snap_coin/core/
difficulty.rs

1use crate::core::{
2    block::Block,
3    economics::{DIFFICULTY_DECAY_PER_TX, MAX_DIFF_CHANGE, TARGET_TIME, TX_TARGET},
4    utils::{clamp_f, max_256_bui},
5};
6use bincode::{Decode, Encode};
7use num_bigint::BigUint;
8
9pub const STARTING_BLOCK_DIFFICULTY: [u8; 32] = [u8::MAX; 32];
10pub const STARTING_TX_DIFFICULTY: [u8; 32] = [u8::MAX; 32];
11
12#[derive(Encode, Decode, Copy, Clone, Debug)]
13pub struct DifficultyManager {
14    pub block_difficulty: [u8; 32],
15    pub transaction_difficulty: [u8; 32],
16    pub last_timestamp: u64,
17}
18
19/// Manages network difficulty and TX POW difficulty
20impl DifficultyManager {
21    /// Create a new empty Difficulty Manager timestamped now
22    pub fn new(last_timestamp: u64) -> Self {
23        DifficultyManager {
24            block_difficulty: STARTING_BLOCK_DIFFICULTY,
25            transaction_difficulty: STARTING_TX_DIFFICULTY,
26            last_timestamp,
27        }
28    }
29
30    /// Update the network difficulties after adding a new block to the blockchain
31    pub fn update_difficulty(&mut self, new_block: &Block) {
32        // Block difficulty
33        let time_ratio = (clamp_f(
34            (new_block.timestamp.saturating_sub(self.last_timestamp)) as f64 / TARGET_TIME as f64,
35            MAX_DIFF_CHANGE,
36            2.0 - MAX_DIFF_CHANGE,
37        ) * 1000.0) as u64;
38
39        let mut block_big = BigUint::from_bytes_be(&self.block_difficulty);
40        block_big = block_big * BigUint::from(time_ratio) / BigUint::from(1000u64);
41        self.block_difficulty =
42            biguint_to_32_bytes(block_big.min(max_256_bui()).max(BigUint::ZERO));
43
44        // Transaction difficulty
45        let tx_ratio = (clamp_f(
46            TX_TARGET as f64 / new_block.transactions.len() as f64,
47            MAX_DIFF_CHANGE,
48            2.0 - MAX_DIFF_CHANGE,
49        ) * 1000.0) as u64;
50
51        let mut tx_big = BigUint::from_bytes_be(&self.transaction_difficulty);
52        tx_big = tx_big * BigUint::from(tx_ratio) / BigUint::from(1000u64);
53        self.transaction_difficulty = biguint_to_32_bytes(tx_big.min(max_256_bui()).max(BigUint::ZERO));
54
55        // Update last timestamp
56        self.last_timestamp = new_block.timestamp;
57    }
58}
59
60/// Calculate blockchain block difficulty transaction decay based on the current, base difficulty and amount of transactions in block
61pub fn calculate_block_difficulty(block_difficulty: &[u8; 32], tx_count: usize) -> [u8; 32] {
62    let big = BigUint::from_bytes_be(block_difficulty);
63    biguint_to_32_bytes(
64        (big * BigUint::from(((1f64 + DIFFICULTY_DECAY_PER_TX * tx_count as f64) * 1000f64) as u64)
65            / BigUint::from(1000u64)).min(max_256_bui()),
66    )
67}
68
69fn biguint_to_32_bytes(value: BigUint) -> [u8; 32] {
70    let mut bytes = value.to_bytes_be();
71    if bytes.len() < 32 {
72        let mut padded = vec![0u8; 32 - bytes.len()];
73        padded.extend(bytes);
74        bytes = padded;
75    } else if bytes.len() > 32 {
76        bytes = bytes[bytes.len() - 32..].to_vec();
77    }
78    let mut array = [0u8; 32];
79    array.copy_from_slice(&bytes);
80    array
81}
snap_coin/core/difficulty.rs

snap_coin/core/
difficulty.rs
