arch_program 0.6.4

A Rust library for building programs that run inside the Arch Virtual Machine. Provides core functionality for creating instructions, managing accounts, handling program errors, and interacting with the Arch runtime environment. Includes utilities for logging, transaction handling, and Bitcoin UTXO management.
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//! A type to hold data for the [`StakeHistory` sysvar][sv].
//!
//! [sv]: https://docs.solanalabs.com/runtime/sysvars#stakehistory
//!
//! The sysvar ID is declared in [`sysvar::stake_history`].
//!
//! [`sysvar::stake_history`]: crate::sysvar::stake_history

use std::ops::Deref;

pub const MAX_ENTRIES: usize = 512; // it should never take as many as 512 epochs to warm up or cool down

#[repr(C)]
#[derive(Debug, Serialize, Deserialize, PartialEq, Eq, Default, Clone)]
pub struct StakeHistoryEntry {
    pub effective: u64,    // effective stake at this epoch
    pub activating: u64,   // sum of portion of stakes not fully warmed up
    pub deactivating: u64, // requested to be cooled down, not fully deactivated yet
}

impl StakeHistoryEntry {
    pub fn with_effective(effective: u64) -> Self {
        Self {
            effective,
            ..Self::default()
        }
    }

    pub fn with_effective_and_activating(effective: u64, activating: u64) -> Self {
        Self {
            effective,
            activating,
            ..Self::default()
        }
    }

    pub fn with_deactivating(deactivating: u64) -> Self {
        Self {
            effective: deactivating,
            deactivating,
            ..Self::default()
        }
    }
}

impl std::ops::Add for StakeHistoryEntry {
    type Output = StakeHistoryEntry;
    fn add(self, rhs: StakeHistoryEntry) -> Self::Output {
        Self {
            effective: self.effective.saturating_add(rhs.effective),
            activating: self.activating.saturating_add(rhs.activating),
            deactivating: self.deactivating.saturating_add(rhs.deactivating),
        }
    }
}

#[repr(C)]
#[derive(Debug, Serialize, Deserialize, PartialEq, Eq, Default, Clone)]
pub struct StakeHistory(Vec<(u64, StakeHistoryEntry)>);

impl StakeHistory {
    pub fn get(&self, epoch: u64) -> Option<&StakeHistoryEntry> {
        self.binary_search_by(|probe| epoch.cmp(&probe.0))
            .ok()
            .map(|index| &self[index].1)
    }

    pub fn add(&mut self, epoch: u64, entry: StakeHistoryEntry) {
        match self.binary_search_by(|probe| epoch.cmp(&probe.0)) {
            Ok(index) => (self.0)[index] = (epoch, entry),
            Err(index) => (self.0).insert(index, (epoch, entry)),
        }
        (self.0).truncate(MAX_ENTRIES);
    }
}

impl Deref for StakeHistory {
    type Target = Vec<(u64, StakeHistoryEntry)>;
    fn deref(&self) -> &Self::Target {
        &self.0
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_stake_history() {
        let mut stake_history = StakeHistory::default();

        for i in 0..MAX_ENTRIES as u64 + 1 {
            stake_history.add(
                i,
                StakeHistoryEntry {
                    activating: i,
                    ..StakeHistoryEntry::default()
                },
            );
        }
        assert_eq!(stake_history.len(), MAX_ENTRIES);
        assert_eq!(stake_history.iter().map(|entry| entry.0).min().unwrap(), 1);
        assert_eq!(stake_history.get(0), None);
        assert_eq!(
            stake_history.get(1),
            Some(&StakeHistoryEntry {
                activating: 1,
                ..StakeHistoryEntry::default()
            })
        );
    }
}