miraland_program/
rent.rs

1//! Configuration for network [rent].
2//!
3//! [rent]: https://docs.solana.com/implemented-proposals/rent
4
5#![allow(clippy::arithmetic_side_effects)]
6
7use {crate::clock::DEFAULT_SLOTS_PER_EPOCH, miraland_sdk_macro::CloneZeroed};
8
9/// Configuration of network rent.
10#[repr(C)]
11#[derive(Serialize, Deserialize, PartialEq, CloneZeroed, Debug, AbiExample)]
12pub struct Rent {
13    /// Rental rate in lamports/byte-year.
14    pub lamports_per_byte_year: u64,
15
16    /// Amount of time (in years) a balance must include rent for the account to
17    /// be rent exempt.
18    pub exemption_threshold: f64,
19
20    /// The percentage of collected rent that is burned.
21    ///
22    /// Valid values are in the range [0, 100]. The remaining percentage is
23    /// distributed to validators.
24    pub burn_percent: u8,
25}
26
27/// Default rental rate in lamports/byte-year.
28///
29/// This calculation is based on:
30/// - 10^9 lamports per MLN
31/// - $1 per MLN
32/// - $0.01 per megabyte day
33/// - $3.65 per megabyte year
34pub const DEFAULT_LAMPORTS_PER_BYTE_YEAR: u64 = 1_000_000_000 / 100 * 365 / (1024 * 1024);
35
36/// Default amount of time (in years) the balance has to include rent for the
37/// account to be rent exempt.
38pub const DEFAULT_EXEMPTION_THRESHOLD: f64 = 2.0;
39
40/// Default percentage of collected rent that is burned.
41///
42/// Valid values are in the range [0, 100]. The remaining percentage is
43/// distributed to validators.
44pub const DEFAULT_BURN_PERCENT: u8 = 50;
45
46/// Account storage overhead for calculation of base rent.
47///
48/// This is the number of bytes required to store an account with no data. It is
49/// added to an accounts data length when calculating [`Rent::minimum_balance`].
50pub const ACCOUNT_STORAGE_OVERHEAD: u64 = 128;
51
52impl Default for Rent {
53    fn default() -> Self {
54        Self {
55            lamports_per_byte_year: DEFAULT_LAMPORTS_PER_BYTE_YEAR,
56            exemption_threshold: DEFAULT_EXEMPTION_THRESHOLD,
57            burn_percent: DEFAULT_BURN_PERCENT,
58        }
59    }
60}
61
62impl Rent {
63    /// Calculate how much rent to burn from the collected rent.
64    ///
65    /// The first value returned is the amount burned. The second is the amount
66    /// to distribute to validators.
67    pub fn calculate_burn(&self, rent_collected: u64) -> (u64, u64) {
68        let burned_portion = (rent_collected * u64::from(self.burn_percent)) / 100;
69        (burned_portion, rent_collected - burned_portion)
70    }
71
72    /// Minimum balance due for rent-exemption of a given account data size.
73    pub fn minimum_balance(&self, data_len: usize) -> u64 {
74        let bytes = data_len as u64;
75        (((ACCOUNT_STORAGE_OVERHEAD + bytes) * self.lamports_per_byte_year) as f64
76            * self.exemption_threshold) as u64
77    }
78
79    /// Whether a given balance and data length would be exempt.
80    pub fn is_exempt(&self, balance: u64, data_len: usize) -> bool {
81        balance >= self.minimum_balance(data_len)
82    }
83
84    /// Rent due on account's data length with balance.
85    pub fn due(&self, balance: u64, data_len: usize, years_elapsed: f64) -> RentDue {
86        if self.is_exempt(balance, data_len) {
87            RentDue::Exempt
88        } else {
89            RentDue::Paying(self.due_amount(data_len, years_elapsed))
90        }
91    }
92
93    /// Rent due for account that is known to be not exempt.
94    pub fn due_amount(&self, data_len: usize, years_elapsed: f64) -> u64 {
95        let actual_data_len = data_len as u64 + ACCOUNT_STORAGE_OVERHEAD;
96        let lamports_per_year = self.lamports_per_byte_year * actual_data_len;
97        (lamports_per_year as f64 * years_elapsed) as u64
98    }
99
100    /// Creates a `Rent` that charges no lamports.
101    ///
102    /// This is used for testing.
103    pub fn free() -> Self {
104        Self {
105            lamports_per_byte_year: 0,
106            ..Rent::default()
107        }
108    }
109
110    /// Creates a `Rent` that is scaled based on the number of slots in an epoch.
111    ///
112    /// This is used for testing.
113    pub fn with_slots_per_epoch(slots_per_epoch: u64) -> Self {
114        let ratio = slots_per_epoch as f64 / DEFAULT_SLOTS_PER_EPOCH as f64;
115        let exemption_threshold = DEFAULT_EXEMPTION_THRESHOLD * ratio;
116        let lamports_per_byte_year = (DEFAULT_LAMPORTS_PER_BYTE_YEAR as f64 / ratio) as u64;
117        Self {
118            lamports_per_byte_year,
119            exemption_threshold,
120            ..Self::default()
121        }
122    }
123}
124
125/// The return value of [`Rent::due`].
126#[derive(Debug, Copy, Clone, Eq, PartialEq)]
127pub enum RentDue {
128    /// Used to indicate the account is rent exempt.
129    Exempt,
130    /// The account owes this much rent.
131    Paying(u64),
132}
133
134impl RentDue {
135    /// Return the lamports due for rent.
136    pub fn lamports(&self) -> u64 {
137        match self {
138            RentDue::Exempt => 0,
139            RentDue::Paying(x) => *x,
140        }
141    }
142
143    /// Return 'true' if rent exempt.
144    pub fn is_exempt(&self) -> bool {
145        match self {
146            RentDue::Exempt => true,
147            RentDue::Paying(_) => false,
148        }
149    }
150}
151
152#[cfg(test)]
153mod tests {
154    use super::*;
155
156    #[test]
157    fn test_due() {
158        let default_rent = Rent::default();
159
160        assert_eq!(
161            default_rent.due(0, 2, 1.2),
162            RentDue::Paying(
163                (((2 + ACCOUNT_STORAGE_OVERHEAD) * DEFAULT_LAMPORTS_PER_BYTE_YEAR) as f64 * 1.2)
164                    as u64
165            ),
166        );
167        assert_eq!(
168            default_rent.due(
169                (((2 + ACCOUNT_STORAGE_OVERHEAD) * DEFAULT_LAMPORTS_PER_BYTE_YEAR) as f64
170                    * DEFAULT_EXEMPTION_THRESHOLD) as u64,
171                2,
172                1.2
173            ),
174            RentDue::Exempt,
175        );
176
177        let custom_rent = Rent {
178            lamports_per_byte_year: 5,
179            exemption_threshold: 2.5,
180            ..Rent::default()
181        };
182
183        assert_eq!(
184            custom_rent.due(0, 2, 1.2),
185            RentDue::Paying(
186                (((2 + ACCOUNT_STORAGE_OVERHEAD) * custom_rent.lamports_per_byte_year) as f64 * 1.2)
187                    as u64,
188            )
189        );
190
191        assert_eq!(
192            custom_rent.due(
193                (((2 + ACCOUNT_STORAGE_OVERHEAD) * custom_rent.lamports_per_byte_year) as f64
194                    * custom_rent.exemption_threshold) as u64,
195                2,
196                1.2
197            ),
198            RentDue::Exempt
199        );
200    }
201
202    #[test]
203    fn test_rent_due_lamports() {
204        assert_eq!(RentDue::Exempt.lamports(), 0);
205
206        let amount = 123;
207        assert_eq!(RentDue::Paying(amount).lamports(), amount);
208    }
209
210    #[test]
211    fn test_rent_due_is_exempt() {
212        assert!(RentDue::Exempt.is_exempt());
213        assert!(!RentDue::Paying(0).is_exempt());
214    }
215
216    #[test]
217    fn test_clone() {
218        let rent = Rent {
219            lamports_per_byte_year: 1,
220            exemption_threshold: 2.2,
221            burn_percent: 3,
222        };
223        #[allow(clippy::clone_on_copy)]
224        let cloned_rent = rent.clone();
225        assert_eq!(cloned_rent, rent);
226    }
227}
miraland_program/rent.rs

miraland_program/
rent.rs
