From 2b04f28c7b6984ab241812ac3228879e96dd6c30 Mon Sep 17 00:00:00 2001
From: Yueh-Hsuan Chiang <93241502+yhchiang-sol@users.noreply.github.com>
Date: Thu, 1 Jun 2023 14:48:27 -0700
Subject: [PATCH] [TieredStorage] AccountMetaFlags (#31913)

#### Summary of Changes
This PR implements AccountMetaFlags, which will later be used in
the tiered accounts storage to support optional fields.

#### Test Plan
Unit tests are included in this PR.
---
 runtime/src/tiered_storage.rs      |  1 +
 runtime/src/tiered_storage/meta.rs | 72 ++++++++++++++++++++++++++++++
 2 files changed, 73 insertions(+)
 create mode 100644 runtime/src/tiered_storage/meta.rs

diff --git a/runtime/src/tiered_storage.rs b/runtime/src/tiered_storage.rs
index ab9a779fd..2c8478363 100644
--- a/runtime/src/tiered_storage.rs
+++ b/runtime/src/tiered_storage.rs
@@ -2,6 +2,7 @@ pub mod byte_block;
 pub mod error;
 pub mod file;
 pub mod footer;
+pub mod meta;
 pub mod mmap_utils;
 
 use crate::tiered_storage::error::TieredStorageError;
diff --git a/runtime/src/tiered_storage/meta.rs b/runtime/src/tiered_storage/meta.rs
new file mode 100644
index 000000000..ed95d2f68
--- /dev/null
+++ b/runtime/src/tiered_storage/meta.rs
@@ -0,0 +1,72 @@
+#![allow(dead_code)]
+//! The account meta and related structs for the tiered storage.
+
+use modular_bitfield::prelude::*;
+
+/// The struct that handles the account meta flags.
+#[bitfield(bits = 32)]
+#[repr(C)]
+#[derive(Debug, Default, Copy, Clone, Eq, PartialEq)]
+pub(crate) struct AccountMetaFlags {
+    /// whether the account meta has rent epoch
+    has_rent_epoch: bool,
+    /// whether the account meta has account hash
+    has_account_hash: bool,
+    /// whether the account meta has write version
+    has_write_version: bool,
+    /// the reserved bits.
+    reserved: B29,
+}
+
+#[cfg(test)]
+pub mod tests {
+    use crate::tiered_storage::meta::*;
+
+    #[test]
+    fn test_account_meta_flags_new() {
+        let flags = AccountMetaFlags::new();
+
+        assert!(!flags.has_rent_epoch());
+        assert!(!flags.has_account_hash());
+        assert!(!flags.has_write_version());
+        assert_eq!(flags.reserved(), 0u32);
+
+        assert_eq!(
+            std::mem::size_of::<AccountMetaFlags>(),
+            std::mem::size_of::<u32>()
+        );
+    }
+
+    fn verify_flags_serialization(flags: &AccountMetaFlags) {
+        assert_eq!(AccountMetaFlags::from_bytes(flags.into_bytes()), *flags);
+    }
+
+    #[test]
+    fn test_account_meta_flags_set() {
+        let mut flags = AccountMetaFlags::new();
+
+        flags.set_has_rent_epoch(true);
+
+        assert!(flags.has_rent_epoch());
+        assert!(!flags.has_account_hash());
+        assert!(!flags.has_write_version());
+        verify_flags_serialization(&flags);
+
+        flags.set_has_account_hash(true);
+
+        assert!(flags.has_rent_epoch());
+        assert!(flags.has_account_hash());
+        assert!(!flags.has_write_version());
+        verify_flags_serialization(&flags);
+
+        flags.set_has_write_version(true);
+
+        assert!(flags.has_rent_epoch());
+        assert!(flags.has_account_hash());
+        assert!(flags.has_write_version());
+        verify_flags_serialization(&flags);
+
+        // make sure the reserved bits are untouched.
+        assert_eq!(flags.reserved(), 0u32);
+    }
+}