CodeDweller/roller.hpp

// roller.hpp
// Copyright (C) 2022 MicroNeil Research Corporation.
//
// This software is released under the MIT license. See LICENSE.TXT.
//
// Roller is a naive rolling hash system for rapid string searches.
// Roller32 accommodates matches up to 4 bytes.
// Roller64 accommodates matches up to 8 bytes.

#pragma once

#include <cstdint>
#include <ctype.h>
#include <string>
#include <vector>

#include <iostream>
#include <bitset>

namespace codedweller {

    class Roller32 {
        private:
            uint_fast32_t roller;

        public:
            Roller32() : roller(0) {}
            uint_fast32_t value() const { return roller; }
            uint_fast32_t add(uint8_t byte) { 
                roller = roller << 8 | byte;
                return roller;
            }
    };

    class Roller64 {
        private:
            uint_fast64_t roller;

        public:
            Roller64() : roller(0) {}
            uint_fast64_t value() const { return roller; }
            uint_fast64_t add(uint8_t byte) {
                roller = roller << 8 | byte;
                return roller;
            }
    };

    namespace roller{
        static const unsigned char caseBit = 'A' ^ 'a';
        static const unsigned char caseMask = ~caseBit;

        unsigned char applyCaseSensitivity(unsigned char byte, bool caseSensitive) {
            if (true==caseSensitive) return byte;
            if (false==isalpha(byte) && 0xFF != byte) return byte;
            unsigned char insensitiveByte = byte & caseMask;
            return insensitiveByte;
        }

        unsigned char appropriateBitMask(unsigned char byte, bool caseSensitive) {
            if (true==caseSensitive) return 0xff;
            if (false==isalpha(byte)) return 0xff;
            return caseMask;
        }

        template <class D, class T>
        void compute(D data, bool caseSensitive, T& matcher, T& masker) {
            size_t ingest = std::min(sizeof(matcher.value()), data.size());
            for(size_t count = 0; count < ingest; count++) {
                unsigned char theByte = data.at(count);
                matcher.add(roller::applyCaseSensitivity(theByte, caseSensitive));
                masker.add(roller::appropriateBitMask(theByte, caseSensitive));
            }
        }
    }
    
    class RollerMatch32 {
        private:
            uint_fast32_t match;
            uint_fast32_t mask;

        public:
            RollerMatch32(const std::vector<unsigned char> pattern, bool caseSensitive=true) {
                Roller32 matcher, masker;
                roller::compute(pattern, caseSensitive, matcher, masker);
                match = matcher.value();
                mask = masker.value();
            }

            RollerMatch32(const std::string pattern, bool caseSensitive=true) {
                Roller32 matcher, masker;
                roller::compute(pattern, caseSensitive, matcher, masker);
                match = matcher.value();
                mask = masker.value();
            }

            bool matches(const Roller32 roller) {
                return (match == (roller.value() & mask));
            }

    };

    class RollerMatch64 {
        private:
            uint_fast64_t match;
            uint_fast64_t mask;

        public:
            RollerMatch64(const std::vector<unsigned char> pattern, bool caseSensitive=true) {
                Roller64 matcher, masker;
                roller::compute(pattern, caseSensitive, matcher, masker);
                match = matcher.value();
                mask = masker.value();
            }

            RollerMatch64(const std::string pattern, bool caseSensitive=true) {
                Roller64 matcher, masker;
                roller::compute(pattern, caseSensitive, matcher, masker);
                match = matcher.value();
                mask = masker.value();
            }

            bool matches(const Roller64 roller) {
                return (match == (roller.value() & mask));
            }
    };
}