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

// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License..

use crate::lock_api::RawMutex;
use crate::sys::locks::mutex as imp;

/// An SGX-based mutual exclusion lock, meant for use in static variables.
///
/// This mutex has a const constructor ([`StaticMutex::new`]), does not
/// implement `Drop` to cleanup resources, and causes UB when used reentrantly.
///
/// This mutex does not implement poisoning.
///
/// This is a wrapper around `imp::Mutex` that does *not* call `init()` and
/// `destroy()`.
pub struct StaticMutex(imp::Mutex);

unsafe impl Sync for StaticMutex {}

impl StaticMutex {
    /// Creates a new mutex for use.
    #[inline]
    pub const fn new() -> StaticMutex {
        StaticMutex(imp::Mutex::new())
    }

    /// Calls raw_lock() and then returns an RAII guard to guarantee the mutex
    /// will be unlocked.
    ///
    /// It is undefined behaviour to call this function while locked by the
    /// same thread.
    #[inline]
    pub unsafe fn lock(&'static self) -> StaticMutexGuard {
        self.0.lock();
        StaticMutexGuard(&self.0)
    }
}

#[must_use]
pub struct StaticMutexGuard(&'static imp::Mutex);

impl Drop for StaticMutexGuard {
    #[inline]
    fn drop(&mut self) {
        unsafe {
            self.0.unlock();
        }
    }
}

/// An SGX-based mutual exclusion lock.
///
/// This mutex cleans up its resources in its `Drop` implementation, may safely
/// be moved (when not borrowed), and does not cause UB when used reentrantly.
///
/// This mutex does not implement poisoning.
///
/// This is either a wrapper around `LazyBox<imp::Mutex>` or `imp::Mutex`,
/// depending on the platform. It is boxed on platforms where `imp::Mutex` may
/// not be moved.
pub struct MovableMutex(imp::MovableMutex);

unsafe impl Sync for MovableMutex {}

impl MovableMutex {
    /// Creates a new mutex.
    #[inline]
    pub const fn new() -> MovableMutex {
        MovableMutex(imp::MovableMutex::new())
    }

    pub(crate) fn raw(&self) -> &imp::Mutex {
        &self.0
    }

    /// Locks the mutex blocking the current thread until it is available.
    #[inline]
    pub fn raw_lock(&self) {
        unsafe { self.0.lock() }
    }

    /// Attempts to lock the mutex without blocking, returning whether it was
    /// successfully acquired or not.
    #[inline]
    pub fn try_lock(&self) -> bool {
        unsafe { self.0.try_lock() }
    }

    /// Unlocks the mutex.
    ///
    /// Behavior is undefined if the current thread does not actually hold the
    /// mutex.
    #[inline]
    pub unsafe fn raw_unlock(&self) {
        self.0.unlock()
    }
}

impl Default for MovableMutex {
    fn default() -> MovableMutex {
        MovableMutex::new()
    }
}

impl RawMutex for MovableMutex {
    fn lock(&self) {
        self.raw_lock()
    }

    fn try_lock(&self) -> bool {
        self.try_lock()
    }

    unsafe fn unlock(&self) {
        self.raw_unlock()
    }
}