diff options
| -rw-r--r-- | rust/kernel/id_pool.rs | 77 |
1 files changed, 61 insertions, 16 deletions
diff --git a/rust/kernel/id_pool.rs b/rust/kernel/id_pool.rs index afde05f53588..384753fe0e44 100644 --- a/rust/kernel/id_pool.rs +++ b/rust/kernel/id_pool.rs @@ -23,22 +23,22 @@ use crate::bitmap::BitmapVec; /// Basic usage /// /// ``` -/// use kernel::alloc::{AllocError, flags::GFP_KERNEL}; -/// use kernel::id_pool::IdPool; +/// use kernel::alloc::AllocError; +/// use kernel::id_pool::{IdPool, UnusedId}; /// /// let mut pool = IdPool::with_capacity(64, GFP_KERNEL)?; /// for i in 0..64 { -/// assert_eq!(i, pool.acquire_next_id(i).ok_or(ENOSPC)?); +/// assert_eq!(i, pool.find_unused_id(i).ok_or(ENOSPC)?.acquire()); /// } /// /// pool.release_id(23); -/// assert_eq!(23, pool.acquire_next_id(0).ok_or(ENOSPC)?); +/// assert_eq!(23, pool.find_unused_id(0).ok_or(ENOSPC)?.acquire()); /// -/// assert_eq!(None, pool.acquire_next_id(0)); // time to realloc. +/// assert!(pool.find_unused_id(0).is_none()); // time to realloc. /// let resizer = pool.grow_request().ok_or(ENOSPC)?.realloc(GFP_KERNEL)?; /// pool.grow(resizer); /// -/// assert_eq!(pool.acquire_next_id(0), Some(64)); +/// assert_eq!(pool.find_unused_id(0).ok_or(ENOSPC)?.acquire(), 64); /// # Ok::<(), Error>(()) /// ``` /// @@ -52,8 +52,8 @@ use crate::bitmap::BitmapVec; /// fn get_id_maybe_realloc(guarded_pool: &SpinLock<IdPool>) -> Result<usize, AllocError> { /// let mut pool = guarded_pool.lock(); /// loop { -/// match pool.acquire_next_id(0) { -/// Some(index) => return Ok(index), +/// match pool.find_unused_id(0) { +/// Some(index) => return Ok(index.acquire()), /// None => { /// let alloc_request = pool.grow_request(); /// drop(pool); @@ -221,18 +221,18 @@ impl IdPool { self.map = resizer.new; } - /// Acquires a new ID by finding and setting the next zero bit in the - /// bitmap. + /// Finds an unused ID in the bitmap. /// /// Upon success, returns its index. Otherwise, returns [`None`] /// to indicate that a [`Self::grow_request`] is needed. #[inline] - pub fn acquire_next_id(&mut self, offset: usize) -> Option<usize> { - let next_zero_bit = self.map.next_zero_bit(offset); - if let Some(nr) = next_zero_bit { - self.map.set_bit(nr); - } - next_zero_bit + #[must_use] + pub fn find_unused_id(&mut self, offset: usize) -> Option<UnusedId<'_>> { + // INVARIANT: `next_zero_bit()` returns None or an integer less than `map.len()` + Some(UnusedId { + id: self.map.next_zero_bit(offset)?, + pool: self, + }) } /// Releases an ID. @@ -242,6 +242,51 @@ impl IdPool { } } +/// Represents an unused id in an [`IdPool`]. +/// +/// # Invariants +/// +/// The value of `id` is less than `pool.map.len()`. +pub struct UnusedId<'pool> { + id: usize, + pool: &'pool mut IdPool, +} + +impl<'pool> UnusedId<'pool> { + /// Get the unused id as an usize. + /// + /// Be aware that the id has not yet been acquired in the pool. The + /// [`acquire`] method must be called to prevent others from taking the id. + /// + /// [`acquire`]: UnusedId::acquire() + #[inline] + #[must_use] + pub fn as_usize(&self) -> usize { + self.id + } + + /// Get the unused id as an u32. + /// + /// Be aware that the id has not yet been acquired in the pool. The + /// [`acquire`] method must be called to prevent others from taking the id. + /// + /// [`acquire`]: UnusedId::acquire() + #[inline] + #[must_use] + pub fn as_u32(&self) -> u32 { + // CAST: By the type invariants: + // `self.id < pool.map.len() <= BitmapVec::MAX_LEN = i32::MAX`. + self.id as u32 + } + + /// Acquire the unused id. + #[inline] + pub fn acquire(self) -> usize { + self.pool.map.set_bit(self.id); + self.id + } +} + impl Default for IdPool { #[inline] fn default() -> Self { |