Files
adler32
backtrace
backtrace_sys
base64
bigtable
bitflags
byteorder
bytes
cfg_if
cookie
cookie_store
crc32fast
crossbeam_deque
crossbeam_epoch
crossbeam_queue
crossbeam_utils
curl
curl_sys
dtoa
either
encoding_rs
error_chain
failure
failure_derive
flate2
fnv
foreign_types
foreign_types_shared
futures
futures_cpupool
goauth
h2
http
http_body
httparse
hyper
hyper_tls
idna
indexmap
iovec
itoa
lazy_static
libc
libz_sys
lock_api
log
matches
maybe_uninit
memoffset
mime
mime_guess
miniz_oxide
mio
native_tls
net2
num_cpus
num_traits
openssl
openssl_probe
openssl_sys
parking_lot
parking_lot_core
percent_encoding
proc_macro2
protobuf
protobuf_json
publicsuffix
quote
rand
rand_chacha
rand_core
rand_hc
rand_isaac
rand_jitter
rand_os
rand_pcg
rand_xorshift
regex
regex_syntax
reqwest
rustc_demangle
rustc_serialize
ryu
scopeguard
serde
serde_codegen_internals
serde_derive
serde_json
serde_urlencoded
slab
smallvec
smpl_jwt
socket2
string
syn
synom
synstructure
time
tokio
tokio_buf
tokio_current_thread
tokio_executor
tokio_io
tokio_reactor
tokio_sync
tokio_tcp
tokio_threadpool
tokio_timer
try_from
try_lock
unicase
unicode_bidi
unicode_normalization
unicode_xid
url
uuid
want
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
use std::mem;

use futures::{Future, IntoFuture, Poll};

pub(crate) trait Started: Future {
    fn started(&self) -> bool;
}

pub(crate) fn lazy<F, R>(func: F) -> Lazy<F, R>
where
    F: FnOnce() -> R,
    R: IntoFuture,
{
    Lazy {
        inner: Inner::Init(func),
    }
}

// FIXME: allow() required due to `impl Trait` leaking types to this lint
#[allow(missing_debug_implementations)]
pub(crate) struct Lazy<F, R: IntoFuture> {
    inner: Inner<F, R::Future>
}

enum Inner<F, R> {
    Init(F),
    Fut(R),
    Empty,
}

impl<F, R> Started for Lazy<F, R>
where
    F: FnOnce() -> R,
    R: IntoFuture,
{
    fn started(&self) -> bool {
        match self.inner {
            Inner::Init(_) => false,
            Inner::Fut(_) |
            Inner::Empty => true,
        }
    }
}

impl<F, R> Future for Lazy<F, R>
where
    F: FnOnce() -> R,
    R: IntoFuture,
{
    type Item = R::Item;
    type Error = R::Error;

    fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
        match self.inner {
            Inner::Fut(ref mut f) => return f.poll(),
            _ => (),
        }

        match mem::replace(&mut self.inner, Inner::Empty) {
            Inner::Init(func) => {
                let mut fut = func().into_future();
                let ret = fut.poll();
                self.inner = Inner::Fut(fut);
                ret
            },
            _ => unreachable!("lazy state wrong"),
        }
    }
}