U32Variant0124

U32Variant0124 is an alternative u32 codec where zero values consume no data bytes at all. The byte-width options are 0, 1, 2, or 4. There is no 3-byte option.

Wire-compatible with the Lemire "0124" variant and the streamvbyte64::Coder0124.

Tag table

Note that values in the range 65536–16777215 require 4 bytes (not 3), which is worse than U32Classic for that range. The benefit comes from sparse data where many values are zero.

Example

#![allow(unused)]
fn main() {
use svb::u32::U32Variant0124;

// Zero-valued elements cost 0 bytes in the data stream.
let values: Vec<u32> = vec![0, 0, 42, 0, 0, 255, 0];
let encoded = U32Variant0124.encode(&values);
let decoded = U32Variant0124.decode(&encoded, values.len()).unwrap();
assert_eq!(decoded, values);
}

When to use

Use U32Variant0124 when a significant fraction of values are exactly zero, such as sparse histograms, run-length-style data, or delta-encoded sorted lists where many differences are zero. For general data with few zeros, U32Classic is typically better because it can use 3 bytes for values in the 65536–16777215 range.