dvmvocoder/vocoder/ecc.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Digital Voice Modem - MBE Vocoder
 * GPLv2 Open Source. Use is subject to license terms.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 */

/*
 * Copyright (C) 2010 mbelib Author
 * GPG Key ID: 0xEA5EFE2C (9E7A 5527 9CDC EBF7 BF1B  D772 4F98 E863 EA5E FE2C)
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
 * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 * PERFORMANCE OF THIS SOFTWARE.
 */

#define _USE_MATH_DEFINES
#include <math.h>

#include "ecc_const.h"

// ---------------------------------------------------------------------------
//  Global Functions
// ---------------------------------------------------------------------------

/* */

void mbe_checkGolayBlock(long int* block)
{
    static int i, syndrome, eccexpected, eccbits, databits;
    long int mask, block_l;

    block_l = *block;

    mask = 0x400000l;
    eccexpected = 0;
    for (i = 0; i < 12; i++) {
        if ((block_l & mask) != 0l) {
            eccexpected ^= golayGenerator[i];
        }

        mask = mask >> 1;
    }

    eccbits = (int)(block_l & 0x7ffl);
    syndrome = eccexpected ^ eccbits;

    databits = (int)(block_l >> 11);
    databits = databits ^ golayMatrix[syndrome];

    *block = (long)databits;
}

/* */

int mbe_golay2312(char* in, char* out)
{
    int i, errs;
    long block;

    block = 0;
    for (i = 22; i >= 0; i--) {
        block = block << 1;
        block = block + in[i];
    }

    mbe_checkGolayBlock(&block);

    for (i = 22; i >= 11; i--) {
        out[i] = (block & 2048) >> 11;
        block = block << 1;
    }

    for (i = 10; i >= 0; i--) {
        out[i] = in[i];
    }

    errs = 0;
    for (i = 22; i >= 11; i--) {
        if (out[i] != in[i]) {
            errs++;
        }
    }
    return (errs);
}

/* */

int mbe_hamming1511(char* in, char* out)
{
    int i, j, errs, block, syndrome, stmp, stmp2;

    errs = 0;

    block = 0;
    for (i = 14; i >= 0; i--) {
        block <<= 1;
        block |= in[i];
    }

    syndrome = 0;
    for (i = 0; i < 4; i++) {
        syndrome <<= 1;
        stmp = block;
        stmp &= hammingGenerator[i];

        stmp2 = (stmp % 2);
        for (j = 0; j < 14; j++)
        {
            stmp >>= 1;
            stmp2 ^= (stmp % 2);
        }

        syndrome |= stmp2;
    }

    if (syndrome > 0) {
        errs++;
        block ^= hammingMatrix[syndrome];
    }

    for (i = 14; i >= 0; i--) {
        out[i] = (block & 0x4000) >> 14;
        block = block << 1;
    }
    return (errs);
}

/* */

int mbe_7100x4400Hamming1511(char* in, char* out)
{
    int i, j, errs, block, syndrome, stmp, stmp2;

    errs = 0;

    block = 0;
    for (i = 14; i >= 0; i--) {
        block <<= 1;
        block |= in[i];
    }

    syndrome = 0;
    for (i = 0; i < 4; i++) {
        syndrome <<= 1;
        stmp = block;
        stmp &= imbe7100x4400hammingGenerator[i];

        stmp2 = (stmp % 2);
        for (j = 0; j < 14; j++)
        {
            stmp >>= 1;
            stmp2 ^= (stmp % 2);
        }

        syndrome |= stmp2;
    }

    if (syndrome > 0) {
        errs++;
        block ^= hammingMatrix[syndrome];
    }

    for (i = 14; i >= 0; i--) {
        out[i] = (block & 0x4000) >> 14;
        block = block << 1;
    }

    return (errs);
}