60 lines
1.6 KiB
Rust
60 lines
1.6 KiB
Rust
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// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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use prelude::v1::*;
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use boxed;
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use cell::UnsafeCell;
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use rt;
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use sync::{StaticMutex, Arc};
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pub struct Lazy<T> {
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pub lock: StaticMutex,
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pub ptr: UnsafeCell<*mut Arc<T>>,
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pub init: fn() -> Arc<T>,
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}
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unsafe impl<T> Sync for Lazy<T> {}
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macro_rules! lazy_init {
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($init:expr) => (::io::lazy::Lazy {
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lock: ::sync::MUTEX_INIT,
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ptr: ::cell::UnsafeCell { value: 0 as *mut _ },
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init: $init,
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})
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}
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impl<T: Send + Sync + 'static> Lazy<T> {
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pub fn get(&'static self) -> Option<Arc<T>> {
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let _g = self.lock.lock();
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unsafe {
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let mut ptr = *self.ptr.get();
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if ptr.is_null() {
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ptr = boxed::into_raw(self.init());
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*self.ptr.get() = ptr;
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} else if ptr as usize == 1 {
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return None
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}
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Some((*ptr).clone())
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}
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}
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fn init(&'static self) -> Box<Arc<T>> {
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rt::at_exit(move || unsafe {
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let g = self.lock.lock();
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let ptr = *self.ptr.get();
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*self.ptr.get() = 1 as *mut _;
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drop(g);
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drop(Box::from_raw(ptr))
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});
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Box::new((self.init)())
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}
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}
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