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
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186

// Copyright 2020-2022 IOTA Stiftung
// SPDX-License-Identifier: Apache-2.0

use crate::{guard::BaseGuard, Result, TransactionError, RLU};
use log::*;
use std::sync::{
    atomic::{AtomicUsize, Ordering},
    Arc, Mutex, RwLock,
};

/// This type represents an rlu managed type. The type is is not being constructed directly
/// but with the help of [`RLU`].
pub struct RLUVar<T>
where
    T: Clone,
{
    pub(crate) inner: Arc<InnerVar<T>>,
}

impl<T> RLUVar<T>
where
    T: Clone,
{
    pub fn get(&self) -> T {
        self.inner.get()
    }

    /// Tries to get a [`BaseGuard`]
    pub fn try_inner(&self) -> Result<BaseGuard<'_, T>> {
        info!("Locking inner data");
        match self.inner.data.lock() {
            Ok(guard) => Ok(BaseGuard::new(guard, None)),
            Err(e) => Err(TransactionError::Inner(e.to_string())),
        }
    }

    /// Returns true, if this object is an original and references a copy
    pub(crate) fn is_locked(&self) -> bool {
        self.inner.copy.lock().expect("").is_some()
    }

    /// Returns true, if this object is an original and does not references a copy
    pub(crate) fn is_unlocked(&self) -> bool {
        self.inner.copy.lock().expect("").is_none()
    }
}

impl<T> From<T> for RLUVar<T>
where
    T: Clone,
{
    fn from(value: T) -> Self {
        RLUVar {
            inner: Arc::new(InnerVar::from(value)),
        }
    }
}

impl<T> Clone for RLUVar<T>
where
    T: Clone,
{
    fn clone(&self) -> Self {
        Self {
            inner: self.inner.clone(),
        }
    }
}

pub struct InnerVarCopy<T>
where
    T: Clone,
{
    pub locked_thread_id: Option<AtomicUsize>,
    pub data: Arc<RwLock<T>>,
    pub original: Arc<InnerVar<T>>,
}

impl<T> Clone for InnerVarCopy<T>
where
    T: Clone,
{
    fn clone(&self) -> Self {
        Self {
            locked_thread_id: self
                .locked_thread_id
                .as_ref()
                .map(|thread_id| AtomicUsize::new(thread_id.load(Ordering::SeqCst))),
            data: self.data.clone(),
            original: self.original.clone(),
        }
    }
}

impl<T> InnerVarCopy<T>
where
    T: Clone,
{
    /// Writes the data back to original
    ///
    /// # Safety
    ///
    /// This method is safe, as dereferencing ptr to original will be checked against null
    pub(crate) fn write_back(&self) -> Result<()> {
        let lock_id = self
            .locked_thread_id
            .as_ref()
            .map_or(-1, |inner| inner.load(Ordering::SeqCst) as isize);

        info!("({}) Locking data read", lock_id);
        let data_guard = self.data.try_read().expect("cannot get lock in copy -> data");
        let copy = data_guard.clone();
        info!("({}) Unlocking data read", lock_id);
        drop(data_guard);

        info!("({}) Locking original data", lock_id);
        let mut guard = self.original.data.try_lock().map_err(|e| TransactionError::Blocking)?;

        *guard = copy;

        info!("({}) Unlocking original data", lock_id);
        drop(guard);

        Ok(())
    }
}

pub struct InnerVar<T>
where
    T: Clone,
{
    pub locked_thread_id: Option<AtomicUsize>,
    pub ctrl: Option<RLU<T>>,
    pub data: Arc<Mutex<T>>,
    pub copy: Arc<Mutex<Option<InnerVarCopy<T>>>>,
}

impl<T> InnerVar<T>
where
    T: Clone,
{
    /// Returns true, if this object is an original and references a copy
    pub(crate) fn is_locked(&self) -> bool {
        self.copy.lock().expect("").is_some()
    }

    /// Returns true, if this object is an original and does not references a copy
    pub(crate) fn is_unlocked(&self) -> bool {
        self.copy.lock().expect("").is_none()
    }

    pub fn get(&self) -> T {
        self.data.lock().expect("").clone()
    }
}

impl<T> From<T> for InnerVar<T>
where
    T: Clone,
{
    fn from(value: T) -> Self {
        Self {
            data: Arc::new(Mutex::new(value)),
            locked_thread_id: None,
            copy: Arc::new(Mutex::new(None)),
            ctrl: None,
        }
    }
}

impl<T> Clone for InnerVar<T>
where
    T: Clone,
{
    fn clone(&self) -> Self {
        Self {
            ctrl: self.ctrl.clone(),
            data: self.data.clone(),
            locked_thread_id: Some(AtomicUsize::new(match &self.locked_thread_id {
                Some(inner) => inner.load(Ordering::SeqCst),
                None => 0,
            })),
            copy: Arc::new(Mutex::new(None)),
        }
    }
}