Move Feature struct to solana-program

sdk/program/src/feature.rs

@@ -0,0 +1,86 @@
+/// Runtime features.
+///
+/// Feature activation is accomplished by:
+/// 1. Activation is requested by the feature authority, who issues a transaction to create the
+///    feature account.  The newly created feature account will have the value of
+///    `Feature::default()`
+/// 2. When the next epoch is entered the runtime will check for new activation requests and
+///    active them.  When this occurs, the activation slot is recorded in the feature account
+///
+use crate::{
+    account_info::AccountInfo, clock::Slot, instruction::Instruction, program_error::ProgramError,
+    pubkey::Pubkey, rent::Rent, system_instruction,
+};
+
+crate::declare_id!("Feature111111111111111111111111111111111111");
+
+#[derive(Default, Debug, Serialize, Deserialize, PartialEq)]
+pub struct Feature {
+    pub activated_at: Option<Slot>,
+}
+
+impl Feature {
+    pub fn size_of() -> usize {
+        bincode::serialized_size(&Feature {
+            activated_at: Some(0),
+        })
+        .unwrap() as usize
+    }
+
+    pub fn from_account_info(account_info: &AccountInfo) -> Result<Self, ProgramError> {
+        if *account_info.owner != id() {
+            return Err(ProgramError::InvalidArgument);
+        }
+        bincode::deserialize(&account_info.data.borrow()).map_err(|_| ProgramError::InvalidArgument)
+    }
+}
+
+/// Activate a feature
+pub fn activate(feature_id: &Pubkey, funding_address: &Pubkey, rent: &Rent) -> Vec<Instruction> {
+    activate_with_lamports(
+        feature_id,
+        funding_address,
+        rent.minimum_balance(Feature::size_of()),
+    )
+}
+
+pub fn activate_with_lamports(
+    feature_id: &Pubkey,
+    funding_address: &Pubkey,
+    lamports: u64,
+) -> Vec<Instruction> {
+    vec![
+        system_instruction::transfer(funding_address, feature_id, lamports),
+        system_instruction::allocate(feature_id, Feature::size_of() as u64),
+        system_instruction::assign(feature_id, &id()),
+    ]
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use solana_program::clock::Slot;
+
+    #[test]
+    fn feature_sizeof() {
+        assert!(
+            Feature::size_of() >= bincode::serialized_size(&Feature::default()).unwrap() as usize
+        );
+        assert_eq!(Feature::default(), Feature { activated_at: None });
+
+        let features = [
+            Feature {
+                activated_at: Some(0),
+            },
+            Feature {
+                activated_at: Some(Slot::MAX),
+            },
+        ];
+        for feature in &features {
+            assert_eq!(
+                Feature::size_of(),
+                bincode::serialized_size(feature).unwrap() as usize
+            );
+        }
+    }
+}

sdk/program/src/lib.rs

@@ -12,6 +12,7 @@ pub mod decode_error;
 pub mod entrypoint;
 pub mod entrypoint_deprecated;
 pub mod epoch_schedule;
+pub mod feature;
 pub mod fee_calculator;
 pub mod hash;
 pub mod incinerator;