openethereum/sync/src/range_collection.rs

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// Copyright 2015, 2016 Ethcore (UK) Ltd.
// This file is part of Parity.
// Parity is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// Parity is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License
// along with Parity. If not, see <http://www.gnu.org/licenses/>.
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/// This module defines a trait for a collection of ranged values and an implementation
/// for this trait over sorted vector.
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use std::ops::{Add, Sub, Range};
pub trait ToUsize {
fn to_usize(&self) -> usize;
}
pub trait FromUsize {
fn from_usize(s: usize) -> Self;
}
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/// A key-value collection orderd by key with sequential key-value pairs grouped together.
/// Such group is called a range.
/// E.g. a set of collection of 5 pairs {1, a}, {2, b}, {10, x}, {11, y}, {12, z} will be grouped into two ranges: {1, [a,b]}, {10, [x,y,z]}
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pub trait RangeCollection<K, V> {
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/// Check if the given key is present in the collection.
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fn have_item(&self, key: &K) -> bool;
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/// Get value by key.
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fn find_item(&self, key: &K) -> Option<&V>;
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/// Get a range of keys from `key` till the end of the range that has `key`
/// Returns an empty range is key does not exist.
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fn get_tail(&mut self, key: &K) -> Range<K>;
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/// Remove all elements < `start` in the range that contains `start` - 1
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fn remove_head(&mut self, start: &K);
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/// Remove all elements >= `start` in the range that contains `start`
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fn remove_tail(&mut self, start: &K);
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/// Remove all elements >= `tail`
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fn insert_item(&mut self, key: K, value: V);
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/// Get an iterator over ranges
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fn range_iter(& self) -> RangeIterator<K, V>;
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}
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/// Range iterator. For each range yelds a key for the first element of the range and a vector of values.
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pub struct RangeIterator<'c, K:'c, V:'c> {
range: usize,
collection: &'c Vec<(K, Vec<V>)>
}
impl<'c, K:'c, V:'c> Iterator for RangeIterator<'c, K, V> where K: Add<Output = K> + FromUsize + ToUsize + Copy {
type Item = (K, &'c [V]);
// The 'Iterator' trait only requires the 'next' method to be defined. The
// return type is 'Option<T>', 'None' is returned when the 'Iterator' is
// over, otherwise the next value is returned wrapped in 'Some'
fn next(&mut self) -> Option<(K, &'c [V])> {
if self.range > 0 {
self.range -= 1;
}
else {
return None;
}
match self.collection.get(self.range) {
Some(&(ref k, ref vec)) => {
Some((*k, &vec))
},
None => None
}
}
}
impl<K, V> RangeCollection<K, V> for Vec<(K, Vec<V>)> where K: Ord + PartialEq + Add<Output = K> + Sub<Output = K> + Copy + FromUsize + ToUsize {
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fn range_iter(&self) -> RangeIterator<K, V> {
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RangeIterator {
range: self.len(),
collection: self
}
}
fn have_item(&self, key: &K) -> bool {
match self.binary_search_by(|&(k, _)| k.cmp(key).reverse()) {
Ok(_) => true,
Err(index) => match self.get(index) {
Some(&(ref k, ref v)) => k <= key && (*k + FromUsize::from_usize(v.len())) > *key,
_ => false
},
}
}
fn find_item(&self, key: &K) -> Option<&V> {
match self.binary_search_by(|&(k, _)| k.cmp(key).reverse()) {
Ok(index) => self.get(index).unwrap().1.get(0),
Err(index) => match self.get(index) {
Some(&(ref k, ref v)) if k <= key && (*k + FromUsize::from_usize(v.len())) > *key => v.get((*key - *k).to_usize()),
_ => None
},
}
}
fn get_tail(&mut self, key: &K) -> Range<K> {
let kv = *key;
match self.binary_search_by(|&(k, _)| k.cmp(key).reverse()) {
Ok(index) => kv..(kv + FromUsize::from_usize(self[index].1.len())),
Err(index) => {
match self.get_mut(index) {
Some(&mut (ref k, ref mut v)) if k <= key && (*k + FromUsize::from_usize(v.len())) > *key => {
kv..(*k + FromUsize::from_usize(v.len()))
}
_ => kv..kv
}
},
}
}
/// Remove element key and following elements in the same range
fn remove_tail(&mut self, key: &K) {
match self.binary_search_by(|&(k, _)| k.cmp(key).reverse()) {
Ok(index) => { self.remove(index); },
Err(index) =>{
let mut empty = false;
match self.get_mut(index) {
Some(&mut (ref k, ref mut v)) if k <= key && (*k + FromUsize::from_usize(v.len())) > *key => {
v.truncate((*key - *k).to_usize());
empty = v.is_empty();
}
_ => {}
}
if empty {
self.remove(index);
}
},
}
}
/// Remove range elements up to key
fn remove_head(&mut self, key: &K) {
if *key == FromUsize::from_usize(0) {
return
}
let prev = *key - FromUsize::from_usize(1);
match self.binary_search_by(|&(k, _)| k.cmp(key).reverse()) {
Ok(_) => { }, //start of range, do nothing.
Err(index) => {
let mut empty = false;
match self.get_mut(index) {
Some(&mut (ref mut k, ref mut v)) if *k <= prev && (*k + FromUsize::from_usize(v.len())) > prev => {
let tail = v.split_off((*key - *k).to_usize());
empty = tail.is_empty();
let removed = ::std::mem::replace(v, tail);
let new_k = *k + FromUsize::from_usize(removed.len());
::std::mem::replace(k, new_k);
}
_ => {}
}
if empty {
self.remove(index);
}
},
}
}
fn insert_item(&mut self, key: K, value: V) {
assert!(!self.have_item(&key));
let lower = match self.binary_search_by(|&(k, _)| k.cmp(&key).reverse()) {
Ok(index) => index,
Err(index) => index,
};
let mut to_remove: Option<usize> = None;
if lower < self.len() && self[lower].0 + FromUsize::from_usize(self[lower].1.len()) == key {
// extend into existing chunk
self[lower].1.push(value);
}
else {
// insert a new chunk
let range: Vec<V> = vec![value];
self.insert(lower, (key, range));
};
if lower > 0 {
let next = lower - 1;
if next < self.len()
{
{
let (mut next, mut inserted) = self.split_at_mut(lower);
let mut next = next.last_mut().unwrap();
let mut inserted = inserted.first_mut().unwrap();
if next.0 == key + FromUsize::from_usize(1)
{
inserted.1.append(&mut next.1);
to_remove = Some(lower - 1);
}
}
if let Some(r) = to_remove {
self.remove(r);
}
}
}
}
}
#[test]
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#[allow(cyclomatic_complexity)]
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fn test_range() {
use std::cmp::{Ordering};
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let mut ranges: Vec<(u64, Vec<char>)> = Vec::new();
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assert_eq!(ranges.range_iter().next(), None);
assert_eq!(ranges.find_item(&1), None);
assert!(!ranges.have_item(&1));
assert_eq!(ranges.get_tail(&0), 0..0);
ranges.insert_item(17, 'q');
assert_eq!(ranges.range_iter().cmp(vec![(17, &['q'][..])]), Ordering::Equal);
assert_eq!(ranges.find_item(&17), Some(&'q'));
assert!(ranges.have_item(&17));
assert_eq!(ranges.get_tail(&17), 17..18);
ranges.insert_item(18, 'r');
assert_eq!(ranges.range_iter().cmp(vec![(17, &['q', 'r'][..])]), Ordering::Equal);
assert_eq!(ranges.find_item(&18), Some(&'r'));
assert!(ranges.have_item(&18));
assert_eq!(ranges.get_tail(&17), 17..19);
ranges.insert_item(16, 'p');
assert_eq!(ranges.range_iter().cmp(vec![(16, &['p', 'q', 'r'][..])]), Ordering::Equal);
assert_eq!(ranges.find_item(&16), Some(&'p'));
assert_eq!(ranges.find_item(&17), Some(&'q'));
assert_eq!(ranges.find_item(&18), Some(&'r'));
assert!(ranges.have_item(&16));
assert_eq!(ranges.get_tail(&17), 17..19);
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assert_eq!(ranges.get_tail(&16), 16..19);
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ranges.insert_item(2, 'b');
assert_eq!(ranges.range_iter().cmp(vec![(2, &['b'][..]), (16, &['p', 'q', 'r'][..])]), Ordering::Equal);
assert_eq!(ranges.find_item(&2), Some(&'b'));
ranges.insert_item(3, 'c');
ranges.insert_item(4, 'd');
assert_eq!(ranges.get_tail(&3), 3..5);
assert_eq!(ranges.range_iter().cmp(vec![(2, &['b', 'c', 'd'][..]), (16, &['p', 'q', 'r'][..])]), Ordering::Equal);
let mut r = ranges.clone();
r.remove_head(&1);
assert_eq!(r.range_iter().cmp(vec![(2, &['b', 'c', 'd'][..]), (16, &['p', 'q', 'r'][..])]), Ordering::Equal);
r.remove_head(&2);
assert_eq!(r.range_iter().cmp(vec![(2, &['b', 'c', 'd'][..]), (16, &['p', 'q', 'r'][..])]), Ordering::Equal);
r.remove_head(&3);
assert_eq!(r.range_iter().cmp(vec![(3, &['c', 'd'][..]), (16, &['p', 'q', 'r'][..])]), Ordering::Equal);
r.remove_head(&10);
assert_eq!(r.range_iter().cmp(vec![(3, &['c', 'd'][..]), (16, &['p', 'q', 'r'][..])]), Ordering::Equal);
r.remove_head(&5);
assert_eq!(r.range_iter().cmp(vec![(16, &['p', 'q', 'r'][..])]), Ordering::Equal);
r.remove_head(&19);
assert_eq!(r.range_iter().next(), None);
let mut r = ranges.clone();
r.remove_tail(&20);
assert_eq!(r.range_iter().cmp(vec![(2, &['b', 'c', 'd'][..]), (16, &['p', 'q', 'r'][..])]), Ordering::Equal);
r.remove_tail(&17);
assert_eq!(r.range_iter().cmp(vec![(2, &['b', 'c', 'd'][..]), (16, &['p'][..])]), Ordering::Equal);
r.remove_tail(&16);
assert_eq!(r.range_iter().cmp(vec![(2, &['b', 'c', 'd'][..])]), Ordering::Equal);
r.remove_tail(&3);
assert_eq!(r.range_iter().cmp(vec![(2, &['b'][..])]), Ordering::Equal);
r.remove_tail(&2);
assert_eq!(r.range_iter().next(), None);
}