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| 1 | +// Copyright (c) 2019-2025 Provable Inc. |
| 2 | +// This file is part of the snarkVM library. |
| 3 | + |
| 4 | +// Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | +// you may not use this file except in compliance with the License. |
| 6 | +// You may obtain a copy of the License at: |
| 7 | + |
| 8 | +// http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | + |
| 10 | +// Unless required by applicable law or agreed to in writing, software |
| 11 | +// distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | +// See the License for the specific language governing permissions and |
| 14 | +// limitations under the License. |
| 15 | + |
| 16 | +use crate::block::{Block, Network}; |
| 17 | + |
| 18 | +use snarkvm_utilities::ensure_equals; |
| 19 | + |
| 20 | +use std::collections::VecDeque; |
| 21 | + |
| 22 | +use anyhow::{Result, ensure}; |
| 23 | + |
| 24 | +/// Helper struct for caching the most recent blocks. |
| 25 | +pub(super) struct BlockCache<N: Network> { |
| 26 | + /// Contains the most recent blocks ordered by height. |
| 27 | + /// We do not use a BTreeMap here as the cache is small and updates to a vector are more efficient |
| 28 | + /// |
| 29 | + /// Invariant: all entries in this vector (except the first) a height equal to h+1 (where h` is the previous block entry) |
| 30 | + blocks: VecDeque<Block<N>>, |
| 31 | +} |
| 32 | + |
| 33 | +impl<N: Network> BlockCache<N> { |
| 34 | + /// The maximum size of the cache in blocks. |
| 35 | + pub(super) const BLOCK_CACHE_SIZE: u32 = 10; |
| 36 | + |
| 37 | + /// Initialize the cache with the given blocks. |
| 38 | + pub fn new(blocks: Vec<Block<N>>) -> Result<Self> { |
| 39 | + ensure!(blocks.len() <= Self::BLOCK_CACHE_SIZE as usize, "Too many blocks to fit in the cache"); |
| 40 | + |
| 41 | + if let Some(block) = blocks.first() { |
| 42 | + ensure!(block.height() != 0, "Cannot cache the genesis block"); |
| 43 | + } |
| 44 | + for idx in 1..blocks.len() { |
| 45 | + ensure!(blocks[idx - 1].height() + 1 == blocks[idx].height(), "Not a continuous chain of blocks"); |
| 46 | + } |
| 47 | + |
| 48 | + Ok(Self { blocks: VecDeque::from(blocks) }) |
| 49 | + } |
| 50 | + |
| 51 | + /// Insert a new block into the cache. |
| 52 | + /// Must be the successor of the last block inserted into the cache. |
| 53 | + #[inline] |
| 54 | + pub fn insert(&mut self, block: Block<N>) -> Result<()> { |
| 55 | + ensure!(block.height() != 0, "Cannot cache the genesis block"); |
| 56 | + |
| 57 | + if let Some(prev) = self.blocks.back() { |
| 58 | + ensure_equals!( |
| 59 | + prev.height() + 1, |
| 60 | + block.height(), |
| 61 | + "Block is not the successor of the last block inserted into the cache" |
| 62 | + ); |
| 63 | + } |
| 64 | + |
| 65 | + self.blocks.push_back(block.clone()); |
| 66 | + if self.blocks.len() > (Self::BLOCK_CACHE_SIZE as usize) { |
| 67 | + self.blocks.pop_front(); |
| 68 | + } |
| 69 | + |
| 70 | + Ok(()) |
| 71 | + } |
| 72 | + |
| 73 | + /// Return the block at the given height if it is in the cache.i |
| 74 | + #[inline] |
| 75 | + pub fn get_block(&self, block_height: u32) -> Option<&Block<N>> { |
| 76 | + let first_block = self.blocks.front()?; |
| 77 | + |
| 78 | + // Determine to location of the cached block (if any). |
| 79 | + // This returns `None` if `block_height` is lower than the height of the first cached block. |
| 80 | + let offset = block_height.checked_sub(first_block.height())?; |
| 81 | + |
| 82 | + self.blocks.get(offset as usize) |
| 83 | + } |
| 84 | + |
| 85 | + /// Return the block with the given hash if it is in the cache. |
| 86 | + #[inline] |
| 87 | + pub fn get_block_by_hash(&self, block_hash: &N::BlockHash) -> Option<&Block<N>> { |
| 88 | + // Perform a linear search through the cache. |
| 89 | + // This is cheap, as the cache is very small. |
| 90 | + self.blocks.iter().find(|block| &block.hash() == block_hash) |
| 91 | + } |
| 92 | + |
| 93 | + /// Remove the last `n` blocks from the cache. |
| 94 | + #[inline] |
| 95 | + pub fn remove_last_n(&mut self, n: u32) -> Result<()> { |
| 96 | + for _ in 0..n { |
| 97 | + self.blocks.pop_back(); |
| 98 | + } |
| 99 | + Ok(()) |
| 100 | + } |
| 101 | +} |
| 102 | + |
| 103 | +#[cfg(test)] |
| 104 | +mod tests { |
| 105 | + use super::*; |
| 106 | + |
| 107 | + use crate::test_helpers::CurrentNetwork; |
| 108 | + |
| 109 | + use snarkvm_console::{ |
| 110 | + account::{Field, PrivateKey}, |
| 111 | + prelude::{Rng, TestRng}, |
| 112 | + }; |
| 113 | + use snarkvm_ledger_authority::Authority; |
| 114 | + use snarkvm_ledger_block::{Header, Metadata, Ratifications, Transactions}; |
| 115 | + |
| 116 | + type BlockCache = super::BlockCache<CurrentNetwork>; |
| 117 | + |
| 118 | + #[test] |
| 119 | + fn eviction() { |
| 120 | + // The number of blocks to insert during the test |
| 121 | + // (must be more than the cache size) |
| 122 | + const NUM_BLOCKS: u32 = 15; |
| 123 | + const { assert!(NUM_BLOCKS > BlockCache::BLOCK_CACHE_SIZE) }; |
| 124 | + |
| 125 | + let rng = &mut TestRng::default(); |
| 126 | + let private_key = PrivateKey::<CurrentNetwork>::new(rng).unwrap(); |
| 127 | + |
| 128 | + // Construct a chain of blocks. |
| 129 | + let mut previous_hash = None; |
| 130 | + let blocks: Vec<_> = (0..NUM_BLOCKS) |
| 131 | + .map(|h| { |
| 132 | + let transactions = Transactions::from(&[]); |
| 133 | + let ratifications = Ratifications::try_from(vec![]).unwrap(); |
| 134 | + let header = if h == 0 { |
| 135 | + Header::genesis(&ratifications, &transactions, vec![]).unwrap() |
| 136 | + } else { |
| 137 | + // Use mock metadata to save compute time. |
| 138 | + let metadata = Metadata::new( |
| 139 | + CurrentNetwork::ID, |
| 140 | + (h * 2) as u64, |
| 141 | + h, |
| 142 | + 0, |
| 143 | + (h * 1000) as u128, |
| 144 | + CurrentNetwork::GENESIS_COINBASE_TARGET, |
| 145 | + CurrentNetwork::GENESIS_PROOF_TARGET + 1, |
| 146 | + CurrentNetwork::GENESIS_COINBASE_TARGET, |
| 147 | + CurrentNetwork::GENESIS_TIMESTAMP + ((h - 1) * 100) as i64, |
| 148 | + CurrentNetwork::GENESIS_TIMESTAMP + (h * 100) as i64, |
| 149 | + ) |
| 150 | + .unwrap(); |
| 151 | + |
| 152 | + let previous_state_root: <CurrentNetwork as Network>::StateRoot = rng.r#gen(); |
| 153 | + Header::<CurrentNetwork>::from( |
| 154 | + previous_state_root, |
| 155 | + Field::from_u32(1), |
| 156 | + Field::from_u32(1), |
| 157 | + Field::from_u32(1), |
| 158 | + Field::from_u32(1), |
| 159 | + Field::from_u32(1), |
| 160 | + metadata, |
| 161 | + ) |
| 162 | + .unwrap() |
| 163 | + }; |
| 164 | + let block_hash = rng.r#gen(); |
| 165 | + let authority = Authority::<CurrentNetwork>::new_beacon(&private_key, block_hash, rng).unwrap(); |
| 166 | + |
| 167 | + let block = Block::from_unchecked( |
| 168 | + block_hash.into(), |
| 169 | + previous_hash.unwrap_or_default(), |
| 170 | + header, |
| 171 | + authority, |
| 172 | + ratifications, |
| 173 | + None.into(), |
| 174 | + vec![], |
| 175 | + transactions, |
| 176 | + vec![], |
| 177 | + ) |
| 178 | + .unwrap(); |
| 179 | + |
| 180 | + previous_hash = Some(block.hash()); |
| 181 | + block |
| 182 | + }) |
| 183 | + .collect(); |
| 184 | + |
| 185 | + let mut cache = BlockCache::new(vec![]).unwrap(); |
| 186 | + let mut blocks = blocks.into_iter().skip(1); |
| 187 | + |
| 188 | + // First, fill up the cache. |
| 189 | + while cache.blocks.len() < (BlockCache::BLOCK_CACHE_SIZE as usize) { |
| 190 | + cache.insert(blocks.next().unwrap()).unwrap(); |
| 191 | + } |
| 192 | + |
| 193 | + // Then, continue insertions and check that old blocks are evicted. |
| 194 | + for block in blocks { |
| 195 | + let hash = block.hash(); |
| 196 | + let height = block.height(); |
| 197 | + |
| 198 | + cache.insert(block).unwrap(); |
| 199 | + |
| 200 | + // Ensure eviction work. |
| 201 | + assert_eq!(cache.blocks.len(), BlockCache::BLOCK_CACHE_SIZE as usize); |
| 202 | + |
| 203 | + // Ensure the correct block is returned. |
| 204 | + let ret1 = cache.get_block(height).unwrap(); |
| 205 | + let ret2 = cache.get_block_by_hash(&hash).unwrap(); |
| 206 | + |
| 207 | + assert_eq!(ret1.hash(), hash); |
| 208 | + assert_eq!(ret2.hash(), hash); |
| 209 | + assert_eq!(ret1.height(), height); |
| 210 | + assert_eq!(ret2.height(), height); |
| 211 | + |
| 212 | + assert_eq!(cache.blocks[0].height(), height - BlockCache::BLOCK_CACHE_SIZE + 1); |
| 213 | + } |
| 214 | + |
| 215 | + // Fetch something that isn't the last block. |
| 216 | + let block = cache.get_block(10).unwrap(); |
| 217 | + assert_eq!(block.height(), 10); |
| 218 | + |
| 219 | + // Fetch the last thing that must be in the cache. |
| 220 | + assert!(cache.get_block(NUM_BLOCKS - BlockCache::BLOCK_CACHE_SIZE).is_some()); |
| 221 | + // Fetch something that must not be in the cache. |
| 222 | + assert!(cache.get_block(NUM_BLOCKS - BlockCache::BLOCK_CACHE_SIZE - 1).is_none()); |
| 223 | + } |
| 224 | +} |
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