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

/// The Finalize trait. Can be specialized for a specific type to define
/// finalization logic for that type.
pub trait Finalize {
    fn finalize(&self);
}

impl<T: ?Sized> Finalize for T {
    // XXX: Should this function somehow tell its caller (which is presumably
    // the GC runtime) that it did nothing?
    #[inline]
    default fn finalize(&self) {}
}

/// The Trace trait, which needs to be implemented on garbage-collected objects.
pub unsafe trait Trace : Finalize {
    /// Marks all contained `Gc`s.
    unsafe fn trace(&self);

    /// Increments the root-count of all contained `Gc`s.
    unsafe fn root(&self);

    /// Decrements the root-count of all contained `Gc`s.
    unsafe fn unroot(&self);

    /// Runs Finalize::finalize() on this object and all
    /// contained subobjects
    fn finalize_glue(&self);
}

/// This rule implements the trace methods with empty implementations.
///
/// Use this for marking types as not containing any `Trace` types.
#[macro_export]
macro_rules! unsafe_empty_trace {
    () => {
        #[inline]
        unsafe fn trace(&self) {}
        #[inline]
        unsafe fn root(&self) {}
        #[inline]
        unsafe fn unroot(&self) {}
        #[inline]
        fn finalize_glue(&self) {
            $crate::Finalize::finalize(self)
        }
    }
}

/// This rule implements the trace method.
///
/// You define a `this` parameter name and pass in a body, which should call `mark` on every
/// traceable element inside the body. The mark implementation will automatically delegate to the
/// correct method on the argument.
#[macro_export]
macro_rules! custom_trace {
    ($this:ident, $body:expr) => {
        #[inline]
        unsafe fn trace(&self) {
            #[inline]
            unsafe fn mark<T: $crate::Trace>(it: &T) {
                $crate::Trace::trace(it);
            }
            let $this = self;
            $body
        }
        #[inline]
        unsafe fn root(&self) {
            #[inline]
            unsafe fn mark<T: $crate::Trace>(it: &T) {
                $crate::Trace::root(it);
            }
            let $this = self;
            $body
        }
        #[inline]
        unsafe fn unroot(&self) {
            #[inline]
            unsafe fn mark<T: $crate::Trace>(it: &T) {
                $crate::Trace::unroot(it);
            }
            let $this = self;
            $body
        }
        #[inline]
        fn finalize_glue(&self) {
            $crate::Finalize::finalize(self);
            #[inline]
            fn mark<T: $crate::Trace>(it: &T) {
                $crate::Trace::finalize_glue(it);
            }
            let $this = self;
            $body
        }
    }
}

unsafe impl<T: ?Sized> Trace for &'static T {
    unsafe_empty_trace!();
}

unsafe impl Trace for usize { unsafe_empty_trace!(); }
unsafe impl Trace for bool { unsafe_empty_trace!(); }
unsafe impl Trace for i8  { unsafe_empty_trace!(); }
unsafe impl Trace for u8  { unsafe_empty_trace!(); }
unsafe impl Trace for i16 { unsafe_empty_trace!(); }
unsafe impl Trace for u16 { unsafe_empty_trace!(); }
unsafe impl Trace for i32 { unsafe_empty_trace!(); }
unsafe impl Trace for u32 { unsafe_empty_trace!(); }
unsafe impl Trace for i64 { unsafe_empty_trace!(); }
unsafe impl Trace for u64 { unsafe_empty_trace!(); }

unsafe impl Trace for f32 { unsafe_empty_trace!(); }
unsafe impl Trace for f64 { unsafe_empty_trace!(); }

unsafe impl Trace for String { unsafe_empty_trace!(); }

unsafe impl<T: Trace> Trace for Box<T> {
    custom_trace!(this, {
        mark(&**this);
    });
}

unsafe impl<T: Trace> Trace for Vec<T> {
    custom_trace!(this, {
        for e in this {
            mark(e);
        }
    });
}

unsafe impl<T: Trace> Trace for Option<T> {
    custom_trace!(this, {
        if let Some(ref v) = *this {
            mark(v);
        }
    });
}