[PATCH v6 4/7] rust: id_pool: add contiguous area allocation

[Eliot Courtney <ecourtney@nvidia.com>]

Add `IdPool::alloc_area` which allocates a contiguous area with the
given offset, count, and alignment.

Signed-off-by: Eliot Courtney <ecourtney@nvidia.com>
---
 rust/kernel/id_pool.rs | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/rust/kernel/id_pool.rs b/rust/kernel/id_pool.rs
index 384753fe0e44..a4a2ff417fe8 100644
--- a/rust/kernel/id_pool.rs
+++ b/rust/kernel/id_pool.rs
@@ -4,8 +4,14 @@
 
 //! Rust API for an ID pool backed by a [`BitmapVec`].
 
+use core::{
+    num::NonZero,
+    ops::Range, //
+};
+
 use crate::alloc::{AllocError, Flags};
 use crate::bitmap::BitmapVec;
+use crate::ptr::Alignment;
 
 /// Represents a dynamic ID pool backed by a [`BitmapVec`].
 ///
@@ -240,6 +246,32 @@ pub fn find_unused_id(&mut self, offset: usize) -> Option<UnusedId<'_>> {
     pub fn release_id(&mut self, id: usize) {
         self.map.clear_bit(id);
     }
+
+    /// Allocates a contiguous area of `count` IDs at or after `offset`.
+    ///
+    /// The start of the returned area is a multiple of `align`.
+    ///
+    /// Returns the allocated range upon success, or [`None`] if no such area could be found.
+    #[inline]
+    #[must_use]
+    pub fn alloc_area(
+        &mut self,
+        offset: usize,
+        count: NonZero<usize>,
+        align: Alignment,
+    ) -> Option<Range<usize>> {
+        let start = self.map.next_zero_area(offset, count, align)?;
+        self.map.set(start, count);
+        Some(start..start + count.get())
+    }
+
+    /// Releases a contiguous area of IDs.
+    #[inline]
+    pub fn release_area(&mut self, range: &Range<usize>) {
+        if let Some(nbits) = NonZero::new(range.len()) {
+            self.map.clear(range.start, nbits);
+        }
+    }
 }
 
 /// Represents an unused id in an [`IdPool`].

-- 
2.55.0