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
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165

use crate::future::Future;
use crate::runtime::task::{Cell, Harness, Header, Schedule, State};

use std::ptr::NonNull;
use std::task::{Poll, Waker};

/// Raw task handle
pub(super) struct RawTask {
    ptr: NonNull<Header>,
}

pub(super) struct Vtable {
    /// Polls the future.
    pub(super) poll: unsafe fn(NonNull<Header>),

    /// Deallocates the memory.
    pub(super) dealloc: unsafe fn(NonNull<Header>),

    /// Reads the task output, if complete.
    pub(super) try_read_output: unsafe fn(NonNull<Header>, *mut (), &Waker),

    /// Try to set the waker notified when the task is complete. Returns true if
    /// the task has already completed. If this call returns false, then the
    /// waker will not be notified.
    pub(super) try_set_join_waker: unsafe fn(NonNull<Header>, &Waker) -> bool,

    /// The join handle has been dropped.
    pub(super) drop_join_handle_slow: unsafe fn(NonNull<Header>),

    /// The task is remotely aborted.
    pub(super) remote_abort: unsafe fn(NonNull<Header>),

    /// Scheduler is being shutdown.
    pub(super) shutdown: unsafe fn(NonNull<Header>),
}

/// Get the vtable for the requested `T` and `S` generics.
pub(super) fn vtable<T: Future, S: Schedule>() -> &'static Vtable {
    &Vtable {
        poll: poll::<T, S>,
        dealloc: dealloc::<T, S>,
        try_read_output: try_read_output::<T, S>,
        try_set_join_waker: try_set_join_waker::<T, S>,
        drop_join_handle_slow: drop_join_handle_slow::<T, S>,
        remote_abort: remote_abort::<T, S>,
        shutdown: shutdown::<T, S>,
    }
}

impl RawTask {
    pub(super) fn new<T, S>(task: T, scheduler: S) -> RawTask
    where
        T: Future,
        S: Schedule,
    {
        let ptr = Box::into_raw(Cell::<_, S>::new(task, scheduler, State::new()));
        let ptr = unsafe { NonNull::new_unchecked(ptr as *mut Header) };

        RawTask { ptr }
    }

    pub(super) unsafe fn from_raw(ptr: NonNull<Header>) -> RawTask {
        RawTask { ptr }
    }

    pub(super) fn header_ptr(&self) -> NonNull<Header> {
        self.ptr
    }

    /// Returns a reference to the task's meta structure.
    ///
    /// Safe as `Header` is `Sync`.
    pub(super) fn header(&self) -> &Header {
        unsafe { self.ptr.as_ref() }
    }

    /// Safety: mutual exclusion is required to call this function.
    pub(super) fn poll(self) {
        let vtable = self.header().vtable;
        unsafe { (vtable.poll)(self.ptr) }
    }

    pub(super) fn dealloc(self) {
        let vtable = self.header().vtable;
        unsafe {
            (vtable.dealloc)(self.ptr);
        }
    }

    /// Safety: `dst` must be a `*mut Poll<super::Result<T::Output>>` where `T`
    /// is the future stored by the task.
    pub(super) unsafe fn try_read_output(self, dst: *mut (), waker: &Waker) {
        let vtable = self.header().vtable;
        (vtable.try_read_output)(self.ptr, dst, waker);
    }

    pub(super) fn try_set_join_waker(self, waker: &Waker) -> bool {
        let vtable = self.header().vtable;
        unsafe { (vtable.try_set_join_waker)(self.ptr, waker) }
    }

    pub(super) fn drop_join_handle_slow(self) {
        let vtable = self.header().vtable;
        unsafe { (vtable.drop_join_handle_slow)(self.ptr) }
    }

    pub(super) fn shutdown(self) {
        let vtable = self.header().vtable;
        unsafe { (vtable.shutdown)(self.ptr) }
    }

    pub(super) fn remote_abort(self) {
        let vtable = self.header().vtable;
        unsafe { (vtable.remote_abort)(self.ptr) }
    }
}

impl Clone for RawTask {
    fn clone(&self) -> Self {
        RawTask { ptr: self.ptr }
    }
}

impl Copy for RawTask {}

unsafe fn poll<T: Future, S: Schedule>(ptr: NonNull<Header>) {
    let harness = Harness::<T, S>::from_raw(ptr);
    harness.poll();
}

unsafe fn dealloc<T: Future, S: Schedule>(ptr: NonNull<Header>) {
    let harness = Harness::<T, S>::from_raw(ptr);
    harness.dealloc();
}

unsafe fn try_read_output<T: Future, S: Schedule>(
    ptr: NonNull<Header>,
    dst: *mut (),
    waker: &Waker,
) {
    let out = &mut *(dst as *mut Poll<super::Result<T::Output>>);

    let harness = Harness::<T, S>::from_raw(ptr);
    harness.try_read_output(out, waker);
}

unsafe fn try_set_join_waker<T: Future, S: Schedule>(ptr: NonNull<Header>, waker: &Waker) -> bool {
    let harness = Harness::<T, S>::from_raw(ptr);
    harness.try_set_join_waker(waker)
}

unsafe fn drop_join_handle_slow<T: Future, S: Schedule>(ptr: NonNull<Header>) {
    let harness = Harness::<T, S>::from_raw(ptr);
    harness.drop_join_handle_slow()
}

unsafe fn remote_abort<T: Future, S: Schedule>(ptr: NonNull<Header>) {
    let harness = Harness::<T, S>::from_raw(ptr);
    harness.remote_abort()
}

unsafe fn shutdown<T: Future, S: Schedule>(ptr: NonNull<Header>) {
    let harness = Harness::<T, S>::from_raw(ptr);
    harness.shutdown()
}