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// Copyright (c) the JPEG XL Project Authors. All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
use std::ops::DerefMut;
use crate::{
error::Result,
frame::modular::{IMAGE_OFFSET, IMAGE_PADDING},
image::Image,
util::AtomicRefMut,
};
use super::{ModularBufferInfo, ModularChannel};
pub fn with_buffers<T>(
buffers: &[ModularBufferInfo],
indices: &[usize],
grid: usize,
f: impl FnOnce(Vec<&mut ModularChannel>) -> Result<T>,
) -> Result<T> {
let mut bufs = vec![];
for i in indices {
// Allocate buffers if they are not present.
let buf = &buffers[*i];
let b = &buf.buffer_grid[grid];
let mut data = b.data.borrow_mut();
if data.is_none() {
*data = Some(ModularChannel {
data: Image::new_with_padding(b.size, IMAGE_OFFSET, IMAGE_PADDING)?,
auxiliary_data: None,
shift: buf.info.shift,
bit_depth: buf.info.bit_depth,
});
}
// Skip zero-sized *tiles*.
//
// Note that some bitstreams can contain channels with one dimension being 0 (e.g. palette
// meta-channel with 0 colors has size (0, 3)). Those must still participate in channel
// numbering (but carry no entropy-coded pixels), so we only skip when both dimensions are 0.
if b.size.0 == 0 && b.size.1 == 0 {
continue;
}
bufs.push(AtomicRefMut::map(data, |x| x.as_mut().unwrap()));
}
f(bufs.iter_mut().map(|x| x.deref_mut()).collect())
}