cfx_storage/impls/delta_mpt/
row_number.rs

1// Copyright 2019 Conflux Foundation. All rights reserved.
2// Conflux is free software and distributed under GNU General Public License.
3// See http://www.gnu.org/licenses/
4
5use super::super::errors::*;
6// TODO: make it Delta MPT only. Add another type for Persistent MPT later.
7#[cfg(not(feature = "u64_mpt_db_key"))]
8pub type RowNumberUnderlyingType = u32;
9#[cfg(feature = "u64_mpt_db_key")]
10pub type RowNumberUnderlyingType = u64;
11/// Because the Merkle Hash is too large to store for links to children in MPT,
12/// and it's only useful for persistence, in delta MPT we use row number as
13/// storage key.
14///
15/// Using RowNumber as node index is also more space/time efficient than other
16/// Maps in standard library, given that our goal of
17#[derive(Copy, Clone, Default)]
18pub struct RowNumber {
19    pub value: RowNumberUnderlyingType,
20}
21
22impl RowNumber {
23    /// It's an error for row number to go higher than max u32 4_294_967_296. It
24    /// shouldn't happen because for 2h lifetime it requires 596523 nodes /
25    /// sec.
26    pub const ROW_NUMBER_LIMIT: RowNumberUnderlyingType =
27        1 << (RowNumberUnderlyingType::BITS - 1) - 1;
28
29    pub fn get_next(&self) -> Result<RowNumber> {
30        if self.value != Self::ROW_NUMBER_LIMIT {
31            Ok(Self {
32                value: self.value + 1,
33            })
34        } else {
35            Err(Error::MPTTooManyNodes.into())
36        }
37    }
38}
39
40impl ToString for RowNumber {
41    fn to_string(&self) -> String { self.value.to_string() }
42}
cfx_storage/impls/delta_mpt/row_number.rs

cfx_storage/impls/delta_mpt/
row_number.rs
