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use super::super::uleb128;
use super::{super::ceil8, HybridEncoded};
#[derive(Debug, Clone)]
pub struct Decoder<'a> {
values: &'a [u8],
num_bits: u32,
}
impl<'a> Decoder<'a> {
pub fn new(values: &'a [u8], num_bits: u32) -> Self {
Self { values, num_bits }
}
#[inline]
pub fn num_bits(&self) -> u32 {
self.num_bits
}
}
impl<'a> Iterator for Decoder<'a> {
type Item = HybridEncoded<'a>;
fn next(&mut self) -> Option<Self::Item> {
if self.values.is_empty() {
return None;
}
let (indicator, consumed) = uleb128::decode(self.values);
self.values = &self.values[consumed..];
if indicator & 1 == 1 {
let bytes = (indicator as usize >> 1) * self.num_bits as usize;
let bytes = std::cmp::min(bytes, self.values.len());
let result = Some(HybridEncoded::Bitpacked(&self.values[..bytes]));
self.values = &self.values[bytes..];
result
} else {
let run_length = indicator as usize >> 1;
let rle_bytes = ceil8(self.num_bits as usize);
let result = Some(HybridEncoded::Rle(&self.values[..rle_bytes], run_length));
self.values = &self.values[rle_bytes..];
result
}
}
}
#[cfg(test)]
mod tests {
use super::*;
use super::super::super::bitpacking;
#[test]
fn basics_1() {
let bit_width = 1;
let length = 5;
let values = vec![
2, 0, 0, 0,
0b00000011, 0b00001011,
];
let mut decoder = Decoder::new(&values[4..6], bit_width);
let run = decoder.next().unwrap();
if let HybridEncoded::Bitpacked(values) = run {
assert_eq!(values, &[0b00001011]);
let result =
bitpacking::Decoder::new(values, bit_width as u8, length).collect::<Vec<_>>();
assert_eq!(result, &[1, 1, 0, 1, 0]);
} else {
panic!()
};
}
#[test]
fn basics_2() {
let bit_width = 1;
let values = vec![
3, 0, 0, 0,
0b00000101, 0b11101011, 0b00000010,
];
let expected = &[1, 1, 0, 1, 0, 1, 1, 1, 0, 1];
let mut decoder = Decoder::new(&values[4..4 + 3], bit_width);
let run = decoder.next().unwrap();
if let HybridEncoded::Bitpacked(values) = run {
assert_eq!(values, &[0b11101011, 0b00000010]);
let result = bitpacking::Decoder::new(values, bit_width as u8, 10).collect::<Vec<_>>();
assert_eq!(result, expected);
} else {
panic!()
};
}
#[test]
fn basics_3() {
let bit_width = 1;
let length = 8;
let values = vec![
2, 0, 0, 0,
0b00010000,
0b00000001,
];
let mut decoder = Decoder::new(&values[4..4 + 2], bit_width);
let run = decoder.next().unwrap();
if let HybridEncoded::Rle(values, items) = run {
assert_eq!(values, &[0b00000001]);
assert_eq!(items, length);
} else {
panic!()
};
}
}