/rust/registry/src/index.crates.io-1949cf8c6b5b557f/dashmap-6.1.0/src/util.rs

Source
//! This module is full of hackery and dark magic.
//! Either spend a day fixing it and quietly submit a PR or don't mention it to anybody.
use core::cell::UnsafeCell;
use core::{mem, ptr};

pub const fn ptr_size_bits() -> usize {
    mem::size_of::<usize>() * 8
}

pub fn map_in_place_2<T, U, F: FnOnce(U, T) -> T>((k, v): (U, &mut T), f: F) {
    unsafe {
        // # Safety
        //
        // If the closure panics, we must abort otherwise we could double drop `T`
        let promote_panic_to_abort = AbortOnPanic;

        ptr::write(v, f(k, ptr::read(v)));

        // If we made it here, the calling thread could have already have panicked, in which case
        // We know that the closure did not panic, so don't bother checking.
        std::mem::forget(promote_panic_to_abort);
    }
}

/// A simple wrapper around `T`
///
/// This is to prevent UB when using `HashMap::get_key_value`, because
/// `HashMap` doesn't expose an api to get the key and value, where
/// the value is a `&mut T`.
///
/// See [#10](https://github.com/xacrimon/dashmap/issues/10) for details
///
/// This type is meant to be an implementation detail, but must be exposed due to the `Dashmap::shards`
#[repr(transparent)]
pub struct SharedValue<T> {
    value: UnsafeCell<T>,
}

impl<T: Clone> Clone for SharedValue<T> {
    fn clone(&self) -> Self {
        let inner = self.get().clone();

        Self {
            value: UnsafeCell::new(inner),
        }
    }
}

unsafe impl<T: Send> Send for SharedValue<T> {}

unsafe impl<T: Sync> Sync for SharedValue<T> {}

impl<T> SharedValue<T> {
    /// Create a new `SharedValue<T>`
    pub const fn new(value: T) -> Self {
        Self {
            value: UnsafeCell::new(value),
        }
    }

    /// Get a shared reference to `T`
    pub fn get(&self) -> &T {
        unsafe { &*self.value.get() }
    }

    /// Get an unique reference to `T`
    pub fn get_mut(&mut self) -> &mut T {
        unsafe { &mut *self.value.get() }
    }

    /// Unwraps the value
    pub fn into_inner(self) -> T {
        self.value.into_inner()
    }

    /// Get a mutable raw pointer to the underlying value
    pub(crate) fn as_ptr(&self) -> *mut T {
        self.value.get()
    }
}

struct AbortOnPanic;

impl Drop for AbortOnPanic {
    fn drop(&mut self) {
        if std::thread::panicking() {
            std::process::abort()
        }
    }
}

Line	Count	Source
1		//! This module is full of hackery and dark magic.
2		//! Either spend a day fixing it and quietly submit a PR or don't mention it to anybody.
3		use core::cell::UnsafeCell;
4		use core::{mem, ptr};
5
6	176	pub const fn ptr_size_bits() -> usize {
7	176	mem::size_of::<usize>() * 8
8	176	}
9
10	0	pub fn map_in_place_2<T, U, F: FnOnce(U, T) -> T>((k, v): (U, &mut T), f: F) {
11	0	unsafe {
12	0	// # Safety
13	0	//
14	0	// If the closure panics, we must abort otherwise we could double drop `T`
15	0	let promote_panic_to_abort = AbortOnPanic;
16	0
17	0	ptr::write(v, f(k, ptr::read(v)));
18	0
19	0	// If we made it here, the calling thread could have already have panicked, in which case
20	0	// We know that the closure did not panic, so don't bother checking.
21	0	std::mem::forget(promote_panic_to_abort);
22	0	}
23	0	}
24
25		/// A simple wrapper around `T`
26		///
27		/// This is to prevent UB when using `HashMap::get_key_value`, because
28		/// `HashMap` doesn't expose an api to get the key and value, where
29		/// the value is a `&mut T`.
30		///
31		/// See [#10](https://github.com/xacrimon/dashmap/issues/10) for details
32		///
33		/// This type is meant to be an implementation detail, but must be exposed due to the `Dashmap::shards`
34		#[repr(transparent)]
35		pub struct SharedValue<T> {
36		value: UnsafeCell<T>,
37		}
38
39		impl<T: Clone> Clone for SharedValue<T> {
40	0	fn clone(&self) -> Self {
41	0	let inner = self.get().clone();
42
43	0	Self {
44	0	value: UnsafeCell::new(inner),
45	0	}
46	0	}
47		}
48
49		unsafe impl<T: Send> Send for SharedValue<T> {}
50
51		unsafe impl<T: Sync> Sync for SharedValue<T> {}
52
53		impl<T> SharedValue<T> {
54		/// Create a new `SharedValue<T>`
55	0	pub const fn new(value: T) -> Self {
56	0	Self {
57	0	value: UnsafeCell::new(value),
58	0	}
59	0	} Unexecuted instantiation: <dashmap::util::SharedValue<alloc::sync::Arc<(lock_api::mutex::Mutex<parking_lot::raw_mutex::RawMutex, u32>, parking_lot::condvar::Condvar)>>>::new Unexecuted instantiation: <dashmap::util::SharedValue<_>>::new Unexecuted instantiation: <dashmap::util::SharedValue<alloc::sync::Arc<(lock_api::mutex::Mutex<parking_lot::raw_mutex::RawMutex, u32>, parking_lot::condvar::Condvar)>>>::new
60
61		/// Get a shared reference to `T`
62	0	pub fn get(&self) -> &T {
63	0	unsafe { &*self.value.get() }
64	0	} Unexecuted instantiation: <dashmap::util::SharedValue<alloc::sync::Arc<(lock_api::mutex::Mutex<parking_lot::raw_mutex::RawMutex, u32>, parking_lot::condvar::Condvar)>>>::get Unexecuted instantiation: <dashmap::util::SharedValue<_>>::get Unexecuted instantiation: <dashmap::util::SharedValue<alloc::sync::Arc<(lock_api::mutex::Mutex<parking_lot::raw_mutex::RawMutex, u32>, parking_lot::condvar::Condvar)>>>::get
65
66		/// Get an unique reference to `T`
67	0	pub fn get_mut(&mut self) -> &mut T {
68	0	unsafe { &mut *self.value.get() }
69	0	} Unexecuted instantiation: <dashmap::util::SharedValue<alloc::sync::Arc<(lock_api::mutex::Mutex<parking_lot::raw_mutex::RawMutex, u32>, parking_lot::condvar::Condvar)>>>::get_mut Unexecuted instantiation: <dashmap::util::SharedValue<_>>::get_mut Unexecuted instantiation: <dashmap::util::SharedValue<alloc::sync::Arc<(lock_api::mutex::Mutex<parking_lot::raw_mutex::RawMutex, u32>, parking_lot::condvar::Condvar)>>>::get_mut
70
71		/// Unwraps the value
72	0	pub fn into_inner(self) -> T {
73	0	self.value.into_inner()
74	0	} Unexecuted instantiation: <dashmap::util::SharedValue<alloc::sync::Arc<(lock_api::mutex::Mutex<parking_lot::raw_mutex::RawMutex, u32>, parking_lot::condvar::Condvar)>>>::into_inner Unexecuted instantiation: <dashmap::util::SharedValue<_>>::into_inner Unexecuted instantiation: <dashmap::util::SharedValue<alloc::sync::Arc<(lock_api::mutex::Mutex<parking_lot::raw_mutex::RawMutex, u32>, parking_lot::condvar::Condvar)>>>::into_inner
75
76		/// Get a mutable raw pointer to the underlying value
77	0	pub(crate) fn as_ptr(&self) -> *mut T {
78	0	self.value.get()
79	0	} Unexecuted instantiation: <dashmap::util::SharedValue<alloc::sync::Arc<(lock_api::mutex::Mutex<parking_lot::raw_mutex::RawMutex, u32>, parking_lot::condvar::Condvar)>>>::as_ptr Unexecuted instantiation: <dashmap::util::SharedValue<_>>::as_ptr Unexecuted instantiation: <dashmap::util::SharedValue<alloc::sync::Arc<(lock_api::mutex::Mutex<parking_lot::raw_mutex::RawMutex, u32>, parking_lot::condvar::Condvar)>>>::as_ptr
80		}
81
82		struct AbortOnPanic;
83
84		impl Drop for AbortOnPanic {
85	0	fn drop(&mut self) {
86	0	if std::thread::panicking() {
87	0	std::process::abort()
88	0	}
89	0	}
90		}

Coverage Report

Created: 2026-03-26 07:41