55 lines
1.7 KiB
Rust
55 lines
1.7 KiB
Rust
// Copyright 2015-2017 Parity Technologies (UK) Ltd.
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// This file is part of Parity.
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// Parity is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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// Parity is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//! Canonical hash trie definitions and helper functions.
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/// The size of each CHT.
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pub const SIZE: u64 = 2048;
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/// Convert a block number to a CHT number.
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/// Returns `None` for `block_num` == 0, `Some` otherwise.
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pub fn block_to_cht_number(block_num: u64) -> Option<u64> {
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match block_num {
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0 => None,
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n => Some((n - 1) / SIZE),
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}
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}
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/// Get the starting block of a given CHT.
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/// CHT 0 includes block 1...SIZE,
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/// CHT 1 includes block SIZE + 1 ... 2*SIZE
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/// More generally: CHT N includes block (1 + N*SIZE)...((N+1)*SIZE).
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/// This is because the genesis hash is assumed to be known
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/// and including it would be redundant.
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pub fn start_number(cht_num: u64) -> u64 {
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(cht_num * SIZE) + 1
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}
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#[cfg(test)]
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mod tests {
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#[test]
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fn block_to_cht_number() {
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assert!(::cht::block_to_cht_number(0).is_none());
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assert_eq!(::cht::block_to_cht_number(1).unwrap(), 0);
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assert_eq!(::cht::block_to_cht_number(::cht::SIZE + 1).unwrap(), 1);
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assert_eq!(::cht::block_to_cht_number(::cht::SIZE).unwrap(), 0);
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}
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#[test]
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fn start_number() {
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assert_eq!(::cht::start_number(0), 1);
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assert_eq!(::cht::start_number(1), ::cht::SIZE + 1);
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assert_eq!(::cht::start_number(2), ::cht::SIZE * 2 + 1);
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}
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}
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