Add PageRef

bustubx/src/buffer/buffer_pool.rs

@@ -20,7 +20,7 @@ pub struct BufferPoolManager {
     pub replacer: Arc<RwLock<LRUKReplacer>>,
     pub disk_manager: Arc<DiskManager>,
     // 缓冲池中的页号与frame号的映射
-    page_table: DashMap<PageId, FrameId>,
+    page_table: Arc<DashMap<PageId, FrameId>>,
     // 缓冲池中空闲的frame
     free_list: Arc<RwLock<VecDeque<FrameId>>>,
 }
@@ -37,7 +37,7 @@ impl BufferPoolManager {
             pool,
             replacer: Arc::new(RwLock::new(LRUKReplacer::new(num_pages, 2))),
             disk_manager,
-            page_table: DashMap::new(),
+            page_table: Arc::new(DashMap::new()),
             free_list: Arc::new(RwLock::new(free_list)),
         }
     }

bustubx/src/buffer/page.rs

@@ -1,5 +1,11 @@
+use crate::buffer::buffer_pool::FrameId;
+use crate::buffer::replacer::LRUKReplacer;
+use dashmap::DashMap;
 use derive_with::With;
+use log::error;
+use std::ops::Deref;
 use std::sync::atomic::AtomicU32;
+use std::sync::{Arc, RwLock};
 
 pub type PageId = u32;
 pub type AtomicPageId = AtomicU32;
@@ -52,3 +58,69 @@ impl Page {
         self.is_dirty = other.is_dirty;
     }
 }
+
+pub struct PageRef {
+    page: Arc<RwLock<Page>>,
+    page_table: Arc<DashMap<PageId, FrameId>>,
+    replacer: Arc<RwLock<LRUKReplacer>>,
+}
+
+impl Deref for PageRef {
+    type Target = Arc<RwLock<Page>>;
+
+    fn deref(&self) -> &Self::Target {
+        &self.page
+    }
+}
+
+impl Drop for PageRef {
+    fn drop(&mut self) {
+        if self.page.read().unwrap().pin_count == 0 {
+            return;
+        }
+        let page_id = self.page.read().unwrap().page_id;
+        if let Some(frame_id) = self.page_table.get(&page_id) {
+            self.page.write().unwrap().pin_count -= 1;
+            if self.page.read().unwrap().pin_count == 0 {
+                if let Err(e) = self
+                    .replacer
+                    .write()
+                    .unwrap()
+                    .set_evictable(*frame_id, true)
+                {
+                    panic!(
+                        "Failed to set evictable to frame {}, err: {:?}",
+                        *frame_id, e
+                    );
+                }
+            }
+        } else {
+            error!("Cannot unpin page id {} as it is not in the pool", page_id);
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::buffer::replacer::LRUKReplacer;
+    use crate::buffer::{Page, PageRef};
+    use dashmap::DashMap;
+    use std::sync::{Arc, RwLock};
+
+    #[test]
+    fn page_ref() {
+        let page = Arc::new(RwLock::new(Page::new(1)));
+        let page_table = Arc::new(DashMap::new());
+        let replacer = Arc::new(RwLock::new(LRUKReplacer::new(10, 2)));
+
+        let page_ref = PageRef {
+            page: page.clone(),
+            page_table,
+            replacer,
+        };
+        assert_eq!(Arc::strong_count(&page), 2);
+        assert_eq!(page_ref.read().unwrap().page_id, 1);
+        drop(page_ref);
+        assert_eq!(Arc::strong_count(&page), 1);
+    }
+}