once.rs.html -- source

Files

adler32

aho_corasick

packed

teddy

compile.rs mod.rs runtime.rs

api.rs mod.rs pattern.rs rabinkarp.rs vector.rs

ahocorasick.rs automaton.rs buffer.rs byte_frequencies.rs classes.rs dfa.rs error.rs lib.rs nfa.rs prefilter.rs state_id.rs

ansi_term

ansi.rs debug.rs difference.rs display.rs lib.rs style.rs windows.rs write.rs

atty

backtrace

backtrace

libunwind.rs mod.rs

symbolize

dladdr.rs libbacktrace.rs mod.rs

capture.rs lib.rs print.rs types.rs

backtrace_sys

base64

write

encoder.rs mod.rs

chunked_encoder.rs decode.rs display.rs encode.rs lib.rs tables.rs

base_x

alphabet.rs bigint.rs decoder.rs encoder.rs lib.rs

bitflags

block_buffer

block_padding

bstr

byteset

mod.rs scalar.rs

search

byte_frequencies.rs mod.rs prefilter.rs twoway.rs

ascii.rs bstr.rs bstring.rs cow.rs ext_slice.rs ext_vec.rs impls.rs io.rs lib.rs utf8.rs

byte_tools

byteorder

bytes

buf

buf.rs buf_mut.rs chain.rs from_buf.rs into_buf.rs iter.rs mod.rs reader.rs take.rs vec_deque.rs writer.rs

bytes.rs debug.rs either.rs lib.rs

cargo_metadata

dependency.rs errors.rs lib.rs

cargo_web

cfg_if

clap

cookie

builder.rs delta.rs draft.rs jar.rs lib.rs parse.rs

cookie_store

cookie.rs cookie_domain.rs cookie_expiration.rs cookie_path.rs cookie_store.rs lib.rs utils.rs

crc32fast

specialized

mod.rs pclmulqdq.rs

baseline.rs combine.rs lib.rs table.rs

crossbeam_channel

flavors

after.rs array.rs list.rs mod.rs never.rs tick.rs zero.rs

channel.rs context.rs counter.rs err.rs lib.rs select.rs select_macro.rs utils.rs waker.rs

crossbeam_deque

crossbeam_epoch

sync

list.rs mod.rs queue.rs

atomic.rs collector.rs default.rs deferred.rs epoch.rs guard.rs internal.rs lib.rs

crossbeam_queue

array_queue.rs err.rs lib.rs seg_queue.rs

crossbeam_utils

atomic

atomic_cell.rs consume.rs mod.rs seq_lock.rs

sync

mod.rs parker.rs sharded_lock.rs wait_group.rs

backoff.rs cache_padded.rs lib.rs thread.rs

digest

digest.rs dyn_digest.rs errors.rs lib.rs

directories

dirs_sys

lib.rs xdg_user_dirs.rs

dtoa

diyfp.rs dtoa.rs lib.rs

either

embed_wasm

embed_wasm_build

encoding_rs

ascii.rs big5.rs data.rs euc_jp.rs euc_kr.rs gb18030.rs handles.rs iso_2022_jp.rs lib.rs macros.rs mem.rs replacement.rs shift_jis.rs single_byte.rs utf_16.rs utf_8.rs variant.rs x_user_defined.rs

env_logger

filter

mod.rs regex.rs

fmt

humantime

extern_impl.rs mod.rs

writer

termcolor

extern_impl.rs mod.rs

error_chain

backtrace.rs error_chain.rs impl_error_chain_kind.rs lib.rs quick_main.rs

failure

backtrace

internal.rs mod.rs

error

error_impl.rs mod.rs

as_fail.rs box_std.rs compat.rs context.rs error_message.rs lib.rs macros.rs result_ext.rs sync_failure.rs

failure_derive

fake_simd

filetime

unix

linux.rs mod.rs utimes.rs

flate2

deflate

bufread.rs mod.rs read.rs write.rs

ffi

gz

bufread.rs mod.rs read.rs write.rs

zlib

bufread.rs mod.rs read.rs write.rs

bufreader.rs crc.rs lib.rs mem.rs zio.rs

fnv

foreign_types

foreign_types_shared

futures

future

sink

buffer.rs fanout.rs flush.rs from_err.rs map_err.rs mod.rs send.rs send_all.rs wait.rs with.rs with_flat_map.rs

stream

sync

mpsc

mod.rs queue.rs

bilock.rs mod.rs oneshot.rs

task_impl

std

data.rs mod.rs task_rc.rs unpark_mutex.rs

atomic_task.rs core.rs mod.rs

unsync

mod.rs mpsc.rs oneshot.rs

executor.rs lib.rs lock.rs poll.rs resultstream.rs task.rs

futures_channel

mpsc

mod.rs queue.rs

lib.rs lock.rs oneshot.rs

futures_core

task

__internal

atomic_waker.rs mod.rs

future.rs lib.rs stream.rs

futures_cpupool

futures_sink

futures_task

future_obj.rs lib.rs noop_waker.rs spawn.rs

futures_util

future

stream

task

mod.rs spawn.rs

lib.rs never.rs

generic_array

arr.rs functional.rs hex.rs impls.rs iter.rs lib.rs sequence.rs

getrandom

error.rs error_impls.rs lib.rs linux_android.rs use_file.rs util.rs util_libc.rs

globset

glob.rs lib.rs pathutil.rs

h2

handlebars

headers

common

accept_ranges.rs access_control_allow_credentials.rs access_control_allow_headers.rs access_control_allow_methods.rs access_control_allow_origin.rs access_control_expose_headers.rs access_control_max_age.rs access_control_request_headers.rs access_control_request_method.rs allow.rs authorization.rs cache_control.rs connection.rs content_disposition.rs content_encoding.rs content_length.rs content_location.rs content_range.rs content_type.rs cookie.rs date.rs etag.rs expect.rs expires.rs host.rs if_match.rs if_modified_since.rs if_none_match.rs if_range.rs if_unmodified_since.rs last_modified.rs location.rs mod.rs origin.rs pragma.rs proxy_authorization.rs range.rs referer.rs referrer_policy.rs retry_after.rs sec_websocket_accept.rs sec_websocket_key.rs sec_websocket_version.rs server.rs set_cookie.rs strict_transport_security.rs te.rs transfer_encoding.rs upgrade.rs user_agent.rs vary.rs

util

csv.rs entity.rs flat_csv.rs fmt.rs http_date.rs iter.rs mod.rs seconds.rs value_string.rs

lib.rs map_ext.rs

headers_core

heck

camel.rs kebab.rs lib.rs mixed.rs shouty_snake.rs snake.rs title.rs

http

header

map.rs mod.rs name.rs value.rs

uri

authority.rs builder.rs mod.rs path.rs port.rs scheme.rs

byte_str.rs convert.rs error.rs extensions.rs lib.rs method.rs request.rs response.rs status.rs version.rs

http_body

httparse

simd

avx2.rs mod.rs sse42.rs

iter.rs lib.rs macros.rs

humantime

date.rs duration.rs lib.rs wrapper.rs

hyper

body

body.rs chunk.rs mod.rs payload.rs

client

connect

dns.rs http.rs mod.rs

conn.rs dispatch.rs mod.rs pool.rs

common

io

mod.rs rewind.rs

buf.rs drain.rs exec.rs lazy.rs mod.rs never.rs task.rs

proto

h1

conn.rs date.rs decode.rs dispatch.rs encode.rs io.rs mod.rs role.rs

h2

client.rs mod.rs server.rs

server

conn.rs mod.rs shutdown.rs tcp.rs

service

make_service.rs mod.rs new_service.rs service.rs

error.rs headers.rs lib.rs rt.rs upgrade.rs

hyper_tls

client.rs lib.rs stream.rs

idna

lib.rs punycode.rs uts46.rs

ignore

default_types.rs dir.rs gitignore.rs lib.rs overrides.rs pathutil.rs types.rs walk.rs

indexmap

equivalent.rs lib.rs macros.rs map.rs mutable_keys.rs set.rs util.rs

inotify

events.rs fd_guard.rs inotify.rs lib.rs util.rs watches.rs

inotify_sys

iovec

sys

itoa

language_tags

lazy_static

inline_lazy.rs lib.rs

lazycell

libc

unix

linux_like

linux

gnu

b64

x86_64

align.rs mod.rs not_x32.rs

align.rs mod.rs

align.rs mod.rs

align.rs mod.rs

fixed_width_ints.rs lib.rs macros.rs

libflate

deflate

decode.rs encode.rs mod.rs symbol.rs

lz77

default.rs mod.rs

non_blocking

deflate

decode.rs mod.rs

gzip.rs mod.rs transaction.rs zlib.rs

bit.rs checksum.rs finish.rs gzip.rs huffman.rs lib.rs util.rs zlib.rs

lock_api

lib.rs mutex.rs remutex.rs rwlock.rs

log

lib.rs macros.rs

maplit

matches

maybe_uninit

memchr

x86

avx.rs mod.rs sse2.rs

fallback.rs iter.rs lib.rs naive.rs

memmap

memoffset

lib.rs offset_of.rs span_of.rs

mime

mime_guess

miniz_oxide

deflate

buffer.rs core.rs mod.rs stream.rs

inflate

core.rs mod.rs output_buffer.rs stream.rs

lib.rs shared.rs

mio

mio_extras

channel.rs lib.rs timer.rs

mio_uds

datagram.rs lib.rs listener.rs socket.rs stream.rs

native_tls

imp

net2

sys

unix

impls.rs mod.rs

ext.rs lib.rs socket.rs tcp.rs udp.rs unix.rs utils.rs

notify

debounce

mod.rs timer.rs

inotify.rs lib.rs null.rs poll.rs

num_cpus

lib.rs linux.rs

opaque_debug

open

openssl

openssl_probe

openssl_sys

parity_wasm

parking_lot

condvar.rs deadlock.rs elision.rs lib.rs mutex.rs once.rs raw_mutex.rs raw_rwlock.rs remutex.rs rwlock.rs util.rs

parking_lot_core

thread_parker

linux.rs mod.rs

lib.rs parking_lot.rs spinwait.rs util.rs word_lock.rs

pbr

tty

lib.rs multi.rs pb.rs

percent_encoding

pest

iterators

flat_pairs.rs mod.rs pair.rs pairs.rs queueable_token.rs tokens.rs

unicode

binary.rs category.rs mod.rs

error.rs lib.rs macros.rs parser.rs parser_state.rs position.rs prec_climber.rs span.rs stack.rs token.rs

pest_derive

pest_generator

generator.rs lib.rs macros.rs

pest_meta

optimizer

concatenator.rs factorizer.rs mod.rs restorer.rs rotater.rs skipper.rs unroller.rs

ast.rs grammar.rs lib.rs parser.rs validator.rs

phf

lib.rs map.rs ordered_map.rs ordered_set.rs set.rs

phf_codegen

phf_generator

phf_shared

pin_project

pin_project_internal

pin_project

attribute.rs derive.rs mod.rs

lib.rs pinned_drop.rs project.rs utils.rs

pin_project_lite

pin_utils

lib.rs projection.rs stack_pin.rs

ppv_lite86

x86_64

lib.rs soft.rs types.rs

proc_macro2

fallback.rs lib.rs strnom.rs wrapper.rs

publicsuffix

errors.rs lib.rs

quick_error

quote

ext.rs format.rs ident_fragment.rs lib.rs runtime.rs spanned.rs to_tokens.rs

rand

rand_chacha

chacha.rs guts.rs lib.rs

rand_core

block.rs error.rs impls.rs le.rs lib.rs os.rs

rand_hc

hc128.rs lib.rs

rand_isaac

isaac.rs isaac64.rs isaac_array.rs lib.rs

rand_jitter

dummy_log.rs error.rs lib.rs platform.rs

rand_os

dummy_log.rs lib.rs linux_android.rs random_device.rs

rand_pcg

lib.rs pcg128.rs pcg64.rs

rand_xorshift

regex

regex_syntax

remove_dir_all

reqwest

rle_decode_fast

rustc_demangle

legacy.rs lib.rs v0.rs

ryu

buffer

pretty

exponent.rs mantissa.rs mod.rs

common.rs d2s.rs d2s_full_table.rs d2s_intrinsics.rs digit_table.rs f2s.rs lib.rs

safemem

same_file

scoped_tls

scopeguard

semver

lib.rs version.rs version_req.rs

semver_parser

common.rs lib.rs range.rs recognize.rs version.rs

serde

de

from_primitive.rs ignored_any.rs impls.rs mod.rs utf8.rs value.rs

private

de.rs macros.rs mod.rs ser.rs

ser

impls.rs impossible.rs mod.rs

export.rs integer128.rs lib.rs macros.rs

serde_derive

internals

ast.rs attr.rs case.rs check.rs ctxt.rs mod.rs symbol.rs

bound.rs de.rs dummy.rs fragment.rs lib.rs pretend.rs ser.rs try.rs

serde_json

features_check

io

value

de.rs from.rs index.rs mod.rs partial_eq.rs ser.rs

de.rs error.rs iter.rs lib.rs macros.rs map.rs number.rs read.rs ser.rs

serde_urlencoded

ser

key.rs mod.rs pair.rs part.rs value.rs

sha1

consts.rs lib.rs utils.rs

sha2

consts.rs lib.rs sha256.rs sha256_utils.rs sha512.rs sha512_utils.rs

siphasher

lib.rs sip.rs sip128.rs

slab

smallvec

string

strsim

structopt

structopt_derive

attrs.rs lib.rs

syn

synstructure

lib.rs macros.rs

take_mut

lib.rs scoped.rs

tar

archive.rs builder.rs entry.rs entry_type.rs error.rs header.rs lib.rs pax.rs

tempfile

file

imp

dir.rs error.rs lib.rs spooled.rs util.rs

termcolor

textwrap

indentation.rs lib.rs splitting.rs

thread_local

cached.rs lib.rs thread_id.rs unreachable.rs

time

display.rs duration.rs lib.rs parse.rs sys.rs

tokio

codec

length_delimited.rs mod.rs

executor

current_thread

reactor

mod.rs poll_evented.rs

runtime

current_thread

builder.rs mod.rs runtime.rs

threadpool

builder.rs mod.rs shutdown.rs task_executor.rs

util

enumerate.rs future.rs mod.rs stream.rs

clock.rs fs.rs io.rs lib.rs net.rs prelude.rs sync.rs timer.rs

tokio_buf

util

chain.rs collect.rs from.rs iter.rs limit.rs mod.rs stream.rs

lib.rs never.rs size_hint.rs str.rs u8.rs

tokio_codec

bytes_codec.rs lib.rs lines_codec.rs

tokio_core

tokio_current_thread

lib.rs scheduler.rs

tokio_executor

enter.rs error.rs executor.rs global.rs lib.rs park.rs typed.rs

tokio_fs

tokio_io

tokio_reactor

background.rs lib.rs poll_evented.rs registration.rs sharded_rwlock.rs

tokio_sync

mpsc

block.rs bounded.rs chan.rs list.rs mod.rs unbounded.rs

task

atomic_task.rs mod.rs

lib.rs lock.rs loom.rs oneshot.rs semaphore.rs watch.rs

tokio_tcp

incoming.rs lib.rs listener.rs stream.rs

tokio_threadpool

tokio_timer

tokio_tls

tokio_udp

frame.rs lib.rs recv_dgram.rs send_dgram.rs socket.rs

tokio_uds

datagram.rs frame.rs incoming.rs lib.rs listener.rs recv_dgram.rs send_dgram.rs stream.rs ucred.rs

tokio_util

codec

bytes_codec.rs decoder.rs encoder.rs framed.rs framed_read.rs framed_write.rs length_delimited.rs lines_codec.rs mod.rs

toml

datetime.rs de.rs lib.rs macros.rs ser.rs spanned.rs tokens.rs value.rs

tower_service

traitobject

impls.rs lib.rs

try_from

char.rs int.rs lib.rs

try_lock

typeable

typenum

array.rs bit.rs int.rs lib.rs marker_traits.rs operator_aliases.rs private.rs type_operators.rs uint.rs

ucd_trie

lib.rs owned.rs

unicase

unicode

ascii.rs lib.rs

unicode_bidi

char_data

mod.rs tables.rs

deprecated.rs explicit.rs format_chars.rs implicit.rs level.rs lib.rs prepare.rs

unicode_categories

lib.rs tables.rs

unicode_normalization

__test_api.rs decompose.rs lib.rs lookups.rs normalize.rs perfect_hash.rs quick_check.rs recompose.rs stream_safe.rs tables.rs

unicode_segmentation

grapheme.rs lib.rs sentence.rs tables.rs word.rs

unicode_width

lib.rs tables.rs

unicode_xid

lib.rs tables.rs

url

encoding.rs form_urlencoded.rs host.rs lib.rs origin.rs parser.rs path_segments.rs quirks.rs slicing.rs

uuid

adapter

core_support

parser

core_support.rs mod.rs std_support.rs

builder.rs core_support.rs lib.rs prelude.rs std_support.rs v4.rs

vec_map

walkdir

dent.rs error.rs lib.rs util.rs

want

websocket

client

async.rs builder.rs mod.rs sync.rs

codec

http.rs mod.rs ws.rs

header

accept.rs extensions.rs key.rs mod.rs origin.rs protocol.rs version.rs

server

upgrade

async.rs mod.rs sync.rs

async.rs mod.rs sync.rs

ws

util

header.rs mask.rs mod.rs

dataframe.rs message.rs mod.rs receiver.rs sender.rs

dataframe.rs lib.rs message.rs receiver.rs result.rs sender.rs stream.rs

xattr

sys

linux_macos

linux.rs mod.rs

error.rs lib.rs util.rs

use core::pin::Pin;
use futures_core::future::Future;
use futures_core::stream::{Stream, FusedStream};
use futures_core::task::{Context, Poll};
use pin_utils::unsafe_pinned;

/// Creates a stream of a single element.
///
/// ```
/// # futures::executor::block_on(async {
/// use futures::stream::{self, StreamExt};
///
/// let stream = stream::once(async { 17 });
/// let collected = stream.collect::<Vec<i32>>().await;
/// assert_eq!(collected, vec![17]);
/// # });
/// ```
pub fn once<Fut: Future>(future: Fut) -> Once<Fut> {
    Once { future: Some(future) }
}

/// A stream which emits single element and then EOF.
///
/// This stream will never block and is always ready.
#[derive(Debug)]
#[must_use = "streams do nothing unless polled"]
pub struct Once<Fut> {
    future: Option<Fut>
}

impl<Fut: Unpin> Unpin for Once<Fut> {}

impl<Fut> Once<Fut> {
    unsafe_pinned!(future: Option<Fut>);
}

impl<Fut: Future> Stream for Once<Fut> {
    type Item = Fut::Output;

    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
        let v = match self.as_mut().future().as_pin_mut() {
            Some(fut) => ready!(fut.poll(cx)),
            None => return Poll::Ready(None),
        };

        self.as_mut().future().set(None);
        Poll::Ready(Some(v))
    }

    fn size_hint(&self) -> (usize, Option<usize>) {
        if self.future.is_some() {
            (1, Some(1))
        } else {
            (0, Some(0))
        }
    }
}

impl<Fut: Future> FusedStream for Once<Fut> {
    fn is_terminated(&self) -> bool {
        self.future.is_none()
    }
}

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