Struct FrequencyTable 

pub struct FrequencyTable { /* private fields */ }

A frequency model for rANS with total (T = 2^{precision_bits}).

Implementations

impl FrequencyTable

pub fn from_counts( counts: &[u32], precision_bits: u32, ) -> Result<Self, AnsError>

Build a normalized frequency table from raw counts.

precision_bits sets (T = 2^{precision_bits}), the total frequency mass. Counts are scaled to sum to (T), with a minimal correction pass to preserve nonzero symbols where possible.

pub fn precision_bits(&self) -> u32

The number of precision bits, i.e. log2(total).

pub fn total(&self) -> u32

Total frequency mass: 2^precision_bits.

pub fn alphabet_size(&self) -> usize

Number of symbols in the alphabet.

pub fn freq(&self, sym: u32) -> Option<u32>

Normalized frequency for sym, or None if out of range.

pub fn cum_freq(&self, sym: u32) -> Option<u32>

Cumulative frequency (CDF value) for sym, or None if out of range.

pub fn symbol_at_slot(&self, slot: u32) -> Option<u32>

Look up the symbol that owns a cumulative-frequency slot.

slot must be in 0..total. Returns None if out of range. This is the inverse of the CDF: given a slot in [0, T), it returns the symbol whose frequency interval contains that slot.

Trait Implementations

impl Clone for FrequencyTable

fn clone(&self) -> FrequencyTable

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for FrequencyTable

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.