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Combine bound checks

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This commit is contained in:
Kornel 2021-02-04 17:51:35 +00:00
parent 790a410a55
commit 1021e9845a
1 changed files with 11 additions and 16 deletions
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27
src/filters.rs
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@ -72,11 +72,9 @@ pub fn unfilter_line(filter: u8, bpp: usize, data: &[u8], last_line: &[u8], buf:
}
1 => {
for (i, &cur) in data.iter().enumerate() {
buf.push(match i.checked_sub(bpp) {
Some(x) => {
let b = buf[x];
cur.wrapping_add(b)
}
let prev_byte = i.checked_sub(bpp).and_then(|x| buf.get(x).copied());
buf.push(match prev_byte {
Some(b) => cur.wrapping_add(b),
None => cur,
});
}
@ -90,23 +88,20 @@ pub fn unfilter_line(filter: u8, bpp: usize, data: &[u8], last_line: &[u8], buf:
}
3 => {
for (i, (&cur, &last)) in data.iter().zip(last_line).enumerate() {
buf.push(match i.checked_sub(bpp) {
Some(x) => {
let b = buf[x];
cur.wrapping_add(((u16::from(b) + u16::from(last)) >> 1) as u8)
}
let prev_byte = i.checked_sub(bpp).and_then(|x| buf.get(x).copied());
buf.push(match prev_byte {
Some(b) => cur.wrapping_add(((u16::from(b) + u16::from(last)) >> 1) as u8),
None => cur.wrapping_add(last >> 1),
});
}
}
4 => {
for (i, (&cur, &last)) in data.iter().zip(last_line).enumerate() {
buf.push(match i.checked_sub(bpp) {
Some(x) => {
let b = buf[x];
cur.wrapping_add(paeth_predictor(b, last, last_line[x]))
for (i, (&cur, &up)) in data.iter().zip(last_line).enumerate() {
buf.push(match i.checked_sub(bpp).map(|x| (buf.get(x).copied(), last_line.get(x).copied())) {
Some((Some(left), Some(left_up))) => {
cur.wrapping_add(paeth_predictor(left, up, left_up))
}
None => cur.wrapping_add(last),
_ => cur.wrapping_add(up),
});
}
}