openethereum/util/table/src/lib.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/>.
//! A collection associating pair of keys (row and column) with a single value.
use std::hash::Hash;
use std::collections::HashMap;
/// Structure to hold double-indexed values
///
/// You can obviously use `HashMap<(Row,Col), Val>`, but this structure gives
/// you better access to all `Columns` in Specific `Row`. Namely you can get sub-hashmap
/// `HashMap<Col, Val>` for specific `Row`
#[derive(Default, Debug, PartialEq)]
pub struct Table<Row, Col, Val>
where Row: Eq + Hash + Clone,
Col: Eq + Hash {
map: HashMap<Row, HashMap<Col, Val>>,
}
impl<Row, Col, Val> Table<Row, Col, Val>
where Row: Eq + Hash + Clone,
Col: Eq + Hash {
/// Creates new Table
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pub fn new() -> Self {
Table {
map: HashMap::new(),
}
}
/// Removes all elements from this Table
pub fn clear(&mut self) {
self.map.clear();
}
/// Returns length of the Table (number of (row, col, val) tuples)
pub fn len(&self) -> usize {
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self.map.values().fold(0, |acc, v| acc + v.len())
}
/// Check if there is any element in this Table
pub fn is_empty(&self) -> bool {
self.map.is_empty() || self.map.values().all(|v| v.is_empty())
}
/// Get mutable reference for single Table row.
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pub fn row_mut(&mut self, row: &Row) -> Option<&mut HashMap<Col, Val>> {
self.map.get_mut(row)
}
/// Checks if row is defined for that table (note that even if defined it might be empty)
pub fn has_row(&self, row: &Row) -> bool {
self.map.contains_key(row)
}
/// Get immutable reference for single row in this Table
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pub fn row(&self, row: &Row) -> Option<&HashMap<Col, Val>> {
self.map.get(row)
}
/// Get element in cell described by `(row, col)`
pub fn get(&self, row: &Row, col: &Col) -> Option<&Val> {
self.map.get(row).and_then(|r| r.get(col))
}
/// Remove value from specific cell
///
/// It will remove the row if it's the last value in it
pub fn remove(&mut self, row: &Row, col: &Col) -> Option<Val> {
let (val, is_empty) = {
let row_map = self.map.get_mut(row);
if let None = row_map {
return None;
}
let mut row_map = row_map.unwrap();
let val = row_map.remove(col);
(val, row_map.is_empty())
};
// Clean row
if is_empty {
self.map.remove(row);
}
val
}
/// Remove given row from Table if there are no values defined in it
///
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/// When using `#row_mut` it may happen that all values from some row are drained.
/// Table however will not be aware that row is empty.
/// You can use this method to explicitly remove row entry from the Table.
pub fn clear_if_empty(&mut self, row: &Row) {
let is_empty = self.map.get(row).map_or(false, |m| m.is_empty());
if is_empty {
self.map.remove(row);
}
}
/// Inserts new value to specified cell
///
/// Returns previous value (if any)
pub fn insert(&mut self, row: Row, col: Col, val: Val) -> Option<Val> {
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self.map.entry(row).or_insert_with(HashMap::new).insert(col, val)
}
}
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#[cfg(test)]
mod test {
use super::*;
#[test]
fn should_create_empty_table() {
// when
let table : Table<usize, usize, bool> = Table::new();
// then
assert!(table.is_empty());
assert_eq!(table.len(), 0);
}
#[test]
fn should_insert_elements_and_return_previous_if_any() {
// given
let mut table = Table::new();
// when
let r1 = table.insert(5, 4, true);
let r2 = table.insert(10, 4, true);
let r3 = table.insert(10, 10, true);
let r4 = table.insert(10, 10, false);
// then
assert!(r1.is_none());
assert!(r2.is_none());
assert!(r3.is_none());
assert!(r4.is_some());
assert!(!table.is_empty());
assert_eq!(r4.unwrap(), true);
assert_eq!(table.len(), 3);
}
#[test]
fn should_remove_element() {
// given
let mut table = Table::new();
table.insert(5, 4, true);
assert!(!table.is_empty());
assert_eq!(table.len(), 1);
// when
let r = table.remove(&5, &4);
// then
assert!(table.is_empty());
assert_eq!(table.len() ,0);
assert_eq!(r.unwrap(), true);
}
#[test]
fn should_return_none_if_trying_to_remove_non_existing_element() {
// given
let mut table : Table<usize, usize, usize> = Table::new();
assert!(table.is_empty());
// when
let r = table.remove(&5, &4);
// then
assert!(r.is_none());
}
#[test]
fn should_clear_row_if_removing_last_element() {
// given
let mut table = Table::new();
table.insert(5, 4, true);
assert!(table.has_row(&5));
// when
let r = table.remove(&5, &4);
// then
assert!(r.is_some());
assert!(!table.has_row(&5));
}
#[test]
fn should_return_element_given_row_and_col() {
// given
let mut table = Table::new();
table.insert(1551, 1234, 123);
// when
let r1 = table.get(&1551, &1234);
let r2 = table.get(&5, &4);
// then
assert!(r1.is_some());
assert!(r2.is_none());
assert_eq!(r1.unwrap(), &123);
}
#[test]
fn should_clear_table() {
// given
let mut table = Table::new();
table.insert(1, 1, true);
table.insert(1, 2, false);
table.insert(2, 2, false);
assert_eq!(table.len(), 3);
// when
table.clear();
// then
assert!(table.is_empty());
assert_eq!(table.len(), 0);
assert_eq!(table.has_row(&1), false);
assert_eq!(table.has_row(&2), false);
}
#[test]
fn should_return_mutable_row() {
// given
let mut table = Table::new();
table.insert(1, 1, true);
table.insert(1, 2, false);
table.insert(2, 2, false);
// when
{
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let mut row = table.row_mut(&1).unwrap();
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row.remove(&1);
row.remove(&2);
}
assert!(table.has_row(&1));
table.clear_if_empty(&1);
// then
assert!(!table.has_row(&1));
assert_eq!(table.len(), 1);
}
}