Module abac 

Adaptive binary arithmetic coding — integer only, bit-exact everywhere.

A carry-propagating 32-bit range coder (the LZMA construction) driven by 16-bit probabilities. Everything from a probability to an output byte is integer arithmetic, so any backend that feeds the same probabilities produces and consumes the same bytes. Probabilities come either from BitModel (two-rate adaptive counter) or straight from a model (e.g. the fixed-point network in crate::learned) via Encoder::encode_p.

Structs

BitModel

Two-rate adaptive bit model (fast + slow exponential counters, averaged).

Decoder

Range decoder over a byte slice (reads past the end as zeros).

Encoder

Range encoder.

UintModel

Adaptive Elias-gamma style coder for unbounded non-negative integers: unary bucket k = ⌊log₂(v+1)⌋ with one model per bucket position, then the k mantissa bits (top MODELED with models, the rest raw).

Constants

ONE

Probability scale: p1 ∈ [P_MIN, ONE − P_MIN] means P(bit = 1) = p1 / ONE.

P_MIN

Smallest probability either symbol may get.

Functions

clamp_p

Clamp a probability of a one into the codable range.

cost_bits

Ideal code length in bits of coding bit at P(1) = p1 / 2^16.