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

// Copyright (C) 2017-2018 Baidu, Inc. All Rights Reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
//
//  * Redistributions of source code must retain the above copyright
//    notice, this list of conditions and the following disclaimer.
//  * Redistributions in binary form must reproduce the above copyright
//    notice, this list of conditions and the following disclaimer in
//    the documentation and/or other materials provided with the
//    distribution.
//  * Neither the name of Baidu, Inc., nor the names of its
//    contributors may be used to endorse or promote products derived
//    from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

use sync::SgxThreadMutex;
use sys_common;
use alloc::sync::Arc;
use core::cell::{Cell, UnsafeCell};
use core::ptr;

pub struct Lazy<T> {
    lock: SgxThreadMutex,
    ptr: Cell<*mut Arc<T>>,
    init: fn() -> Arc<T>,
}

unsafe impl<T> Sync for Lazy<T> {}

impl<T: Send + Sync + 'static> Lazy<T> {

    pub const fn new(init: fn() -> Arc<T>) -> Lazy<T> {
        Lazy {
            lock: SgxThreadMutex::new(),
            ptr: Cell::new(ptr::null_mut()),
            init: init
        }
    }

    pub fn get(&'static self) -> Option<Arc<T>> {
        unsafe {
            let r = self.lock.lock();
            if r.is_err() {
                return None;
            }
            let ptr = self.ptr.get();
            let ret = if ptr.is_null() {
                Some(self.init())
            } else if ptr as usize == 1 {
                None
            } else {
                Some((*ptr).clone())
            };
            self.lock.unlock();
            return ret
        }
    }
    /*
    #[cfg(not(feature = "global_exit"))]
    pub unsafe fn destroy(&'static self) {

        self.lock.lock();
        let ptr = self.ptr.get();
        if ptr.is_null() || ptr as usize == 1 {
            self.lock.unlock();
            return;
        }
        self.ptr.set(1 as *mut _);
        self.lock.unlock();
        drop(Box::from_raw(ptr))
    }

    #[cfg(not(feature = "global_exit"))]
    unsafe fn init(&'static self) -> Arc<T> {

        let ret = (self.init)();
        self.ptr.set(Box::into_raw(Box::new(ret.clone())));
        ret
    }
    */

    unsafe fn init(&'static self) -> Arc<T> {
        // If we successfully register an at exit handler, then we cache the
        // `Arc` allocation in our own internal box (it will get deallocated by
        // the at exit handler). Otherwise we just return the freshly allocated
        // `Arc`.
        let registered = sys_common::at_exit(move || {
            self.lock.lock();
            let ptr = self.ptr.get();
            if ptr.is_null() || ptr as usize == 1 {
                self.lock.unlock();
                return;
            }
            self.ptr.set(1 as *mut _);
            self.lock.unlock();
            drop(Box::from_raw(ptr))
        });
        let ret = (self.init)();
        if registered.is_ok() {
            self.ptr.set(Box::into_raw(Box::new(ret.clone())));
        }
        ret
    }
}

#[allow(dead_code)]
pub struct LazyStatic<T> {
    lock: SgxThreadMutex,
    opt: UnsafeCell<Option<Arc<T>>>,
    init: fn() -> Arc<T>,
}

unsafe impl<T> Sync for LazyStatic<T> {}

#[allow(dead_code)]
impl<T: Send + Sync + 'static> LazyStatic<T> {

    pub const fn new(init: fn() -> Arc<T>) -> LazyStatic<T> {
        LazyStatic {
            lock: SgxThreadMutex::new(),
            opt: UnsafeCell::new(None),
            init: init
        }
    }

    pub fn get(&'static self) -> Option<Arc<T>> {
        unsafe {
            let r = self.lock.lock();
            if r.is_err() {
                return None;
            }

            let ret = match *self.opt.get() {
                Some(ref arc) => Some(arc.clone()),
                None => Some(self.init()),
            };
            self.lock.unlock();
            ret
        }
    }

    unsafe fn init(&'static self) -> Arc<T> {

        let ret = (self.init)();
        *self.opt.get() = Some(ret.clone());
        ret
    }
}