use crate::docset::DocSet;
/// Postings (also called inverted list)
///
/// For a given term, it is the list of doc ids of the doc
/// containing the term. Optionally, for each document,
/// it may also give access to the term frequency
/// as well as the list of term positions.
///
/// Its main implementation is `SegmentPostings`,
/// but other implementations mocking `SegmentPostings` exist,
/// for merging segments or for testing.
pub trait Postings: DocSet + 'static {
/// The number of times the term appears in the document.
fn term_freq(&self) -> u32;
/// Returns the positions offsetted with a given value.
/// The output vector will be resized to the `term_freq`.
fn positions_with_offset(&mut self, offset: u32, output: &mut Vec<u32>);
/// Returns the positions of the term in the given document.
/// The output vector will be resized to the `term_freq`.
fn positions(&mut self, output: &mut Vec<u32>) {
self.positions_with_offset(0u32, output);
}
}