     1
     2
     3
     4
     5
     6
     7
     8
     9
    10
    11
    12
    13
    14
    15
    16
    17
    18
    19
    20
    21
    22
    23
    24
    25
    26
    27
    28
    29
    30
    31
    32
    33
    34
    35
    36
    37
    38
    39
    40
    41
    42
    43
    44
    45
    46
    47
    48
    49
    50
    51
    52
    53
    54
    55
    56
    57
    58
    59
    60
    61
    62
    63
    64
    65
    66
    67
    68
    69
    70
    71
    72
    73
    74
    75
    76
    77

    // Copyright 2015-2017 Parity Technologies (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/>.

    use std::collections::{VecDeque, HashSet};
    use std::hash::Hash;

    const COLLECTION_QUEUE_SIZE: usize = 8;

    pub struct CacheManager<T> where T: Eq + Hash {
    	pref_cache_size: usize,
    	max_cache_size: usize,
    	bytes_per_cache_entry: usize,
    	cache_usage: VecDeque<HashSet<T>>
    }

    impl<T> CacheManager<T> where T: Eq + Hash {
    	pub fn new(pref_cache_size: usize, max_cache_size: usize, bytes_per_cache_entry: usize) -> Self {
    		CacheManager {
    			pref_cache_size: pref_cache_size,
    			max_cache_size: max_cache_size,
    			bytes_per_cache_entry: bytes_per_cache_entry,
    			cache_usage: (0..COLLECTION_QUEUE_SIZE).into_iter().map(|_| Default::default()).collect(),
    		}
    	}

    	pub fn note_used(&mut self, id: T) {
    		if !self.cache_usage[0].contains(&id) {
    			if let Some(c) = self.cache_usage.iter_mut().skip(1).find(|e| e.contains(&id)) {
    				c.remove(&id);
    			}
    			self.cache_usage[0].insert(id);
    		}
    	}

    	/// Collects unused objects from cache.
    	/// First params is the current size of the cache.
    	/// Second one is an with objects to remove. It should also return new size of the cache.
    	pub fn collect_garbage<F>(&mut self, current_size: usize, mut notify_unused: F) where F: FnMut(HashSet<T>) -> usize {
    		if current_size < self.pref_cache_size {
    			self.rotate_cache_if_needed();
    			return;
    		}

    		for _ in 0..COLLECTION_QUEUE_SIZE {
    			if let Some(back) = self.cache_usage.pop_back() {
    				let current_size = notify_unused(back);
    				self.cache_usage.push_front(Default::default());
    				if current_size < self.max_cache_size {
    					break
    				}
    			}
    		}
    	}

    	fn rotate_cache_if_needed(&mut self) {
    		if self.cache_usage.is_empty() { return }

    		if self.cache_usage[0].len() * self.bytes_per_cache_entry > self.pref_cache_size / COLLECTION_QUEUE_SIZE {
    			if let Some(cache) = self.cache_usage.pop_back() {
    				self.cache_usage.push_front(cache);
    			}
    		}
    	}
    }

# Help

## Keyboard Shortcuts

?
  Show this help dialog
S
  Focus the search field
⇤
  Move up in search results
⇥
  Move down in search results
⏎
  Go to active search result
+
  Collapse/expand all sections

## Search Tricks

Prefix searches with a type followed by a colon (e.g. `fn:`) to restrict the search to a given type.

Accepted types are: `fn`, `mod`, `struct`, `enum`, `trait`, `type`, `macro`, and `const`.

Search functions by type signature (e.g. `vec -> usize` or `* -> vec`)