uint8_t cpc_compressor::determine_pseudo_phase()

in cpc/include/cpc_compressor_impl.hpp [445:465]

• 18 lines of code
• 10 McCabe index (conditional complexity)

uint8_t cpc_compressor<A>::determine_pseudo_phase(uint8_t lg_k, uint32_t c) {
  const uint32_t k = 1 << lg_k;
  // This mid-range logic produces pseudo-phases. They are used to select encoding tables.
  // The thresholds were chosen by hand after looking at plots of measured compression.
  if (1000 * c < 2375 * k) {
    if      (   4 * c <    3 * k) return 16 + 0; // mid-range table
    else if (  10 * c <   11 * k) return 16 + 1; // mid-range table
    else if ( 100 * c <  132 * k) return 16 + 2; // mid-range table
    else if (   3 * c <    5 * k) return 16 + 3; // mid-range table
    else if (1000 * c < 1965 * k) return 16 + 4; // mid-range table
    else if (1000 * c < 2275 * k) return 16 + 5; // mid-range table
    else return 6;  // steady-state table employed before its actual phase
  } else { // This steady-state logic produces true phases. They are used to select
         // encoding tables, and also column permutations for the "Sliding" flavor.
    if (lg_k < 4) throw std::logic_error("lgK < 4");
    const size_t tmp = c >> (lg_k - 4);
    const uint8_t phase = tmp & 15;
    if (phase >= 16) throw std::out_of_range("wrong phase");
    return phase;
  }
}