From 32aa2463001c0af9f87633a1ff78858dd4157eb9 Mon Sep 17 00:00:00 2001 From: Alex Auvolat Date: Fri, 8 Mar 2024 17:39:17 +0100 Subject: [rm-sled] Make proper use of pinning in LMDB adapter + comment unsafe --- src/db/sqlite_adapter.rs | 44 +++++++++++++++++++++++++------------------- 1 file changed, 25 insertions(+), 19 deletions(-) (limited to 'src/db/sqlite_adapter.rs') diff --git a/src/db/sqlite_adapter.rs b/src/db/sqlite_adapter.rs index 077c1f1b..2c6a4159 100644 --- a/src/db/sqlite_adapter.rs +++ b/src/db/sqlite_adapter.rs @@ -444,17 +444,23 @@ impl<'a> DbValueIterator<'a> { let mut boxed = Box::pin(res); trace!("make iterator with sql: {}", sql); - unsafe { - let db = NonNull::from(&boxed.db); - let stmt = db.as_ref().db.prepare(sql)?; + // This unsafe allows us to bypass lifetime checks + let db = unsafe { NonNull::from(&boxed.db).as_ref() }; + let stmt = db.db.prepare(sql)?; - let mut_ref: Pin<&mut DbValueIterator<'a>> = Pin::as_mut(&mut boxed); + let mut_ref = Pin::as_mut(&mut boxed); + // This unsafe allows us to write in a field of the pinned struct + unsafe { Pin::get_unchecked_mut(mut_ref).stmt = Some(stmt); + } - let mut stmt = NonNull::from(&boxed.stmt); - let iter = stmt.as_mut().as_mut().unwrap().query(args)?; + // This unsafe allows us to bypass lifetime checks + let stmt = unsafe { NonNull::from(&boxed.stmt).as_mut() }; + let iter = stmt.as_mut().unwrap().query(args)?; - let mut_ref: Pin<&mut DbValueIterator<'a>> = Pin::as_mut(&mut boxed); + let mut_ref = Pin::as_mut(&mut boxed); + // This unsafe allows us to write in a field of the pinned struct + unsafe { Pin::get_unchecked_mut(mut_ref).iter = Some(iter); } @@ -476,10 +482,9 @@ impl<'a> Iterator for DbValueIteratorPin<'a> { type Item = Result<(Value, Value)>; fn next(&mut self) -> Option { - let next = unsafe { - let mut_ref: Pin<&mut DbValueIterator<'a>> = Pin::as_mut(&mut self.0); - Pin::get_unchecked_mut(mut_ref).iter.as_mut()?.next() - }; + let mut_ref = Pin::as_mut(&mut self.0); + // This unsafe allows us to mutably access the iterator field + let next = unsafe { Pin::get_unchecked_mut(mut_ref).iter.as_mut()?.next() }; let row = match next { Err(e) => return Some(Err(e.into())), Ok(None) => return None, @@ -522,11 +527,13 @@ impl<'a> TxValueIterator<'a> { let mut boxed = Box::pin(res); trace!("make iterator with sql: {}", sql); - unsafe { - let mut stmt = NonNull::from(&boxed.stmt); - let iter = stmt.as_mut().query(args)?; + // This unsafe allows us to bypass lifetime checks + let stmt = unsafe { NonNull::from(&boxed.stmt).as_mut() }; + let iter = stmt.query(args)?; - let mut_ref: Pin<&mut TxValueIterator<'a>> = Pin::as_mut(&mut boxed); + let mut_ref = Pin::as_mut(&mut boxed); + // This unsafe allows us to write in a field of the pinned struct + unsafe { Pin::get_unchecked_mut(mut_ref).iter = Some(iter); } @@ -547,10 +554,9 @@ impl<'a> Iterator for TxValueIteratorPin<'a> { type Item = TxOpResult<(Value, Value)>; fn next(&mut self) -> Option { - let next = unsafe { - let mut_ref: Pin<&mut TxValueIterator<'a>> = Pin::as_mut(&mut self.0); - Pin::get_unchecked_mut(mut_ref).iter.as_mut()?.next() - }; + let mut_ref = Pin::as_mut(&mut self.0); + // This unsafe allows us to mutably access the iterator field + let next = unsafe { Pin::get_unchecked_mut(mut_ref).iter.as_mut()?.next() }; let row = match next { Err(e) => return Some(Err(e.into())), Ok(None) => return None, -- cgit v1.2.3