Refactor: move sysvar cache to new module

program-runtime/src/sysvar_cache.rs

@@ -0,0 +1,39 @@
+use {
+    solana_sdk::{
+        account::{AccountSharedData, ReadableAccount},
+        pubkey::Pubkey,
+    },
+    std::ops::Deref,
+};
+
+#[cfg(RUSTC_WITH_SPECIALIZATION)]
+impl ::solana_frozen_abi::abi_example::AbiExample for SysvarCache {
+    fn example() -> Self {
+        // SysvarCache is not Serialize so just rely on Default.
+        SysvarCache::default()
+    }
+}
+
+#[derive(Default, Clone, Debug)]
+pub struct SysvarCache(Vec<(Pubkey, Vec<u8>)>);
+
+impl Deref for SysvarCache {
+    type Target = Vec<(Pubkey, Vec<u8>)>;
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl SysvarCache {
+    pub fn push_entry(&mut self, pubkey: Pubkey, data: Vec<u8>) {
+        self.0.push((pubkey, data));
+    }
+
+    pub fn update_entry(&mut self, pubkey: &Pubkey, new_account: &AccountSharedData) {
+        if let Some(position) = self.iter().position(|(id, _data)| id == pubkey) {
+            self.0[position].1 = new_account.data().to_vec();
+        } else {
+            self.0.push((*pubkey, new_account.data().to_vec()));
+        }
+    }
+}