pic_scale/
threading_policy.rs

1/*
2 * Copyright (c) Radzivon Bartoshyk. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without modification,
5 * are permitted provided that the following conditions are met:
6 *
7 * 1.  Redistributions of source code must retain the above copyright notice, this
8 * list of conditions and the following disclaimer.
9 *
10 * 2.  Redistributions in binary form must reproduce the above copyright notice,
11 * this list of conditions and the following disclaimer in the documentation
12 * and/or other materials provided with the distribution.
13 *
14 * 3.  Neither the name of the copyright holder nor the names of its
15 * contributors may be used to endorse or promote products derived from
16 * this software without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
19 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
21 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
24 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
25 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
26 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
27 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28 */
29#![forbid(unsafe_code)]
30use rayon::ThreadPool;
31#[cfg(not(target_arch = "wasm32"))]
32use std::num::NonZeroUsize;
33#[cfg(not(target_arch = "wasm32"))]
34use std::thread::available_parallelism;
35
36use crate::ImageSize;
37
38#[repr(C)]
39#[derive(Debug, Copy, Clone, Ord, PartialOrd, Eq, PartialEq)]
40/// Declares thread policy usage
41pub enum ThreadingPolicy {
42    /// Will use only one current thread
43    Single,
44    /// Spawn provided threads count, will not work for wasm - fallback to Single
45    #[cfg(not(target_arch = "wasm32"))]
46    Fixed(usize),
47    /// Computes adaptive thread count between 1...`available parallelism`
48    /// for given image bounds, will not work for wasm - fallback to Single
49    #[cfg(not(target_arch = "wasm32"))]
50    Adaptive,
51}
52
53impl ThreadingPolicy {
54    #[cfg(not(target_arch = "wasm32"))]
55    /// Returns the number of threads to use for the given image dimensions under the
56    /// selected policy variant.
57    pub fn thread_count(&self, for_size: ImageSize) -> usize {
58        match self {
59            ThreadingPolicy::Single => 1,
60            ThreadingPolicy::Fixed(thread_count) => (*thread_count).max(1),
61            ThreadingPolicy::Adaptive => (for_size.width * for_size.height / (256 * 256))
62                .clamp(1, Self::available_parallelism()),
63        }
64    }
65
66    fn available_parallelism() -> usize {
67        available_parallelism()
68            .unwrap_or_else(|_| NonZeroUsize::new(1).unwrap())
69            .get()
70    }
71
72    #[cfg(target_arch = "wasm32")]
73    pub fn thread_count(&self, _: ImageSize) -> usize {
74        1
75    }
76}
77
78impl ThreadingPolicy {
79    #[cfg(not(target_arch = "wasm32"))]
80    pub fn get_pool(&self, for_size: ImageSize) -> Option<ThreadPool> {
81        if *self == ThreadingPolicy::Single {
82            return None;
83        }
84        let thread_count = self.thread_count(for_size);
85        rayon::ThreadPoolBuilder::new()
86            .num_threads(thread_count)
87            .build()
88            .ok()
89    }
90
91    #[cfg(target_arch = "wasm32")]
92    pub fn get_pool(&self, _: ImageSize) -> Option<ThreadPool> {
93        None
94    }
95}
pic_scale/threading_policy.rs

pic_scale/
threading_policy.rs
