bacon_rajan_cc 0.3.1

A reference counted type with cycle collection.
Documentation 
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// Copyright 2015 The Rust Project Developers. See the COPYRIGHT file at the
// top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT
// or http://opensource.org/licenses/MIT>, at your option. This file may not be
// copied, modified, or distributed except according to those terms.

use super::{CcBoxData, Color};
use trace::Trace;
use std::ptr::NonNull;

/// A trait to group all of the operations we need to be able to do on
/// `CcBox<T>`'s, potentially across different T types.
pub trait CcBoxPtr: Trace {
    /// Get this `CcBoxPtr`'s CcBoxData.
    fn data(&self) -> &CcBoxData;

    /// Get the color of this node.
    #[inline]
    fn color(&self) -> Color { self.data().color.get() }

    /// Return true if this node is in the buffer of possible cycle roots, false
    /// otherwise.
    #[inline]
    fn buffered(&self) -> bool { self.data().buffered.get() }

    /// Return the strong reference count.
    #[inline]
    fn strong(&self) -> usize { self.data().strong.get() }

    /// Increment this node's strong reference count.
    #[inline]
    fn inc_strong(&self) {
        self.data().strong.set(self.strong() + 1);
        self.data().color.set(Color::Black);
    }

    /// Decrement this node's strong reference count.
    #[inline]
    fn dec_strong(&self) { self.data().strong.set(self.strong() - 1); }

    /// Get this node's weak reference count, including the "strong weak"
    /// reference.
    #[inline]
    fn weak(&self) -> usize { self.data().weak.get() }

    /// Increment this node's weak reference count.
    #[inline]
    fn inc_weak(&self) { self.data().weak.set(self.weak() + 1); }

    /// Decrement this node's weak reference count.
    #[inline]
    fn dec_weak(&self) { self.data().weak.set(self.weak() - 1); }
}

/// Drop the boxed value and deallocate the box if possible.
pub unsafe fn free(mut s: NonNull<dyn CcBoxPtr>) {
    debug_assert!(s.as_mut().strong() == 0);
    debug_assert!(!s.as_mut().buffered());

    crate::drop_value(s);

    // Remove the implicit "strong weak" pointer now that we've destroyed
    // the contents.
    s.as_mut().dec_weak();


    if s.as_mut().weak() == 0 {
        crate::deallocate(s);
    }
}