Function create_legacy_dict_from_slice 

pub fn create_legacy_dict_from_slice<W: Write>(
    samples: &[u8],
    sample_sizes: &[usize],
    output: &mut W,
    dict_size: usize,
    selectivity: u32,
    finalize: FinalizeOptions,
) -> Result<()>

Available on crate feature dict-builder only.

Train and finalize a dictionary with the reference’s original trainer, the one zstd --train-legacy runs (ZDICT_trainFromBuffer_legacy).

samples is every sample back to back and sample_sizes their lengths: the trainer searches the corpus as a whole, and the number of samples sets how often a segment has to repeat to be kept, samples >> selectivity times and at least 4. A higher selectivity keeps more, rarer segments; zero is DEFAULT_SELECTIVITY. Corpus past 2000 MiB is dropped a whole sample at a time from the end.

Errors

InvalidInput when the corpus is under 512 bytes (carrying TrainingError::Samples), when dict_size is below 256 bytes (carrying TrainingError::DictionaryTooSmall), when it repeats too little to yield 128 bytes of content, or when sample_sizes does not add up to samples.len().

Examples

use structured_zstd::dictionary::{create_legacy_dict_from_slice, FinalizeOptions};

let mut samples = Vec::new();
let mut sizes = Vec::new();
for i in 0..200u32 {
    let line = format!("tenant=demo table=orders key={i} region=eu status=shipped\n");
    sizes.push(line.len());
    samples.extend_from_slice(line.as_bytes());
}
let mut dict = Vec::new();
create_legacy_dict_from_slice(&samples, &sizes, &mut dict, 4096, 0, FinalizeOptions::default())
    .unwrap();
assert!(dict.starts_with(&[0x37, 0xA4, 0x30, 0xEC]));