SNFMulti/snf_saccades.hpp

// snf_saccades.hpp
// Saccades engine adaptation for MessageSniffer
// Copyright 2014-2020 MicroNeil Research Corporation (www.microneil.com)
// Licensed to ARM Research Labs for use in Message Sniffer.

#pragma once

#include <set>
#include <vector>

class saccades_engine;
class saccade {
  friend class saccades_engine;
  private:
    const static unsigned int stretchSize = 8;
    const static unsigned int stretchMark = stretchSize / 2;
    const static unsigned int stretchMask = ((~0U) ^ (stretchSize - 1));

    unsigned int stretchLeft(unsigned int s) {
        s = (stretchMark > s) ? s : (s - (stretchMark));
        return (s & stretchMask);
    }

    unsigned int stretchRight(unsigned int f) {
        f = (start > f) ? start : f;
        return ((f + stretchSize + stretchMark) & stretchMask);
    }

    saccade() : start(0), finish(0) {}
    static saccade unstretched(unsigned int s, unsigned int f) {
        saccade u;
        u.start = s;
        u.finish = f;
        return u;
    }

  public:
    unsigned int start;
    unsigned int finish;

    saccade(unsigned int s, unsigned int f) :
      start(stretchLeft(s)),
      finish(stretchRight(f)) {}

    bool operator<(const saccade& r) const {
        if(start < r.start) return true;
        if(start > r.start) return false;
        return (finish < r.finish);
    }

    bool operator==(const saccade& r) const {
        return (
          start == r.start &&
          finish == r.finish
        );
    }
};

class saccade_marker {
  public:
    const saccade theSaccade;
    unsigned int theSlot;
    saccade_marker(saccade key, unsigned int slot) :
      theSaccade(key),
      theSlot(slot) {}

    bool operator<(const saccade_marker& r) const {
        return (theSaccade < r.theSaccade);
    }
};

struct saccade_engram {
    static const int NoneMore = -1;
    int nextFresh;
    int nextStale;
    saccade theSaccade;

    saccade_engram() :
      nextFresh(NoneMore),
      nextStale(NoneMore),
      theSaccade(0,0) {}

    saccade_engram(saccade s) :
      nextFresh(NoneMore),
      nextStale(NoneMore),
      theSaccade(s) {}
};

class saccades_engine {
  private:
    std::vector<saccade_engram> engrams;
    std::set<saccade_marker> markers;

    const unsigned int capacity;
    int mostFresh;
    int mostStale;

    void evoke(saccade s);

    void disconnectEngram(int theSlot);
    void connectFreshestEngram(int theSlot);
    void freshenEngram(int theSlot);
    void makeEngram(saccade s);
    void recycleEngram(saccade s);

  public:

    saccades_engine(unsigned int c) :
        capacity(c),
        mostFresh(saccade_engram::NoneMore),
        mostStale(saccade_engram::NoneMore) {
          engrams.reserve(capacity);
        }

    std::vector<saccade> recall();
    void learn(std::vector<saccade>& experiences);

};