diff --git a/src/hole.rs b/src/hole.rs index 8e57749..dfc6af5 100644 --- a/src/hole.rs +++ b/src/hole.rs @@ -92,16 +92,9 @@ impl HoleList { pub fn allocate_first_fit(&mut self, layout: Layout) -> Result<(NonNull, Layout), ()> { let aligned_layout = Self::align_layout(layout); - allocate_first_fit(&mut self.first, aligned_layout).map(|allocation| { - if let Some(padding) = allocation.front_padding { - deallocate(&mut self.first, padding.addr, padding.size); - } - if let Some(padding) = allocation.back_padding { - deallocate(&mut self.first, padding.addr, padding.size); - } - + allocate_first_fit(&mut self.first, aligned_layout).map(|holeinfo| { ( - NonNull::new(allocation.info.addr as *mut u8).unwrap(), + NonNull::new(holeinfo.addr as *mut u8).unwrap(), aligned_layout, ) }) @@ -242,13 +235,12 @@ fn split_hole(hole: HoleInfo, required_layout: Layout) -> Option { } /// Searches the list starting at the next hole of `previous` for a big enough hole. A hole is big -/// enough if it can hold an allocation of `layout.size()` bytes with the given `layou.align()`. +/// enough if it can hold an allocation of `layout.size()` bytes with the given `layout.align()`. /// When a hole is used for an allocation, there may be some needed padding before and/or after -/// the allocation. This padding is returned as part of the `Allocation`. The caller must take -/// care of freeing it again. +/// the allocation. The padding will then merge back to linked-list /// This function uses the “first fit” strategy, so it breaks as soon as a big enough hole is /// found (and returns it). -fn allocate_first_fit(mut previous: &mut Hole, layout: Layout) -> Result { +fn allocate_first_fit(mut previous: &mut Hole, layout: Layout) -> Result { loop { let allocation: Option = previous .next @@ -256,9 +248,34 @@ fn allocate_first_fit(mut previous: &mut Hole, layout: Layout) -> Result { - // hole is big enough, so remove it from the list by updating the previous pointer + // link the front/back padding + // Note that there must be no hole between following pair: + // previous - front_padding + // front_padding - back_padding + // back_padding - previous.next previous.next = previous.next.as_mut().unwrap().next.take(); - return Ok(allocation); + if let Some(padding) = allocation.front_padding { + let ptr = padding.addr as *mut Hole; + unsafe { + ptr.write (Hole { + size: padding.size, + next: previous.next.take(), + }) + } + previous.next = Some(unsafe { &mut *ptr }); + previous = move_helper(previous).next.as_mut().unwrap(); + } + if let Some(padding) = allocation.back_padding { + let ptr = padding.addr as *mut Hole; + unsafe { + ptr.write (Hole { + size: padding.size, + next: previous.next.take(), + }) + } + previous.next = Some(unsafe { &mut *ptr }); + } + return Ok(allocation.info); } None if previous.next.is_some() => { // try next hole