lib_crc.cc

//------------------------------------------------------------------------
//  CRC : Cyclic Rendundancy Check
//------------------------------------------------------------------------
//
//  OBSIDIAN Level Maker
//
//  Copyright (C) 2021-2022 The OBSIDIAN Team
//  Copyright (C) 2006-2017 Andrew Apted
//
//  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
//  of the License, 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.
//
//------------------------------------------------------------------------
//
//  This is the Adler-32 algorithm as described in RFC-1950.
//
//------------------------------------------------------------------------

#include "lib_crc.h"

#include "headers.h"

// ---- Primitive routines ----

crc32_c &crc32_c::operator+=(u8_t data) {
    u32_t s1 = raw & 0xFFFF;
    u32_t s2 = (raw >> 16) & 0xFFFF;

    s1 = (s1 + data) % 65521;
    s2 = (s2 + s1) % 65521;

    raw = (s2 << 16) | s1;

    return *this;
}

crc32_c &crc32_c::AddBlock(const u8_t *data, int len) {
    u32_t s1 = raw & 0xFFFF;
    u32_t s2 = (raw >> 16) & 0xFFFF;

    for (; len > 0; data++, len--) {
        s1 = (s1 + *data) % 65521;
        s2 = (s2 + s1) % 65521;
    }

    raw = (s2 << 16) | s1;

    return *this;
}

// ---- non-primitive routines ----

crc32_c &crc32_c::operator+=(u16_t value) {
    *this += (u8_t)(value >> 8);
    *this += (u8_t)(value);

    return *this;
}

crc32_c &crc32_c::operator+=(u32_t value) {
    *this += (u8_t)(value >> 24);
    *this += (u8_t)(value >> 16);
    *this += (u8_t)(value >> 8);
    *this += (u8_t)(value);

    return *this;
}

crc32_c &crc32_c::operator+=(float value) {
    bool neg = (value < 0.0f);
    value = (float)fabs(value);

    int exp;
    u32_t mant = (u32_t)(ldexp(frexp(value, &exp), 30));

    *this += (u8_t)(neg ? '-' : '+');
    *this += (u32_t)exp;
    *this += mant;

    return *this;
}

crc32_c &crc32_c::AddCStr(const char *str) {
    return AddBlock((const u8_t *)str, (int)strlen(str));
}

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