add epoch_schedule sysvar (#6256)

* add epoch_schedule sysvar

* book sheesh!

sdk/src/sysvar/epoch_schedule.rs

@@ -0,0 +1,57 @@
+//! This account contains the current cluster rent
+//!
+use crate::{
+    account::{Account, KeyedAccount},
+    account_info::AccountInfo,
+    epoch_schedule::EpochSchedule,
+    instruction::InstructionError,
+    sysvar,
+};
+
+///  epoch_schedule account pubkey
+const ID: [u8; 32] = [
+    6, 167, 213, 23, 24, 220, 63, 238, 2, 211, 228, 127, 1, 0, 248, 176, 84, 247, 148, 46, 96, 89,
+    30, 63, 80, 135, 25, 168, 5, 0, 0, 0,
+];
+
+crate::solana_name_id!(ID, "SysvarEpochSchedu1e111111111111111111111111");
+
+impl EpochSchedule {
+    pub fn deserialize(account: &Account) -> Result<Self, bincode::Error> {
+        account.deserialize_data()
+    }
+    pub fn from_account(account: &Account) -> Option<Self> {
+        account.deserialize_data().ok()
+    }
+    pub fn to_account(&self, account: &mut Account) -> Option<()> {
+        account.serialize_data(self).ok()
+    }
+    pub fn from_account_info(account: &AccountInfo) -> Option<Self> {
+        account.deserialize_data().ok()
+    }
+    pub fn to_account_info(&self, account: &mut AccountInfo) -> Option<()> {
+        account.serialize_data(self).ok()
+    }
+    pub fn from_keyed_account(account: &KeyedAccount) -> Result<EpochSchedule, InstructionError> {
+        if !check_id(account.unsigned_key()) {
+            return Err(InstructionError::InvalidArgument);
+        }
+        EpochSchedule::from_account(account.account).ok_or(InstructionError::InvalidArgument)
+    }
+}
+
+pub fn create_account(lamports: u64, epoch_schedule: &EpochSchedule) -> Account {
+    Account::new_data(lamports, epoch_schedule, &sysvar::id()).unwrap()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_create_account() {
+        let account = create_account(42, &EpochSchedule::default());
+        let epoch_schedule = EpochSchedule::from_account(&account).unwrap();
+        assert_eq!(epoch_schedule, EpochSchedule::default());
+    }
+}