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Add buffer_map.rs; implement LayerBuffer recycling
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eschweic
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Aug 20, 2013
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,135 @@ | ||
| /* This Source Code Form is subject to the terms of the Mozilla Public | ||
| * License, v. 2.0. If a copy of the MPL was not distributed with this | ||
| * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ | ||
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| use std::hashmap::HashMap; | ||
| use std::to_bytes::Cb; | ||
| use geom::size::Size2D; | ||
| use servo_msg::compositor_msg::Tile; | ||
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| /// This is a struct used to store buffers when they are not in use. | ||
| /// The render task can quickly query for a particular size of buffer when it | ||
| /// needs it. | ||
| pub struct BufferMap<T> { | ||
| /// A HashMap that stores the Buffers. | ||
| map: HashMap<BufferKey, BufferValue<T>>, | ||
| /// The current amount of memory stored by the BufferMap's buffers. | ||
| mem: uint, | ||
| /// The maximum allowed memory. Unused buffers willl be deleted | ||
| /// when this threshold is exceeded. | ||
| max_mem: uint, | ||
| /// A monotonically increasing counter to track how recently tile sizes were used. | ||
| counter: uint, | ||
| } | ||
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| /// A key with which to store buffers. It is based on the size of the buffer. | ||
| struct BufferKey([uint, ..2]); | ||
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| impl IterBytes for BufferKey { | ||
| fn iter_bytes(&self, lsb0: bool, f: Cb) -> bool { | ||
| let i = if lsb0 {0} else {1}; | ||
| self[i].iter_bytes(lsb0, |x| f(x)) && self[1 - i].iter_bytes(lsb0, |x| f(x)) | ||
| } | ||
| } | ||
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| impl Eq for BufferKey { | ||
| fn eq(&self, other: &BufferKey) -> bool { | ||
| self[0] == other[0] && self[1] == other[1] | ||
| } | ||
| } | ||
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| /// Create a key from a given size | ||
| impl BufferKey { | ||
| fn get(input: Size2D<uint>) -> BufferKey { | ||
| BufferKey([input.width, input.height]) | ||
| } | ||
| } | ||
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| /// A helper struct to keep track of buffers in the HashMap | ||
| struct BufferValue<T> { | ||
| /// An array of buffers, all the same size | ||
| buffers: ~[T], | ||
| /// The counter when this size was last requested | ||
| last_action: uint, | ||
| } | ||
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| impl<T: Tile> BufferMap<T> { | ||
| // Creates a new BufferMap with a given buffer limit. | ||
| pub fn new(max_mem: uint) -> BufferMap<T> { | ||
| BufferMap { | ||
| map: HashMap::new(), | ||
| mem: 0u, | ||
| max_mem: max_mem, | ||
| counter: 0u, | ||
| } | ||
| } | ||
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| // Insert a new buffer into the map. | ||
| pub fn insert(&mut self, new_buffer: T) { | ||
| let new_key = BufferKey::get(new_buffer.get_size_2d()); | ||
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| // If all our buffers are the same size and we're already at our | ||
| // memory limit, no need to store this new buffer; just let it drop. | ||
| if self.mem + new_buffer.get_mem() > self.max_mem && self.map.len() == 1 && | ||
| self.map.contains_key(&new_key) { | ||
| return; | ||
| } | ||
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| self.mem += new_buffer.get_mem(); | ||
| // use lazy insertion function to prevent unnecessary allocation | ||
| self.map.find_or_insert_with(new_key, |_| BufferValue { | ||
| buffers: ~[], | ||
| last_action: self.counter | ||
| }).buffers.push(new_buffer); | ||
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| let mut opt_key: Option<BufferKey> = None; | ||
| while self.mem > self.max_mem { | ||
| let old_key = match opt_key { | ||
| Some(key) => key, | ||
| None => { | ||
| match self.map.iter().min_by(|&(_, x)| x.last_action) { | ||
| Some((k, _)) => *k, | ||
| None => fail!("BufferMap: tried to delete with no elements in map"), | ||
| } | ||
| } | ||
| }; | ||
| if { | ||
| let list = &mut self.map.get_mut(&old_key).buffers; | ||
| self.mem -= list.pop().get_mem(); | ||
| list.is_empty() | ||
| } | ||
| { // then | ||
| self.map.pop(&old_key); // Don't store empty vectors! | ||
| opt_key = None; | ||
| } else { | ||
| opt_key = Some(old_key); | ||
| } | ||
| } | ||
| } | ||
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| // Try to find a buffer for the given size. | ||
| pub fn find(&mut self, size: Size2D<uint>) -> Option<T> { | ||
| let mut flag = false; // True if key needs to be popped after retrieval. | ||
| let key = BufferKey::get(size); | ||
| let ret = match self.map.find_mut(&key) { | ||
| Some(ref mut buffer_val) => { | ||
| buffer_val.last_action = self.counter; | ||
| self.counter += 1; | ||
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| let buffer = buffer_val.buffers.pop(); | ||
| self.mem -= buffer.get_mem(); | ||
| if buffer_val.buffers.is_empty() { | ||
| flag = true; | ||
| } | ||
| Some(buffer) | ||
| } | ||
| None => None, | ||
| }; | ||
|
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| if flag { | ||
| self.map.pop(&key); // Don't store empty vectors! | ||
| } | ||
|
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| ret | ||
| } | ||
| } |
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