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Rework the decoder so it's safe, add bytemuck dep

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This commit is contained in:
Ivan Smirnov 2021-12-31 01:44:59 +03:00
parent 6ce544950d
commit a9a01c6fbd
4 changed files with 79 additions and 76 deletions
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3
Cargo.toml
View file

@ -15,6 +15,9 @@ exclude = [
"assets/*",
]
[dependencies]
bytemuck = "1.7"
[workspace]
members = ["qoi-bench"]

144
src/decode.rs
View file

@ -1,4 +1,5 @@
use std::mem;
// TODO: can be removed once https://github.com/rust-lang/rust/issues/74985 is stable
use bytemuck::{cast_slice_mut, Pod};
use crate::consts::{
QOI_HEADER_SIZE, QOI_OP_DIFF, QOI_OP_INDEX, QOI_OP_LUMA, QOI_OP_RGB, QOI_OP_RGBA, QOI_OP_RUN,
@ -7,11 +8,12 @@ use crate::consts::{
use crate::error::{Error, Result};
use crate::header::Header;
use crate::pixel::{Pixel, SupportedChannels};
use crate::utils::{cold, likely, unlikely};
use crate::utils::{cold, unlikely};
pub fn qoi_decode_impl<const N: usize>(data: &[u8], n_pixels: usize) -> Result<Vec<u8>>
where
Pixel<N>: SupportedChannels,
[u8; N]: Pod,
{
if unlikely(data.len() < QOI_HEADER_SIZE + QOI_PADDING_SIZE) {
return Err(Error::InputBufferTooSmall {
@ -20,93 +22,83 @@ where
});
}
let mut pixels = vec![Pixel::<N>::new(); n_pixels];
let mut index = [Pixel::new(); 256];
let mut px = Pixel::new().with_a(0xff);
const QOI_OP_INDEX_END: u8 = QOI_OP_INDEX | 0x3f;
const QOI_OP_RUN_END: u8 = QOI_OP_RUN | 0x3d; // <- note, 0x3d (not 0x3f)
const QOI_OP_DIFF_END: u8 = QOI_OP_DIFF | 0x3f;
const QOI_OP_LUMA_END: u8 = QOI_OP_LUMA | 0x3f;
{
let mut pixels = &mut pixels[..];
let mut data = &data[QOI_HEADER_SIZE..];
loop {
match pixels {
[px_out, tail @ ..] => {
pixels = tail;
match data {
[b1 @ QOI_OP_INDEX..=QOI_OP_INDEX_END, dtail @ ..] => {
px = index[usize::from(*b1)];
*px_out = px;
data = dtail;
continue;
}
[QOI_OP_RGB, r, g, b, dtail @ ..] => {
px = Pixel::from_rgb(Pixel::from_array([*r, *g, *b]), px.a_or(0xff));
data = dtail;
}
[QOI_OP_RGBA, r, g, b, a, dtail @ ..] => {
if N == 4 {
cold();
}
px = Pixel::from_array([*r, *g, *b, *a]);
data = dtail;
}
[b1 @ QOI_OP_RUN..=QOI_OP_RUN_END, dtail @ ..] => {
let run = usize::from(b1 & 0x3f).min(pixels.len());
*px_out = px;
if likely(run != 0) {
let (phead, ptail) = pixels.split_at_mut(run); // can't panic
phead.fill(px);
pixels = ptail;
}
data = dtail;
continue;
}
[b1 @ QOI_OP_DIFF..=QOI_OP_DIFF_END, dtail @ ..] => {
px.rgb_add(
((b1 >> 4) & 0x03).wrapping_sub(2),
((b1 >> 2) & 0x03).wrapping_sub(2),
(b1 & 0x03).wrapping_sub(2),
);
data = dtail;
}
[b1 @ QOI_OP_LUMA..=QOI_OP_LUMA_END, b2, dtail @ ..] => {
let vg = (b1 & 0x3f).wrapping_sub(32);
let vg_8 = vg.wrapping_sub(8);
let vr = vg_8.wrapping_add((b2 >> 4) & 0x0f);
let vb = vg_8.wrapping_add(b2 & 0x0f);
px.rgb_add(vr, vg, vb);
data = dtail;
}
_ => {
let mut out = vec![0; n_pixels * N]; // unnecessary zero-init, but w/e
let mut pixels = cast_slice_mut::<_, [u8; N]>(&mut out);
let mut data = &data[QOI_HEADER_SIZE..];
let mut index = [Pixel::<N>::new(); 256];
let mut px = Pixel::<N>::new().with_a(0xff);
loop {
match pixels {
[px_out, ptail @ ..] => {
pixels = ptail;
match data {
[b1 @ QOI_OP_INDEX..=QOI_OP_INDEX_END, dtail @ ..] => {
px = index[usize::from(*b1)];
*px_out = px.into();
data = dtail;
continue;
}
[QOI_OP_RGB, r, g, b, dtail @ ..] => {
px = Pixel::from_rgb(Pixel::from_array([*r, *g, *b]), px.a_or(0xff));
data = dtail;
}
[QOI_OP_RGBA, r, g, b, a, dtail @ ..] => {
if N == 4 {
cold();
if unlikely(data.len() < 8) {
return Err(Error::UnexpectedBufferEnd);
}
}
px = Pixel::from_array([*r, *g, *b, *a]);
data = dtail;
}
[b1 @ QOI_OP_RUN..=QOI_OP_RUN_END, dtail @ ..] => {
*px_out = px.into();
let run = usize::from(b1 & 0x3f).min(pixels.len());
let (phead, ptail) = pixels.split_at_mut(run); // can't panic
phead.fill(px.into());
pixels = ptail;
data = dtail;
continue;
}
[b1 @ QOI_OP_DIFF..=QOI_OP_DIFF_END, dtail @ ..] => {
px.rgb_add(
((b1 >> 4) & 0x03).wrapping_sub(2),
((b1 >> 2) & 0x03).wrapping_sub(2),
(b1 & 0x03).wrapping_sub(2),
);
data = dtail;
}
[b1 @ QOI_OP_LUMA..=QOI_OP_LUMA_END, b2, dtail @ ..] => {
let vg = (b1 & 0x3f).wrapping_sub(32);
let vg_8 = vg.wrapping_sub(8);
let vr = vg_8.wrapping_add((b2 >> 4) & 0x0f);
let vb = vg_8.wrapping_add(b2 & 0x0f);
px.rgb_add(vr, vg, vb);
data = dtail;
}
_ => {
cold();
if unlikely(data.len() < 8) {
return Err(Error::UnexpectedBufferEnd);
}
}
index[usize::from(px.hash_index())] = px;
*px_out = px;
}
_ => {
cold();
break;
}
index[usize::from(px.hash_index())] = px;
*px_out = px.into();
}
_ => {
cold();
break;
}
}
}
let ptr = pixels.as_mut_ptr();
mem::forget(pixels);
let bytes = unsafe {
// Safety: this is safe because we have previously set all the lengths ourselves
Vec::from_raw_parts(ptr.cast(), n_pixels * N, n_pixels * N)
};
Ok(bytes)
Ok(out)
}
pub trait MaybeChannels {

7
src/pixel.rs
View file

@ -102,6 +102,13 @@ impl<const N: usize> Pixel<N> {
}
}
impl<const N: usize> From<Pixel<N>> for [u8; N] {
#[inline(always)]
fn from(px: Pixel<N>) -> Self {
px.0
}
}
pub trait SupportedChannels {}
impl SupportedChannels for Pixel<3> {}

1
src/utils.rs
View file

@ -3,6 +3,7 @@
pub const fn cold() {}
#[inline(always)]
#[allow(unused)]
pub const fn likely(b: bool) -> bool {
if !b {
cold()