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// Copyright (C) 2023 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//! A Buffer Pool containing and managing HardwareBuffers
use std::{
collections::HashMap,
sync::{Arc, Mutex, Weak},
};
use nativewindow::*;
use crate::StreamConfig;
use super::{Buffer, BufferOwner};
pub(super) struct BufferPoolInner {
size: usize,
hardware_buffers: HashMap<u64, HardwareBuffer>,
available_buffers: Vec<u64>,
}
impl BufferPoolInner {
pub(super) fn return_buffer(&mut self, buffer_id: u64) {
assert!(self.hardware_buffers.contains_key(&buffer_id));
assert!(!self.available_buffers.contains(&buffer_id));
self.available_buffers.push(buffer_id);
}
}
struct BufferPoolOwner(Weak<Mutex<BufferPoolInner>>);
impl BufferOwner for BufferPoolOwner {
fn on_return(&self, buffer: &Buffer) {
if let Some(locked_buffer_pool) = self.0.upgrade() {
let mut buffer_pool = locked_buffer_pool.lock().unwrap();
buffer_pool.return_buffer(buffer.id());
}
}
}
/// A thread-safe collection of buffers.
///
/// A buffer pool can be of arbitrary size. It creates and then holds references to all buffers
/// associated with it.
pub struct BufferPool(Arc<Mutex<BufferPoolInner>>);
impl BufferPool {
/// Creates a new buffer pool of size pool_size. All buffers will be created according to
/// the stream config.
///
/// This constructor creates all buffers at initialization.
pub fn new(pool_size: usize, stream_config: StreamConfig) -> Option<Self> {
let mut hardware_buffers = HashMap::new();
let mut available_buffers = Vec::new();
for _ in 0..pool_size {
if let Some(buffer) = stream_config.create_hardware_buffer() {
available_buffers.push(buffer.id());
hardware_buffers.insert(buffer.id(), buffer);
} else {
return None;
}
}
Some(Self(Arc::new(Mutex::new(BufferPoolInner {
size: pool_size,
hardware_buffers,
available_buffers,
}))))
}
/// Try to acquire the next available buffer in the buffer pool.
///
/// If all buffers are in use it will return None.
pub fn next_buffer(&mut self) -> Option<Buffer> {
let mut inner = self.0.lock().unwrap();
if let Some(buffer_id) = inner.available_buffers.pop() {
Some(Buffer::new(
Box::new(BufferPoolOwner(Arc::downgrade(&self.0))),
inner.hardware_buffers[&buffer_id].clone(),
))
} else {
None
}
}
/// Gets the size of the buffer pool.
pub fn size(&self) -> usize {
let inner = self.0.lock().unwrap();
inner.size
}
}
#[cfg(test)]
mod test {
use super::*;
const STREAM_CONFIG: StreamConfig = StreamConfig {
width: 1,
height: 1,
layers: 1,
format: AHardwareBuffer_Format::AHARDWAREBUFFER_FORMAT_R8G8B8A8_UNORM,
usage: AHardwareBuffer_UsageFlags::AHARDWAREBUFFER_USAGE_CPU_READ_OFTEN,
stride: 0,
};
#[test]
fn buffer_pool_next_buffer() {
let mut buffer_pool = BufferPool::new(1, STREAM_CONFIG).unwrap();
let next_buffer = buffer_pool.next_buffer();
assert!(next_buffer.is_some());
assert!(buffer_pool.next_buffer().is_none());
}
#[test]
fn drop_buffer_returns_to_pool() {
let mut buffer_pool = BufferPool::new(1, STREAM_CONFIG).unwrap();
let next_buffer = buffer_pool.next_buffer();
assert!(next_buffer.is_some());
drop(next_buffer);
assert!(buffer_pool.next_buffer().is_some());
}
}
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