, V)> for WeakKeyHashMap<K, V, S>

where K: WeakKey, S: BuildHasher + Default,

impl<K, V, S> FromIterator<(K, <V as WeakElement>::Strong)> for WeakValueHashMap<K, V, S>

where K: Eq + Hash, V: WeakElement, S: BuildHasher + Default,

impl<K, V, S> FromIterator<(K, V)> for tor_hsservice::internal_prelude::HashMap<K, V, S>

where K: Eq + Hash, S: BuildHasher + Default,

impl<K, V, S> FromIterator<(K, V)> for IndexMap<K, V, S>

where K: Hash + Eq, S: BuildHasher + Default,

impl<K, V, S, A> FromIterator<(K, V)> for HashMap<K, V, S, A>

where K: Eq + Hash, S: BuildHasher + Default, A: Default + Allocator,

impl<P> FromIterator<P> for tor_hsservice::internal_prelude::PathBuf

where P: AsRef<Path>,

impl<P> FromIterator<P> for PathBuf

where P: AsRef<Path>,

impl<St> FromIterator<St> for SelectAll<St>

where St: Stream + Unpin,

impl<T> FromIterator<(usize, T)> for Slab<T>

Create a slab from an iterator of key-value pairs.

If the iterator produces duplicate keys, the previous value is replaced with the later one. The keys does not need to be sorted beforehand, and this function always takes O(n) time. Note that the returned slab will use space proportional to the largest key, so don’t use Slab with untrusted keys.

Examples

let vec = vec![(2,'a'), (6,'b'), (7,'c')];
let slab = vec.into_iter().collect::<Slab<char>>();
assert_eq!(slab.len(), 3);
assert!(slab.capacity() >= 8);
assert_eq!(slab[2], 'a');

With duplicate and unsorted keys:

let vec = vec![(20,'a'), (10,'b'), (11,'c'), (10,'d')];
let slab = vec.into_iter().collect::<Slab<char>>();
assert_eq!(slab.len(), 3);
assert_eq!(slab[10], 'd');

impl<T> FromIterator<(HeaderName, T)> for HeaderMap<T>

impl<T> FromIterator<Range<T>> for RangeSet<T>

where T: Ord + Clone,

impl<T> FromIterator<RangeInclusive<T>> for RangeInclusiveSet<T>

where T: Ord + Clone + StepLite,

impl<T> FromIterator<T> for serde_json::value::Value

where T: Into<Value>,

impl<T> FromIterator<T> for Arc<[T]>

Available on non-no_global_oom_handling only.

impl<T> FromIterator<T> for BinaryHeap<T>

where T: Ord,

impl<T> FromIterator<T> for VecDeque<T>

impl<T> FromIterator<T> for BTreeSet<T>

where T: Ord,

impl<T> FromIterator<T> for LinkedList<T>

impl<T> FromIterator<T> for Rc<[T]>

Available on non-no_global_oom_handling only.

impl<T> FromIterator<T> for alloc::vec::Vec<T>

Available on non-no_global_oom_handling only.

Collects an iterator into a Vec, commonly called via Iterator::collect()

Allocation behavior

In general Vec does not guarantee any particular growth or allocation strategy. That also applies to this trait impl.

Note: This section covers implementation details and is therefore exempt from stability guarantees.

Vec may use any or none of the following strategies, depending on the supplied iterator:

• preallocate based on Iterator::size_hint()
  • and panic if the number of items is outside the provided lower/upper bounds
• use an amortized growth strategy similar to pushing one item at a time
• perform the iteration in-place on the original allocation backing the iterator

The last case warrants some attention. It is an optimization that in many cases reduces peak memory consumption and improves cache locality. But when big, short-lived allocations are created, only a small fraction of their items get collected, no further use is made of the spare capacity and the resulting Vec is moved into a longer-lived structure, then this can lead to the large allocations having their lifetimes unnecessarily extended which can result in increased memory footprint.

In cases where this is an issue, the excess capacity can be discarded with Vec::shrink_to(), Vec::shrink_to_fit() or by collecting into Box<[T]> instead, which additionally reduces the size of the long-lived struct.

static LONG_LIVED: Mutex<Vec<Vec<u16>>> = Mutex::new(Vec::new());

for i in 0..10 {
    let big_temporary: Vec<u16> = (0..1024).collect();
    // discard most items
    let mut result: Vec<_> = big_temporary.into_iter().filter(|i| i % 100 == 0).collect();
    // without this a lot of unused capacity might be moved into the global
    result.shrink_to_fit();
    LONG_LIVED.lock().unwrap().push(result);
}

impl<T> FromIterator<T> for Vec<T>

Available on non-no_global_oom_handling only.

impl<T, F> FromIterator<F> for JoinSet<T>

where F: Future<Output = T> + Send + 'static, T: Send + 'static,

Collect an iterator of futures into a [JoinSet].

This is equivalent to calling [JoinSet::spawn] on each element of the iterator.

Examples

The main example from [JoinSet]’s documentation can also be written using collect:

use tokio::task::JoinSet;

#[tokio::main]
async fn main() {
    let mut set: JoinSet<_> = (0..10).map(|i| async move { i }).collect();

    let mut seen = [false; 10];
    while let Some(res) = set.join_next().await {
        let idx = res.unwrap();
        seen[idx] = true;
    }

    for i in 0..10 {
        assert!(seen[i]);
    }
}

impl<T, N> FromIterator<T> for GenericArray<T, N>

where N: ArrayLength<T>,

impl<T, O> FromIterator<bool> for BitVec<T, O>

where T: BitStore, O: BitOrder,

Available on non-tarpaulin_include only.

Bit-Vector Collection

This collects a bit-vector from anything that produces individual bits.

Original

impl<T> FromIterator<T> for Vec<T>

Notes

This .collect() call is the second-slowest possible way to collect bits into a bit-vector, faster only than calling iter.for_each(|bit| bv.push(bit)). DO NOT use this if you have any other choice.

If you are collecting a bit-vector from the contents of a bit-slice, then you should use ::from_bitslice() instead. That method is specialized to perform upfront allocation and, where possible, use a batch copy rather than copying each bit individually from the source into the bit-vector.

impl<T, O> FromIterator<T> for BitVec<T, O>

where T: BitStore, O: BitOrder,

Available on non-tarpaulin_include only.

impl<T, O, I> FromIterator<I> for BitBox<T, O>

where T: BitStore, O: BitOrder, BitVec<T, O>: FromIterator<I>,

Available on non-tarpaulin_include only.

impl<T, S> FromIterator<<T as WeakElement>::Strong> for PtrWeakHashSet<T, S>

where T: WeakElement, <T as WeakElement>::Strong: Deref, S: BuildHasher + Default,

impl<T, S> FromIterator<<T as WeakElement>::Strong> for WeakHashSet<T, S>

where T: WeakKey, S: BuildHasher + Default,

impl<T, S> FromIterator<T> for tor_hsservice::internal_prelude::HashSet<T, S>

where T: Eq + Hash, S: BuildHasher + Default,

impl<T, S> FromIterator<T> for IndexSet<T, S>

where T: Hash + Eq, S: BuildHasher + Default,

impl<T, S, A> FromIterator<T> for HashSet<T, S, A>

where T: Eq + Hash, S: BuildHasher + Default, A: Default + Allocator,

impl<T, const CAP: usize> FromIterator<T> for arrayvec::arrayvec::ArrayVec<T, CAP>

Create an ArrayVec from an iterator.

Panics if the number of elements in the iterator exceeds the arrayvec’s capacity.

impl<V> FromIterator<V> for Array

where V: Into<Value>,

impl<V> FromIterator<V> for Value

where V: Into<Value>,