1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138
#![cfg_attr(not(test), no_std)] use arrayref::array_ref; use bonsai::expand; use sha2::{Digest, Sha256}; type K = u128; type V = u128; pub struct Oof<'a> { pub keys: &'a [K], pub values: &'a mut [V], pub height: u32, is_dirty: bool, } #[cfg_attr(test, derive(Debug, PartialEq))] pub enum Error { EntryNotFound(K), } impl<'a> Oof<'a> { pub fn new(keys: &'a [K], values: &'a mut [V], height: u32) -> Self { Oof { keys, values, height, is_dirty: false, } } pub fn get(&self, key: &K) -> Option<&V> { match self.keys.binary_search(&key) { Ok(index) => Some(&self.values[index]), Err(_) => None, } } pub fn set(&mut self, key: K, value: V) -> Result<V, Error> { match self.keys.binary_search(&key) { Ok(index) => { let old = self.values[index]; self.values[index] = value; self.is_dirty = true; Ok(old) } Err(_) => Err(Error::EntryNotFound(key)), } } pub fn root(&mut self) -> Result<&V, Error> { if self.is_dirty { self.refresh()?; } Ok(self.get(&1).ok_or(Error::EntryNotFound(1))?) } fn refresh(&mut self) -> Result<(), Error> { let mut position = self.keys.len() - 1; while position > 0 { let (left, right, parent) = expand(self.keys[position]); let left = self.get(&left).ok_or(Error::EntryNotFound(left))?; let right = self.get(&right).ok_or(Error::EntryNotFound(right))?; let mut buf = [0u8; 32]; hash_children(&mut buf, left, right); self.set(parent, u128::from_le_bytes(*array_ref![buf, 0, 16]))?; position -= 1; } self.is_dirty = false; Ok(()) } } fn hash_children(buf: &mut [u8; 32], left: &V, right: &V) { buf[0..16].copy_from_slice(&left.to_le_bytes()); buf[16..32].copy_from_slice(&right.to_le_bytes()); let tmp = Sha256::digest(buf); buf[0..32].copy_from_slice(tmp.as_ref()); } #[cfg(test)] mod tests { use super::*; #[test] fn get() { let oof = Oof { keys: &[1, 2, 3], values: &mut [1, 2, 3], height: 1, is_dirty: false, }; assert_eq!(oof.get(&1), Some(&1)); assert_eq!(oof.get(&2), Some(&2)); assert_eq!(oof.get(&3), Some(&3)); assert_eq!(oof.get(&4), None); } #[test] fn set() { let mut oof = Oof { keys: &[1, 2, 3], values: &mut [1, 2, 3], height: 1, is_dirty: false, }; assert_eq!(oof.set(1, 2), Ok(1)); assert_eq!(oof.set(2, 3), Ok(2)); assert_eq!(oof.set(3, 4), Ok(3)); assert_eq!(oof.set(4, 5), Err(Error::EntryNotFound(4))); } #[test] fn root() { let mut oof = Oof { keys: &[1, 2, 3], values: &mut [1, 2, 3], height: 2, is_dirty: true, }; let mut buf = [0u8; 32]; hash_children(&mut buf, &oof.values[1], &oof.values[2]); let root = u128::from_le_bytes(*array_ref![buf, 0, 16]); assert_eq!(oof.root(), Ok(&root)); } }