[WIP][Dont review] Page manager with buffer pool

Cargo.toml

@@ -18,6 +18,9 @@ zerocopy = { version = "0.8.24", features = ["derive"] }
 parking_lot = { version = "0.12.4", features = ["send_guard"] }
 fxhash = "0.2.1"
 static_assertions = "1.1.0"
+evict = "0.3.1"
+dashmap = "6.1.0"
+libc = "0.2.174"
 
 [dev-dependencies]
 criterion = "0.6.0"

src/database.rs

@@ -468,7 +468,7 @@ mod tests {
             assert_eq!(
                 db.storage_engine
                     .page_manager
-                    .get(1, *page_id)
+                    .get(*page_id)
                     .unwrap_or_else(|err| panic!("page {page_id} not found: {err:?}"))
                     .snapshot_id(),
                 1
@@ -497,7 +497,7 @@ mod tests {
             let page = db
                 .storage_engine
                 .page_manager
-                .get(1, *page_id)
+                .get(*page_id)
                 .unwrap_or_else(|err| panic!("page {page_id} not found: {err:?}"));
             if old_page_ids.contains(page_id) {
                 assert_eq!(page.snapshot_id(), 1);

src/page.rs

@@ -11,7 +11,10 @@ mod page;
 mod slotted_page;
 mod state;
 
-pub use manager::{mmap::PageManager, options::PageManagerOptions, PageError};
+pub use manager::{
+    buffer_pool::BufferPoolManager, mmap::PageManager, options::PageManagerOptions, PageError,
+    PageManagerTrait,
+};
 pub use page::{Page, PageMut};
 pub use slotted_page::{SlottedPage, SlottedPageMut, CELL_POINTER_SIZE};
 

src/page/manager.rs

@@ -1,5 +1,12 @@
-use crate::page::PageId;
+use std::io;
 
+use crate::{
+    page::{Page, PageId, PageMut},
+    snapshot::SnapshotId,
+};
+
+pub(super) mod buffer_pool;
+pub(super) mod cache_evict;
 pub(super) mod mmap;
 pub(super) mod options;
 
@@ -18,5 +25,30 @@ pub enum PageError {
     IO(std::io::Error),
     InvalidValue,
     InvalidPageContents(PageId),
+    OutOfMemory,
+    EvictionPolicy,
     // TODO: add more errors here for other cases.
 }
+
+pub trait PageManagerTrait: Send + Sync + std::fmt::Debug {
+    /// Retrieves a read-only page from the page manager
+    fn get(&self, page_id: PageId) -> Result<Page<'_>, PageError>;
+
+    /// Retrieves a mutable page from the page manager
+    fn get_mut(&self, snapshot_id: SnapshotId, page_id: PageId) -> Result<PageMut<'_>, PageError>;
+
+    /// Allocates a new page
+    fn allocate(&self, snapshot_id: SnapshotId) -> Result<PageMut<'_>, PageError>;
+
+    /// Returns the number of pages currently stored
+    fn size(&self) -> u32;
+
+    /// Returns the maximum number of pages that can be allocated
+    fn capacity(&self) -> u32;
+
+    /// Syncs pages to the backing store
+    fn sync(&self) -> io::Result<()>;
+
+    /// Syncs and closes the page manager
+    fn close(&self) -> io::Result<()>;
+}