Add AccountsDataMeter to InvokeContext (#21813) (#22299)

(cherry picked from commit 800472ddf5)

Co-authored-by: Brooks Prumo <brooks@solana.com>

program-runtime/src/accounts_data_meter.rs

@@ -0,0 +1,170 @@
+//! The accounts data space has a maximum size it is permitted to grow to.  This module contains
+//! the constants and types for tracking and metering the accounts data space during program
+//! runtime.
+use solana_sdk::instruction::InstructionError;
+
+/// The maximum allowed size, in bytes, of the accounts data
+/// 128 GB was chosen because it is the RAM amount listed under Hardware Recommendations on
+/// [Validator Requirements](https://docs.solana.com/running-validator/validator-reqs), and
+/// validators often put the ledger on a RAM disk (i.e. tmpfs).
+pub const MAX_ACCOUNTS_DATA_LEN: u64 = 128_000_000_000;
+
+/// Meter and track the amount of available accounts data space
+#[derive(Debug, Default, Clone, Copy, Eq, PartialEq)]
+pub struct AccountsDataMeter {
+    /// The maximum amount of accounts data space that can be used (in bytes)
+    maximum: u64,
+
+    /// The current amount of accounts data space used (in bytes)
+    current: u64,
+}
+
+impl AccountsDataMeter {
+    /// Make a new AccountsDataMeter
+    pub fn new(current_accounts_data_len: u64) -> Self {
+        let accounts_data_meter = Self {
+            maximum: MAX_ACCOUNTS_DATA_LEN,
+            current: current_accounts_data_len,
+        };
+        debug_assert!(accounts_data_meter.current <= accounts_data_meter.maximum);
+        accounts_data_meter
+    }
+
+    /// Return the maximum amount of accounts data space that can be used (in bytes)
+    pub fn maximum(&self) -> u64 {
+        self.maximum
+    }
+
+    /// Return the current amount of accounts data space used (in bytes)
+    pub fn current(&self) -> u64 {
+        self.current
+    }
+
+    /// Get the remaining amount of accounts data space (in bytes)
+    pub fn remaining(&self) -> u64 {
+        self.maximum.saturating_sub(self.current)
+    }
+
+    /// Consume accounts data space, in bytes.  If `amount` is positive, we are *increasing* the
+    /// amount of accounts data space used.  If `amount` is negative, we are *decreasing* the
+    /// amount of accounts data space used.
+    pub fn consume(&mut self, amount: i64) -> Result<(), InstructionError> {
+        if amount == 0 {
+            // nothing to do here; lets us skip doing unnecessary work in the 'else' case
+            return Ok(());
+        }
+
+        if amount.is_positive() {
+            let amount = amount as u64;
+            if amount > self.remaining() {
+                return Err(InstructionError::AccountsDataBudgetExceeded);
+            }
+            self.current = self.current.saturating_add(amount);
+        } else {
+            let amount = amount.abs() as u64;
+            self.current = self.current.saturating_sub(amount);
+        }
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_new() {
+        let current = 1234;
+        let accounts_data_meter = AccountsDataMeter::new(current);
+        assert_eq!(accounts_data_meter.maximum, MAX_ACCOUNTS_DATA_LEN);
+        assert_eq!(accounts_data_meter.current, current);
+    }
+
+    #[test]
+    fn test_new_can_use_max_len() {
+        let _ = AccountsDataMeter::new(MAX_ACCOUNTS_DATA_LEN);
+    }
+
+    #[test]
+    #[should_panic]
+    fn test_new_panics_if_current_len_too_big() {
+        let _ = AccountsDataMeter::new(MAX_ACCOUNTS_DATA_LEN + 1);
+    }
+
+    #[test]
+    fn test_remaining() {
+        let current_accounts_data_len = 0;
+        let accounts_data_meter = AccountsDataMeter::new(current_accounts_data_len);
+        assert_eq!(accounts_data_meter.remaining(), MAX_ACCOUNTS_DATA_LEN);
+    }
+
+    #[test]
+    fn test_remaining_saturates() {
+        let current_accounts_data_len = 0;
+        let mut accounts_data_meter = AccountsDataMeter::new(current_accounts_data_len);
+        // To test that remaining() saturates, need to break the invariant that current <= maximum
+        accounts_data_meter.current = MAX_ACCOUNTS_DATA_LEN + 1;
+        assert_eq!(accounts_data_meter.remaining(), 0);
+    }
+
+    #[test]
+    fn test_consume() {
+        let current_accounts_data_len = 0;
+        let mut accounts_data_meter = AccountsDataMeter::new(current_accounts_data_len);
+
+        // Test: simple, positive numbers
+        let result = accounts_data_meter.consume(0);
+        assert!(result.is_ok());
+        let result = accounts_data_meter.consume(1);
+        assert!(result.is_ok());
+        let result = accounts_data_meter.consume(4);
+        assert!(result.is_ok());
+        let result = accounts_data_meter.consume(9);
+        assert!(result.is_ok());
+
+        // Test: can consume the remaining amount
+        let remaining = accounts_data_meter.remaining() as i64;
+        let result = accounts_data_meter.consume(remaining);
+        assert!(result.is_ok());
+        assert_eq!(accounts_data_meter.remaining(), 0);
+    }
+
+    #[test]
+    fn test_consume_deallocate() {
+        let current_accounts_data_len = 10_000;
+        let mut accounts_data_meter = AccountsDataMeter::new(current_accounts_data_len);
+        let remaining_before = accounts_data_meter.remaining();
+
+        let amount = (current_accounts_data_len / 2) as i64;
+        let amount = -amount;
+        let result = accounts_data_meter.consume(amount);
+        assert!(result.is_ok());
+        let remaining_after = accounts_data_meter.remaining();
+        assert_eq!(remaining_after, remaining_before + amount.abs() as u64);
+    }
+
+    #[test]
+    fn test_consume_too_much() {
+        let current_accounts_data_len = 0;
+        let mut accounts_data_meter = AccountsDataMeter::new(current_accounts_data_len);
+
+        // Test: consuming more than what's available (1) returns an error, (2) does not consume
+        let remaining = accounts_data_meter.remaining();
+        let result = accounts_data_meter.consume(remaining as i64 + 1);
+        assert!(result.is_err());
+        assert_eq!(accounts_data_meter.remaining(), remaining);
+    }
+
+    #[test]
+    fn test_consume_zero() {
+        // Pre-condition: set up the accounts data meter such that there is no remaining space
+        let current_accounts_data_len = 1234;
+        let mut accounts_data_meter = AccountsDataMeter::new(current_accounts_data_len);
+        accounts_data_meter.maximum = current_accounts_data_len;
+        assert_eq!(accounts_data_meter.remaining(), 0);
+
+        // Test: can always consume zero, even if there is no remaining space
+        let result = accounts_data_meter.consume(0);
+        assert!(result.is_ok());
+    }
+}