Initial population of solana-program-sdk

sdk/program/src/sysvar/rent.rs

@@ -0,0 +1,42 @@
+//! This account contains the current cluster rent
+//!
+pub use crate::rent::Rent;
+
+use crate::{
+    account::{Account, KeyedAccount},
+    instruction::InstructionError,
+    sysvar::Sysvar,
+};
+
+crate::declare_sysvar_id!("SysvarRent111111111111111111111111111111111", Rent);
+
+impl Sysvar for Rent {}
+
+pub fn create_account(lamports: u64, rent: &Rent) -> Account {
+    rent.create_account(lamports)
+}
+
+pub fn verify_rent_exemption(
+    keyed_account: &KeyedAccount,
+    rent_sysvar_account: &KeyedAccount,
+) -> Result<(), InstructionError> {
+    let rent = Rent::from_keyed_account(rent_sysvar_account)?;
+    if !rent.is_exempt(keyed_account.lamports()?, keyed_account.data_len()?) {
+        Err(InstructionError::InsufficientFunds)
+    } else {
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_rent_create_account() {
+        let lamports = 42;
+        let account = create_account(lamports, &Rent::default());
+        let rent = Rent::from_account(&account).unwrap();
+        assert_eq!(rent, Rent::default());
+    }
+}