diff --git a/util/src/lib.rs b/util/src/lib.rs index 2a47eb438..ea60418db 100644 --- a/util/src/lib.rs +++ b/util/src/lib.rs @@ -144,6 +144,7 @@ pub mod network; pub mod log; pub mod panics; pub mod keys; +pub mod table; pub use common::*; pub use misc::*; diff --git a/util/src/table.rs b/util/src/table.rs new file mode 100644 index 000000000..572d81f84 --- /dev/null +++ b/util/src/table.rs @@ -0,0 +1,122 @@ +// 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 . + +//! 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` for specific `Row` +pub struct Table + where Row: Eq + Hash + Clone, + Col: Eq + Hash { + map: HashMap>, +} + +impl Table + where Row: Eq + Hash + Clone, + Col: Eq + Hash { + /// Creates new Table + pub fn new() -> Table { + 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 { + self.map.iter().fold(0, |acc, (_k, v)| acc + v.len()) + } + + /// Check if there is any element in this Table + pub fn is_empty(&self) -> bool { + self.len() == 0 + } + + /// Get mutable reference for single Table row. + pub fn get_row_mut(&mut self, row: &Row) -> Option<&mut HashMap> { + 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 + pub fn get_row(&self, row: &Row) -> Option<&HashMap> { + 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 { + 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 + /// + /// When using `#get_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 { + if !self.map.contains_key(&row) { + let m = HashMap::new(); + self.map.insert(row.clone(), m); + } + + let mut columns = self.map.get_mut(&row).unwrap(); + columns.insert(col, val) + } +}