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use std::mem::{forget, transmute};
use std::ops::{Deref, DerefMut};
use parking_lot::{
MappedRwLockReadGuard,
MappedRwLockWriteGuard,
RwLock,
RwLockReadGuard,
RwLockWriteGuard,
};
use crate::type_name::TypeName;
#[derive(Debug, Default)]
pub struct Lock<Value>
where
Value: TypeName,
{
inner: RwLock<Value>,
}
impl<Value> Lock<Value>
where
Value: TypeName,
{
pub fn new(value: Value) -> Self
{
Self { inner: RwLock::new(value) }
}
/// Tries to a acquire a handle to the resource with read access.
///
/// # Errors
/// Returns `Err` if unavailable (A mutable handle is hold).
pub fn read_nonblock(&self) -> Result<ReadGuard<Value>, Error>
{
let guard = self.inner.try_read().ok_or(Error::ReadUnavailable)?;
tracing::trace!("Acquired lock to value of type {}", guard.type_name());
Ok(ReadGuard { inner: guard })
}
/// Tries to a acquire a handle to the resource with mutable access.
///
/// # Errors
/// Returns `Err` if unavailable (A mutable or immutable handle is hold).
pub fn write_nonblock(&self) -> Result<WriteGuard<Value>, Error>
{
let guard = self.inner.try_write().ok_or(Error::WriteUnavailable)?;
tracing::trace!(
"Acquired mutable lock to value of type {}",
guard.type_name()
);
Ok(WriteGuard { inner: guard })
}
pub fn into_inner(self) -> Value
{
self.inner.into_inner()
}
}
#[derive(Debug, thiserror::Error)]
pub enum Error
{
#[error("Lock is unavailable for reading")]
ReadUnavailable,
#[error("Lock is unavailable for writing")]
WriteUnavailable,
}
#[derive(Debug)]
pub struct ReadGuard<'guard, Value>
where
Value: TypeName,
{
inner: RwLockReadGuard<'guard, Value>,
}
impl<'guard, Value> ReadGuard<'guard, Value>
where
Value: TypeName,
{
pub fn map<NewValue>(
self,
func: impl FnOnce(&Value) -> &NewValue,
) -> MappedReadGuard<'guard, NewValue>
where
NewValue: TypeName,
{
// The 'inner' field cannot be moved out of ReadGuard in a normal way since
// ReadGuard implements Drop
let inner = unsafe { std::ptr::read(&self.inner) };
forget(self);
MappedReadGuard {
inner: RwLockReadGuard::map(inner, func),
}
}
/// Converts the `ReadGuard` to a `ReadGuard` with a possibly longer lifetime.
///
/// # Safety
/// The returned `ReadGuard` must **NOT** be used for longer than the original
/// lifetime.
#[must_use]
pub unsafe fn upgrade_lifetime<'new>(self) -> ReadGuard<'new, Value>
{
unsafe { transmute(self) }
}
}
impl<'guard, Value> Deref for ReadGuard<'guard, Value>
where
Value: TypeName,
{
type Target = Value;
fn deref(&self) -> &Self::Target
{
&self.inner
}
}
impl<'guard, Value> Drop for ReadGuard<'guard, Value>
where
Value: TypeName,
{
fn drop(&mut self)
{
tracing::trace!("Dropped lock to value of type {}", self.type_name());
}
}
#[derive(Debug)]
pub struct MappedReadGuard<'guard, Value>
where
Value: TypeName,
{
inner: MappedRwLockReadGuard<'guard, Value>,
}
impl<'guard, Value> Deref for MappedReadGuard<'guard, Value>
where
Value: TypeName,
{
type Target = Value;
fn deref(&self) -> &Self::Target
{
&self.inner
}
}
impl<'guard, Value> Drop for MappedReadGuard<'guard, Value>
where
Value: TypeName,
{
fn drop(&mut self)
{
tracing::trace!("Dropped mapped lock to value of type {}", self.type_name());
}
}
#[derive(Debug)]
pub struct WriteGuard<'guard, Value>
where
Value: TypeName,
{
inner: RwLockWriteGuard<'guard, Value>,
}
impl<'guard, Value> WriteGuard<'guard, Value>
where
Value: TypeName,
{
pub fn map<NewValue>(
self,
func: impl FnOnce(&mut Value) -> &mut NewValue,
) -> MappedWriteGuard<'guard, NewValue>
where
NewValue: TypeName,
{
// The 'inner' field cannot be moved out of ReadGuard in a normal way since
// ReadGuard implements Drop
let inner = unsafe { std::ptr::read(&self.inner) };
forget(self);
MappedWriteGuard {
inner: RwLockWriteGuard::map(inner, func),
}
}
}
impl<'guard, Value> Deref for WriteGuard<'guard, Value>
where
Value: TypeName,
{
type Target = Value;
fn deref(&self) -> &Self::Target
{
&self.inner
}
}
impl<'guard, Value> DerefMut for WriteGuard<'guard, Value>
where
Value: TypeName,
{
fn deref_mut(&mut self) -> &mut Self::Target
{
&mut self.inner
}
}
impl<'guard, Value> Drop for WriteGuard<'guard, Value>
where
Value: TypeName,
{
fn drop(&mut self)
{
tracing::trace!("Dropped mutable lock to value of type {}", self.type_name());
}
}
#[derive(Debug)]
pub struct MappedWriteGuard<'guard, Value>
where
Value: TypeName,
{
inner: MappedRwLockWriteGuard<'guard, Value>,
}
impl<'guard, Value> Deref for MappedWriteGuard<'guard, Value>
where
Value: TypeName,
{
type Target = Value;
fn deref(&self) -> &Self::Target
{
&self.inner
}
}
impl<'guard, Value> DerefMut for MappedWriteGuard<'guard, Value>
where
Value: TypeName,
{
fn deref_mut(&mut self) -> &mut Self::Target
{
&mut self.inner
}
}
impl<'guard, Value> Drop for MappedWriteGuard<'guard, Value>
where
Value: TypeName,
{
fn drop(&mut self)
{
tracing::trace!(
"Dropped mapped mutable lock to value of type {}",
self.type_name()
);
}
}
|
