portapack-mayhem/firmware/common/crc.hpp

/*
 * Copyright (C) 2014 Jared Boone, ShareBrained Technology, Inc.
 *
 * This file is part of PortaPack.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; see the file COPYING.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street,
 * Boston, MA 02110-1301, USA.
 */

#ifndef __CRC_H__
#define __CRC_H__

#include <cstddef>
#include <cstdint>
#include <limits>
#include <array>

/* Inspired by
 * http://www.barrgroup.com/Embedded-Systems/How-To/CRC-Calculation-C-Code
 *
 * ...then munged into a simplified implementation of boost::crc_basic and
 * boost::crc_optimal.
 * http://www.boost.org/doc/libs/release/libs/crc/
 *
 *  Copyright 2001, 2004 Daryle Walker.  Use, modification, and distribution are
 *  subject to the Boost Software License, Version 1.0.  (See accompanying file
 *  LICENSE_1_0.txt or a copy at <http://www.boost.org/LICENSE_1_0.txt>.)
 *
 */

template <size_t Width, bool RevIn = false, bool RevOut = false>
class CRC {
   public:
    using value_type = uint32_t;

    constexpr CRC(
        const value_type truncated_polynomial,
        const value_type initial_remainder = 0,
        const value_type final_xor_value = 0)
        : truncated_polynomial{truncated_polynomial},
          initial_remainder{initial_remainder},
          final_xor_value{final_xor_value},
          remainder{initial_remainder} {
    }

    value_type get_initial_remainder() const {
        return initial_remainder;
    }

    void reset(value_type new_initial_remainder) {
        remainder = new_initial_remainder;
    }

    void reset() {
        remainder = initial_remainder;
    }

    void process_bit(bool bit) {
        remainder ^= (bit ? top_bit() : 0U);
        const auto do_poly_div = static_cast<bool>(remainder & top_bit());
        remainder <<= 1;
        if (do_poly_div) {
            remainder ^= truncated_polynomial;
        }
    }

    void process_bits(value_type bits, size_t bit_count) {
        if (RevIn) {
            process_bits_lsb_first(bits, bit_count);
        } else {
            process_bits_msb_first(bits, bit_count);
        }
    }

    void process_byte(const uint8_t byte) {
        process_bits(byte, 8);
    }

    void process_bytes(const void* const data, const size_t length) {
        const uint8_t* const p = reinterpret_cast<const uint8_t*>(data);
        for (size_t i = 0; i < length; i++) {
            process_byte(p[i]);
        }
    }

    template <size_t N>
    void process_bytes(const std::array<uint8_t, N>& data) {
        process_bytes(data.data(), data.size());
    }

    value_type checksum() const {
        return ((RevOut ? reflect(remainder) : remainder) ^ final_xor_value) & mask();
    }

   private:
    const value_type truncated_polynomial;
    const value_type initial_remainder;
    const value_type final_xor_value;
    value_type remainder;

    static constexpr size_t width() {
        return Width;
    }

    static constexpr value_type top_bit() {
        return 1U << (width() - 1);
    }

    static constexpr value_type mask() {
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wshift-count-overflow"
        return (~(~(0UL) << width()));
#pragma GCC diagnostic pop
    }

    static value_type reflect(value_type x) {
        value_type reflection = 0;
        for (size_t i = 0; i < width(); ++i) {
            reflection <<= 1;
            reflection |= (x & 1);
            x >>= 1;
        }
        return reflection;
    }

    void process_bits_msb_first(value_type bits, size_t bit_count) {
        constexpr auto digits = std::numeric_limits<value_type>::digits;
        constexpr auto mask = static_cast<value_type>(1) << (digits - 1);

        bits <<= (std::numeric_limits<value_type>::digits - bit_count);
        for (size_t i = bit_count; i > 0; --i, bits <<= 1) {
            process_bit(static_cast<bool>(bits & mask));
        }
    }

    void process_bits_lsb_first(value_type bits, size_t bit_count) {
        for (size_t i = bit_count; i > 0; --i, bits >>= 1) {
            process_bit(static_cast<bool>(bits & 0x01));
        }
    }
};

class Adler32 {
   public:
    void feed(const uint8_t v) {
        feed_one(v);
    }

    void feed(const void* const data, const size_t n) {
        const uint8_t* const p = reinterpret_cast<const uint8_t*>(data);
        for (size_t i = 0; i < n; i++) {
            feed_one(p[i]);
        }
    }

    template <typename T>
    void feed(const T& a) {
        feed(a.data(), sizeof(T));
    }

    std::array<uint8_t, 4> bytes() const {
        return {
            static_cast<uint8_t>((b >> 8) & 0xff),
            static_cast<uint8_t>((b >> 0) & 0xff),
            static_cast<uint8_t>((a >> 8) & 0xff),
            static_cast<uint8_t>((a >> 0) & 0xff)};
    }

   private:
    static constexpr uint32_t mod = 65521;

    uint32_t a{1};
    uint32_t b{0};

    void feed_one(const uint8_t c) {
        a = (a + c) % mod;
        b = (b + a) % mod;
    }
};

#endif /*__CRC_H__*/