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

use std::borrow::Borrow;
use std::cell::UnsafeCell;
use std::ops::{Deref, DerefMut};
use std::ptr;

use crate::context::blocked::BlockedClient;
use crate::{raw, Context, ValkeyResult};

pub struct RedisGILGuardScope<'ctx, 'mutex, T, G: RedisLockIndicator> {
    _context: &'ctx G,
    mutex: &'mutex RedisGILGuard<T>,
}

impl<'ctx, 'mutex, T, G: RedisLockIndicator> Deref for RedisGILGuardScope<'ctx, 'mutex, T, G> {
    type Target = T;

    fn deref(&self) -> &Self::Target {
        unsafe { &*self.mutex.obj.get() }
    }
}

impl<'ctx, 'mutex, T, G: RedisLockIndicator> DerefMut for RedisGILGuardScope<'ctx, 'mutex, T, G> {
    fn deref_mut(&mut self) -> &mut Self::Target {
        unsafe { &mut *self.mutex.obj.get() }
    }
}

/// Whenever the user gets a reference to a struct that
/// implements this trait, it can assume that the Redis GIL
/// is held. Any struct that implements this trait can be
/// used to retrieve objects which are GIL protected (see
/// [RedisGILGuard] for more information)
///
/// Notice that this trait only gives indication that the
/// GIL is locked, unlike [RedisGILGuard] which protect data
/// access and make sure the protected data is only accesses
/// when the GIL is locked.
///
/// # Safety
///
/// In general this trait should not be implemented by the
/// user, the crate knows when the Redis GIL is held and will
/// make sure to implement this trait correctly on different
/// struct (such as [Context], [ConfigurationContext], [ContextGuard]).
/// User might also decide to implement this trait but he should
/// carefully consider that because it is easy to make mistakes,
/// this is why the trait is marked as unsafe.
pub unsafe trait RedisLockIndicator {}

/// This struct allows to guard some data and makes sure
/// the data is only access when the Redis GIL is locked.
/// From example, assuming you module want to save some
/// statistics inside some global variable, but without the
/// need to protect this variable with some mutex (because
/// we know this variable is protected by Redis lock).
/// For example, look at examples/threads.rs
pub struct RedisGILGuard<T> {
    obj: UnsafeCell<T>,
}

impl<T> RedisGILGuard<T> {
    pub fn new(obj: T) -> RedisGILGuard<T> {
        RedisGILGuard {
            obj: UnsafeCell::new(obj),
        }
    }

    pub fn lock<'mutex, 'ctx, G: RedisLockIndicator>(
        &'mutex self,
        context: &'ctx G,
    ) -> RedisGILGuardScope<'ctx, 'mutex, T, G> {
        RedisGILGuardScope {
            _context: context,
            mutex: self,
        }
    }
}

impl<T: Default> Default for RedisGILGuard<T> {
    fn default() -> Self {
        Self::new(T::default())
    }
}

unsafe impl<T> Sync for RedisGILGuard<T> {}
unsafe impl<T> Send for RedisGILGuard<T> {}

pub struct ContextGuard {
    ctx: Context,
}

unsafe impl RedisLockIndicator for ContextGuard {}

impl Drop for ContextGuard {
    fn drop(&mut self) {
        unsafe {
            raw::RedisModule_ThreadSafeContextUnlock.unwrap()(self.ctx.ctx);
            raw::RedisModule_FreeThreadSafeContext.unwrap()(self.ctx.ctx);
        };
    }
}

impl Deref for ContextGuard {
    type Target = Context;

    fn deref(&self) -> &Self::Target {
        &self.ctx
    }
}

impl Borrow<Context> for ContextGuard {
    fn borrow(&self) -> &Context {
        &self.ctx
    }
}

/// A ``ThreadSafeContext`` can either be bound to a blocked client, or detached from any client.
pub struct DetachedFromClient;

pub struct ThreadSafeContext<B: Send> {
    pub(crate) ctx: *mut raw::RedisModuleCtx,

    /// This field is only used implicitly by `Drop`, so avoid a compiler warning
    #[allow(dead_code)]
    blocked_client: B,
}

unsafe impl<B: Send> Send for ThreadSafeContext<B> {}
unsafe impl<B: Send> Sync for ThreadSafeContext<B> {}

impl ThreadSafeContext<DetachedFromClient> {
    #[must_use]
    pub fn new() -> Self {
        let ctx = unsafe { raw::RedisModule_GetThreadSafeContext.unwrap()(ptr::null_mut()) };
        Self {
            ctx,
            blocked_client: DetachedFromClient,
        }
    }
}

impl Default for ThreadSafeContext<DetachedFromClient> {
    fn default() -> Self {
        Self::new()
    }
}

impl ThreadSafeContext<BlockedClient> {
    #[must_use]
    pub fn with_blocked_client(blocked_client: BlockedClient) -> Self {
        let ctx = unsafe { raw::RedisModule_GetThreadSafeContext.unwrap()(blocked_client.inner) };
        Self {
            ctx,
            blocked_client,
        }
    }

    /// The Redis modules API does not require locking for `Reply` functions,
    /// so we pass through its functionality directly.
    #[allow(clippy::must_use_candidate)]
    pub fn reply(&self, r: ValkeyResult) -> raw::Status {
        let ctx = Context::new(self.ctx);
        ctx.reply(r)
    }
}

impl<B: Send> ThreadSafeContext<B> {
    /// All other APIs require locking the context, so we wrap it in a way
    /// similar to `std::sync::Mutex`.
    pub fn lock(&self) -> ContextGuard {
        unsafe { raw::RedisModule_ThreadSafeContextLock.unwrap()(self.ctx) };
        let ctx = unsafe { raw::RedisModule_GetThreadSafeContext.unwrap()(ptr::null_mut()) };
        let ctx = Context::new(ctx);
        ContextGuard { ctx }
    }
}

impl<B: Send> Drop for ThreadSafeContext<B> {
    fn drop(&mut self) {
        unsafe { raw::RedisModule_FreeThreadSafeContext.unwrap()(self.ctx) };
    }
}