move Account to solana-sdk (#13198)

sdk/src/account_utils.rs

@@ -0,0 +1,50 @@
+//! useful extras for Account state
+use crate::{account::Account, instruction::InstructionError};
+use bincode::ErrorKind;
+
+/// Convenience trait to covert bincode errors to instruction errors.
+pub trait StateMut<T> {
+    fn state(&self) -> Result<T, InstructionError>;
+    fn set_state(&mut self, state: &T) -> Result<(), InstructionError>;
+}
+pub trait State<T> {
+    fn state(&self) -> Result<T, InstructionError>;
+    fn set_state(&self, state: &T) -> Result<(), InstructionError>;
+}
+
+impl<T> StateMut<T> for Account
+where
+    T: serde::Serialize + serde::de::DeserializeOwned,
+{
+    fn state(&self) -> Result<T, InstructionError> {
+        self.deserialize_data()
+            .map_err(|_| InstructionError::InvalidAccountData)
+    }
+    fn set_state(&mut self, state: &T) -> Result<(), InstructionError> {
+        self.serialize_data(state).map_err(|err| match *err {
+            ErrorKind::SizeLimit => InstructionError::AccountDataTooSmall,
+            _ => InstructionError::GenericError,
+        })
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::{account::Account, pubkey::Pubkey};
+
+    #[test]
+    fn test_account_state() {
+        let state = 42u64;
+
+        assert!(Account::default().set_state(&state).is_err());
+        let res = Account::default().state() as Result<u64, InstructionError>;
+        assert!(res.is_err());
+
+        let mut account = Account::new(0, std::mem::size_of::<u64>(), &Pubkey::default());
+
+        assert!(account.set_state(&state).is_ok());
+        let stored_state: u64 = account.state().unwrap();
+        assert_eq!(stored_state, state);
+    }
+}