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|
const TEN_MASK: u64 = 1023; // ten bits
pub fn tenbit(packd: &[u8], count: usize, upack: &mut [u16]) {
let required_len_packd = (count as f32 * (10.0 / 8.0)).ceil() as usize;
println!(
"requires {required_len_packd} bytes | {} groups of 5",
count / 4
);
if count > upack.len() {
panic!(
"expected output buffer to be {count} bytes, got {} bytes",
upack.len()
)
}
if required_len_packd > packd.len() {
panic!(
"expected input to be at least {required_len_packd} bytes, it was {}",
packd.len()
)
}
let mut packd = packd[..required_len_packd].to_vec();
packd.reverse();
let chunker = packd.chunks_exact(5);
let remain = chunker.remainder();
for (idx, chnk) in chunker.enumerate() {
let long = u64::from_be_bytes([
0x00, 0x00, 0x00, chnk[0], chnk[1], chnk[2], chnk[3], chnk[4],
]);
let b4 = long & TEN_MASK;
let b3 = (long >> 10) & TEN_MASK;
let b2 = (long >> 20) & TEN_MASK;
let b1 = (long >> 30) & TEN_MASK;
let idx = idx * 4;
upack[idx] = b1 as u16;
upack[idx + 1] = b2 as u16;
upack[idx + 2] = b3 as u16;
upack[idx + 3] = b4 as u16;
}
if remain.len() > 0 {
let mut long_bytes = [0x00; 8];
for (idx, byte) in remain.iter().enumerate() {
long_bytes[idx] = *byte;
}
let long = u64::from_le_bytes(long_bytes);
let count_remain = count % 4;
let start = count - count_remain;
for idx in 0..count_remain {
upack[start + idx] = ((long >> (10 * idx)) & TEN_MASK) as u16;
}
}
}
|
