select.rs.html -- source

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sync

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

csv

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connection

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mysql

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h2

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uri

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http_body

httparse

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iter.rs lib.rs macros.rs

hyper

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client

connect

dns.rs http.rs mod.rs

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

common

io

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

proto

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client.rs mod.rs server.rs

server

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service

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hyper_rustls

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idna

lib.rs punycode.rs uts46.rs

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inflate

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sys

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jpeg_decoder

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language_tags

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inline_lazy.rs lib.rs

libc

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linux_like

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gnu

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fixed_width_ints.rs lib.rs macros.rs

lock_api

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log

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matches

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x86

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memoffset

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embed_migrations.rs lib.rs migrations.rs util.rs

mime

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lib.rs shared.rs

mio

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server

boundary.rs field.rs mod.rs save.rs

mysqlclient_sys

bindings_macos.rs lib.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

nodrop

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lib.rs roots.rs

num_iter

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ops

checked.rs inv.rs mod.rs mul_add.rs saturating.rs wrapping.rs

bounds.rs cast.rs float.rs identities.rs int.rs lib.rs macros.rs pow.rs real.rs sign.rs

openssl

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parking_lot_core

thread_parker

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percent_encoding

phf

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phf_shared

png

decoder

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chunk.rs common.rs encoder.rs filter.rs lib.rs traits.rs utils.rs

proc_macro2

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

publicsuffix

errors.rs lib.rs

quick_error

quote

ext.rs lib.rs runtime.rs to_tokens.rs

r2d2

config.rs event.rs lib.rs

rand

rand_chacha

chacha.rs lib.rs

rand_core

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hc128.rs lib.rs

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join

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regex

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classes.rs dense.rs dfa.rs lib.rs regex.rs sparse.rs state_id.rs

regex_syntax

remove_dir_all

reqwest

ring

rouille

rustc_demangle

legacy.rs lib.rs v0.rs

rustls

rusttype

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

scheduled_thread_pool

lib.rs thunk.rs

scoped_threadpool

scopeguard

sct

serde

de

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

private

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ser

impls.rs impossible.rs mod.rs

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

serde_derive

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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

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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

simplelog

loggers

comblog.rs logging.rs mod.rs simplelog.rs termlog.rs writelog.rs

config.rs lib.rs

siphasher

lib.rs sip.rs sip128.rs

slab

smallvec

stable_deref_trait

stb_truetype

string

syn

synom

helper.rs lib.rs space.rs

synstructure

lib.rs macros.rs

tempdir

term

terminfo

parser

compiled.rs names.rs

mod.rs parm.rs searcher.rs

thread_local

lib.rs thread_id.rs unreachable.rs

threadpool

tiff

decoder

ifd.rs mod.rs stream.rs

encoder

colortype.rs mod.rs writer.rs

error.rs lib.rs

time

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

tiny_http

util

custom_stream.rs equal_reader.rs messages_queue.rs mod.rs refined_tcp_stream.rs sequential.rs task_pool.rs

client.rs common.rs lib.rs request.rs response.rs

tokio

executor

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runtime

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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 io.rs lib.rs net.rs prelude.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_current_thread

lib.rs scheduler.rs

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

tokio_io

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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

traitobject

impls.rs lib.rs

try_from

char.rs int.rs lib.rs

try_lock

twoway

bmh.rs lib.rs util.rs

typeable

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_normalization

decompose.rs lib.rs normalize.rs quick_check.rs recompose.rs stream_safe.rs tables.rs

unicode_xid

lib.rs tables.rs

untrusted

url

form_urlencoded.rs host.rs lib.rs origin.rs parser.rs path_segments.rs query_encoding.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

want

webdev_lib

chemicals

models.rs requests.rs schema.rs

permissions

models.rs requests.rs schema.rs

tests

question_categories

models.rs requests.rs schema.rs

questions

models.rs requests.rs schema.rs

test_sessions

models.rs requests.rs schema.rs

tests

models.rs requests.rs schema.rs

question_categories.rs questions.rs test_sessions.rs tests.rs

users

models.rs requests.rs schema.rs

chemicals.rs errors.rs lib.rs permissions.rs search.rs tests.rs users.rs

webpki

calendar.rs cert.rs der.rs name.rs signed_data.rs time.rs trust_anchor_util.rs verify_cert.rs webpki.rs

webpki_roots

use {Poll, Async};
use stream::{Stream, Fuse};

/// An adapter for merging the output of two streams.
///
/// The merged stream produces items from either of the underlying streams as
/// they become available, and the streams are polled in a round-robin fashion.
/// Errors, however, are not merged: you get at most one error at a time.
#[derive(Debug)]
#[must_use = "streams do nothing unless polled"]
pub struct Select<S1, S2> {
    stream1: Fuse<S1>,
    stream2: Fuse<S2>,
    flag: bool,
}

pub fn new<S1, S2>(stream1: S1, stream2: S2) -> Select<S1, S2>
    where S1: Stream,
          S2: Stream<Item = S1::Item, Error = S1::Error>
{
    Select {
        stream1: stream1.fuse(),
        stream2: stream2.fuse(),
        flag: false,
    }
}

impl<S1, S2> Stream for Select<S1, S2>
    where S1: Stream,
          S2: Stream<Item = S1::Item, Error = S1::Error>
{
    type Item = S1::Item;
    type Error = S1::Error;

    fn poll(&mut self) -> Poll<Option<S1::Item>, S1::Error> {
        let (a, b) = if self.flag {
            (&mut self.stream2 as &mut Stream<Item=_, Error=_>,
             &mut self.stream1 as &mut Stream<Item=_, Error=_>)
        } else {
            (&mut self.stream1 as &mut Stream<Item=_, Error=_>,
             &mut self.stream2 as &mut Stream<Item=_, Error=_>)
        };
        self.flag = !self.flag;

        let a_done = match a.poll()? {
            Async::Ready(Some(item)) => return Ok(Some(item).into()),
            Async::Ready(None) => true,
            Async::NotReady => false,
        };

        match b.poll()? {
            Async::Ready(Some(item)) => {
                // If the other stream isn't finished yet, give them a chance to
                // go first next time as we pulled something off `b`.
                if !a_done {
                    self.flag = !self.flag;
                }
                Ok(Some(item).into())
            }
            Async::Ready(None) if a_done => Ok(None.into()),
            Async::Ready(None) | Async::NotReady => Ok(Async::NotReady),
        }
    }
}