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

use super::{Pointer, Tag};
use crate::stable_hasher::{HashStable, StableHasher};
use std::fmt;

use super::CopyTaggedPtr;

/// A TaggedPtr implementing `Drop`.
///
/// If `COMPARE_PACKED` is true, then the pointers will be compared and hashed without
/// unpacking. Otherwise we don't implement PartialEq/Eq/Hash; if you want that,
/// wrap the TaggedPtr.
pub struct TaggedPtr<P, T, const COMPARE_PACKED: bool>
where
    P: Pointer,
    T: Tag,
{
    raw: CopyTaggedPtr<P, T, COMPARE_PACKED>,
}

impl<P, T, const COMPARE_PACKED: bool> Clone for TaggedPtr<P, T, COMPARE_PACKED>
where
    P: Pointer + Clone,
    T: Tag,
{
    fn clone(&self) -> Self {
        unsafe { Self::new(P::with_ref(self.raw.pointer_raw(), |p| p.clone()), self.raw.tag()) }
    }
}

// We pack the tag into the *upper* bits of the pointer to ease retrieval of the
// value; a right shift is a multiplication and those are embeddable in
// instruction encoding.
impl<P, T, const COMPARE_PACKED: bool> TaggedPtr<P, T, COMPARE_PACKED>
where
    P: Pointer,
    T: Tag,
{
    pub fn new(pointer: P, tag: T) -> Self {
        TaggedPtr { raw: CopyTaggedPtr::new(pointer, tag) }
    }

    pub fn pointer_ref(&self) -> &P::Target {
        self.raw.pointer_ref()
    }
    pub fn tag(&self) -> T {
        self.raw.tag()
    }
}

impl<P, T, const COMPARE_PACKED: bool> std::ops::Deref for TaggedPtr<P, T, COMPARE_PACKED>
where
    P: Pointer,
    T: Tag,
{
    type Target = P::Target;
    fn deref(&self) -> &Self::Target {
        self.raw.pointer_ref()
    }
}

impl<P, T, const COMPARE_PACKED: bool> std::ops::DerefMut for TaggedPtr<P, T, COMPARE_PACKED>
where
    P: Pointer + std::ops::DerefMut,
    T: Tag,
{
    fn deref_mut(&mut self) -> &mut Self::Target {
        self.raw.pointer_mut()
    }
}

impl<P, T, const COMPARE_PACKED: bool> Drop for TaggedPtr<P, T, COMPARE_PACKED>
where
    P: Pointer,
    T: Tag,
{
    fn drop(&mut self) {
        // No need to drop the tag, as it's Copy
        unsafe {
            drop(P::from_usize(self.raw.pointer_raw()));
        }
    }
}

impl<P, T, const COMPARE_PACKED: bool> fmt::Debug for TaggedPtr<P, T, COMPARE_PACKED>
where
    P: Pointer,
    P::Target: fmt::Debug,
    T: Tag + fmt::Debug,
{
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("TaggedPtr")
            .field("pointer", &self.pointer_ref())
            .field("tag", &self.tag())
            .finish()
    }
}

impl<P, T> PartialEq for TaggedPtr<P, T, true>
where
    P: Pointer,
    T: Tag,
{
    fn eq(&self, other: &Self) -> bool {
        self.raw.eq(&other.raw)
    }
}

impl<P, T> Eq for TaggedPtr<P, T, true>
where
    P: Pointer,
    T: Tag,
{
}

impl<P, T> std::hash::Hash for TaggedPtr<P, T, true>
where
    P: Pointer,
    T: Tag,
{
    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
        self.raw.hash(state);
    }
}

impl<P, T, HCX, const COMPARE_PACKED: bool> HashStable<HCX> for TaggedPtr<P, T, COMPARE_PACKED>
where
    P: Pointer + HashStable<HCX>,
    T: Tag + HashStable<HCX>,
{
    fn hash_stable(&self, hcx: &mut HCX, hasher: &mut StableHasher) {
        self.raw.hash_stable(hcx, hasher);
    }
}